Dosimetric characteristics of tomotherapy and three-dimensional conformal radiotherapy for head and neck cancer

This study aims to evaluate and compare Three-Dimensional Conformal Radiotherapy (3D-CRT) versus Helical Tomotherapy (HT) based on treatment planning and selection of the most appropriate method to reduce side effects.

Treatment planning was performed on images of 20 patients with head and neck cancer with lymph node involvement by HT and 3D-CRT techniques in Seyed Al-Shohada hospital, Isfahan, Iran. The quality of target coverage, the exposure of normal tissue, and radiation delivery efficiency in two studied methods were compared.

Tomotherapy showed significant improvement over 3D-CRT in terms of D2%, D50% Dmean, V95%, CI (conformity index), and HI (homogeneity index) for PTV (planning target volume) and in terms of D2%, D98%, Dmean, V95%, CI and HI for PTV Nodal. The mean dose received by 98% of PTV (D98%) increased in HT compared to 3D-CRT. Whereas, higher doses received in organs at risk (OARs) in 3D-CRT compared to HT.

Results showed improvements in target quality for HT over 3D-CRT, including dosimetric coverage of target volumes, homogeneity and conformity indices, and reduction of the volume of cold and hot spots. Tomotherapy also performed better than that of 3D-CRT in OARs. Overall, with the satisfactory results obtained here, HT technique has considerable promise for treating head and neck cancers with the involvement of regional lymph nodes.