Small bowel toxicity in pelvic radiotherapy for postoperative gynecological cancer: comparison between conformal radiotherapy and intensity modulated radiotherapy

Abstract

Aims: To compare the dosimetric advantages of pelvic intensity modulated radiotherapy (IMRT) with three-dimensional conformal radiotherapy (3D CRT) in small bowel dose reduction and dosimetrically correlate the clinical benefit, if any.

Methods: This retrospective study included 60 patients with gynecological cancers treated postoperatively with radiotherapy to the whole pelvis. Radiation Therapy Oncology Group (RTOG) contouring guidelines were used for contouring the pelvic nodal stations. All plans were generated using Plato Sunrise treatment planning system. The RTOG acute morbidity scoring criteria were used to define acute small bowel toxicity in our patients. Treatment was delivered using the Elekta Precise system. Patients were followed up twice weekly while on treatment. Statistical analyses (Spearman's rho and Kruskal-Wallis test) were performed using SPSS software (vers. 15).

Results: In all, 65% were postoperative endometrium carcinoma and 35% were postoperative cervix carcinoma patients; 34 patients were treated with IMRT and 26 patients underwent 3D CRT. In all, 28 patients experienced ≥ grade 2 small bowel toxicity (eight in the IMRT group). IMRT was able to significantly reduce the dose to bowel for doses above 30 Gy. Small bowel toxicity showed no correlation with doses below 30 Gy. The volume of the small bowel receiving more than 35 Gy of radiation was a significant predictor of the need for medication to control diarrhea during radiotherapy.

Conclusion: Use of IMRT resulted in lower doses to the small bowel, resulting in lesser toxicity, and translated to the better tolerability of pelvic radiotherapy.

Keywords: IMRT; bowel toxicity; pelvic radiotherapy.