Abstract

Purpose The optimal radiation dose fractionation schedule for localized prostate cancer is unclear. This study was designed to compare two dose fractionation schemes (a shorter 4-week radiation schedule v a longer 6.5-week schedule). Patients and Methods Patients with early-stage (T1 or T2) prostate cancer were randomly assigned to 66 Gy in 33 fractions over 45 days (long arm) or 52.5 Gy in 20 fractions over 28 days (short arm). The study was designed as a noninferiority investigation with a predefined tolerance of −7.5%. The primary outcome was a composite of biochemical or clinical failure (BCF). Secondary outcomes included presence of tumor on prostate biopsy at 2 years, survival, and toxicity. Results From March 1995 to December 1998, 936 men were randomly assigned to treatment; 470 were assigned to the long arm, and 466 were assigned to the short arm. The median follow-up time was 5.7 years. At 5 years, the BCF probability was 52.95% in the long arm and 59.95% in the short arm (difference = −7.0%; 90% CI, −12.6% to −1.4%), favoring the long arm. No difference in 2-year postradiotherapy biopsy or in overall survival was detected between the arms. Acute toxicity was found to be slightly higher in the short arm (11.4%) compared with the long arm (7%; difference = −4.4%; 95% CI, −8.1% to −0.6%); however, late toxicity was similarly low in both arms (3.2%). Conclusion Given the results, we cannot exclude the possibility that the chosen hypofractionated radiation regimen may be inferior to the standard regimen. Further evaluation involving higher dose hypofractionated radiation regimens in contemporary radiation settings is necessary.