2. Materials and Methods
2.1. Ethics statement
This study was approved by University of Health Sciences Antalya
Training and Research Hospital Ethics Committee and written informed
consent was obtained all patients before procedure
2.2. Study design and the
patients
Thirty-two patients with PHPT from February 2017 to August 2020 who are
eligible to study protocol were included. The adenoma of all patients
enrolled in the study were thought to be benign. In case of malignancy
findings, surgical resection was recommended instead of fine needle
aspiration biopsy 16. The inclusion criteria, based on
the guidelines 4 were as follows: patients with
symptomatic PHPT; patients with asymptomatic PHPT, whose serum Ca
concentration is at least 0.25 mmol/L higher than the upper limit of
normal range; who have skeletal involvement as a decrease in bone
mineral density patients with renal involvement as creatinine clearance
less than 60 ml/min, nephrolithiasis or nephrocalcinosis, patients who
have hypercalciuria (>10 mmol per day) or patients younger
than 50 years old. Preablation data of the study group was summarized in
Table 1.
For the prediction assay, age, gender, parathyroid adenoma volume,
microwave ablation time (sec) and power (Watt), baseline level of Ca,
phosphorous (P), alkane phosphate (ALP) and PTH, vitamin D level,
location of parathyroid adenoma were recorded. Afterwards, depending on
the treatment efficacy, which has the criteria of treatment success if
the six-month follow-up of PTH has lesser than 88.0 ng/L and Ca is at
the normal range, patients divided into response and no response groups.
Then, the predictive abilities of the potential factors were
investigated by logistic regression to evaluate its role in the MWA
efficacy.
2.3. Laboratory assessment
Ca, P, ALP, PTH, and Vitamin D levels were measured before the MWA
procedure and 1 day, 1 month, and 6 months after MWA therapy. Ca, P and
ALP were measured using AU5800 Series Chemistry Analyzers (Beckman
Coulter Inc., Brea, CA, USA). PTH and vitamin D levels were measured
with Dx1 800 DxI 800 Access Immunoassay System (Beckman Coulter Inc.,
Brea, CA, USA). The normal ranges were as follows: Ca, 2.2-2.65 mmol/L;
P, 0.81-1.45 mmol/L, PTH, 12-88 ng/L; ALP, 30-120 u/L and vitamin D,
74.8-249.6 nmol/L. The volume and the location of parathyroid adenomas
were localized by ultrasound and 99mTc sestamibi (MIBI). Parathyroid
wash out was only performed when the lesion could not be clearly
localized with these imaging methods.
2.4. Microwave ablation
procedure
Three orthogonal diameters of the parathyroid adenoma were measured
before ablation and follow-up with a real-time ultrasound system with a
5-14 MHz linear probe. The volume of the nodule was calculated
automatically through the software program of the Aplio 500, Toshiba
Medical Systems, Tokyo, Japan. Microwave ablation system (ECO-100AI3),
consisting of a microwave generator producing 30-40 W of power at 2450
MHz either continuously or in a pulse; a flexible cable, and
internally-cooled 16-gauge thyroid antenna with 10 cm shaft length with
a 3 mm active tip was used. Parathyroid adenoma ablation was performed
on an outpatient basis under local anesthesia without sedation. The
patient was placed in a supine position with the neck mildly
hyperextended. After determining the appropriate puncture side, a
mixture of 30/70% lidocaine (Osel Pharmaceuticals, Istanbul, Turkey)
and saline was applied along the puncture path from the skin to the
thyroid capsule after then infused into the surrounding thyroid capsule
to protect vital recurrent laryngeal nerves, esophagus and trachea
adjacent to the parathyroid adenoma. Internally cooled thyroid microwave
ablation antenna was positioned under ultrasound guidance via
trans-isthmic approach or lateral cervical approach. A moving shot
technique was used to ablate the parathyroid adenoma throughout the
procedure. Therapy was completed when the entire nodule was covered with
hyperechoic microbubbles, which is used indicative of ablation. Heart
rate and oxygen saturation were continuously monitored during the
procedure. After the procedure, all patients were followed by cold
compression to prevent neck hematoma. The patients who were informed
about the symptoms of hypocalcemia were discharged after 4 hours of
follow-up.
2.5. Statistical analysis
The analysis of data was conducted by SPSS® 20.0
(Statistical Packages for Social Sciences; SPSS Inc, Chicago, Illinois,
USA). The normality of the data was assessed with Shapiro-Wilk test of
normality (P >0.05). All the normally distributed
continues variables were presented as mean ± standard deviations whereas
the rest and the categorical variables were reports as median
(interquartile ranges) and percentages. Due to the non-normal
distribution in Ca, P, ALP and PTH values, Friedman and Wilcoxon’ signed
rank tests was used in their comparison with time difference.
Mann-Whitney U test was used for the comparison of the values in two
non-normal distributed groups. Fischer exact test was also used to
compare categorical variables between response and no response groups.
The significance level was based on a P value of less than 0.05.
Age, gender, Parathyroid adenoma volume, baseline levels of Ca, P, ALP,
vitamin D, location of parathyroid adenoma, microwave ablation time and
power were compared and identified as possible predictive factors
between response and no response group. The no response group was
considered as the control group. The differences between the control
group and the response group were evaluated by using Mann-Whitney U and
χ2 test. The detailed further investigations of the
possible factors were explored by using logistic regression.