Combination of body mass index and albumin predicts the survival in metastatic castration‐resistant prostate cancer patients treated with abiraterone: A post hoc analysis of two randomized trials

Background Low body mass index (BMI) and low serum albumin levels are suggested indicators of malnutrition and are associated with poor outcomes in cancer patients. Decreasing androgen can alter lipid metabolism, so the prognostic value of BMI may change in metastatic castration‐resistant prostate cancer (mCRPC) patients receiving abiraterone. We aimed to delineate the prognostic value of BMI, serum albumin, and BMI and serum albumin (ALB) combined. Materials and methods A post hoc analysis was performed on data from two randomized clinical trials evaluating the efficacy of abiraterone in chemotherapy‐pretreated and ‐naïve mCRPC patients. Survival analysis was conducted using Kaplan–Meier and Cox proportional hazard methods. Results A total of 2,205 mCRPC patients were included in this study. Low ALB independently predicted the OS in both cohorts (HR, 1.54; 95%CI, 1.34–1.78 and HR, 1.40; 95%CI, 1.21–1.64, respectively), while low BMI independently predicted the OS only in the post‐chemotherapy cohort (HR, 1.30; 95%CI, 1.12–1.50) but not in the pre‐chemotherapy cohort (HR, 1.19; 95%CI, 0.98–1.43). By combining BMI (<25 kg/m 2 or ≥30 kg/m 2 ) and ALB (<4 g/dl or >4 g/dl), the four groups were characterized and their HRs were 1, 0.60 (95%CI, 0.47–0.76, p  < 0.001), 0.75 (95%CI,0.61–0.92 p  = 0.006), and 0.49 (95%CI, 0.41–0.60, p  < 0.001) in post‐chemotherapy patients and 1, 0.64 (95%CI, 0.46–0.89, p  = 0.008), 0.75 (95%CI,0.58–0.98 p  = 0.034), and 0.55 (95%CI, 0.42–0.72, p  < 0.001) in chemotherapy‐naïve patients, respectively. Conclusions Our results demonstrate that the combination of BMI and ALB better characterizes the risk groups irrespective of previous chemotherapy. Patients with high BMI but low ALB have higher risk of death than patients with low BMI but high ALB.