The impact of body mass index on oncological and surgical outcomes of patients undergoing nephrectomy: a systematic review and meta-analysis

ObjectiveTo perform a systematic review and meta-analysis to evaluate the impact of body mass index (BMI) on oncological (primary) and surgical (secondary) outcomes of patients who underwent nephrectomy, as obesity or high BMI is a known risk factor for renal cell carcinoma (RCC) and predictor of poorer outcomes. MethodsStudies were identified from four electronic databases from database inception to 2 June 2021, according to the Preferred Reporting Items for Systematic Review and Meta-analysis statement. The review protocol was registered in the International Prospective Register of Systematic Reviews with the identification number: CRD42021275124. ResultsA total of 18 studies containing 13 865 patients were identified for the final meta-analysis. Regarding oncological outcomes, higher BMI predicted higher overall survival (BMI >25 vs BMI <25 kg/m(2): hazard ratio [HR] 0.70, 95% confidence interval [CI] 0.58-0.85), cancer-specific survival (BMI >25 vs BMI <25 kg/m(2): HR 0.60, 95% CI 0.50-0.73; BMI 25-30 vs BMI <25 kg/m(2): HR 0.46, 95% CI 0.23-0.95; BMI >30 vs BMI <25 kg/m(2): HR 0.50, 95% CI 0.36-0.69), and recurrence-free survival rates (BMI >25 vs BMI <25 kg/m(2): HR 0.72, 95% CI 0.63-0.82; BMI 25-30 vs BMI <25 kg/m(2): HR 0.59, 95% CI 0.42-0.82). Those with a lower BMI fared better in surgical outcomes, such as operation time and warm ischaemic time, although the absolute difference was minimal and unlikely to be clinically significant. There was no difference between groups for length of hospital stay, intraoperative or postoperative complications, blood transfusion requirements, and conversion to open surgery. ConclusionOur study suggests that a higher BMI is associated with improved long-term oncological survival and similar perioperative outcomes as a lower BMI. More research into the underlying biological and physiological mechanisms will enable better understanding of the effect of BMI, beyond mere association, on post-nephrectomy outcomes.