Serum PSA half-life as a predictor of survival for hormone-refractory prostate cancer patients: modelization using a standardized set of response criteria.

OBJECTIVE: Changes of serum prostate-specific antigen (PSA) during chemotherapy have been validated as a marker of response for hormone-refractory prostate cancer (HRPC) patients. We retrospectively established new response criteria to assess the risk of death.
METHODS: Two hundred fifty-six chemonaive HRPC patients treated with chemotherapy were included in the analysis. According to PSA half-life (HL) dynamics, three response categories were defined: responders (R), late-progressors (LP) and initial-progressors (IP), that were compared with Working Group (WG) criteria. PSA HL time to failure (TTF) and overall survival (OS) were estimated and compared between HT categories. Multivariate regression analysis was performed to isolate the impact on OS of these response categories. A new predictor of survival, delta-time PSA interval (DeltaT) was described.
RESULTS: PSA HL categories were strongly related with WG criteria (P = 0.0001). PSA HL TTF differed among PSA HL categories: 4.2, 2.3, and 0.9 months for R, LP, and IP patients, respectively, and their respective median OS were 27, 19.7, and 12.3 months (P = 0.0001). For DeltaT > or = 3 versus <3 months, median OS significantly differed: 24.9 months versus 13.2 months (P = 0.0001).
CONCLUSIONS: PSA HL dynamics during chemotherapy were able to accurately predict survival, earlier than WG-defined progression criteria. This criterion should be prospectively evaluated in randomized trials for HRPC patients in order to better estimate the risk of death.