Is prostate-specific antigen a surrogate for survival in advanced prostate cancer?

4551 Background: Surrogate endpoints are needed to shorten the duration of Phase III clinical trials in advanced prostate cancer. Prostate-specific antigen (PSA) is the most studied biomarker in prostate cancer. This study attempts to validate PSA endpoints as surrogates for overall survival (OS). Methods: Individual data from 2161 patients with advanced prostate cancer treated in studies comparing bicalutamide (‘Casodex’), either as monotherapy or in combination with an LHRHa, with castration were used in a meta-analytical approach to surrogate endpoint validation. PSA response, several definitions of time to PSA progression and longitudinal PSA measurements were considered. Results: The analyses confirmed the known association between the PSA endpoints and OS at the individual patient level (biomarker association). However, when comparing patients treated with bicalutamide-based treatment or castration, the effect of hormonal intervention on the PSA endpoint did not predict the effect on OS with a high ...