REFERENCE RANGE FOR PROSTATE-SPECIFIC ANTIGEN LEVELS AFTER EXTERNAL-BEAM RADIATION-THERAPY FOR ADENOCARCINOMA OF THE PROSTATE

Objectives. To determine a reference range for prostate-specific antigen (PSA) in patients who have had external beam radiation therapy for adenocarcinoma of the prostate. Methods. Serum PSA levels were serially measured with the Hybritech Tandem-R assay in 35 patients who had completed radiation therapy for a mean of 51 +/- 32 months (range, 10 to 133). Results. Serum PSA levels that were greater than 2.0 ng/mL (n = 20) continued to rise at a rate of more than 1 ng/mL per year, whereas levels between 0.0 and 2.0 ng/mL (n = 15) remained stable for an average of 71 +/- 32 months (range, 22 to 133). One of these latter 15 patients had a false-negative PSA level when he experienced a biopsy-positive prostate nodule and positive bone scan 43 months after therapy. Conclusions. Prostate cancer control after radiation therapy was indicated in most men by a PSA reference range of 0.0 to 2.0 ng/mL. Cancer activity was indicated in all men with levels above this range.