3D conformal radiation therapy (3DCRT) for high grade prostate cancer: a multi-institutional review

Abstract

Purpose: To evaluate the results of 3DCRT and the effect of higher than traditional doses in patients with high grade prostate cancer, we compiled data from three institutions and analyzed the outcome of this relatively uncommon subset of prostate cancer patients. Methods and Materials: The 180 patients with Gleason score 8–10 adenocarcinoma of the prostate were treated with 3DCRT at the University of Michigan Health System, University of California-San Francisco, or Fox Chase Cancer Center. Eligible patients had T1-T4 N0 or NX M0 adenocarcinoma with a pretreatment PSA. Pretreatment characteristics included: median age 72 years, 60.6% Gleason score 8 tumors, 57.6% T1-T2, and median pretreatment PSA 17.1 ng/ml (range 0.3–257.1). The total dose received was <70 Gy in 30%, 70–75 Gy in 37%, and >75 Gy in 33%; 27% received adjuvant or neoadjuvant hormonal therapy. The median follow-up was 3.0 years for all patients and 16% of patients were followed up for at least 5 years. Results: The 5-year freedom from PSA failure was 62.5% for all patients and 79.3% in T1-T2 patients. Univariate analysis revealed that T-stage (T1-T2 vs. T3-T4), pretreatment PSA, and RT dose predicted for freedom from PSA failure. A 5-year overall survival for all patients was 67.3%. Only RT dose was predictive of 5-year overall survival on univariate analysis. Because a significant association was seen between T-stage and RT dose, the Cox proportional hazards model was performed separately for T1-T2 and T3-T4 tumors. None of the prognostic factors reached statistical significance for overall survival or freedom from PSA failure in T3-T4 patients or for overall survival in T1-T2 patients. Lower RT dose and higher pretreatment PSA predicted for PSA failure on multivariate analysis in T1-T2 patients. Conclusion: This retrospective study from three institutions with experience in dose escalation suggests a dose effect for PSA control above 70 Gy in patients with T1-T2 high grade prostate cancer. These results are superior to surgery and emphasize the need for dose escalation in treating Gleason 8–10 prostate cancer.