A phase II trial of arc-based hypofractionated IMRT in localized prostate cancer.

Abstract

e15016 Background: To evaluate acute and late genitourinary (GU) and gastrointestinal (GI) toxicity and biochemical control of hypofractionated, image guided (fiducial markers and/or ultrasound guidance), simplified intensity modulated arc therapy (SIMAT) for localized prostate cancer. Methods: This phase II prospective clinical trial for T1a-2cNXM0 prostate cancer enrolled 66 patients who received 63.2Gy in 20 fractions over four weeks. Fiducial markers were used for image guidance in 30 patients and daily ultrasound (SonArray or ReStitu) for the remainder. Toxicity was scored according to the National Cancer Institute Common Terminology Criteria for Adverse Events version 3.0. Results: Median follow-up was 36 months. Acute phase grade 2 toxicity was 34% and 25% for GU and GI symptoms, respectively. Acute grade 3 toxicity was 9% and 10% for GU and GI symptoms respectively. One patient with unrecognized Crohn's disease developed an acute grade 4 acute GI toxicity. Late grade 2 GU and GI toxicity was 14% and 25% respectively. Late grade 3 GU and GI toxicity was observed in 5% and 3% respectively. One late GI grade 4 toxicity was observed in a patient with significant comorbidities (anticoagulation, vascular disease). Acute GI toxicity > grade 2 was shown to be a predictor for late GI toxicity grade > 2 (p < 0.001). This trend was not seen for GU toxicity. The biochemical disease-free survival at three years was 95%. Conclusions: Hypofractionated SIMAT radiotherapy given as 63.2 Gy in 20 fractions is feasible with promising biochemical control rates. However, ongoing randomized controlled trials will ultimately clarify issues regarding patient selection and the true rate of severe toxicity that can be directly attributed to hypofractionated radiotherapy. No significant financial relationships to disclose.