Intensity-modulated radiotherapy, volume-modulated arc therapy and helical tomotherapy for locally advanced nasopharyngeal carcinoma: a dosimetric comparison

Nasopharyngeal carcinoma (NPC) has been one of the most common cancers in southern China, particularly in the provinces of Guangdong, Guangxi and Hunan. For a long time, radiation therapy (RT) has remained a primary treatment modality for non-metastatic NPC due to its structural proximity to tumor with high radiation sensitivity. Over the last decade, many encouraging advances have been made in improving therapeutic index of RT for NPC. Of note, the development of intensity-modulated radiation therapy (IMRT) has greatly improved the quality-of-life for NPC patients (1-3). However, IMRT has some inherent drawbacks. The plan of a step-and-shoot IMRT (SaS-IMRT) delivered by a linear accelerator is generally so complex that approximately 7 to 9 beams are usually required for achieving a decent dose distribution within target. It greatly increased delivery time and monitor units (MUs). Firstly, prolonged delivery time decreased efficiency and increased intrafraction setup errors during treatment (4,5). Secondly, high number of MUs boosted scattered radiation and integral radiation dose so as to elevate the risks of secondary tumors in patients (6)