Outcome and Toxicity for Patients Treated with Intensity Modulated Radiation Therapy for Localized Prostate Cancer

Purpose: We evaluate long-term disease control and chronic toxicities observed in patients treated with intensity modulated radiation therapy for clinically localized prostate cancer. Materials and Methods: A total of 302 patients with localized prostate cancer treated with image guided intensity modulated radiation therapy between July 2000 and May 2005 were retrospectively analyzed. Risk groups (low, intermediate and high) were designated based on National Comprehensive Cancer Network guidelines. Biochemical control was based on the American Society for Therapeutic Radiology and Oncology (Phoenix) consensus definition. Chronic toxicity was measured at peak symptoms and at last visit. Toxicity was scored based on Common Terminology Criteria for Adverse Events v4. Results: The median radiation dose delivered was 75.6 Gy (range 70.2 to 77.4) and 35.4% of patients received androgen deprivation therapy. Patients were followed until death or from 6 to 138 months (median 91) for those alive at last evaluation. Local and distant recurrence rates were 5% and 8.6%, respectively. At 9 years biochemical control rates were 77.4% for low risk, 69.6% for intermediate risk and 53.3% for high risk cases (log rank p = 0.05). On multivariate analysis T stage and prostate specific antigen group were prognostic for biochemical control. At last followup only 0% and 0.7% of patients had persistent grade 3 or greater gastrointestinal and genitourinary toxicity, respectively. High risk group was associated with higher distant metastasis rate (p = 0.02) and death from prostate cancer (p = 0.0012). Conclusions: This study represents one of the longest experiences with intensity modulated radiation therapy for prostate cancer. With a median followup of 91 months, intensity modulated radiation therapy resulted in durable biochemical control rates with low chronic toxicity.