Individualized Clinical Target Volume Delineation and Efficacy Analysis in Unilateral Nasopharyngeal Carcinoma Treated with Intensity-Modulated Radiotherapy (IMRT): 10-Year Summary and Results

Abstract Purpose: To evaluate the long-term local control, failure patterns, and toxicities after individualized clinical target volume (CTV) delineation in unilateral nasopharyngeal carcinoma (NPC) treated with intensity-modulated radiotherapy (IMRT).Methods: Unilateral NPC was defined as nasopharyngeal mass confined to one side of nasopharynx and did not significantly exceed the midline of nasopharyngeal apex/posterior wall. From November 2003 to December 2017, 95 patients with long-term follow-up were retrospectively included. All patients received IMRT. The CTVs were determined based on the distance from the gross tumor, the contralateral parapharyngeal space and skull base orifices were spared from irradiation.Results: There were 3 local recurrence and 8 regional recurrences in 10 patients during 84- month follow-up. All local recurrences were PGTVnx-in-field, and no recurrences in traditional high-risk area including contralateral parapharyngeal space and skull base orifices. The 10-year local-recurrence free survival, regional-recurrence free survival and overall survival were 96.2%, 90.5% and 84.7%, respectively. The dosimetry parameters of the tumor-contralateral organs were all lower than the values of the tumor-ipsilateral side (P < 0.05). The late toxicities occurred mainly in the tumor-ipsilateral organs, including radiation-induced temporal lobe injury, impaired visuality, hearing loss and subcutaneous fibrosis.Conclusion: Individualized CTV delineation in unilateral NPC could yield excellent long-term local control with limited out-of-field recurrences, reduced dose to tumor- contralateral organs and mild late toxicities, which is worthy of further exploration.