['Primary androgen deprivation therapy (PADT) is the most effective systemic therapy for patients with metastatic prostate cancer. Nevertheless, once PSA progression develops, the prognosis is serious and mortal. We sought to identify factors that predicted the prognosis in a series of patients with metastatic prostate cancer.', "Two-hundred eighty-six metastatic prostate cancer patients who received PADT from 1998 to 2005 in Nara Uro-Oncology Research Group were enrolled. The log-rank test and Cox's proportional hazards model were used to determine the predictive factors for prognosis; rate of castration-resistant prostate cancer (CRPC) and overall survival.", 'The median age, follow-up period and PSA level at diagnosis were 73 years, 47 months and 174 ng/mL, respectively. The 5-year overall survival rate was 63.0%. The multivariable analysis showed that Gleason score (Hazard ratio [HR]:1.362; 95% confidence interval [C.I.], 1.023-1.813), nadir PSA (HR:6.332; 95% C.I., 4.006-9.861) and time from PADT to nadir (HR:4.408; 95% C.I., 3.099-6.271) were independent prognostic factors of the incidence of CRPC. The independent parameters in the multivariate analysis that predicted overall survival were nadir PSA (HR:5.221; 95% C.I., 2.757-9.889) and time from PADT to nadir (HR:4.008; 95% C.I., 2.137-7.517).'] Are nadir PSA level and time to nadir PSA prognostic factors in patients with metastatic prostate cancer?