Correlation between Irradiated Small Bowel Volume and Toxicity in Rectal Cancer Patients Receiving Concomitant Pelvic Irradiation and 5-Fluorouracil Chemotherapy

Abstract

The aim is to study the relationship between radiation induced small bowel toxicity and radiation dose received by the small bowel during pelvic irradiation for patients with rectal cancer treated with pelvic radiotherapy and concomitant 5-Fluorouracil. Thirty-two patients with rectal cancer were referred for either a postoperative or preoperative pelvic irradiation concomitant with 5-Fluorouracil chem- otherapy at the Radiotherapy Unit of King Abdulaziz University Hospi- tal. All patients had computerized 3D treatment planning. Radiation therapy was given in two phases, to a total dose of 5040 cGy / 28 frac- tions / 5.5 weeks. Small bowel loops were contoured on CT cuts and a dose volume histogram was constructed and the mean radiation dose received by the small bowel, the volume of the small bowel irradiated and the mean radiation dose / volume of small bowel involved ratio. Univariate analysis showed a significant association between small bowel toxicity and mean radiation therapy dose received by small bowel (p = 0.001), the volume of small bowel involved (P = 0.043) and the type of surgical intervention with higher incidence for those patients who had abdominoperineal resection (P = 0.003). In conclu- sion, this study confirms the relation between small bowel toxicity and the volume of small bowel receiving radiotherapy.