Are quantitative measures of visceral adiposity obtained after neoadjuvant chemoradiation associated with postoperative morbidity in patients with locally advanced rectal cancer?
514 Background: Body mass index (BMI) is an inconsistent predictor of surgical morbidity in cancer patients. Increased visceral obesity measured before neoadjuvant chemoradiation (NCR) has been associated with post-operative morbidity in rectal cancer (RC). We sought to evaluate whether visceral obesity/BMI measured immediately after NCR correlates with postoperative complications in a heterogenous, largely underserved cohort of RC patients. Methods: 116 patients (64% white, 34% black, 2% other) underwent proctectomy for stage II/III RC after NCR. Automated CT segmentation software was used to determine body fat distribution at the L4/L5 level. Patients were classified as obese by BMI (≥ 30 kg/m2) and post-NCR CT measures of adiposity including visceral fat area (VFA; > 100cm2), visceral to subcutaneous fat area ratio (V/S; > 0.4), and perinephric fat thickness (PNF; > median) were obtained. Complications were classified (Clavien-Dindo) into low (1-2) or high (3-4) grade. Associations between measures of adiposity, short-term surgical outcomes and clinicopathologic factors were evaluated with one-way ANOVA, Chi-square, and Fischer’s exact test as appropriate for overall, white, and non-white cohorts. Results: Obese patients by adiposity measures (but not BMI) were more likely to be male by V/S (91.4% vs. 54.3%, p ≤ 0.001) and PNF (62.9% vs. 26.1%, p ≤ 0.001), Caucasian by VFA (mean 135.2 cm2vs. 93.8 cm2, p = 0.002), and have preexisting metabolic comorbidities by VFA and PNF ( p < 0.01). V/S was associated with the presence of key metabolic comorbidities in both white and non-white groups ( p < 0.05). Obesity by V/S but not BMI was associated with development of postoperative complications in the non-white group (65.5% vs. 30.8%, p = 0.049), but not in the overall or white cohorts. Conclusions: V/S as measured after NCR is associated with presence of key metabolic comorbidities in the entire cohort but with postoperative complications only in non-white patients. Given these observations, further evaluation of the impact of socioeconomic factors and change in adiposity between pre- and post-NCR time periods is warranted.