Duration of first off-treatment interval is prognostic for time to castration resistance and death in men with biochemical relapse of prostate cancer treated on a prospective trial of intermittent androgen deprivation.

PURPOSE This was an exploratory analysis of a trial of intermittent androgen deprivation (IAD) in men with biochemical relapse (BR) to establish first cycle characteristics prognostic for progression to castration-resistant prostate cancer (CRPC) and death. PATIENTS AND METHODS Men with BR of prostate cancer after radical prostatectomy (RP) or radiation (RT) were treated with androgen deprivation therapy (ADT) comprised of leuprolide and flutamide. After 9 months on treatment, ADT was stopped, and monthly prostate-specific antigen (PSA) levels were observed during the off-treatment interval. When the PSA reached a threshold value (1 ng/mL for RP, 4 ng/mL for RT), ADT was resumed in a new cycle. Patients were treated intermittently in this manner until CRPC, which was defined as > or = two consecutive increasing PSA values while on ADT with castrate testosterone levels. RESULTS Seventy-two of 100 patients enrolled onto the study met criteria for this analysis. The duration of the first off-treatment interval (< or = v > 40 weeks) was associated with shorter time to CRPC (hazard ratio = 2.9; 95% CI, 1.1 to 7.7; P = .03) and death (hazard ratio = 3.8; 95% CI, 1.1 to 13.6; P = .04) after adjusting for age, stage, grade, and PSA at diagnosis. CONCLUSION In patients who completed the first cycle of IAD, a duration of the first off-treatment interval of < or = 40 weeks defines a subset of patients at higher risk of CRPC and death. Conversely, patients with an off-treatment interval of more than 40 weeks have a significantly better long-term prognosis.