Reliability of prostate-specific antigen-marker in determining biochemical failure during the first 2 years after external beam radiation therapy and hormone therapy in patients with non-operated prostate cancer

ObjectivesThe presence of prostate-specific antigen (PSA)-bounce after external beam radiation therapy (EBRT) and hormone therapy (HT) makes PSA an unreliable marker in determining PSA biochemical failure (PSA-BF) during the first 2 years after EBRT + HT in patients with non-operated prostate cancer (CaP).To determine the reliability of PSA-BF in predicting clinical outcomes, the Kamat definition, which does not consider PSA-BF during the first 24 months after EBRT, was tested against three other more frequently used methods (American Society of Radiation Oncology, Vancouver, and American Society of Radiation Oncology-Phoenix), which do. Secondly, their relative accuracies in predicting the clinical outcomes were also calculated.Materials and methodsIn January 2011, 193 consecutive CaPs, treated with radical EBRT + HT in our institution from 1999 to 2002, were retrospectively investigated. BF was calculated according to the Kamat definition against the other three above-mentioned methods.Each BF-free survival was analyzed in function of every clinical endpoint (clinical-failure-free survival, cause specific survival, and overall survival) using univariate and multivariate Cox regression analyses. The accuracy of each definition in predicting clinical relapse was also calculated and compared.ResultsOnly the Kamat BF definition had both a significant Cox hazard ratio, regarding clinical events or cancer deaths, and the best accuracy values in predicting clinical outcomes. Retrospective study design was the major limitation of the study.ConclusionsOnly the Kamat definition, which does not consider PSA-BF during the first 24 months after EBRT + HT, was shown to be a reliable predictor of clinical events.Thus, our results suggest that solely PSA-based BF should not be considered as a reliable surrogate endpoint during the first 24 months after EBRT + HT. Consequently, caution should be used in adopting rescue treatment without further work-up on an individual basis.