RADIOTHERAPY FOR HIGH-GRADE CLINICALLY LOCALIZED ADENOCARCINOMA OF THE PROSTATE

Purpose: We defined the efficacy of radiotherapy for the treatment of high grade (Gleason scores 8 to 10) adenocarcinoma of the prostate. Ma terials and Methods: A total of 50 patients underwent radiotherapy wit h curative intent for clinically localized prostate cancer with Gleaso n scores of 8 to 10 at 1 of 4 facilities affiliated with the Universit y of California San Francisco. Patients were considered to have bioche mical failure if they had a significant increase in prostate specific antigen (PSA) of 0.5 ng./ml. per year, an increase in PSA to greater t han 1.0 ng./ml. or a positive biopsy. Results: Among the 50 patients m edian PSA was 22.7 ng./ml. (range 1.3 to 93.4). Tumors were clinical s tage T1 or T2 in 46% of the cases and stage T3 or T4 in 54%. The overa ll actuarial probability of freedom from biochemical failure at 4 year s was 23%. In a multivariate analysis including all patients pretreatm ent PSA was the only predictor of PSA failure, with 64% free of progre ssion if the pretreatment PSA was 10 ng./ml. or less compared to only 16% at 3 years if PSA was more than 10 ng./ml. (p = 0.01). In a multiv ariate analysis restricted to patients with PSA less than 20 ng./ml. 8 3% of those treated to more than 71 Gy. were free of progression compa red to 0% for those treated to less than 71 Gy. (p = 0.03). In a multi variate analysis PSA 10 ng./ml. or less (related risk 11.4, p = 0.02), T stage 1 or 2 (relative risk 3.8, p = 0.05) and radiation dose more than 71 Gy. (relative risk 4.0, p = 0.06) were associated with a favor able outcome. Conclusions: At 4 years the freedom from PSA failure fol lowing radiotherapy for high grade prostate cancer was comparable to p reviously reported surgical series. The high failure rate among patien ts with PSA greater than 20 ng./ml. suggests that these patients shoul d be considered for investigational approaches. The apparent improveme nt in freedom from progression with the use of higher doses provides r eason for optimism.