Outcome and predictive factors for patients with Gleason score 7 prostate carcinoma treated with three-dimensional conformal external beam radiation therapy.

Abstract

The purpose of this study was to determine the biochemical outcome and factors predictive of outcome in prostate carcinoma patients with Gleason score 7 tumors who were treated with three-dimensional conformal radiation therapy (3DCRT). Between August 1990 and October 1997, 163 T1-T3NXM0 prostate carcinoma patients with Gleason score 7 were treated with definitive 3DCRT alone. The median follow-up, International Commission on Radiological Units dose, and pretreatment prostate specific antigen (PSA) for the entire group were 50 months, 76 grays (Gy), and 11.4 ng/mL, respectively. Independent predictors based on multivariate results were used to stratify the patients into prognostic groups for which biochemical no evidence of disease (bNED) control was reported. Biochemical NED failure was defined according to the American Society for Therapeutic Radiology and Oncology Consensus Panel definition. The 5-year bNED control for all patients was 66%. Stratified by pretreatment PSA, 5-year bNED control rates were 83%, 65%, and 21% for 0-9.9 ng/mL, 10-19.9 ng/mL, and > or =20 ng/mL, respectively. Dose to the central axis was found to be a significant treatment factor, with patients receiving > or =76 Gy experiencing 76% 5-year bNED control versus 54% when treated with <76 Gy to isocenter. Pretreatment PSA, dose, and palpation stage were significant independent predictors for bNED control upon multivariate analysis. Patients with a PSA <10 ng/mL who received a dose of > or =76 Gy had excellent 5-year bNED control of 100% compared with 50% bNED if patients had PSA >10 ng/mL or received radiation therapy doses of <76 Gy. Patients with Gleason score 7 adenocarcinoma who had a pretreatment PSA <10 ng/mL and received doses of > or =76 Gy had excellent 5-year bNED control, emphasizing the importance of higher central axis doses in treating Gleason 7 tumors. Patients with intermediate PSA (10-19.9 ng/mL) also required doses > or =76 Gy. Pretreatment PSA > or = 20 ng/mL portends a very poor bNED outcome for Gleason 7 patients treated with radiation therapy alone, and thus efforts should be directed toward multimodal or long term hormonal treatment strategies.