Serum prostate-specific antigen in monitoring the response of carcinoma of the prostate to radiation therapy.

In order to assess the value of serum prostate-specific antigen (PSA) levels in the monitoring of patients with localized prostatic carcinoma undergoing radical radiation therapy, 146 previously untreated patients were entered into this study. Sixty to 70 Gy were administered to the prostate over 8 to 9 weeks. Serum PSA levels were measured prior to radiotherapy, every 3 months during the first year and every 6 months thereafter. Median follow-up was 28 months. Pretreatment PSA values exceeded 10 ng/ml in 62% (91/146). Initial PSA values were correlated with tumor size and Gleason score. Six months after completion of radiation therapy, PSA levels decreased as compared to initial value in 88.3% of the patients. It had fallen to 10 ng/ml or less in 54 (59%) out of the 91 patients with initial abnormal PSA levels. Patients whose initial PSA exceeded 50 ng/ml attained levels of 10 ng/ml or less in only 19% of the cases (6/32). Only 3 of the 55 patients (5.5%) with both initial and 6-month PSA values less than or equal to 10 ng/ml developed metastasis. Out of the 91 patients with initial PSA values over 10 ng/ml, 54 (59.6%) had a 6-month PSA level of 10 ng/ml or less, and only 4/54 (7.4%) relapsed. By contrast, 13 of the 37 patients (35.1%) with a 6-month PSA value persistently above 10 ng/ml relapsed. The 3-year relapse-free survival is 85.1% for patients with a 6-month PSA level less than or equal to 10 ng/ml, and 50.2% for patients with persistently elevated PSA values.(ABSTRACT TRUNCATED AT 250 WORDS)