Association of Body Mass Index With Response and Survival in Men With Metastatic Prostate Cancer: Southwest Oncology Group Trials 8894 and 9916

Purpose: We evaluated the effect of body mass index on prostate specific antigen response, and progression-free and overall survival in men with androgen dependent or androgen independent metastatic prostate cancer. Materials and Methods: We examined the prognostic impact of body mass index in patient cohorts from phase III randomized studies coordinated by the Southwest Oncology Group. The first study included 1,006 men treated with androgen deprivation for metastatic prostate cancer. The second study included 671 patients treated with chemotherapy for metastatic, androgen independent prostate cancer. Results: Among men with androgen dependent disease, higher body mass index was associated with longer overall (p <0.001) and progression-free (p = 0.009) survival, as well as with an increased likelihood of achieving a prostate specific antigen nadir less than 4 ng/ml (p = 0.008). In multivariate analysis adjusting for risk factors, increasing body mass index was positively correlated with overall survival (p <0.01) and overweight but not obese patients (body mass index 27 to 29.9) had a significantly improved outcome compared to normal weight patients, with hazard ratios for risk of progression and death of 0.82 (95% CI 0.69, 0.98) and 0.75 (95% CI 0.63, 0.89), respectively. Among men with androgen independent prostate cancer, no clear association could be detected between body mass index and progression-free survival, overall survival or prostate specific antigen response. Conclusions: This study revealed higher body mass index to be associated with better overall and progression-free survival in patients with androgen dependent metastatic prostate cancer. Among men who had androgen independent disease, no significant association was found between body mass index and survival.