The association of body composition with postoperative complications and length of hospital stay after radical or partial nephrectomy in patients with renal cell cancer: a multicenter population-based cohort study

Background: Body mass index (BMI) and body composition have been associated with postoperative outcomes in oncological surgery. Evidence in renal cell cancer (RCC) is limited and inconsistent. Therefore, we examined BMI and body composition in relation to postoperative outcomes in patients with RCC. Methods: We conducted a multicenter population-based historical cohort study including 801 patients with RCC treated with radical (79%) or partial (21%) nephrectomy between 2008-2012. Computed Tomography images at third lumbar vertebrae were assessed for skeletal muscle (SM) index, SM density, visceral adipose tissue (VAT) index and subcutaneous adipose tissue index (SATI). Multivariable multilevel logistic regression analyses were used to examine associations between BMI, body composition and (major) postoperative complications and extended length of hospital stay (LOHS) (=7 days). Discrimination of models for major complications was compared using receiver operating characteristics (ROC) curves. Results: In total, 19.6% of the patients had postoperative complications (6.2% Clavien grade =III) and 24.1% had extended LOHS. A 10-unit increase in SM density was inversely associated with extended LOHS [odds ratio (OR) 0.58; 95% confidence interval (95% CI): 0.44-0.78]. Associations of high BMI and lower SM density with risk of major complications and of higher VAT index with extended LOHS were also observed but statistical significance differed according to surgical procedure. Models predicting major complications with or without body composition parameters were not different. Conclusions: Lower SM density was associated with extended LOHS and non-significantly associated with higher risk of major postoperative complications. High BMI was associated with higher risk of major postoperative complications. Higher VAT was non-significantly associated with higher risk of extended LOHS. Results by surgical procedure were in the same direction but were only statistically significant for some subgroups. Validation of these results and investigation of the added value of body composition parameters to anatomic classification systems is needed.