Main findings
We found that sagittal abdominal diameter (SAD) measured in MRI (especially at the umbilicus) is a reliable method to evaluate intra-abdominal fat in endometrial cancer patients. Umbilical SAD (u-SAD) has an acceptable diagnostic accuracy to predict surgical morbidity in patients undergoing transperitoneal minimally invasive aortic lymphadenectomy, especially using conventional laparoscopy. In our cohort, a patient undergoing a transperitoneal aortic lymphadenectomy with a u-SAD greater than 246 mm would have a probability of 69% of encountering surgical morbidity (positive likelihood ratio=2.8). Those having less than 246 mm had significantly less risk (probability of 31%, negative likelihood ratio=0.55). But its applicability in all patients with endometrial cancer undergoing surgical staging is limited.
U-SAD seems to have a better diagnostic performance than BMI—the most commonly used obesity measurement. Indeed, BMI use is widespread, but its clinical use as a tool to predict morbidity is questionable15,16,31,32. More than obesity alone, visceral obesity has been associated with worse surgical outcomes15–19.
Endometrial cancer patients with abdominal obesity have more visceral fat in areas where the staging surgery is already challenging, particularly during the lymph node dissection. Thus, having more intra-abdominal fat could yield fewer aortic nodes. We found that, in the transperitoneal subgroup, for every additional centimetre in u-SAD the lymphadenectomy obtained one aortic lymph node less (Figure S2). By contrast, aortic node count was independent of u-SAD in the extraperitoneal subgroup, supporting the benefit of this technique that bypasses the intra-abdominal space.
A previous study demonstrated that SAD measured in CT-scans or MRI was superior to BMI when used to predict surgical difficulty33. Our results are in line with these findings (Figures 3c, S1, S2), but in that study, only 49% of patients underwent laparoscopy aortic lymphadenectomy, and they enrolled more obese patients compared with our cohort (median BMI: 37 vs. 29 kg/m2, median SAD: 300 vs. 235 mm).
Another study found that higher intra-abdominal fat was associated with worse surgical outcomes and more conversions 19. We also found that an increasing u-SAD was associated with a higher conversion rate (Figure S1), especially in the transperitoneal subgroup.
Surgical morbidity is critical in gynaecologic oncology because it may delay oncologic treatment, substantially increase costs of care, and worsen patients’ survival and quality of life 34,35. Thus, efforts should focus on establishing a method to preoperatively identify those patients at risk. Several authors have attempted to describe predictors of complications and to validate risk scoring systems specifically in gynaecologic oncology surgery6–10,34,36–39. But the studied populations were too heterogeneous, and yielded poor results, hindering their clinical application. It is difficult to establish a single scoring system valid for all gynaecological malignancies, given the complexity of diseases, treatments, and patients.
Our surgical morbidity results are comparable to the outcomes of large cohorts and a recent meta-analysis 39–41. We observed an intraoperative complication rate of 10.3% and an early postoperative complication rate of 26.5%. We found a higher rate of surgical morbidity in the conventional vs. robotic-assisted laparoscopy subgroup, findings that are consistent with previously reported results4,5,24,42.
Although our findings are similar to other published studies, we cannot compare our main outcome measure since it has not been previously described.
Measuring surgical morbidity is challenging. So far, studies that evaluate the prediction of surgical morbidity have used different outcome measures, but they fail to address specific issues related to the surgical procedure. Thus, we defined a novel core outcome set that identifies the morbidity specifically associated with the laparoscopic aortic lymphadenectomy. Similar core outcome sets have been described in other areas 43, but they are lacking in gynaecologic oncology.
Previously published risk prediction models have performed worse than ours, having a diagnostic power insufficient for clinical use (< 0.70) 7,8.
Very few studies that evaluate surgical morbidity prediction have included the surgical approach in their models (i.e. minimally invasive vs. open), and none of them has considered the surgical technique for para-aortic lymphadenectomy (transperitoneal vs. extraperitoneal).
According to current evidence, both techniques seem to be equivalent. But one meta-analysis suggested that intraoperative complications are more frequent with the transperitoneal technique 4. We found similar results: 14.1% vs. 6.9% in the transperitoneal vs. extraperitoneal subgroups (p =0.08). Surgical morbidity was similar in these groups, but we found that u-SAD measurement was a more powerful predictor in the transperitoneal subgroup (Figure 3d). We believe this difference is due to the challenges of the transperitoneal technique, where surgeons must overcome the intra-abdominal fat during the entire procedure.