Predictive Value Of Psa Halving Index (Psahi) In Patients (Pts) With Hormone Refractory Prostate Cancer (Hprc): Results From A Randomized Phase Ii Trial With Docetaxel (D) +/- Estramustine Phopshate (E)

15548 Background: D-based chemotherapy represents the standard treatment for HRPC pts. For several years PSA has been considered as a surrogate endpoint for studies involving pts with HRPC. The possibility of predicting a clinical advantage through the biochemical response rate is controversial. The PSAHI may represent a predictive parameter more than the simple PSA trend. We retrospectively evaluated the role of PSAHI in a consecutive series of patients affected by HRPC and treated in a randomized phase II trial with D±E. Methods: 95 pts affected by HRPC were randomized to D 70 mg/m2 IV d1 q3w (arm A: 49 pts) or D 70 mg/m2 IV d1 q3w + E 280 mg/TID PO starting 1 day prior to D, for 5 consecutive days (arm B: 46 pts). The treatment continued until best PSA response achievement or PSA progression. PSAHI was calculated comparing basal value (the day before first D administration) with those reached after every cycle at 21, 42, 63 and 84 days: each median value was then correlated across all pts. Correlations were made with response, time to progression (TTP) and overall survival (OS). Results: Responses, in terms of PSA? >50% were: 40% in arm A and 75%in arm B with PSA normalization in 5% and 32% respectively. After a median follow-up of 17 months, 65 patients are died (31 in Arm A and 34 in Arm B). Progression free survival (biochemical) was 20 weeks in arm A and 30 in B. Median PSAHI was 2.1 (0.8–8.8) and resulted significantly related to response and TTP: pts with PSAHI less than 1 and more than 1 had a median TTP of 14 and 34 weeks respectively. Between the 4 PSAHI analyzed (after 21, 42, 63 and 84 day), those at 42 and, particularly, 63 day resulted statistically related to response, TTP and OS. After 3 cycles, the PSA decline (63-PSAHI) was highly predicyive of OS which was 63, 72 and 90 weeks respectively (p=0.03), for pts with PSAHI of less than 1, between 1 and 3 and more than 3. Conclusions: PSAHI seems to be highly predictive of TTP and OS. 63-PSAHI seems to be a good surrogate marker of D response and may help in discriminating pts who need to be further treated with D and those who do not. No significant financial relationships to disclose.