PD16-05 THE INVERSE CORRELATION BETWEEN OBESITY AND MORTALITY IN PATIENTS WITH METASTATIC CASTRATION RESISTANT PROSTATE CANCER: RESULTS FROM THE CONTROL ARMS OF ASCENT2, MAINSAL AND VENICE TRIALS

Abstract

INTRODUCTION AND OBJECTIVE: Previous studies have shown a survival advantage for patients with high body mass index (BMI) and metastatic renal cancer. In prostate cancer patients, findings regarding a correlation between BMI and survival outcomes are conflicting. We aimed to test whether BMI amongst patients with metastatic castration resistant prostate cancer (mCRPC) is associated with improved overall survival (OS) and cancer‐specific survival (CSS) METHODS: We identified 1577 patients with mCRPC from three phase III randomized control trials (i.e., ASCENT2, MAINSAL and VENICE). The trials were selected because of the similar inclusion criteria. The role of BMI on survival outcomes was investigated both as a continuous and categorical variable (<20 vs. 20‐25 vs. 25‐30 vs. >30 km/m2). A BMI >30 kg/m2 was considered obese according to WHO classification. Analyses were adjusted for age, PSA, ECOG, number of metastasis and prior treatment. The Cox semi‐proportional hazard model was used to predict OS, whereas the competing risks regression was used for predicting cancer‐specific mortality (CSM). To exclude possible effects attributable to a higher dose of chemotherapy (titrated according to the body surface), we checked for interactions between BMI and chemotherapy dose RESULTS: Overall, 1577 patients were included. Median (IQR) BMI was 28 (25‐31) kg/m2. With respect to death of any cause, BMI emerged as a protective factor both as a continuous variable (HR: 0.96; 95%CI: 0.94,0.99; p=0.015) and as a categorical variable (obesity: HR: 0.71, 95%CI: 0.53,0.96; p=0.027). The inverse effect BMI on CSM was confirmed both as a continuous (SHR: 0.94; p=0.002) and as a categorical variable (SHR: 0.65; p=0.018). No interaction was detected between the BMI categories and the docetaxel dose at any level of our analyses (all p>0.05) CONCLUSIONS: Obese patients with mCRPC depicted a better cancer specific and overall survival compared to overweight and normal weight patients. The protective effect of BMI was not related to the higher dose of chemotherapy (Figure Presented).