Nadir prostate-specific antigen (PSA) level and time to PSA nadir following primary androgen deprivation therapy as independent prognostic factors in a Japanese large-scale prospective cohort study (J-CaP)

Purpose: The aim of this study was to investigate whether nadir prostate-specific antigen (PSA) level and time to PSA nadir (TTN) are independent prognostic factors equivalent to the pretreatment factors in the data of the Japan Study Group of Prostate Cancer registry, which is a large, multicenter, population-based database of patients undergoing primary androgen deprivation therapy (PADT). Methods: A total of 10,958 patients treated with PADT were enrolled into the present study. Univariate and multivariate Cox proportional hazards regression analysis and Kaplan-Meier analysis were used to evaluate the associations of PSA nadir level and TTN with progression-free survival (PFS) and overall survival (OS), adjusting for the pretreatment factors adopted in the Japan Cancer of the Prostate Risk Assessment (J-CAPRA) score. Results: Of the 10,958 patients, 3,451 (31.5 %) had lymph node and/or distant metastases. The median PSA level was 27.0 ng/ml before treatment, and the nadir PSA level in 6,983 patients (63.7 %) reached below 0.2 ng/ml. Disease progression occurred in 4,736 cases, and 2,163 patients died during a mean follow-up period of 3.86 years. Nadir PSA level and TTN were independent prognostic factors, similar to the pretreatment factors adopted in the J-CAPRA score. The probabilities of PFS and OS showed significant differences among the groups categorized by the combination of nadir PSA level and TTN in all J-CAPRA risk stratifications. Conclusions: The present study demonstrated that nadir PSA level and TTN are strong predictors in patients undergoing PADT in a large-scale prospective cohort study.