Extreme hypofractionation for high-risk prostate cancer: Dosimetric correlations with rectal bleeding

The higher relative dose volumes to the rectum (V20-V40) were most strongly associated with clinically significant bleeding in this analysis and are consistent with findings of series that used H-SIB to treat prostate only. Differences in the prostate target volumes and planning margins likely account for the differences in the rates and grades of rectal bleeding observed between trials.