A Systematic Review and Meta-Analysis of the Significance of Body Mass Index on Kidney Cancer Outcomes.

Obesity is a well-known risk factor for kidney cancer incidence. However, a number of studies have demonstrated more favorable kidney cancer prognosis in patients with elevated body mass index (BMI) conferring a survival advantage, termed 'the obesity paradox'. We aimed to evaluate the association between BMI and kidney cancer outcomes (progression-free survival (PFS), cancer specific survival (CSS), and overall survival (OS)).

A computerized systematic search of Medline, EMBASE, Proquest, Pubmed, and Google scholar for literature published in English was performed between its inception and December 2018 and Preferred Reporting Items for Systematic Reviews and Meta-analysis guidelines were used for reporting.

Overall, 34 publications comprising a total of 50,717 patients were included in the analysis. The majority assessed the association between BMI and CSS. Overweight and obese patients were associated with improved CSS compared to patients with normal BMI (HR 0.85, 95% confidence interval (CI) 0.79-0.93). A similar trend was demonstrated for PFS (HR 0.68, 95% CI 0.59-0.78) and OS (HR 0.66, 95% CI 0.55-0.79). On the contrary, the underweight group was associated with inferior CSS (HR 2.16, 95% CI 1.15-4.04). Main drawbacks limiting the interpretation were the retrospective design in the majority of studies, heterogeneity in study population, BMI classification, and covariates in multivariate analysis.

This is the largest systematic review of evaluating the potential phenomenon of the obesity paradox in kidney cancer outcomes. It demonstrated a favorable effect of BMI on kidney cancer outcomes. However, due to significant heterogeneity of studies, multicenter prospective studies and further research on the fundamental biological mechanisms are warranted to confirm the significance of BMI on kidney cancer prognosis.

The Journal of urology. 2020 Sep 18 [Epub ahead of print]

Lawrence H Kim, Paul Doan, Yilu He, Howard M Lau, Henry Pleass, Manish I Patel

Department of Urology, Westmead Hospital, Westmead, NSW, Australia., Department of Urology, Canberra Hospital, ACT, Australia., Department of Surgery, Westmead Hospital, Sydney, Australia.