Prediction of survival benefit from docetaxel chemotherapy with PSA response and PSA half-life in men with metastatic hormone refractory prostate cancer

Abstract

16126 Background: Docetaxel (D) has been shown to prolong survival in men with hormone refractory prostate cancer (HRPC). However, this treatment is not without side effects and asymptomatic patients may not wish to pursue toxic treatment if they would not be expected to obtain a survival improvement. A prostate specific antigen (PSA) reduction of ≥50% from baseline 90 days post- treatment has been identified as a potential surrogate for survival benefit from D, but if an earlier surrogate could be found, it would allow patients who would not benefit from treatment to stop sooner. PSA doubling time (PSADT) has been identified as a potential surrogate marker for survival in patients at risk for progression after local curative treatment or HRPC. We propose that PSA half-life (PSAHL), may aid in predicting survival patients with HRPC treated with D. Methods: A retrospective chart review of 154 patients with HRPC treated from January 2000 to May 2006 was performed. All patients had metastatic HRPC and received at least one cycle of D. PSA response was calculated and PSAHL was determined for patients with any PSA decline from baseline at 42 and 90 days after starting D. Patients were optimally stratified using the log-rank chi-square statistic and Kaplan-Meier curves were used to estimate overall survival. Results: During the follow-up period, 54% of patients died and 71% experienced biochemical progression. Median overall survival (OS) from initiation of D was 16 months. OS was improved for patients achieving a ≥50% reduction in PSA at 90 days compared to those who did not (22 versus 16 months), but no difference in OS was noted for any stratification based on PSA alone or PSAHL at 42 days. Optimal 90 day PSAHL stratification was obtained at >70 days (OS 15 versus 25 months). Survival benefit found for PSAHL > 70 days remained following multivariate analysis [HR 11.84 (2.95–47.50)]. Conclusions: A 90 day PSAHL > 70 days was associated with a significant OS advantage of 10 months in patients receiving D treatment for HRPC. No survival difference could be predicted by PSA response or PSAHL at 42 days post chemotherapy initiation. No significant financial relationships to disclose.