Individualized clinical target volume delineation and efficacy analysis in unilateral nasopharyngeal carcinoma treated with intensity-modulated radiotherapy (IMRT): 10-year summary

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 a nasopharyngeal mass confined to one side of the nasopharynx and did not exceed the midline. From November 2003 to December 2017, 95 patients were retrospectively included. All patients received IMRT. The CTVs were determined based on the distance from the gross tumor. The contralateral para-pharyngeal space and skull base orifices were spared from irradiation. Results There were three local recurrences and eight regional recurrences in 10 patients during an 84-month follow-up. All local recurrences were within PGTVnx, and all in-field recurrences. No recurrences were found in traditional high-risk areas including contralateral the para-pharyngeal 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.