Hypofractionated radiotherapy beneficial for favorable-risk prostate cancer
MedWire News: Hypofractionated radiotherapy delivering a high biologically equivalent dose (BED) offers excellent biochemical control and an acceptable rate of late toxicity in patients with favorable-risk prostate cancer, Canadian study findings indicate.
In contrast to other tumors, prostate cancer has a low α/β ratio, indicating that hypofractionated radiotherapy would not only improve the therapeutic ratio but also allow a shortening in the overall treatment time.
Noting that there has been little experience with hypofractionated regimens delivering a high BED, compared with conventional fractionated regimens, in prostate cancer, Sergio Faria and colleagues from McGill University Health Centre in Montreal, Quebec, administered three-dimensional conformal radiotherapy plans to a 66-Gy dose in 22 fractions to 129 patients with favorable-risk prostate cancer.
The planning target volume was the prostate plus a uniform 7-mm margin, including the rectal margin. The Common Toxicity Criteria version 3 was used to grade toxicity, and biochemical relapse was defined as a postradiotherapy nadir prostate-specific antigen (PSA) level of +2 ng/ml. Hormonal therapy was not used.
Up to the first 3 months following radiotherapy, 83% of patients had no gastrointestinal (GI) symptoms, 13% had Grade 1 and 4% Grade 2 toxicity. Genitourinary (GU) toxicity was absent in 66% of patients up to 3 months’ follow-up, while 25% had Grade 1, 8% Grade 2, and 1% Grade 3 toxicity. In all, 57% of patients had neither GI nor GU toxicity during the first 3 months following treatment.
Late GI and GU toxicity – defined as toxicity detected at each patient’s last follow-up, was absent in 86% and 77% of patients, respectively. The worst late GI toxicity grade was Grade 2 or 3 in 25% of patients and Grade 1 in 33% of patients. For late GU toxicity, the worst grade was Grade 3 in 4% of patients, Grade 2 in 28%, and Grade 1 in 47%.
The team reports in the International Journal of Radiation Oncology Biology Physics that, after a median follow-up of 51 months, the 5-year actuarial biochemical control rate was 98%. Just six patients died between 10 and 41 months after treatment, none from prostate cancer.
“Overall, the crude risk and severity of chronic late GI and GU toxicity seems to be in line with other fractionation schemes that delivered similar BED and the rate of permanent late complication is low,” the researchers conclude.
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By Liam Davenport