The dosimetric comparision and evalution of 3-dimensional conformal radiation therapy (3D-CRT) , IMRT and tomotherapy techniques in nasopharyngeal cancer

Abstract

Nasopharyngeal cancer is one of the most common head and neck cancers. Approximately 68% of NPC patients suffer from locally advanced disease at the time of diagnosis. The purpose of this study is to compare the dosimetric parameters and evaluate the techniques of Three-Dimensional Conformal Radiotherapy (3D-CRT), intensity modulated radiation therapy (IMRT) and helical tomotherapy (HT) in advanced nasopharyngeal carcinoma (NPC) to help choose the optimal technique for nasopharyngeal patients. Materials and methods: A total of 15 patients with NPC were retrospectively used for replanning radiation therapy techniques with IMRT, HT and 3D-CRT. The prescribed dose of PTV (Planning target volume) for the primary tumor and metastatic lymph nodes was 70 Gy in 33 fractions and for high-risk subclinical areas 59.4 Gy in 33 fractions. Dosimetric parameters of PTVs and organs at risk (OARs) as well as treatment time were measured and compared by paired t test. Results: Compared with 3D-CRT and IMRT plans, HT plans significantly improved the mean conformity index (CI) and homogeneity index (HI) and mean dose of the target volume. Also, it reduced the dose reached to the OARs compared to the 3D-CRT and IMRT. The treatment time of the 3D-CRT was significantly less than the HT and IMRT. But in terms of tumor coverage and dosimetry accuracy and protection of some OARs, it was worse compared to the HT and IMRT.