Association of muscle mass with survival after radical prostatectomy in patients with prostate cancer.

Purpose: Although muscle mass has been associated with survival in patients with various types of solid tumors, the relationship between muscle mass and survival in patients with prostate cancer remains unclear. We retrospectively investigated the association of muscle mass with survival after radical prostatectomy in patients with prostate cancer. Materials and Methods: We reviewed the records of 2,042 patients who underwent radical prostatectomy of prostate cancer between 1998 and 2013. Muscle mass was evaluated by measuring the psoas muscle index on preoperative computerized tomography images. Results: In the lowest, second, third and highest psoas muscle index quartiles the 10-year distant metastasis-free survival rate was 72.5%, 83.8%, 92.3% and 93.7% (p < 0.001), the 10-year cancer specific survival rate was 85.7%, 92.1%, 96.8% and 97.6%, and the 10-year overall survival rate was 74.5%, 79.6%, 89.8% and 90.6%, respectively (each p < 0.001). The psoas muscle index positively correlated with the body mass index, serum concentrations of IGFBP-3 and bioavailable testosterone, and inversely correlated with patient age, the serum SHBG concentration and the neutrophil-to-lymphocyte ratio. On multivariable analysis the psoas muscle index was independently associated with increased risks of biochemical recurrence, distant metastasis, and cancer specific and overall death. Conclusions: Low muscle mass may be associated with increased risks of recurrence and mortality in patients who undergo radical prostatectomy of prostate cancer regardless of the body mass index. Large-scale prospective studies are warranted.