PSA doubling time (PSA-DT) during the "off treatment" interval in men with biochemical relapse of prostate cancer treated with intermittent androgen suppression (IAS).

4670 Background: PSA-DT has been shown to be a surrogate marker for mortality in patients who have biochemical relapse after either RP or XRT (D'Amico, J Urol 172 2004). These men are often treated with IAS. The significance of PSA-DT during the "off treatment" period has not been described.,Eugonadal men with biochemical relapse of prostate cancer were treated with IAS. One cycle consists of 9 mos of LHRH analog plus anti-androgen followed by an "off treatment" interval determined by the rise in PSA to an arbitrary value of 1 or 4 ng/ml for RP or XRT patients respectively. A new cycle is then started. PSA-DTs were calculated for patients while "off" therapy for the first cycle and for the last cycle prior to becoming "hormone refractory" (HRPC) or prior to analysis for hormone sensitive patients. Time to HRPC, defined as 2 rising PSAs on hormonal therapy, was determined relative to PSA-DT.,Of 48 patients with median age of 64.5 yrs (range 51-78), 34 had RP and 14 had XRT as primary therapy. The subjects were divided into tertiles based on PSA-DT. For the first cycle, the average time to HRPC in the low, intermediate and high tertiles was 6.2 yrs, 7 yrs, and 10.5 yrs respectively. Using Kaplan-Meier cumulative hazard analysis, the first cycle of IAS therapy demonstrated shorter time to hormone refractoriness with shorter PSA-DT. During the last cycle of IAS, the average time to HRPC for low, intermediate and high PSA-DT tertiles was 1.8 yrs, 7.6 yrs, and 13.2 yrs respectively.,Shorter PSA-DT during the first or last "off treatment" cycle of IAS appears to be associated with a shorter time to develop HRPC in patients who were treated for biochemical relapse after primary therapy. [Table: see text].