The severity of late rectal and recto-sigmoid complications related to fraction size in irradiation treatment of carcinoma cervix stage III B.

A retrospective analysis of late rectal and recto-sigmoid complications was carried out of the 203 patients with stage III B carcinoma of uterine cervix, treated using radiation therapy alone during January 1979 to December 1983. The patients were treated with a combination of external irradiation and single intracavitary insertion. External irradiation was randomised to one of the four different fractionation regimens having dose per fraction of 2 Gy, 3 Gy, 4 Gy and 5.4 Gy, delivering with five fractions/week, three fractions/week, two fractions/week and one fraction/week, respectively. The total doses in four different regimens were adjusted using the TDF model. There were 39 cases of late radiation induced rectal and recto-sigmoid complications. The complication rate was correlated with the dose per fraction and TDFs delivered in each regimen. The complication rate of 8.2% for 2 Gy per fraction was increased to 33.33% for 5.4 Gy per fraction. It was found that there is strong correlation (P less than 0.05) between size of dose per fraction and the risk of late complications. Present analysis shows that the empirical models as the NSD and TDF do not predict correctly, the late normal tissue damage for different dose fractionations.