Prostate specific antigen levels during radical radiation therapy and the prediction of outcome in localized carcinoma of the prostate

Abstract There has been substantial interest in the effect of radiation therapy upon serum prostate specific antigen (PSA) levels in patients managed by radiation therapy and their ability to predict the eventual outcome. At our institute, an observational prospective longitudinal study was begun in 1989 to identify prognostic factors for biochemical relapse from among several variables, including PSA levels measured prior to treatment, during treatment, and post-treatment, and to summarize what happens to PSA levels over the course of treatment with radical radiation therapy. A total of 142 patients with adenocarcinoma of the prostate (T 1–4 , N 0 , M 0 ) were radically irradiated (6–7 weeks) between February 1989 and January 1991. Serum PSA levels were recorded weekly during radiation therapy in 117 patients. Of these 117, weekly PSA measurements ranged in completeness from 95 to 113 cases. A number of statistical tests were performed on the data with investigative/exploratory intent. There were 60 biochemical relapses documented in the whole group of 142 patients, with a maximum follow-up of 4.6 years and median follow-up of 3.3 years. Of the candidate prognostic variables tested by univariate analysis, the following emerged as statistically significant (i.e. P χ 2 TREND = 40.7; P χ 2 TREND = 41.6; P t 116 = 7.5; P The end-of-treatment PSA and T category emerged as independently statistically significant prognostic variables predicting biochemical relapse. Using the fitted Cox PH model with these two variables, three distinct prognostic groups were identified. The results using pretreatment PSA instead of end-of-treatment PSA produced similarly distinct prognostic groups. Mean weekly PSA levels measured during treatment exhibited a decreasing tendency, and a statistically significant decrease in PSa from pretreatment to the end of treatment was observed.