Acute toxicity after hypofractionated conformal radiotherapy for localized prostate cancer: nonrandomized contemporary comparison with standard fractionation.

PURPOSE: To prospectively study acute rectal and urinary reactions from three-dimensional conformal external beam radiotherapy for localized prostate cancer comparing two hypofractionation regimens with standard fractionation (standard). The hypofractionation regimens were designed to avoid more late reactions in the hypofractionation groups than in the standard group, with the advantage of one-half as many treatment sessions. PATIENTS AND MATERIALS: A total of 56 nonrandomized patients chose hypofractionation delivered at 3 (n = 22) or 3.15 (n = 34) Gy/fraction, 4 d/wk, to a total dose of 60 or 63 Gy within 5 weeks. A total of 74 patients were contemporarily treated with standard fractionation at 2 Gy/fraction, 5 d/wk, to a total dose of 76 to 80 Gy. RESULTS: The differences within patients without complications were not statistically significant in the three groups. However, for acute complications of Grade 2 or worse, the Hypo3.15 group had significantly greater (p = 0.001) complication rates (50%) compared with the standard group (17%). The incidence of patients without acute rectal complications was significantly lower for the Hypo3.15 group compared with the Hypo3 and standard groups. The incidence of rectal Grade 2 or greater complications was correspondingly significantly greater for the Hypo3.15 group than for the Hypo3 and standard groups (p < 0.001). The incidence of patients with urinary complications was not significantly different among the three groups. CONCLUSIONS: Acute rectal reactions were more frequent and intense in the Hypo3.15 group than in the Hypo3 and standard groups. In our study, 60 Gy at 3 Gy/fraction within 5 weeks resulted in acute toxicity similar to that after standard fractionation.