Long-term survival after radiotherapy alone: Radiation therapy oncology group prostate cancer trials

Purpose: We assess the relative importance of the several pretreatment characteristics in predicting death from prostate cancer in patients treated with curative intent with external beam radiotherapy alone. Materials and Methods: Patients entered on 4 prospective phase III randomized trials conducted by the Radiation Therapy Oncology Group between 1975 and 1992 were selected for this analysis if they were deemed evaluable and eligible for the trial, they had received no hormonal therapy with initial treatment and followup information was available. A disease specific survival event was declared if death was certified as due to prostate cancer, complications of treatment or unknown causes with clinically active malignancy. Median followup for patients treated on early and late studies exceeded 11 and 6 years, respectively. Results: Most of the patients (1,557) had tumors clinically staged as T3 (59%), and 87 (36%) with clinically staged T1-2 tumors had pathologically positive lymph nodes. On multivariate analysis Gleason score, clinical stage and nodal status were associated with a less favorable overall and disease specific survival, whereas others factors, such as age and race, were not. A Gleason score of 8 to 10 was associated with a high risk of dying of prostate cancer in the first 5 years (risk ratio 20.0, p = 0.0001). The 10-year disease specific survival for patients with a Gleason score of 2 to 5, 6 to 7 and 8 to 10 was 87, 75 and 44%, respectively, following radiotherapy. Based on published reports these rates were higher than expected with observation alone. Conclusions: In the first 10 years Gleason score was the single most important predictor of death. Gleason score should be incorporated into the current clinical staging system.