Hypofractionated radiotherapy for favorable risk prostate cancer.

Abstract

Since the recognition that prostate cancer probably has a low alpha/beta ratio, hypofractionated radiotherapy has become an attractive treatment option for localized prostate cancer. However, there is little experience with the use of hypofractionation delivering a high biologically equivalent dose. We report our experience with high-dose hypofractionated radiotherapy. A total of 129 patients with favorable risk prostate cancer were treated with three-dimensional conformal radiotherapy treatment plans to the dose of 66 Gy in 22 fractions, prescribed at the isocenter. Planning target volume consisted of the prostate plus a uniform 7-mm margin, including the rectal margin. No patient received hormonal therapy. Toxicity was prospectively graded by the Common Toxicity Criteria version 3. Biochemical relapse was defined as postradiotherapy nadir prostate-specific antigen + 2 ng/mL. With a median follow-up of 51 months, the 5-year actuarial biochemical control rate is 98%. The only 3 cases with biochemical failure did not have a clinical local relapse. More than 50% of patients did not develop acute toxicity. For late toxicity, the worst crude rate of Grade >or=2 genitourinary (GU) and gastrointestinal (GI) toxicity seen at any time during follow-up were 32% and 25%, respectively. There was no Grade 4 or 5 toxicity. At the last follow-up, persistent Grade >or=2 late GU and GI toxicity were 2% and 1.5%, respectively. This hypofractionated regimen provides excellent biochemical control in favorable risk prostate cancer with an acceptable rate of late toxicity. Further studies exploring this hypofractionation regimen are warranted.