Body mass index and weight change in men with prostate cancer: progression and mortality.

PURPOSE: Body mass index (BMI) is a modifiable lifestyle factor that has been associated with an increased risk of fatal prostate cancer and biochemical recurrence. The main purpose of the present study was to investigate the association between the exposure BMI at the time of a prostate cancer diagnosis and weight change after diagnosis, and the outcomes of prostate cancer progression and mortality in a large cohort study.
METHODS: Data from 4,376 men diagnosed with clinically localized prostate cancer between 1997 and 2002 were analyzed. BMI and weight change were self-reported in 2007. Hazard ratios (HRs) with 95 % confidence intervals (CIs) were estimated in complete-case analysis (n = 3,214) using Cox proportional hazards models.
RESULTS: Progression was experienced among 639 (14.6 %) of the study participants, and in total, 450 (10.3 %) deaths of any cause and 134 (3.1 %) prostate cancer-specific deaths were recorded during follow-up. Obese men had a 47 % increased rate of overall mortality compared to normal weight men (HR 1.47, 95 % CI 1.03-2.10). No statistically significant associations were found for BMI and prostate cancer progression or prostate cancer-specific mortality. A weight loss >5 % after diagnosis almost doubled the rate of overall mortality compared to maintaining a stable weight (HR 1.94, 95 % CI 1.41-2.66), while a weight gain >5 % was associated with an almost doubled increased rate of prostate cancer-specific mortality (HR 1.93, 95 % CI 1.18-3.16).
CONCLUSIONS: Being obese was associated with an increased rate of overall mortality, and gaining weight after a prostate cancer diagnosis was associated with an increased rate of prostate cancer-specific mortality.