ABSTRACT
Intensity-modulated radiotherapy (IMRT) is gradually replacing conventional radiation therapy and has become the mainstream radical treatment for patients with nasopharyngeal carcinoma (NPC). IMRT can conform and increase radiation doses to tu-mor-associated regions as well as decrease exposure doses and volumes on normal organs and tissues to avoid damage on critical or-gans. Aside from system and setup errors, other factors, such as the gradual reduction of the primary NPC lesion and the decrease in vol-ume of involved neck lymph nodes as well as body weight loss and changes in the head and neck shape during IMRT, may cause devia-tions in the radiation doses and volume delivered to the NPC targets and the organs at risk. These factors may affect the accuracy of IMRT. Several researchers have attempted to correct such deviations during IMRT for NPC patients by using adaptive radiotherapy (ART). The results indicate that ART is feasible to a certain degree and can correct the deviations, including decrease in tumor volume, body weight loss, and changes in head and neck shape of NPC patients.