Time to testosterone (T) and PSA rises during first “off treatment” interval (1OFF-2ON) of intermittent androgen deprivation (IAD) as prognostic for time to castration resistance (CRPC) and prostate cancer mortality (PCM) in men with biochemical relapse (BR).

4557 Background: A recent phase III trial of intermittent vs. continuous AD supports IAD as standard of care for men treated with AD for BR. To identify potential prognostic factors during 1OFF, times to T and PSA rises from our prospective trial of IAD in men with BR were analyzed in relation to times to CRPC and PCM. Methods: 72 men with BR after definitive local therapy were treated with IAD, each cycle consisting of 9 months of leuprolide and flutamide followed by a variable “off treatment” interval. T and PSA were followed monthly; AD was resumed when PSA reached a pre-specified value. Cycles repeated until CRPC, defined as ≥2 PSA rises with T≤50 ng/dL. Markers of interest from 1OFF-2ON were time to first T>50, time from first T>50 to first PSA rise ≥0.1 ng/mL, time to first PSA rise ≥0.1, and PSA doubling time (PSAdt), calculated using the first 3 PSA measurements starting from first PSA ≥0.1. The associations of these markers with CRPC and PCM were evaluated using Cox proportional hazards models (o...