Abstract 880: Obesity predicts prostate cancer-specific mortality after radical prostatectomy: Results from the SEARCH database

Abstract

Abstract INTRODUCTION: At the population level among otherwise “healthy” men, obesity is associated with prostate cancer mortality. However, few studies analyzed the associations between obesity and long-term progression after surgery, such as castration-resistant prostate cancer (CRPC) and prostate cancer-specific mortality (PCSM). We examined the effect of obesity at the time of radical prostatectomy (RP) on long-term prostate cancer-specific outcomes among men treated at Veterans Affairs Hospitals in the USA. METHODS: We combined data from patients undergoing RP at six Veterans Affairs Medical Centers (West Los Angeles, San Diego, and Palo Alto, CA; Augusta, GA; and Durham and Asheville, NC) into the SEARCH database. Our exposure, body mass index (BMI) was abstracted from the medical records at the time of but prior to RP and categorized as normal weight (<25 kg/m2), overweight (25-29.9kg/m2), and obese (≥30kg/m2). Crude and adjusted Cox models accounting for known risk cofactors were used to examine the associations between BMI and PCSM (primary outcome), biochemical recurrence (BCR) and CRPC. Hazard ratios for the risk of CRPC and PCSM were analyzed using competing-risks regression analysis accounting for non-PC death as a competing risk. RESULTS: Overall, 839 (23%) men had normal weight, 1,675 (45%) were overweight, and 1,184 (32%) were obese. A higher BMI was associated with younger age at surgery (p<0.001), lower PSA (median 6.9 vs. 6.3 vs. 6.1; p<0.001), and a shorter follow-up (p = 0.009). After adjusting for clinical and pathological features, both overweight (HR 2.85, p = 0.039) and obesity (HR 3.38, p = 0.017) were significantly associated with PCSM relative to normal weight. Obesity (vs. normal weight) was also associated with a higher risk of BCR (HR = 1.20, p = 0.026) and CRPC (HR = 2.12, p = 0.026), even after adjusting for clinical and pathological characteristics. Overweight was not associated with BCR (HR = 1.01, p = 0.948) or CRPC (HR = 1.44, p = 0.274) on multivariable analysis. CONCLUSIONS: Our study supports the hypothesis that obese men undergoing RP are at increased risk of worse long-term prostate cancer outcomes including PCSM. Our findings are consistent with a growing body of literature documenting that obesity in general is associated with more aggressive prostate cancer. Citation Format: Adriana C. Vidal, Lauren E. Howard, Matthew R Cooperberg, Christopher J. Kane, William J. Aronson, Martha K. Terris, Christopher L. Amling, Stephen J Freedland. Obesity predicts prostate cancer-specific mortality after radical prostatectomy: Results from the SEARCH database. [abstract]. In: Proceedings of the 106th Annual Meeting of the American Association for Cancer Research; 2015 Apr 18-22; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Res 2015;75(15 Suppl):Abstract nr 880. doi:10.1158/1538-7445.AM2015-880