Integral dose in three-dimensional conformal radiotherapy, intensity-modulated radiotherapy and helical tomotherapy.

AIMS

To evaluate the integral dose to organs at risk (OARs), normal tissue and the whole body in three-dimensional conformal radiotherapy (3DCRT), intensity-modulated radiotherapy (IMRT) and helical tomotherapy for whole pelvic radiotherapy (WPRT) in postoperative endometrial cancer patients.

MATERIALS AND METHODS

We selected 10 patients with endometrial cancer undergoing postoperative WPRT. Plans of 6MV-3DCRT, 18MV-3DCRT, 6MV-IMRT, 18MV-IMRT and helical tomotherapy were developed for each patient. The integral doses to OARs, normal tissue and the whole body were compared.

RESULTS

Compared with 3DCRT, both IMRT and helical tomotherapy significantly improved dose conformity and the integral doses to OARs (8.8-29.9%, P<0.05). Compared with 6MV-3DCRT, IMRT resulted in 13.2 and 11.0% lower integral doses to normal tissue and the whole body, respectively (P=0.00), whereas no significant difference was found with helical tomotherapy. Compared directly with IMRT, helical tomotherapy reduced the integral doses to the rectum and bladder. However, the integral doses to normal tissue were 13.9 and 17.1% higher than 6MV-IMRT and 18MV-IMRT plans, respectively (P=0.00); the integral doses to pelvic bones also slightly increased with helical tomotherapy. The use of 18MV resulted in 5.8 and 2.7% lower integral doses to normal tissue and 4.8 and 2.1% lower integral doses to the whole body in the 3DCRT and IMRT plans, respectively (P=0.00).

CONCLUSIONS

Results show that IMRT and helical tomotherapy offer better conformity and lower integral doses to OARs for postoperative WPRT of endometrial cancers compared with 3DCRT. The integral doses to normal tissue and the whole body were significantly lower with IMRT, whereas no significant difference was found with helical tomotherapy compared with 6MV-3DCRT. Compared directly with IMRT, helical tomotherapy further reduced the integral doses to the rectum and bladder, at the expense of a slightly higher integral dose to pelvic bones and normal tissue. The use of 18MV improved the integral doses to normal tissue and the whole body in both 3DCRT and IMRT.