Prognostic Impact of Prostate-Specific Antigen at 6 Months After Radiotherapy in Localized Prostate Cancer: An Individual Patient Data Analysis of Randomized Trials

PURPOSE We sought to evaluate the prognostic impact of prostate-specific antigen (PSA) at 6 months after completion of radiotherapy (RT) in patients treated with RT alone, RT plus short-term (st; 3-6 months), and RT plus long-term (lt; 24-36 months) androgen-deprivation therapy (ADT). PATIENTS AND METHODS Individual patient data were obtained from 16 randomized trials evaluating RT ± ADT for localized prostate cancer (PCa) between 1987 and 2011. The lowest PSA recorded within 6 months after RT completion was identified and categorized as < or ≥0.1 ng/mL. The primary outcomes were metastasis-free survival (MFS), PCa-specific mortality (PCSM), and overall survival (OS), from 12 months after random assignment. RESULTS Ninety-eight percent (n = 2,339/2,376) of patients allocated to RT alone, 84% (n = 4,756/5,658) allocated to RT + stADT, and 77% (n = 1,258/1,626) allocated to RT + ltADT had PSA ≥0.1 ng/mL within 6 months after completing RT. PSA ≥0.1 ng/mL was associated with lower MFS and OS and higher PCSM among patients allocated to RT ± ADT (RT – MFS: hazard ratio HR, 2.24 95% CI, 1.21 to 4.16; PCSM: subdistribution hazard ratio sHR, 1.82 0.51 to 6.49; OS: HR, 1.72 0.97 to 3.05; RT + stADT – MFS: HR, 1.27 1.12 to 1.44; PCSM: sHR, 2.10 1.52 to 2.92; OS: HR, 1.26 1.11 to 1.44; RT + ltADT – MFS: HR, 1.58 1.27 to 1.96; PCSM: sHR, 1.97 1.11 to 3.49; OS: HR, 1.59 1.27 to 1.99). Five-year MFS rates among patients allocated to RT, RT + stADT, and RT + ltADT were 91% versus 79%, 83% versus 76%, and 87% versus 74%, respectively, based on PSA < or ≥0.1 ng/mL. CONCLUSION PSA ≥0.1 ng/mL within 6 months after RT completion was prognostic for lt outcomes in patients treated with RT ± ADT for localized PCa. This can be used to counsel patients treated with RT ± ADT and in guiding clinical trial design evaluating novel systemic therapies with RT + ADT as well as (de)intensification strategies.