A prospective study on radiation doses to organs at risk (OARs) during intensity-modulated radiotherapy for nasopharyngeal carcinoma patients.

This study is to investigate the dose distribution of organs at risk (OARs) in cases of nasopharyngeal carcinoma (NPC). From July 2013 to October 2014, a prospective cohort study involving 148 patients was carried out at our center. OARs surrounding the nasopharynx were contoured on axial CT planning images in all patients. Dose-volume histograms of OARs and gross tumor volumes (GTV) were calculated. Multivariate analysis showed that radiation dose to OARs was associated with T stage and, especially, GTV. Seven OARs, including the spinal cord, eye and mandible, easily tolerated radiation doses in all patients; six OARs including the brain stem, chiasm and temporal lobe easily tolerated radiation doses in patients with a small GTV, but with difficulty when GTV was large; and other nine OARs including the parotid gland, cochlea and tympanic cavity met tolerance doses with difficulty in all patients. According to the patterns of radiation doses to OARs, it may help us to further reduce subsequent complications by improving the efficiency of plan optimization and evaluation.