The prognostic significance of a single serum prostate-specific antigen value beyond six months after radiation therapy for adenocarcinoma of the prostate.

Abstract

The aim of this study was to define criteria for interpreting a single serum prostate-specific antigen (PSA) level measured at 6 months to 5 years after definitive radiotherapy for prostate cancer. Two hundred and ninety-two patients with Stages A2 to C prostate cancer treated with radiotherapy only and followed up with multiple PSA determinations were studied. The patients were stratified into 5 PSA strata based on the highest PSA level recorded for each patient at 6 to 60 months after treatment. The PSA strata and the number of patients in each were: (a) PSA < or = 1 ng/ml, 114 patients; (b) PSA > 1, but < or = 2 ng/ml, 60 patients; (c) PSA > 2, but < or = 4 ng/ml, 48 patients; (d) PSA > 4, but < or = 10 ng/ml, 47 patients; (e) PSA > 10 ng/ml, 23 patients. Disease outcome specified as relapse, rising PSA profile or both was evaluated in each PSA stratum. The actuarial 3-year incidence of relapse in each PSA stratum was: (a) 5%; (b) 0%; (c) 12%; (d) 31%; and, (e) 84%. If the occurrence of a rising PSA profile was included as an endpoint then the incidence of relapse or rising PSA at 3 years in each PSA stratum was: (a) 5%; (b) 14%; (c) 45%; (d) 84%; and, (e) 100%. Patients with a highest late PSA value < or = 4 ng/ml had a 20% incidence of relapse or rising PSA at 4 years; patients with a highest late PSA value > 4 ng/ml had a 90% incidence of relapse or rising PSA at 3 years. A PSA level of 4 ng/ml is a good criterion for prognostication of a single PSA level obtained at 6 months to 5 years after radiotherapy. Patients whose PSA level in that time interval exceeds 4 ng/ml have a poor outcome.