Yoon, F.

5144 Background: The time course of testosterone (TST) recovery after prolonged androgen suppression (AS) is not well established. We examined TST recovery prospectively in prostate cancer (PCa) patients treated with 2 years of AS. Methods: 153 PCa men with pT3N0 or positive margins after radical prostatectomy (RP), or with PSA relapse (persistently detectable postoperative PSA [= 0.2 ng/mL], delayed detectable PSA = 6 months after surgery, or palpable/biopsy proven local recurrence after RP), were treated with radiation (RT) to the prostate bed (60 - 70 Gy in 30 - 35 fractions) plus 2 years of AS as part of a phase II study. AS consisted of nilutamide 100 mg PO tid for 4 weeks, starting within 1 week after completing RT, and busereline acetate 6.6 mg SC every 2 months for 2 years, starting within 2 weeks of nilutamide. The primary endpoint was PSA relapse-free survival. Serum TST levels were measured at baseline, every 4 months during AS, and every 6 months after completing AS. The planned sample size was 150 patients. Time to TST recovery was analyzed using the Kaplan-Meier method. Cox Proportional Hazards regression was used for a multivariate analysis of predictive factors for TST recovery. Results: 122 men completed the planned AS. Median follow up after finishing AS was 36.4 months (range 9.4 - 76.2). A castrate TST level was defined as =1.7 nmol/L (50 ng/dL), with normal levels being 10 - 40 nmol/L. All men achieved castrate TST levels on AS. Table 1 shows TST recovery at 36 months after completing AS and median times to recovery. Median recovery time to normal TST was 27 months, although 8% of men did not recover to above castrate levels by 3 years. On multivariate analysis, younger age (<60 vs. =60) predicted for a significantly shorter recovery time to normal TST (P = <0.0001), while baseline TST (<10 nmol/L vs. =10.0 nmol/L) was of borderline significance (P = 0.06). Conclusions: TST recovery after 2 years of AS is protracted. Older men have significantly longer recovery times. [Table: see text] [Table: see text]