Impact of nadir PSA level and time to nadir during initial androgen deprivation therapy on prognosis in patients with metastatic castration-resistant prostate cancer

Purpose: We determine whether the nadir prostate-specific antigen level (PSA nadir) and time to nadir (TTN) during initial androgen deprivation therapy (ADT) are prognostic factors in metastatic castration-resistant prostate cancer (mCRPC) patients. Methods: We reviewed the Michinoku Japan Urological Cancer Study Group database, including 321 mCRPC patients. Optimal cutoff values for PSA nadir and TTN on survival were calculated with the receiver operating characteristic (ROC) curve. Patients were stratified into unfavorable (higher PSA nadir and/or shorter TTN) and favorable (lower PSA nadir and longer TTN) groups. The inversed probability of treatment weighing (IPTW)-adjusted Cox proportional hazard model was performed to evaluate the impact of the unfavorable group on overall survival (OS) after CRPC diagnosis. Results: Median age and follow-up period were 71 years and 35 months, respectively. ROC curve analysis demonstrated cutoffs of PSA nadir > 0.64 ng/mL and TTN < 7 months. The unfavorable group included 248 patients who had significantly shorter OS after mCRPC. The IPTW-adjusted multivariate model revealed that the unfavorable group had a negative impact on OS in mCRPC patients [hazards ratio (HR) 2.98, P < 0.001]. Conclusions: Higher PSA nadir and shorter TTN during the initial ADT are poor prognostic factors in patients with mCRPC.