Correlation between serum PSA and testosterone (T) kinetics in patients (pts) with biochemically relapsed prostate cancer (BRPC) (M0), after local treatment (tx), treated with intermittent androgen deprivation (IAD).

Abstract

4641 Background: IAD is often applied in BRPC (M0) after local tx. Criteria for initiation of androgen deprivation therapy (ADT) and evaluation based on PSA dynamics remain poorly defined. Shortening of PSA doubling time (PSADT) following repeated cycles has been reported as a common development in pts treated by IAD. Aims: To analyze the correlation between serum PSA and T dynamics following discontinuation of ADT in pts with BRPC (M0) treated with IAD. Methods: Data on pts with BRPC (M0) treated by IAD were retrospectively analyzed. Pts received 6-9 months (ms) of ADT discontinued when PSA nadired. Pts were followed with PSA, and T every 3 ms. The PSA threshold for re-tx was defined according to PSADT (PSA range of 10-15ng/ml, 15-20 ng/ml, and 20-30ng/ml for PSADT of ≤3ms, 3-9 ms, and ≥ 9 ms, respectively). IAD was continued until PSA refractoriness or development of progression of disease as evident by physical exams or scans. The correlation between the PSADT and T recovery kinetics was analyzed. Mixed effects model was used to study the dynamic change of PSADT over cycles. Results: Between 1994-2008, 76 pts received a median of 2.3 (range 1-9) cycles of IAD.The median off tx time between cycles was 17.9 mos (2-132 range). With an overall mean follow up time of 50.8 months (6-172 range), 52 pts (68%) remain on tx and 21 pts (28%) have demonstrated evidence of PSA refractoriness (n=6) or radiological progression (n=15). 3 pts (4%) were lost to followup. Evaluation of all PSA values from time of discontinuation (nadir PSA) to re-initiation of ADT (off tx period) demonstrated a progressive shortening of PSADT with each consecutive cycle (decrease of 2.11 ms per unit cycle, p<.0001). However, PSADT calculation including only PSA values obtained after a serum T >100ng/ml was reached, did not show significant shortening over time (decrease of 0.05 ms per unit cycle, p=0.2968). Conclusions: Evaluation of PSADT considering T kinetics in pts treated with IAD may provide more reliable information on PSA dynamics. This approach should be investigated prospectively and, if validated, applied in clinical practice and clinical trials. No significant financial relationships to disclose.