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\begin{document}

\title{Effect of surgeon case volume on major surgical complications for
abdominal and laparoscopic radical hysterectomy for cervical cancer in
China, 2004-2016: A retrospective cohort study}



\author[1]{Cong Liang}%
\author[1]{Weili Li}%
\author[1]{Xiaoyun Liu}%
\author[1]{Hongwei Zhao}%
\author[1]{Lu Yin}%
\author[1]{Mingwei Li}%
\author[1]{Yu Guo}%
\author[2]{Jinghe Lang}%
\author[1]{Xiaonong Bin}%
\author[1]{Ping Liu}%
\author[1]{Chunlin Chen}%
\affil[1]{Affiliation not available}%
\affil[2]{Peking Union Medical College Hospital}%


\vspace{-1em}



  
  \date{May 24, 2024}


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\selectlanguage{english}
\begin{abstract}
Abstract Objectives: To examine changes in surgeon volume over time and
evaluate the influence of surgeon volume on complications of abdominal
radical hysterectomy (ARH) and laparoscopic radical hysterectomy (LRH)
for cervical cancer. Design: A retrospective cohort study. Setting: 42
hospitals in China. Population: 14536 patients undergoing ARH and 8148
patients underwent LRH. Methods: The influence of the surgeon volume of
ARH and LRH on surgical complications was examined using multivariable
logistic regression models. Main outcome measures: Intraoperative
complications and postoperative complications. Results: In the ARH
cohort, the mean surgeon case volume increased from 3.5 cases in 2004 to
8.7 cases in 2013 and then decreased to 4.9 cases in 2016. The number of
surgeons performing LRH increased from 1 surgeon with 1 patient (mean
cases=1) in 2004 to 183 surgeons who operated on 2,206 patients in 2016
(mean cases=12.1) (P\textless{} 0.01). In the ARH, patients treated by
intermediate-volume surgeons had more postoperative complications
(OR=1.55, 95\% CI=1.11-2.15). In the laparoscopic surgery cohort,
surgeon volume had no independent effect on intraoperative or
postoperative complications (P=0.46; P=0.13). Conclusions: The
performance of ARH by intermediate-volume surgeons is associated with an
increased risk of postoperative complications. However, surgeon volume
may have little effect on intraoperative or postoperative complications
after LRH.%
\end{abstract}%



\sloppy


\textbf{Effect of surgeon case volume on major surgical complications
for abdominal and laparoscopic radical hysterectomy forcervical cancer
in China, 2004-2016: A retrospective cohort study}

Cong Liang\textsuperscript{1}*, Weili Li\textsuperscript{1}*, Xiaoyun
Liu\textsuperscript{2}*, Hongwei Zhao\textsuperscript{3}*, Lu
Yin\textsuperscript{1}, Mingwei Li\textsuperscript{4}, Yu
Guo\textsuperscript{5}, Jinghe Lang\textsuperscript{6}, Xiaonong
Bin\textsuperscript{7}, Ping Liu\textsuperscript{1}, Chunlin
Chen\textsuperscript{1}

\textsuperscript{1} Department of Obstetrics and Gynecology, Nanfang
Hospital, Southern Medical University, Guangzhou, China

\textsuperscript{2} Department of Gynecology, The Third Affiliated
Hospital of Zunyi Medical College, Zunyi, China

\textsuperscript{3} Department of Gynecology, Shanxi Provincial Cancer
Hospital, Taiyuan, China

\textsuperscript{4} Department of Obstetrics and Gynecology, the
Jiangmen Central Hospital of SUN YAT-SEN University, Jiangmen, China

\textsuperscript{5} Department of Gynecology, Anyang Tumor Hospital,
Anyang, China

\textsuperscript{6} Department of Obstetrics and Gynecology, Peking
Union Medical College Hospital, Peking Union Medical College \& Chinese
Academy of Medical Science, Beijing, China

\textsuperscript{7} Department of Epidemiology, College of Public
Health, Guangzhou Medical University, Guangzhou, China

\textbf{Corresponding Authors:}

Chunlin Chen, PhD.

Department of Obstetrics and Gynecology,

Nanfang Hospital, Southern Medical University,

No. 1838, Guangzhou Avenue, Guangzhou 510515, China

E-mail: \emph{ccl1@smu.edu.cn}

Ping Liu, PhD.

Department of Obstetrics and Gynecology,

Nanfang Hospital, Southern Medical University,

No. 1838, Guangzhou Avenue, Guangzhou 510515, China;

E-mail: \emph{lp2@smu.edu.cn}.

\textbf{Running title:} Effect of surgeon case volume on complications
during RH

\textbf{Abstract}

\textbf{Objectives:} To examine changes in surgeon volume over time and
evaluate the influence of surgeon volume on complications of abdominal
radical hysterectomy (ARH) and laparoscopic radical hysterectomy (LRH)
for cervical cancer.

\textbf{Design:} A retrospective cohort study.

\textbf{Setting:} 42 hospitals in China.

\textbf{Population:} 14536 patients undergoing ARH and 8148 patients
underwent LRH.

\textbf{Methods:} The influence of the surgeon volume of ARH and LRH on
surgical complications was examined using multivariable logistic
regression models.

\textbf{Main outcome measures:} Intraoperative complications and
postoperative complications.

\textbf{Results:} In the ARH cohort, the mean surgeon case volume
increased from 3.5 cases in 2004 to 8.7 cases in 2013 and then decreased
to 4.9 cases in 2016. The number of surgeons performing LRH increased
from 1 surgeon with 1 patient (mean cases=1) in 2004 to 183 surgeons who
operated on 2,206 patients in 2016 (mean cases=12.1) (P\textless{}
0.01). In the ARH, patients treated by intermediate-volume surgeons had
more postoperative complications (OR=1.55, 95\% CI=1.11-2.15). In the
laparoscopic surgery cohort, surgeon volume had no independent effect on
intraoperative or postoperative complications (P=0.46; P=0.13).

\textbf{Conclusions:} The performance of ARH by intermediate-volume
surgeons is associated with an increased risk of postoperative
complications. However, surgeon volume may have little effect on
intraoperative or postoperative complications after LRH.

\textbf{Funding}

The National Science and Technology Support Program of China
(2014BAI05B03);

The Natural Science Fund of Guangdong Province (2015A030311024);

The Science and Technology Plan of Guangzhou (158100075).

They provided financial assistance that played an important role in the
collection of data.

\textbf{Keywords:} cervical cancer; radical hysterectomy; cervical
cancer; major complications

\textbf{Clinical Trial Registration:}
ChiCTR1800017778\textbf{,}\emph{http://www.chictr.org.cn/index.aspx}

\textbf{Tweetable Abstract:} The performance of ARH by
intermediate-volume surgeons is associated with an increased risk of
postoperative complications.

\textbf{Word Count:}

Abstract:238; Manuscript:3124

\textbf{Introduction}

Cervical cancer ranks as the fourth most frequently diagnosed cancer in
women (570,000 cases)\textsuperscript{1}. Radical hysterectomy with
bilateral pelvic lymph node dissection is the recommended surgical
treatment for women with early-stage disease\textsuperscript{2}. Major
complications during radical hysterectomy (RH) depend on many factors,
such as patients characteristics, tumor characteristics, hospital
medical resources, surgical approach\textsuperscript{3}, surgeon volume,
and hospital volume\textsuperscript{4}. Among these, the surgeon's
volume has increasingly received attention\textsuperscript{5}.

Accumulative evidence to date has suggested that higher surgeon volume
leads to improved perioperative outcomes for oncologic surgery, such as
surgery for esophageal cancer\textsuperscript{6}, brain
tumors\textsuperscript{7}, pancreatic cancer\textsuperscript{8}, bladder
cancer\textsuperscript{9}, endometrial cancer\textsuperscript{10},
rectal cancer\textsuperscript{11} and lung cancer\textsuperscript{12}.
However, some scholars argue that surgeon volume is not associated with
complications\textsuperscript{13,14}. Recognition of the volume-outcomes
paradigm in high-risk cancer procedures has led to changes in practice.
Consequently, some health systems are instituting a minimum surgeon
volume standard for high-risk surgery, such as esophagectomy and lung
resection\textsuperscript{6,15}. Wright et al. demonstrated that women
treated by high-volume surgeons had fewer postoperative medical
complications and lower transfusion requirements after abdominal radical
hysterectomy (ARH)\textsuperscript{16}. To date, there are few studies
that have investigated the association between surgeon volume and
outcomes of laparoscopic radical hysterectomy (LRH) based on large
population cohort, although there is a proportionate increase in LRH
{[}17{]}\textsuperscript{17}. In addition, there is a paucity of data
about surgeon volume in Asian populations.

The first objective of this population-based analysis is to explore the
association between surgeon volume and complications after ARH and LRH.
The second objective is to examine changes in the number of surgeons,
mean surgeon case volume and the total number of cases of cervical
cancer over time.

\textbf{Methods}

\textbf{2.1 Data source}

Data from the Major Surgical Complications of Cervical Cancer in China
(MSCCCC) project database were utilized. The MSCCCC database is a
multicenter retrospective database established to measure surgical
quality. Approximately 97.5\% of cases from the database could be
matched to the cases in Chinese Clinical Cervical Cancer (FOUR-C)
project (\emph{http://www.chictr.org.cn/index.aspx}, ChiCTR1800017778).
The MSCCCC database gathers hospitalization information for 36,543
patients from 42 hospitals in 14 provinces of China from 2004-2016
(updated of June 2020). The 42 hospitals consist of 32 general
hospitals, 4 cancer centers and 6 women and children's hospitals (W\&C
hospitals)\textsuperscript{17,18}.

Using the discharge diagnosis of ``cervical cancer'' as the keyword or
the International Classification of Diseases Tenth Revision code C53.9
for computerized search, specially-trained gynecologists abstracted data
from medical records and the hospital information system. The
documentation used for data extraction on complications included
inpatient medical records for surgical treatment, postoperative adjuvant
therapy records within 6 months, outpatient records, and readmission to
the other department for complication treatment within 2
years\textsuperscript{17,18}. The MSCCCC database collects data on
patient demographics, clinical characteristics, and hospital factors.
After completion of double data entry, data checking were carried out by
two independent gynecologists to eliminate input errors and logic
errors. Data masking was used to protect patient privacy. Ethical
approval was obtained from Institutional Ethics Committee of Southern
Medical University Nanfang Hospital (NFEC-2017-135).

\textbf{2.2 Cohort identification}

Women who underwent RH for cervical cancer between 2004 and 2016 were
analyzed. The inclusion criteria were as follows: 1) the patient had
been diagnosed stage IA1 with LVSI (lymphovascular space invasion) to
stage IIB, according to the 2009 International Federation of Gynecology
and Obstetrics (FIGO) staging system; 2) the patient underwent type B or
C RH (Querleu and Morrow classification)\textsuperscript{19} + pelvic
lymphadenectomy (PLN) \selectlanguage{ngerman}± para-aortic lymphadenectomy (PALA); and 3) the
patient underwent ARH or LRH. The exclusion criteria were as follows: 1)
the patient was diagnosed with cervical cancer during pregnancy, was
diagnosed with incidental cervical cancer after extrafascial
hysterectomy or had a prior history of other malignancies; 2) the
patient had an unknown lymphadenectomy status or did not undergo
lymphadenectomy; 3) the patient underwent laparoscopic-assisted radical
vaginal hysterectomy or robot-assisted RH; or 4) the patient had missing
surgeon data or a missing date of operation.

\textbf{2.3 Clinical and demographic characteristics}

The demographic characteristics included age, year of surgery,
urban-rural distribution, mode of delivery, and comorbidities. Clinical
characteristics that were analyzed included FIGO stage, gross type of
tumor, histological type, preoperative anticancer treatment,
hysterectomy type and lymph node dissection. Other operation details
include operative time and estimated blood loss.

The hospitals where patients were treated were characterized based on
hospital function (general hospital, cancer center, or W\&C hospital),
region of the country (north, south, central, east, southwest, northwest
or northeast), and city scale (first-tier, second-tier, and third-tier
or below). The levels of urban economic development were as follows:
first-tier cities \textgreater{} second-tier cities \textgreater{}
third-tier cities.

\textbf{2.4 Surgeon volume}

We calculated the total volume of each surgeon. For each surgeon,
annualized surgeon volumes were calculated as the total number of
procedures that the surgeon performed divided by the number of years in
which an individual surgeon contributed to at least one
RH\textsuperscript{10,16,20}. Patients were stratified into two cohorts
based on the hysterectomy approach: ARH group or LRH group. Surgeon
volume cutoff points were then selected to divide patients into
approximately equal tertiles. Abdominal surgeon cutoff points were: low
volume (\selectlanguage{english}[?] 8.1 procedures per year), intermediate volume (8.2-16.9
procedures per year), and high volume (\textgreater{}16.9 procedures per
year). Laparoscopic surgeon cutoff points were: low volume (\selectlanguage{english}[?] 11.0
procedures per year), intermediate volume (11.1-20.0 procedures per
year), and high volume (\textgreater{}20.0 procedures per year).

\textbf{2.5 Outcomes}

Complications were divided into intraoperative complications and
postoperative complications. The intraoperative complications, which
included ureteral injury, bladder injury, bowel injury, vascular injury,
obturator nerve injury, and stomach injury, were recorded. Postoperative
complications included bowel obstruction, pelvic hematoma, hemorrhage,
vesicovaginal fistula, ureterovaginal fistula, ureteral fistula,
rectovaginal fistula, venous thromboembolism and chylous leakage. We
also recorded deaths from surgical complications.

\textbf{Statistical analysis}

The relationship between the number of surgeons and year was assessed by
a non-parametric Spearman correlation test. Due to discontinuous data,
one of the hospitals was not including in the graphs. Frequency
distributions between categorical variables were compared using \selectlanguage{greek}χ\selectlanguage{english}2 or
the Fisher's exact test, and continuous variables were compared using a
one-way analysis of variance. The median and interquartile range (IQR)
of surgeon volume were also reported for each tertile. Binary logistic
regression models were used to determine predictors of treatment by the
intermediate and high volume (highest 2/3 volume) surgeons. Demographic,
clinical, and hospital characteristics constituted independent
variables. To examine the association between surgeon volume and
outcome, we built binary logistic regression models including surgeon
volume while adjusting for the other variables described above. The
results are reported as odds ratios (ORs) and 95\% confidence intervals
(CIs). A value of \emph{P} \textless{} 0.05 was considered statistically
significant. All analyses were performed with the SPSS 23.0 statistical
software package (SPSS, Inc., Chicago, IL, USA).

\textbf{Results}

\textbf{3.1 Trends in the number of surgeons and patients}

We identified a total of 22,684 patients, including 14536 (64.1\%)
patients who underwent ARH and 8148 (35.9\%) patients who underwent LRH
(Table 1). The number of surgeons performing ARH each year increased
from 89 surgeons who operated on 313 patients in 2004 to 187 surgeons
who operated on 1,294 patients in 2012 (P\textless{}0.01, r=0.99).
However, the number of abdominal surgeons decreased to 122 surgeons with
594 patients in 2016 (P=0.20, r=-0.80). The mean surgeon case volume
increased from 3.5 cases in 2004 to 8.7 cases in 2013 and then decreased
to 4.9 cases in 2016 (Figure 1A). The number of surgeons performing LRH
increased from 1 surgeon with 1 patient in 2004 to 183 surgeons who
operated on 2,206 patients in 2016 (P\textless{}0.01, r=0.99). The mean
number of surgeons performing LRH increased from 1 to 12.1 cases between
2004 and 2016 (Figure 1B).

\textbf{3.2 Characteristics of the cohort}

In the ARH cohort, the median volume of surgeons in the low-volume group
was two (IQR 1.0-3.5) per year and rose to 30.9 (IQR 21.9-42.1) in the
high volume group. Similarly, in the LRH cohort, the median volume of
surgeons in the low-volume group was 2.3 (IQR 1.0-5.0) and increased to
27.8 (IQR 21.6-30.1) in the high-volume group (Table 2). In both the ARH
and LRH cohorts, the operation time and bleeding loss for patients in
the high-volume surgeon group were significantly lower than those for
patients in the intermediate-volume and low-volume groups
(P\textless{}0.001) (Table 2).

In the multivariable model of the ARH cohort, patients diagnosed in
later years, patients living in rural areas, patients with a higher
tumor stage (except stage IIB), patients with the endophytic or
preclinical gross type, patients with preoperative radiotherapy,
patients undergoing type C1 or C2 hysterectomy, patients undergoing
surgery in a W\&C hospital or cancer center, and patients undergoing
surgery in a hospital of a first-tier city were more likely to be
treated by high-volume or intermediate-volume surgeons
(P\textless{}0.05) (Table 3).

Similarly, in the multivariable model of the LRH cohort, age
\textgreater{} 60 years, later year of diagnosis, previous cesarean
section, FIGO stage IIA2 and IIB, PLN+PALA, and type C1 and C2
hysterectomy were associated with treatment by a high-volume or an
intermediate-volume surgeon (P\textless{}0.05). In addition, patients
undergoing surgery in the cancer center, patients undergoing surgery in
the hospital of a second-tier city, and patients undergoing surgery in
the hospital of the southwest area were more likely to be treated by
intermediate- or high-volume surgeons (P\textless{}0.05). Patients with
the endophytic gross type, patients with neoadjuvant chemotherapy, and
patients undergoing surgery in W\&C hospitals were associated with
treatment by a low-volume laparoscopic surgeon (P\textless{}0.05) (Table
3).

\textbf{3.3 The impact of surgeon volume on complications}

In the univariate analysis of the ARH group, the overall complication
rates were 3.06\% for women treated by low-volume surgeons, 3.42\% for
those treated by intermediate-volume surgeons, and 2.01\% for those
treated by high-volume surgeons (P\textless{}0.001) (Table 4). Compared
with patients treated by intermediate-volume surgeons, those operated on
by high-volume surgeons had fewer postoperative complications (2.87\%
vs. 1.69\%, P\textless{}0.001), fewer ureteral injuries (0.45\% vs.
0.16\%, P=0.045), fewer bowel obstructions (1.28\% vs. 0.61\%, P=0.003),
and fewer ureterovaginal fistulas (0.43\% vs. 0.13\%, P=0.006). There
was no significant difference in the frequencies of other complications
(P\textless{}0.05).

In the univariate analysis of the LRH group, patients treated by
intermediate-volume surgeons had the highest ureterovaginal fistula rate
(low vs. intermediate vs. high volume = 1.02\% vs. 1.78\% vs. 1.08\%,
P=0.02). The frequencies of the other complications among laparoscopic
surgery cases were similar across the tertiles (P\textless{}0.05) (Table
4).

In the multivariable analysis of the ARH cohort, patients treated by
intermediate-volume surgeons were more likely to experience
postoperative complications than those treated by high-volume surgeons
(OR=1.55, 95\% CI=1.11-2.15). However, abdominal surgeon volume had no
influence on overall complications or intraoperative complications
(P\textgreater{}0.05). In the multivariable analysis of the LRH cohort,
surgeon volume had no effect on overall complications, intraoperative
complications or postoperative complications (P\textgreater{}0.05)
(Table 5).

\textbf{4.Discussion}

\textbf{4.1 Main findings}

Our findings suggest that trends in the number of surgeons and mean
surgeon case volume over time were different in ARH and LRH. In the ARH
cohort, postoperative complication rates were higher among
intermediate-volume surgeons, while patients treated by high-volume
surgeons had lower postoperative complications. However, in the LRH
cohort, surgeon volume had little effect on intraoperative and
postoperative complications.

\textbf{4.2 Interpretation}

The trends in the number of surgeons and mean surgeon volume over time
were differed between the two surgical approaches. From 2004 to 2016,
the number of laparoscopic surgeons and mean surgeon case volume rose
annually. This increasing acceptance of laparoscopic technique could be
due to the short-term benefits of LRH, including a more cosmetically
pleasing incision, less bleeding, less postoperative pain, and faster
postoperative recovery. However, the opposite trend was observed in ARH
cohort. The number of abdominal surgeons and mean surgeon case volume
have been decreasing since 2013. In addition, it is noteworthy that
categorical definitions of surgeon volume varied substantially among the
different studies. In the study of Wright et al.\textsuperscript{16}, a
high-volume surgeon and a low-volume surgeon were defined as a surgeon
who performed more than 3.75 and less than 2.25 ARHs per year,
respectively; but we defined the same terms as a surgeon who performed
greater than 16.9 and less than or equal to 8.1 ARHs per year,
respectively. The surgeon volume gap between the two groups was much
larger than that of the study by Wright et al.. In addition, our results
revealed a positive correlation between the number of surgeons and the
number of patients. The increasing number of surgeons could effectively
alleviate national disease stress. In patients with endometrial cancer
in the United States, although there was a small increase in the overall
number of patients per year, the surgical treatment of patients has been
limited to a smaller number of surgeons\textsuperscript{10}. They
suggested that the increased complexity of treatment has resulted in
fewer general gynecologists treating these women. Referral of women with
endometrial cancer to gynecologic oncology subspecialists is
recommended\textsuperscript{21}.

Our data demonstrated that the association between surgeon volume and
complications for cervical cancer was complex. In the ARH cohort, the
postoperative complication rate was higher for intermediate-volume
surgeons than for high-volume surgeons (OR=1.55, 95\%=1.11-2.15).
However, the postoperative complication rate was found to be similar in
the low-volume surgeon group and high-volume surgeon group (OR=1.38,
95\%=0.97-1.96). This observation resembles that of Wright et
al.\textsuperscript{16}. Their results showed that the perioperative
complication rate was highest in the intermediate-volume surgeon group
compared with the low-volume and high-volume surgeon groups (low vs.
intermediate vs. high= 2.9\% vs. 6.7\% vs. 1.8\%, P\textless{}0.001).
However, no direct comparisons between intermediate-volume surgeons
group and other groups were performed in their study. We suppose that
surgeon volume had an inverted U-shaped relationship with postoperative
complications, rather than a simple linear relationship. Low-volume
surgeons with limited experience and limited surgical opportunities
performed surgery with utmost caution to prevent complications. The
majority of high-volume surgeons benefited from the effect of sufficient
learning curve and close cooperation with an experienced surgical team,
which translates into a lower complication rate. One possible reason for
highest postoperative complications in the intermediate-volume surgeon
group could be that they were more lenient in their selection of
patients. Patients treated by intermediate-volume surgeons had a higher
frequency of FIGO stage IIB, more preoperative radiotherapy, and a
higher frequency of PLA +PALA and type C2 hysterectomy. In the
Laparoscopic Approach to Cervical Cancer (LACC) trial, ARH was
associated with higher rates of disease-free survival and overall
survival than minimally invasive radical hysterectomy among women with
early-stage cervical cancer\textsuperscript{22}. ARH therefore has
re-emerged as a mainstream treatment for cervical cancer. We may need to
pay more attention to the impact of the abdominal surgeon volume on
complications.

In our laparoscopy surgery cohort, surgeon volume had no significant
effects on intraoperative complications or postoperative complications.
It appears that the effects of surgeon volume on radical hysterectomy
complications of different surgical routes are different. Similar
results have been reported in endometrial cancer. Among patients who
underwent abdominal hysterectomy for endometrial cancer, increased
surgical volume was associated with reductions in perioperative surgical
complications and medical complications\textsuperscript{23}. However,
during laparoscopic hysterectomy, the surgeon volume appear to have
little effect on perioperative morbidity for endometrial
cancer\textsuperscript{20}. A retrospective analysis of 1016
laparoscopic hysterectomies for benign gynecologic problems found that
increasing the surgical volume could not reduce the rate of serious
complications\textsuperscript{24}. In addition, surgeon volumes in terms
of different~surgical procedures~differentially affects surgical
complication outcomes. This population-based study by Sheetz et al.
demonstrated that the comparative safety of laparoscopic and open
colectomy was influenced by surgeon volume, but the relationship was
stronger for laparoscopy\textsuperscript{25}.

Numerous factors affects surgical experience. First, surgical experience
was assessed and quantified by different metrics, such as annual surgeon
volume (frequency), technique-specific volume, surgeon cumulative
volume, and years of experience\textsuperscript{11,26,27}. Yasunaga et
al.\textsuperscript{28} defined surgeon volume as the number of radical
hysterectomies that each gynecologist had performed as an operating
surgeon over his or her professional career. Their study showed that
higher surgeon volume (greater than 200 procedures) was associated with
a reduced incidence of postoperative urinary disorders. However, they
did not mention the surgical route of radical hysterectomy. Second,
surgical educators recognize that skill sets may transfer between
operations\textsuperscript{29}. Modrall et al\textsuperscript{30}.
defined the aggregate annual volume per surgeon of upper
gastrointestinal operations as the ``surrogate volume'', including
excision of esophageal diverticulum, gastrectomy, gastroduodenectomy,
and repair of diaphragmatic hernia. Among surgeons with a low-volume
esophagectomy experience, increasing the volume of surrogate operations
improved the outcomes observed for esophagectomy. However, there has
been little discussion about ``surrogate surgery'' in gynecological
cancer surgery. It was uncertain whether surrogate operative
experiences, such as experiences of extrafascial hysterectomy in benign
disease and cytoreductive surgery in ovarian cancer, yield improvements
in outcomes for radical hysterectomy. Third, the characteristics of the
surgeons may have an effect on surgical experience, such as the age of
the surgeon. Surgeon age [?] 51 and [?] 56 years may increase short- and
long-term mortality after esophagectomy for cancer, and the highest
surgical competence is achieved between 52 and 56 years of surgeon
age\textsuperscript{31}. The reason for the decreasing performance among
older surgeons might be related to mental fatigue, poorer compliance
with evidence-based medicine, and higher administrative positions
leading to reduced surgical frequency\textsuperscript{26}.

\textbf{4.3 Strengths and limitations}

This population-based study is the first to examine changes in the
number of surgeons and annual surgeon volume for cervical cancer over
time, and to explore the association between surgeon volume and
complications after ARH and LRH in China. First, a strength of our study
is its large sample size. We reviewed 22,684 cases treated at 42
hospitals over a 13-year period so that data on the rare adverse events
could be collected. Second, we also included clinical characteristics,
such as FIGO stage, histology, preoperative treatment, hysterectomy
type, and lymph node dissection type that may influence treatment
outcome\textsuperscript{17}.

We also recognize several limitations to our findings. First, this study
was a retrospective study in which the data were obtained from inpatient
medical records or through readmission. Data on complications that may
have occurred after discharge and have been treated by other hospitals,
could not be obtained. Second, we divided the patients into tertiles
based on annualized surgeon volumes, but the results of the present
study could not translate into clinically meaning cutoff points. Third,
although we considered a wide range of clinical characteristics and
tumor characteristics, there might be other unmeasured confounding
factors affecting complications, such as assistant
surgeons\textsuperscript{32}, uterine size, downstream care, surgical
instruments and management of complications. In addition, skill
transference between LRH and ARH remains unclear. Fourth, our study only
included patients from only 42 hospitals and the findings may not be
representative of other areas in China.

\textbf{Conclusion}

In conclusion, patients treated by intermediate-volume surgeons may have
more postoperative complications after ARH, while patients treated by
high-volume surgeons had fewer postoperative complications. In the LRH
cohort, surgeon volume appeared to have no significant predictive value
for complications.

\textbf{Acknowledgements}

We are grateful to Min Hao (Department of Obstetrics and Gynecology, The
Second Hospital of ShanXi Medical University), Wuliang Wang (Department
of Obstetrics and Gynecology, The Second Affiliated Hospital of
Zhengzhou University), Ying Yang (Department of Obstetrics and
Gynecology, Xinqiao Hospital, Third Military Medical University), Shan
Kang (Department of Obstetrics and Gynecology, The Forth Hospital of
Hebei Medical University \& The Tumor Hospital of Hebei Province), Bin
Ling (Department of Obstetrics and Gynecology, China-Japan Friendship
Hospital), Xinli Sun and Hongwei Zhao (Department of Gynecology, Shanxi
Provincial Cancer Hospital), Yu Guo and Lihong Lin (Department of
Gynecology, Anyang Tumor Hospital), Li Wang (Department of Gynecology,
The Affiliated Tumor Hospital of Zhengzhou University), Weidong Zhao
(Department of Gynecology and Oncology, Anhui Provincial Cancer
Hospital), Yan Ni (Department of Obstetrics and Gynecology, The Yuncheng
Central Hospital of Shanxi province), Donglin Li and Wentong Liang
(Department of Obstetrics and Gynecology, Guizhou Provincial People`s
Hospital), Jianxin Guo (Department of Obstetrics and Gynecology, Daping
Hospital, The Third Military Medical University), Xuemei Zhan and
Mingwei Li (Department of Gynecology, Jiangmen Central Hospital),
Weifeng Zhang (Department of Obstetrics and Gynecology, Ningbo Women \&
Children's Hospital), Peiyan Du (Department of Gynecological Oncology,
Cancer Center of Guangzhou Medical University), Ziyu Fang (Department of
Obstetrics and Gynecology, Liuzhou Workers' Hospital), Long Chen
(Department of Obstetrics and Gynecology, Qingdao Municipal Hospital),
Encheng Dai and Ruilei Liu (Department of Obstetrics and Gynecology,
Linyi People's Hospital), Mubiao Liu and Yuanli He (Department of
Obstetrics and Gynecology, Zhujiang Hospital, Southern Medical
University), Jilong Yao and Zhihua Liu (Department of Obstetrics and
Gynecology, Shenzhen Maternity \& Child Healthcare Hospital), Xueqin
Wang (Department of Obstetrics and Gynecology, The Fifth Affiliated
Hospital of Southern Medical University), Yan Xu (Department of
Obstetrics and Gynecology, Guangzhou Panyu Central Hospital), Ben Ma
(Department of Obstetrics and Gynecology, Guangzhou First People's
Hospital), Zhonghai Wang (Department of Obstetrics and Gynecology,
Shenzhen Nanshan People's Hospital), Lin Zhu (Department of Gynecology,
The Second Hospital of Shandong University), Hongxin Pan (Department of
Obstetrics and Gynecology, the 3rd Affiliated Hospital of Shenzhen
University, Luohu People's Hospital), Qianyong Zhu (Department of
Obstetrics and Gynecology, No.153. Center Hospital of Liberation Army,
Hospital No.988 of the Chinese People's Liberation Army Joint Support
Force), Xiaohong Wang (Department of Obstetrics and Gynecology, Jinan
City People's Hospital, Former Laiwu People's Hospital), Dingyuan Zeng
and Zhong Lin (Department of Obstetrics and Gynecology, Maternal and
Child Health Care Hospital of Liuzhou), Shaoguang Wang (Department of
Obstetrics and Gynecology, Yantai Yuhuangding Hospital), Bin Zhu
(Department of Obstetrics and Gynecology, Yiwu Maternal and Child Health
Hospital), Anwei Lu (Department of Obstetrics and Gynecology, Maternal
and Child Health Care Hospital of Guizhou Province), Mei Ji (Department
of Obstetrics and Gynecology, the First Affiliated Hospital of Zhengzhou
University), Qianqing Wang (Department of Obstetrics and Gynecology,
Central Hospital Affiliated to Xinxiang Medical University), Zhumei Cui
(Department of Gynecology, The Affiliated Hospital of Qingdao University
Medical College), Biliang Chen (Department of Gynecology, Xijing
Hospital of Air Force Medical University), Qinghuang Xie (Department of
Gynecology, Foshan Women and Children Hospital), Qiubo Lv (Department of
Gynecology, Beijing Hospital), Chang Liu (Department of Gynecology, the
First Hospital of Lanzhou University), and Yi Zhang (Department of
Gynecology, the First Hospital of China Medical University) for
providing medical records.

\textbf{Disclosure of Interests}

All authors declare they have no relevant conflict of interest.

\textbf{Contribution to Authorship}

Cong Liang: Investigation, Methodology, Data Curation, Writing -
Original Draft, Writing - Review \& Editing, Visualization; Weili Li:
Supervision, Conceptualization; Xiaoyun Liu: Investigation, Resources;
Hongwei Zhao: Investigation, Resources; Lu Yin: Investigation; Mingwei
Li: Investigation, Resources; Yu Guo: Investigation, Resources; Jinghe
Lang: Investigation; Xiaonong Bin: Validation, Formal analysis; Ping
Liu: Conceptualization, Supervision, Project administration; Chunlin
Chen: Conceptualization, Supervision, Project administration, Funding
acquisition.

\textbf{Details of Ethics Approval}

Ethical approval was obtained from Institutional Ethics Committee of
Southern Medical University Nanfang Hospital (NFEC-2017-135).

\textbf{Funding}

The National Science and Technology Support Program of China
(2014BAI05B03);

The Natural Science Fund of Guangdong Province (2015A030311024);

The Science and Technology Plan of Guangzhou (158100075).

They provided financial assistance that played an important role in the
collection of data.

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\textbf{Legends}

Figure 1. Numbers of patients and surgeons by year in abdominal surgery
cohort (A); Numbers of patients and surgeons by year in laparoscopic
surgery cohort (B).

Table 1. Schema of patient selection.

Table 2. Demographic and clinical characteristics of the abdominal and
laparoscopic cohorts stratified by surgeon volume.

Table 3. Predictors of the high and intermediate volume surgeons.

Table 4. Unadjusted complications associated with radical hysterectomy
for cervical cancer stratified by surgeon volume.

Table 5. Multivariable analysis of factors associated with
complications.

\textbf{Table 1. Schema of patient selection.}\selectlanguage{english}
\begin{longtable}[]{@{}ll@{}}
\toprule
Variable & No. of patients\tabularnewline
\midrule
\endhead
1.All patients diagnosed with cervical cancers, 2004-2016 &
36,543\tabularnewline
2. Type B or C radical hysterectomy & 31,581\tabularnewline
3. Pelvic lymphadenectomy \selectlanguage{ngerman}± para-aortic lymphadenectomy &
30,641\tabularnewline
4. 2009 FIGO stage IA1 with LVSI to IIB & 24,447\tabularnewline
5. No pregnancy, incidental cervical cancer or previous malignant
disease & 24,350\tabularnewline
6. Abdominal surgery or total laparoscopic surgery &
23,409\tabularnewline
7. Missing information of surgeon or date of surgery &
22,684\tabularnewline
\bottomrule
\end{longtable}

\textbf{Table 2. Demographic and clinical characteristics of the
abdominal and laparoscopic cohorts stratified by surgeon volume.}\selectlanguage{english}
\begin{longtable}[]{@{}lllllllllllllll@{}}
\toprule
Characteristic & Abdominal surgeon volume & Abdominal surgeon volume &
Abdominal surgeon volume & Abdominal surgeon volume & Abdominal surgeon
volume & Abdominal surgeon volume & \emph{P} value & Laparoscopic
surgeon volume & Laparoscopic surgeon volume & Laparoscopic surgeon
volume & Laparoscopic surgeon volume & Laparoscopic surgeon volume &
Laparoscopic surgeon volume & \emph{P} value\tabularnewline
\midrule
\endhead
& Low & Low & Intermediate & Intermediate & High & High & & Low & Low &
Intermediate & Intermediate & High & High &\tabularnewline
\textbf{Patients} & 4837 & 33.3 & 4913 & 33.8 & 4786 & 32.9 & & 2642 &
32.4 & 2637 & 32.4 & 2869 & 35.2 &\tabularnewline
\textbf{Surgeons} & 362 & & 44 & & 22 & & & 212 & & 33 & & 18 &
&\tabularnewline
\textbf{Annualized hospital volume} & 2.0 (1.0-3.5) & 2.0 (1.0-3.5) &
10.8 (9.1-12.5) & 10.8 (9.1-12.5) & 30.9 (21.9-42.1) & 30.9 (21.9-42.1)
& & 2.3 (1.0-5.0) & 2.3 (1.0-5.0) & 13.5(12.3-16.9) & 13.5(12.3-16.9) &
27.8(21.6-30.1) & 27.8(21.6-30.1) &\tabularnewline
\textbf{Age at surgery, years} & & & & & & & & & & & & &
&\tabularnewline
[?] 60 & 444 & 9.2 & 515 & 10.5 & 798 & 16.7 & \textless{}0.001 & 257 &
9.7 & 299 & 11.3 & 346 & 12.1 & 0.02\tabularnewline
\textless{} 60 & 4393 & 90.8 & 4398 & 89.5 & 3988 & 83.3 & & 2385 & 90.3
& 2338 & 88.7 & 2523 & 87.9 &\tabularnewline
\textbf{Year of diagnosis} & & & & & & & & & & & & & &\tabularnewline
2004-2009 & 1736 & 35.9 & 1748 & 35.6 & 245 & 5.1 & \textless{}0.001 &
149 & 5.6 & 46 & 1.7 & 59 & 2.1 & \textless{}0.001\tabularnewline
2010-2016 & 3101 & 64.1 & 3165 & 64.4 & 4541 & 94.9 & & 2493 & 94.4 &
2591 & 98.3 & 2810 & 97.9 &\tabularnewline
\textbf{Urban-rural distribution} & & & & & & & & & & & & &
&\tabularnewline
Rural & 2316 & 47.9 & 2988 & 60.8 & 3098 & 64.7 & \textless{}0.001 &
1572 & 59.5 & 1450 & 55.0 & 1638 & 57.1 &
\textless{}0.001\tabularnewline
Urban & 1423 & 29.4 & 1539 & 31.3 & 1004 & 21.0 & & 739 & 28.0 & 959 &
36.4 & 1055 & 36.8 &\tabularnewline
Unknown & 1098 & 22.7 & 386 & 7.9 & 684 & 14.3 & & 331 & 12.5 & 228 &
8.6 & 176 & 6.1 &\tabularnewline
\textbf{Hospital function} & & & & & & & & & & & & & &\tabularnewline
General hospital & 3451 & 71.3 & 2893 & 58.9 & 641 & 13.4 &
\textless{}0.001 & 1998 & 75.7 & 2097 & 79.5 & 1526 & 53.2 &
\textless{}0.001\tabularnewline
Cancer center & 1088 & 22.5 & 1626 & 33.1 & 4145 & 86.6 & & 450 & 17.0 &
386 & 14.6 & 1223 & 42.6 &\tabularnewline
W\&C center & 298 & 6.2 & 394 & 8.0 & 0 & 0.0 & & 194 & 7.3 & 154 & 5.8
& 120 & 4.2 &\tabularnewline
\textbf{Region} & & & & & & & & & & & & & &\tabularnewline
North & 724 & 15.0 & 1292 & 26.3 & 2784 & 58.2 & \textless{}0.001 & 589
& 22.3 & 220 & 8.3 & 605 & 21.1 & \textless{}0.001\tabularnewline
South & 1380 & 28.5 & 1095 & 22.3 & 531 & 11.1 & & 688 & 26.1 & 427 &
16.2 & 120 & 4.2 &\tabularnewline
Central & 618 & 12.8 & 410 & 8.3 & 1169 & 24.4 & & 350 & 13.2 & 700 &
26.5 & 231 & 8.1 &\tabularnewline
East & 1490 & 30.8 & 1013 & 20.6 & 302 & 6.3 & & 752 & 28.5 & 396 & 15.0
& 0 & 0.0 &\tabularnewline
Southwest & 307 & 6.3 & 335 & 6.8 & 0 & 0.0 & & 91 & 3.4 & 507 & 19.2 &
1808 & 63.0 &\tabularnewline
Northwest & 158 & 3.3 & 668 & 13.6 & 0 & 0.0 & & 161 & 6.1 & 323 & 12.2
& 105 & 3.7 &\tabularnewline
Northeast & 160 & 3.3 & 100 & 2.0 & 0 & 0.0 & & 11 & 0.4 & 64 & 2.4 & 0
& 0.0 &\tabularnewline
\textbf{City scale} & & & & & & & & & & & & & &\tabularnewline
First-tier & 773 & 16.0 & 745 & 15.2 & 529 & 11.1 & \textless{}0.001 &
560 & 21.2 & 299 & 11.3\% & 0 & 0.0 & \textless{}0.001\tabularnewline
Second-tier & 2458 & 50.8 & 2885 & 58.7 & 3986 & 83.3 & & 1471 & 55.7 &
1916 & 72.7\% & 2362 & 82.3 &\tabularnewline
Third-tier & 1606 & 33.2 & 1283 & 26.1 & 271 & 5.7 & & 611 & 23.1 & 422
& 16.0\% & 507 & 17.7 &\tabularnewline
\textbf{Mode of delivery} & & & & & & & & & & & & & &\tabularnewline
No delivery & 49 & 1.0 & 57 & 1.2 & 22 & 0.5 & \textless{}0.001 & 23 &
0.9 & 23 & 0.9 & 36 & 1.3 & \textless{}0.001\tabularnewline
Vaginal delivery & 3684 & 76.2 & 4026 & 81.9 & 4059 & 84.8 & & 2114 &
80.0 & 2157 & 81.8 & 2541 & 88.6 &\tabularnewline
Cesarean delivery & 253 & 5.2 & 291 & 5.9 & 221 & 4.6 & & 194 & 7.3 &
243 & 9.2 & 261 & 9.1 &\tabularnewline
Unknown & 851 & 17.6 & 539 & 11.0 & 484 & 10.1 & & 311 & 11.8 & 214 &
8.1 & 31 & 1.1 &\tabularnewline
\textbf{Comorbidity} & & & & & & & & & & & & & &\tabularnewline
No & 4526 & 93.6 & 4592 & 93.5 & 4242 & 88.6 & \textless{}0.001 & 2425 &
91.8 & 2436 & 92.4 & 2611 & 91.0 & 0.18\tabularnewline
Yes & 311 & 6.4 & 321 & 6.5 & 544 & 11.4 & & 217 & 8.2 & 201 & 7.6 & 258
& 9.0 &\tabularnewline
\textbf{FIGO stage} & & & & & & & & & & & & & &\tabularnewline
IA1+IA2 & 133 & 2.7 & 76 & 1.5 & 30 & 0.6 & \textless{}0.001 & 70 & 2.7
& 49 & 1.9 & 45 & 1.6 & \textless{}0.001\tabularnewline
IB1 & 2288 & 47.3 & 2117 & 43.1 & 2282 & 47.7 & & 1554 & 58.8 & 1323 &
50.2 & 1318 & 45.9 &\tabularnewline
IB2 & 656 & 13.6 & 690 & 14.0 & 531 & 11.1 & & 289 & 10.9 & 295 & 11.2 &
328 & 11.4 &\tabularnewline
IIA1 & 679 & 14.0 & 680 & 13.8 & 1278 & 26.7 & & 350 & 13.2 & 329 & 12.5
& 586 & 20.4 &\tabularnewline
IIA2 & 297 & 6.1 & 324 & 6.6 & 478 & 10.0 & & 123 & 4.7 & 176 & 6.7 &
270 & 9.4 &\tabularnewline
IIB & 784 & 16.2 & 1026 & 20.9 & 187 & 3.9 & & 256 & 9.7 & 465 & 17.6 &
322 & 11.2 &\tabularnewline
\textbf{Gross type} & & & & & & & & & & & & & &\tabularnewline
Exophytic & 2585 & 53.4 & 2854 & 58.1 & 2058 & 43.0 & \textless{}0.001 &
1287 & 48.7 & 1357 & 51.5 & 1540 & 53.7 &
\textless{}0.001\tabularnewline
Endophytic & 276 & 5.7 & 316 & 6.4 & 1528 & 31.9 & & 128 & 4.8 & 73 &
2.8 & 185 & 6.4 &\tabularnewline
Ulcerated & 900 & 18.6 & 790 & 16.1 & 550 & 11.5 & & 461 & 17.4 & 467 &
17.7 & 699 & 24.4 &\tabularnewline
Endocervical & 105 & 2.2 & 64 & 1.3 & 29 & 0.6 & & 45 & 1.7 & 39 & 1.5 &
44 & 1.5 &\tabularnewline
After conization & 132 & 2.7 & 106 & 2.2 & 74 & 1.5 & & 80 & 3.0 & 97 &
3.7 & 102 & 3.6 &\tabularnewline
Preclinical carcinoma & 342 & 7.1 & 414 & 8.4 & 178 & 3.7 & & 298 & 11.3
& 256 & 9.7 & 140 & 4.9 &\tabularnewline
Unknown & 497 & 10.3 & 369 & 7.5 & 369 & 7.7 & & 343 & 13.0 & 348 & 13.2
& 159 & 5.5 &\tabularnewline
\textbf{Histological types} & & & & & & & & & & & & & &\tabularnewline
Squamous cell & 4178 & 86.4 & 4326 & 88.1 & 4301 & 89.9 &
\textless{}0.001 & 2252 & 85.2 & 2223 & 84.3 & 2481 & 86.5 &
0.008\tabularnewline
Adenocarcinoma & 450 & 9.3 & 397 & 8.1 & 294 & 6.1 & & 262 & 9.9 & 293 &
11.1 & 272 & 9.5 &\tabularnewline
Adenosquamous & 113 & 2.3 & 92 & 1.9 & 94 & 2.0 & & 45 & 1.7 & 54 & 2.0
& 49 & 1.7 &\tabularnewline
Other subtypes & 81 & 1.7 & 90 & 1.8 & 89 & 1.9 & & 48 & 1.8 & 43 & 1.6
& 56 & 2.0 &\tabularnewline
Unknown & 15 & 0.3 & 8 & 0.2 & 8 & 0.2 & & 35 & 1.3 & 24 & 0.9 & 11 &
0.4 &\tabularnewline
\textbf{Preoperative treatment} & & & & & & & & & & & & &
&\tabularnewline
No received & 3457 & 71.5 & 3565 & 72.6 & 3911 & 81.7 & \textless{}0.001
& 2038 & 77.1 & 2098 & 79.6 & 2164 & 75.4 &
\textless{}0.001\tabularnewline
Neoadjuvant chemotherapy & 1243 & 25.7 & 970 & 19.7 & 594 & 12.4 & & 557
& 21.1 & 449 & 17.0 & 667 & 23.2 &\tabularnewline
Preoperative radiotherapy & 137 & 2.8 & 378 & 7.7 & 281 & 5.9 & & 47 &
1.8 & 90 & 3.4\% & 38 & 1.3 &\tabularnewline
\textbf{Lymph node dissection} & & & & & & & & & & & & &
&\tabularnewline
PLA & 4651 & 96.2 & 4604 & 93.7 & 4735 & 98.9 & \textless{}0.001 & 2269
& 85.9 & 2028 & 76.9 & 1905 & 66.4 & \textless{}0.001\tabularnewline
PLA+PALA & 186 & 3.8 & 309 & 6.3 & 51 & 1.1 & & 373 & 14.1 & 609 & 23.1
& 964 & 33.6 &\tabularnewline
\textbf{Hysterectomy types} & & & & & & & & & & & & & &\tabularnewline
Type B & 2852 & 59.0 & 2140 & 43.6 & 3340 & 69.8 & \textless{}0.001 &
1047 & 39.6 & 592 & 22.4 & 242 & 8.4 & \textless{}0.001\tabularnewline
Type C2 & 1962 & 40.6 & 2719 & 55.3 & 1424 & 29.7 & & 1558 & 59.0 & 1991
& 75.5 & 2616 & 91.2 &\tabularnewline
Type C1 & 23 & 0.5 & 54 & 1.1 & 22 & 0.5 & & 37 & 1.4 & 54 & 2.0 & 11 &
0.4 &\tabularnewline
\textbf{Operation time} & 232.8\selectlanguage{ngerman}±64.8 & 232.8\selectlanguage{ngerman}±64.8 & 205.0\selectlanguage{ngerman}±55.4 &
205.0\selectlanguage{ngerman}±55.4 & 164.7\selectlanguage{ngerman}±52.8 & 164.7\selectlanguage{ngerman}±52.8 & \textless{}0.001 & 259.6\selectlanguage{ngerman}±77.1 &
259.6\selectlanguage{ngerman}±77.1 & 234.4\selectlanguage{ngerman}±70.8 & 234.4\selectlanguage{ngerman}±70.8 & 209.6\selectlanguage{ngerman}±64.6 & 209.6\selectlanguage{ngerman}±64.6 &
\textless{}0.001\tabularnewline
\textbf{Blood loss} & 499.2\selectlanguage{ngerman}±363.1 & 499.2\selectlanguage{ngerman}±363.1 & 470.3\selectlanguage{ngerman}±375.14 &
470.3\selectlanguage{ngerman}±375.14 & 241.0\selectlanguage{ngerman}±211.6 & 241.0\selectlanguage{ngerman}±211.6 & \textless{}0.001 &
216.2\selectlanguage{ngerman}±305.7 & 216.2\selectlanguage{ngerman}±305.7 & 193.0\selectlanguage{ngerman}±188.6 & 193.0\selectlanguage{ngerman}±188.6 & 185.1\selectlanguage{ngerman}±170.1 &
185.1\selectlanguage{ngerman}±170.1 & \textless{}0.001\tabularnewline
\bottomrule
\end{longtable}

Abbreviations: PLA, pelvic lymphadenectomy; PALA, para-aortic
lymphadenectomy.

\textbf{Table 3. Predictors of the high and intermediate volume
surgeons.}\selectlanguage{english}
\begin{longtable}[]{@{}lllll@{}}
\toprule
& \textbf{Abdominal cohort} & \textbf{Abdominal cohort} &
\textbf{Laparoscopic cohort} & \textbf{Laparoscopic
cohort}\tabularnewline
\midrule
\endhead
& \textbf{OR (95\% CI)} & \textbf{P value} & \textbf{OR (95\% CI)} &
\textbf{P value}\tabularnewline
\textbf{Age at surgery, years} & & 0.16 & & 0.002\tabularnewline
[?] 60 & Ref & & Ref &\tabularnewline
\textless{} 60 & 0.16 (0.79-1.04) & 0.16 & 0.74 (0.61-0.90) &
0.002\tabularnewline
\textbf{Year of diagnosis} & & \textless{}0.001 & & 0.02\tabularnewline
2004-2009 & Ref & & Ref &\tabularnewline
2010-2016 & 1.55 (1.41-1.69) & \textless{}0.001 & 1.46 (1.06-2.01) &
0.02\tabularnewline
\textbf{Urban-rural distribution} & & \textless{}0.001 & &
0.08\tabularnewline
Rural & Ref & & Ref &\tabularnewline
Urban & 0.87 (0.80-0.96) & 0.005 & 1.11 (0.97-1.27) &
0.13\tabularnewline
Unknown & 0.51 (0.45-0.58) & \textless{}0.001 & 0.87 (0.72-1.08) &
0.20\tabularnewline
\textbf{Hospital function} & & \textless{}0.001 & &
\textless{}0.001\tabularnewline
General hospital & Ref & & Ref &\tabularnewline
Cancer center & 3.43 (3.06-3.86) & \textless{}0.001 & 1.82 (1.49-2.23) &
\textless{}0.001\tabularnewline
W\&C center & 1.55 (1.27-1.89) & \textless{}0.001 & 0.26 (0.20 -0.35) &
\textless{}0.001\tabularnewline
\textbf{Region} & & \textless{}0.001 & & \textless{}0.001\tabularnewline
North & Ref & & Ref &\tabularnewline
South & 0.46 (0.39-0.54) & \textless{}0.001 & 4.90 (3.65-6.57) &
\textless{}0.001\tabularnewline
Central & 0.91 (0.78-1.06) & 0.24 & 2.10 (1.67-2.66) &
\textless{}0.001\tabularnewline
East & 0.37 (0.32-0.42) & \textless{}0.001 & 0.35 (0.28-0.45) &
\textless{}0.001\tabularnewline
Southwest & 1.06 (0.84-1.32) & 0.64 & 82.85 (57.46-116.60) &
\textless{}0.001\tabularnewline
Northwest & 3.30 (2.55-4.25) & \textless{}0.001 & 1.28 (0.88-1.87) &
0.19\tabularnewline
Northeast & 0.22 (0.16-0.29) & \textless{}0.001 & 3.34 (1.70-6.57) &
\textless{}0.001\tabularnewline
\textbf{City scale} & & \textless{}0.001 & &
\textless{}0.001\tabularnewline
First-tier & Ref & & Ref &\tabularnewline
Second-tier & 0.71 (0.59-0.85) & \textless{}0.001 & 8.75 (6.32-12.12) &
\textless{}0.001\tabularnewline
Third-tier & 0.37 (0.31-0.43) & \textless{}0.001 & 1.18 (0.89-1.56) &
0.25\tabularnewline
\textbf{Mode of delivery} & & \textless{}0.001 & & 0.004\tabularnewline
No delivery & 1.01 (0.68-1.49) & 0.97 & 1.06 (0.57-1.98) &
0.84\tabularnewline
Vaginal delivery & Ref & & Ref &\tabularnewline
Cesarean delivery & 1.06 (0.89-1.27) & 0.51 & 1.36 (1.10-1.68) &
0.005\tabularnewline
Unknown & 0.66 (0.59-0.74) & \textless{}0.001 & 1.33 (1.07-1.67) &
0.01\tabularnewline
\textbf{Comorbidity} & & 0.40 & & 0.44\tabularnewline
No & Ref & & Ref &\tabularnewline
Yes & 0.93 (0.79-1.10) & 0.40 & 1.09 (0.88-1.35) & 0.44\tabularnewline
\textbf{FIGO stage} & & \textless{}0.001 & &
\textless{}0.001\tabularnewline
IA1+IA2 & Ref & & Ref &\tabularnewline
IB1 & 1.44 (1.08-1.94) & 0.015 & 1.16 (0.77-1.76) & 0.48\tabularnewline
IB2 & 1.54 (1.12-2.11) & 0.008 & 1.46 (0.93-2.31) & 0.10\tabularnewline
IIA1 & 1.83 (1.34-2.49) & \textless{}0.001 & 1.42 (0.91-2.22) &
0.12\tabularnewline
IIA2 & 1.83 (1.31-2.56) & \textless{}0.001 & 2.62 (1.60-4.29) &
\textless{}0.001\tabularnewline
IIB & 1.07 (0.77-1.48) & 0.71 & 1.85 (1.13-3.03) & 0.02\tabularnewline
\textbf{Gross type} & & \textless{}0.001 & & 0.008\tabularnewline
Exophytic & Ref & & Ref &\tabularnewline
Endophytic & 2.09 (1.78-2.45) & \textless{}0.001 & 0.64 (0.48-0.86) &
0.003\tabularnewline
Ulcerated & 0.87 (0.78-0.98) & 0.018 & 1.16 (0.98-1.38) &
0.08\tabularnewline
Endocervical & 0.55 (0.40-0.77) & \textless{}0.001 & 0.89 (0.56-1.42) &
0.63\tabularnewline
After conization & 0.92 (0.70-1.19) & 0.52 & 1.21 (0.85-1.70) &
0.29\tabularnewline
Preclinical carcinoma & 1.41 (1.20-1.65) & \textless{}0.001 & 0.88
(0.72-1.08) & 0.22\tabularnewline
Unknown & 0.73 (0.64-0.85) & \textless{}0.001 & 1.05 (0.87-1.28) &
0.61\tabularnewline
\textbf{Histological types} & & 0.021 & & 0.97\tabularnewline
Squamous cell & Ref & & Ref &\tabularnewline
Adenocarcinoma & 0.89 (0.77-1.02) & 0.10 & 1.06 (0.87-1.28) &
0.56\tabularnewline
Adenosquamous & 0.81 (0.62-1.07) & 0.14 & 1.00 (0.65-1.55) &
0.98\tabularnewline
Other subtypes & 0.66 (0.49-0.90) & 0.008 & 0.98 (0.64-1.48) &
0.90\tabularnewline
Unknown & 0.75 (0.33-1.72) & 0.50 & 0.89 (0.50-1.57) &
0.68\tabularnewline
\textbf{Preoperative treatment} & & \textless{}0.001 & &
\textless{}0.001\tabularnewline
No received & Ref & & Ref &\tabularnewline
Neoadjuvant chemotherapy & 0.81 (0.72-0.91) & \textless{}0.001 & 0.69
(0.57-0.82) & \textless{}0.001\tabularnewline
Preoperative radiotherapy & 1.91 (1.53-2.39) & \textless{}0.001 & 0.85
(0.58-1.26) & 0.42\tabularnewline
\textbf{Lymph node dissection} & & 0.99 & & 0.04\tabularnewline
PLA & Ref & & Ref &\tabularnewline
PLA+PALA & 0.99 (0.81-1.23) & 0.99 & 1.19 (1.01-1.40) &
0.04\tabularnewline
\textbf{Hysterectomy types} & & \textless{}0.001 & &
\textless{}0.001\tabularnewline
Type B & Ref & & Ref &\tabularnewline
Type C2 & 1.74 (1.59-1.92) & \textless{}0.001 & 2.33 (1.98-2.74) &
\textless{}0.001\tabularnewline
Type C1 & 2.78 (1.63-4.73) & \textless{}0.001 & 3.59 (2.26-5.70) &
\textless{}0.001\tabularnewline
\bottomrule
\end{longtable}

Abbreviations: PLA, pelvic lymphadenectomy; PALA, para-aortic
lymphadenectomy.

\textbf{Table 4. Unadjusted complications associated with radical
hysterectomy for cervical cancer stratified by surgeon volume.}\selectlanguage{english}
\begin{longtable}[]{@{}lllllllllllllll@{}}
\toprule
Outcome & Abdominal surgeon volume & Abdominal surgeon volume &
Abdominal surgeon volume & Abdominal surgeon volume & Abdominal surgeon
volume & Abdominal surgeon volume & \emph{P} value & Laparoscopic
surgeon volume & Laparoscopic surgeon volume & Laparoscopic surgeon
volume & Laparoscopic surgeon volume & Laparoscopic surgeon volume &
Laparoscopic surgeon volume & \emph{P} value\tabularnewline
\midrule
\endhead
& Low & Low & Intermediate & Intermediate & High & High & & Low & Low &
Intermediate & Intermediate & High & High &\tabularnewline
& N & \% & N & \% & N & \% & & N & \% & N & \% & N & \% &\tabularnewline
\textbf{Any 1 complication} & 148 & 3.06\textsuperscript{a} & 168 &
3.42\textsuperscript{a} & 96 & 2.01\textsuperscript{b} &
\textless{}0.001 & 137 & 5.19 & 150 & 5.69 & 148 & 5.16 &
0.62\tabularnewline
\textbf{Intraoperative complication} & 27 & 0.56 & 32 & 0.65 & 16 & 0.33
& 0.08 & 39 & 1.48 & 24 & 0.91 & 44 & 1.53 & 0.09\tabularnewline
Ureteral injury & 15 & 0.31\textsuperscript{ab} & 22 &
0.45\textsuperscript{a} & 8 & 0.16\textsuperscript{b} & 0.045 & 28 &
1.06 & 14 & 0.53 & 24 & 0.84 & 0.10\tabularnewline
Bladder injury & 3 & 0.06 & 4 & 0.08 & 1 & 0.02 & 0.55 & 3 & 0.11 & 4 &
0.15 & 8 & 0.28 & 0.34\tabularnewline
Bowel injury & 0 & 0 & 2 & 0.04 & 0 & 0 & 0.33 & 1 & 0.04 & 1 & 0.04 & 4
& 0.14 & 0.38\tabularnewline
Vascular injury & 9 & 0.18 & 2 & 0.04 & 5 & 0.10 & 0.10 & 4 & 0.15 & 4 &
0.15 & 7 & 0.24 & 0.69\tabularnewline
Obturator nerve injury & 0 & 0 & 2 & 0.04 & 2 & 0.04 & 0.48 & 5 & 0.19 &
1 & 0.04 & 2 & 0.07 & 0.24\tabularnewline
Stomach & 0 & 0 & 0 & 0 & 0 & ------ & ------ & 1 & 0.04 & 0 & 0 & 0 & 0
& 0.65\tabularnewline
\textbf{Postoperative complication} & 122 & 2.52\textsuperscript{a} &
141 & 2.87\textsuperscript{a} & 81 & 1.69\textsuperscript{b} &
\textless{}0.001 & 102 & 3.86 & 127 & 4.81 & 110 & 3.83 &
0.12\tabularnewline
Bowel obstruction & 46 & 0.95\textsuperscript{ab} & 63 &
1.28\textsuperscript{a} & 29 & 0.61\textsuperscript{b} & 0.003 & 18 &
0.68 & 18 & 0.68 & 21 & 0.73 & 0.97\tabularnewline
Pelvic hematoma & 1 & 0.02 & 1 & 0.02 & 0 & 0 & 0.99 & 0 & 0 & 2 & 0.08
& 0 & 0 & 0.11\tabularnewline
Hemorrhage & 3 & 0.06 & 3 & 0.06 & 1 & 0.02 & 0.71 & 5 & 0.19 & 3 & 0.11
& 5 & 0.17 & 0.83\tabularnewline
Vesicovaginal fistula & 8 & 0.16 & 9 & 0.18 & 6 & 0.13 & 0.81 & 19 &
0.72 & 17 & 0.64 & 24 & 0.84 & 0.71\tabularnewline
Ureterovaginal fistula & 9 & 0.19 \textsuperscript{ab} & 21 & 0.43
\textsuperscript{a} & 6 & 0.13 \textsuperscript{b} & 0.006 & 27 &
1.02\textsuperscript{a} & 47 & 1.78\textsuperscript{b} & 31 &
1.08\textsuperscript{a} & 0.02\tabularnewline
Rectovaginal fistula & 1 & 0.02 & 2 & 0.04 & 1 & 0.02 & 0.99 & 3 & 0.11
& 3 & 0.11 & 3 & 0.10 & 0.99\tabularnewline
Ureteral & 3 & 0.06 & 3 & 0.06 & 1 & 0.02 & 0.71 & 4 & 0.15 & 2 & 0.08 &
2 & 0.07 & 0.67\tabularnewline
Venous thromboembolism & 51 & 1.05 & 43 & 0.88 & 37 & 0.77 & 0.34 & 28 &
1.06 & 38 & 1.44 & 24 & 0.84 & 0.10\tabularnewline
Chylous leakage & 1 & 0.02 & 0 & 0 & 0 & 0 & 0.66 & 3 & 0.11 & 5 & 0.19
& 3 & 0.10 & 0.69\tabularnewline
\textbf{Other} & & & & & & & & & & & & & &\tabularnewline
Death & 0 & 0 & 0 & 0 & 2 & 0.04 & 0.11 & 0 & 0 & 1 & 0.04 & 1 & 0.03 &
0.77\tabularnewline
\bottomrule
\end{longtable}

Different letters on the shoulder mark indicate significant differences
(P \textless{} 0.05), and the same letter or no letter indicates that
the difference is not significant (P [?] 0.05).

\textbf{Table 5. Multivariable analysis of factors associated with
complications.}\selectlanguage{english}
\begin{longtable}[]{@{}lllllllllll@{}}
\toprule
& Abdominal surgeon volume & Abdominal surgeon volume & Abdominal
surgeon volume & Abdominal surgeon volume & & Laparoscopic surgeon
volume & Laparoscopic surgeon volume & Laparoscopic surgeon volume &
Laparoscopic surgeon volume &\tabularnewline
\midrule
\endhead
& Low & Intermediate & High & & \emph{P} value & Low & intermediate &
High & & \emph{P} value\tabularnewline
\textbf{Any 1 complication} & 3.06\% & 3.42\% & 2.01\% & & 0.10 & 5.19\%
& 5.69\% & 5.16\% & & 0.26\tabularnewline
& & & 1.20 & 0.87-1.66 & 0.27 & & & 1.14 & 0.82-1.58 &
0.43\tabularnewline
& & & 1.39 & 1.02-1.89 & 0.04 & & & 1.26 & 0.95-1.67 &
0.11\tabularnewline
\textbf{Intraoperative complication} & 0.56\% & 0.65\% & 0.33\% & & 0.21
& 1.48\% & 0.91\% & 1.53\% & & 0.46\tabularnewline
& & & 0.46 & 0.19-1.09 & 0.08 & & & 1.23 & 0.67-2.26 &
0.51\tabularnewline
& & & 0.58 & 0.25-1.38 & 0.22 & & & 0.86 & 0.48-1.54 &
0.61\tabularnewline
\textbf{Postoperative complication} & 2.52\% & 2.87\% & 1.69\% & & 0.04
& 3.86\% & 4.81\% & 3.83\% & & 0.13\tabularnewline
& & & 1.38 & 0.97-1.96 & 0.07 & & & 1.09 & 0.75-1.58 &
0.65\tabularnewline
& & & 1.55 & 1.11-2.15 & 0.01 & & & 1.34 & 0.98-1.83 &
0.07\tabularnewline
\bottomrule
\end{longtable}

The middle row for each complication class was adjusted for clinical and
demographic factors, including age, year of diagnosis, urban-rural
distribution, hospital function, region, city scale, mode of delivery,
comorbidity, FIGO stage, gross type, histological type, preoperative
treatment, lymph node dissection, and hysterectomy type reported, with
the odds ratio (95\% CI) of low vs. high volume. The bottom row for each
complication class is adjusted for the factors mentioned above, with the
odds ratio (95\% CI) of intermediate vs. high volume.\selectlanguage{english}
\begin{figure}[H]
\begin{center}
\includegraphics[width=0.70\columnwidth]{figures/FIGURE1/FIGURE1}

\end{center}
\end{figure}

\selectlanguage{english}
\FloatBarrier
\end{document}

