Race and Survival of Men Treated for Prostate Cancer on Radiation Therapy Oncology Group Phase III Randomized Trials

Abstract

We assessed the impact of race on survival in men treated with external beam radiotherapy with or without hormonal therapy for localized prostate cancer in Radiation Therapy Oncology Group randomized trials. Between 1975 and 1992, 2,048 men were treated for clinically localized prostate cancer in 1 of 4 consecutive prospective phase III randomized trials. After excluding nonblack and nonwhite men 2,012 remained for analysis. Patients were included in this analysis if they were deemed evaluable and eligible for the trial, and followup information and centrally reviewed pathological results were available. Short-term hormonal therapy consisted of goserelin acetate and flutamide administered 2 months before and during radiotherapy. Long-term hormonal therapy consisted of adjuvant goserelin acetate, which was generally given for 2 years or more. Pretreatment prostate specific antigen (PSA) findings were available in 430 cases (21%), including 213 treated with radiotherapy alone, 60 treated with short-term hormonal therapy and 157 on long-term hormonal therapy. Mean pretreatment PSA was 68.8 and 35.2 ng./ml. in black and white patients, respectively. Cox proportional hazards models were used to identify the impact of previously defined risk groups on overall and disease specific survival. Multivariate analysis was done for the significance of race using a stratified Cox model. Median followup in patients treated in early and late studies exceeded 11 and 6 years, respectively. On univariate analysis black race was associated with lower overall and disease specific survival (p = 0.04, RR = 1.24 and p = 0.016, RR = 1.41, respectively). After adjusting for risk group and treatment type (with or without short-term or long-term hormonal therapy) race was no longer associated with outcome (p >0.05). The trend for a persistent difference in survival was likely due to the higher tumor burden in black men, as reflected in higher PSA. As previously reported, tumor grade (Gleason score), palpation T stage, lymph node status, pretreatment PSA and treatment type are major predictors of overall and disease specific survival. We noted no evidence that race has independent prognostic significance in patients treated for prostate cancer in Radiation Therapy Oncology Group prospective randomized trials.