Intensity-modulated proton therapy for nasopharyngeal carcinoma: Decreased radiation dose to normal structures and encouraging clinical outcomes.

BACKGROUND Intensity-modulated proton therapy (IMPT) has the potential to spare dose to organs at risk (OAR) when compared to intensity-modulated radiotherapy (IMRT) while maintaining excellent clinical outcomes. METHODS Ten patients with nasopharyngeal carcinoma (NPC) were identified for whom IMPT was planned; 9 patients also had a comparison photon-based IMRT plan generated. Dosimetric comparison of mean radiation dose to 29 adjacent OAR was performed. Disease control, survival, and toxicity outcomes were collected from the medical records. RESULTS There were significant differences in mean doses in 15 of the 29 OAR; 13 OAR received lower mean dose with proton-based plans. Median follow-up was 24.5 months (range, 19-32 months). Two-year locoregional control was 100% and the 2-year overall survival was 88.9%. CONCLUSION We observed dosimetric advantages conferred by IMPT compared to IMRT. Further study is needed to determine if these translate into reduced toxicity and/or improved disease control. © 2015 Wiley Periodicals, Inc. Head Neck 38: E1886-E1895, 2016.