In recent series, severe late rectal morbidity is inferior to 5 %93,131-136. Dose and volume of irradiated rectum are closely connected to late rectal morbidity. Perez137 showed that conformal versus conventional radiotherapy allows a two third reduction in normal bladder or rectum receiving 70 Gy or more; with this technique proctitis was significantly lower (1.7% vs 9.1%). Dearnaley138 in a randomised trial confirmed these results: 5% vs 15% superior or equal RTOG grade 2 proctitis with conformal versus conventional radiotherapy (p=0.01). Boersma131 reported in a dose escalation study the limits above which rectal bleeding was significantly increased: >65Gy to more than 40% of the rectum wall volume, >70 Gy to more than 30%, and >75 Gy to more than 5%. Watcher139 using dose-volume histograms as predictive factors, showed an actuarial incidence of 31% of late rectal bleeding at 3 years (EORTC/RTOG grade 2) if more than 57% of the rectum volume was included in the 90% isodose (60 Gy), versus 11 % if this volume is lower than 57% (p<0.03).
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