Cumulative late genitourinary and gastrointestinal toxicity was more common with hypofractionated radiotherapy compared with that of conventionally fractionated radiotherapy in patients with prostate cancer, a study published in the journal The Lancet Oncology has shown.1
Because previous research has suggested that hypofractionation may enhance the biological tumor dose without increasing genitourinary and gastrointestinal toxicity, researchers sought to evaluate this theory in patients with intermediate- and high-risk prostate cancer.
Previously reported data on the incidence of acute toxicity in this trial demonstrated that hypofractionated radiotherapy was not non-inferior to standard fractionated radiotherapy. Here, researchers reported the incidence of late toxicity.
For the study, researchers enrolled 820 intermediate-risk or high-risk patients aged between 44 and 85 years with T1b-T4NX-0MX-0 prostate cancer. Patients had a prostate-specific antigen of 60 ng/mL or lower and a WHO performance status of 0 to 2.
Participants were randomly assigned 1:1 to receive either standard fractionation with 39 fractions of 2 Gy in 8 weeks (5 fractions per week) or hypofractionation with 19 fractions of 3.4 Gy in 6.5 weeks (3 fractions per week).
Results showed that after a median follow-up of 60 months, the incidence of grade 2 or worse genitourinary toxicity at 3 years was 39.0% (95% CI, 34.2 – 44.1) in the standard fractionation group compared with 41.3% (95% CI, 36.6 – 46.4) in the hypofractionation group (HR, 1.16; 90% CI, 0.98 – 1.38).
Furthermore, researchers found that he incidence of grade 2 or worse gastrointestinal toxicity at 3 years was 17.7% (95% CI, 14.1 – 21.9) in standard fractionation arm vs 21.9% (95% CI, 18.1 – 26.4) with hypofractionated radiotherapy (HR, 1.19; 90% CI, 0.93 – 1.52).
Cumulative grade 3 or worse late genitourinary adverse events were significantly more common in the hypofractionation group (19.0%; 95% CI, 15.2 – 23.2) than in the conventional fractionation group (12.9%; 95% CI, 9.7 – 16.7; P = .021); however, there was no significant difference in the incidence of cumulative grade 3 or worse late gastrointestinal toxicity between the 2 groups (P = .55).
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Although these findings suggest that hypofractionated radiotherapy was not non-inferior to standard fractionation with respect to late toxicity, efficacy outcomes are necessary to fully determine the utility of hypofractionation in this setting.
- Aluwini S, Pos F, Schimmel E, et al. Hypofractionated versus conventionally fractionated radiotherapy for patients with prostate cancer (HYPRO): late toxicity results from a randomised, non-inferiority, phase 3 trial [published online ahead of print March 8, 2016]. Lancet Oncol. doi: 10.1016/S1470-2045(15)00567-7.