Dosimetric comparison of postoperative whole pelvic radiotherapy for endometrial cancer using three-dimensional conformal radiotherapy, intensity-modulated radiotherapy, and helical tomotherapy.

BACKGROUND

The use of Intensity-modulated radiotherapy (IMRT) and Helical tomotherapy (HT) is increasing in gynecological cancer patients. No published studies have performed a dosimetric evaluation of whole pelvic radiotherapy (WPRT) using HT for postoperative endometrial cancer. The purpose of this study was to perform a direct dosimetric comparison of three-dimensional conformal radiotherapy (3D-CRT), IMRT and HT plans for WPRT in postoperative endometrial cancer patients, and to evaluate the integral dose to organs at risk (OARs) and normal tissue.

MATERIAL AND METHODS

We selected ten patients with endometrial cancer undergoing postoperative WPRT. Plans for 3D-CRT, IMRT and HT were developed for each patient. All plans were normalized to deliver 50 Gy to 95% of the PTV. The dosimetry and integral dose to OARs and normal tissue were compared. The significance of differences was tested using a paired two-tailed Student t-test.

RESULTS

IMRT were superior to 3D-CRT in dose conformity (conformity index: 0.87 vs. 0.61, p = 0.00) and integral dose to OARs and normal tissue, although a greater volume of normal tissue receiving dose below 10 Gy was observed. The results were similar in HT except that the integral dose to normal tissue increased slightly. Compared directly with IMRT, HT showed better dose homogeneity and lower integral dose to rectum and bladder, but the integral dose to pelvic bones and normal tissue slightly increased.

CONCLUSIONS

In postoperative WPRT of endometrial cancer, IMRT and HT result in better conformity and lower integral dose to OARs compared with 3D-CRT. The integral dose to normal tissue did not increase significantly in IMRT, although a greater volume of normal tissue is irradiated to the dose below 10 Gy. HT further improves the dose homogeneity and integral dose to rectum and bladder, at the expense of a slightly higher integral dose to pelvic bones and normal tissue.