CUAJ – Original Research Mason et al Link between adiposity and BCR after prostatectomy Examining the association between adiposity and biochemical recurrence after radical prostatectomy

Introduction: Herein we examined the association between adiposity, as measured with computed tomography (CT), and biochemical recurrence (BCR) after 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 NHANES standards for obesity (FMI >9 kg/m). 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/m increase in FMI). Additionally, not visceral adiposity, subcutaneous adiposity, or visceral-to-subcutaneous adiposity ratio were associated with BCR (all p>0.05) in multivariable analyses. CUAJ – Original Research Mason et al Link between adiposity and BCR after prostatectomy 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. Introduction The association between obesity and malignancy is a major public health concern with obesity being recognized as a significant risk factor for the development of several human cancers (1, . However, obesity appears to have a variable effect on oncologic aggressiveness and survival. Specific to prostate cancer, obesity is associated with an increased incidence of clinically significant prostate cancer (2, 4, 5) but there are conflicting reports on whether obesity is independently associated with biochemical recurrence (BCR) and cancer-specific outcomes among men treated for localized prostate cancer . Currently available studies investigating the association between body composition and prostate cancer outcomes are limited by the abundant use of body mass index (BMI). BMI is a crude measure of obesity that does not account for differences in body composition and is not linearly associated with adiposity . Indeed, more accurate measures of body composition are available with cross sectional imaging being considered the gold standard . Cross-sectional imaging can accurately quantify adiposity and also allows for the measurement of fat distribution. Recognizing the conflicting results and limitations of currently available studies, we examined the association between both total abdominal adiposity and the distribution of adiposity (visceral and subcutaneous adipose tissue), as measured using axial computed tomography (CT), and BCR in men undergoing RP for localized prostate cancer.