Examining the association between adiposity and biochemical recurrence after radical prostatectomy

Introduction: Herein, we examined the association between adiposity, as measured by computed tomography (CT), and biochemical recurrence (BCR) after radical prostatectomy (RP). Methods: Using axial CT images, preoperative fat mass index (FMI) was calculated for 698 men who underwent RP from 2007–2010 by using measurements of total surface area of adipose tissue at the L3 level. Obesity was classified according to National Health and Nutrition Examination Survey (NHANES) standards for obesity (FMI >9 kg/m²). The associations between obesity and the distribution of adiposity (visceral vs. subcutaneous) with BCR were examined using the Kaplan-Meier method and Cox proportional hazards regression analyses. Results: Obese men were older than non-obese men (63.0 vs. 60.7 years; p<0.001), but were similar with regards to all other clinical and pathological characteristics. With a median followup of six years, 152 patients were diagnosed with BCR. Five-year BCR-free survival was similar between obese and non-obese patients (80.6% vs. 82.1%; p=0.27). Furthermore, in multivariable analyses, obesity was not independently associated with the risk of BCR (hazard ratio [HR] 1.02; 95% confidence interval [CI] 0.73–1.43). Similar results were obtained when analyzing FMI as a continuous variable (HR 1.02; 95% CI 0.94–1.09 for each 1 kg/m² increase in FMI). Additionally, neither visceral adiposity, subcutaneous adiposity, or visceral-to-subcutaneous adiposity ratio were associated with BCR (all p>0.05) in multivariable analyses. Conclusions: Neither total abdominal adiposity nor the distribution of adiposity were independently associated with BCR after RP in this study. As such, the presence of obesity may not be a marker of increased oncological risk after RP.