Determinants of small bowel toxicity in postoperative pelvic irradiation for gynaecological malignancies

Patients treated with postoperative radiotherapy for endometrial and cervical carcinomas from 1981 to 2000 were retrospectively analysed in order to assess the rate of late small bowel toxicity.

Eight hundred and six patients had received pelvic irradiation, with total doses of 40-55 Gy. The mean age was 57 years. Three hundred and eighteen patients had been treated for cervical and 488 for endometrial cancer; 46 had diabetes and 22 vascular diseases; 141 had a history of smoking and 367 were previously submitted to surgery for benign diseases. A CT treatment plan had been applied in 285 patients; 256 had been treated by arc moving therapy, 232 with 2 opposed beams (AP-PA) and 318 with 3 or 4 coplanar beams. Three hundred and forty-six were treated with X photons of 10 MV or more, 202 with 4-5 MV and 258 with cobalt gamma rays. Personalized blocks had been used in 389. Thirty-four women had received chemotherapy. Five hundred and eighty-four had been treated with dose fractions of 180 cGy or more and 56 had received a boost with brachytherapy or external beams. Eighty-one had needed treatment discontinuation due to acute small bowel toxicity.

The median follow-up was 70 months. Thirty five patients had bowel obstructions, after a median time of 31 months. The 5- and 10-year toxicity rates were 4 and 7%. Uni- and multivariate comparisons identified age, acute toxicity and dose fraction as predictors for complications.

Postoperative pelvic irradiation with standard techniques for gynaecological carcinomas results in tolerable rates of clinically significant late bowel damage, while older patients suffering from significant acute toxicity seem to be at higher risk.