Evaluating the reduction of elective radiotherapy fields for de novo metastatic nasopharyngeal carcinoma in the immunotherapy era

Background: This study evaluates the outcomes of omitting the high- and low-risk clinical tumor volume (CTV1 and CTV2) radiation in de novo metastatic nasopharyngeal carcinoma (dnm-NPC) patients in the immunotherapy era. Methods: We retrospectively analyzed 45 consecutive dnm-NPC patients receiving chemotherapy and immunotherapy combined with radiotherapy (CIR) from October 9, 2018 to June 1, 2022. Irradiation was only delivered to the primary tumor and retropharyngeal nodes (GTVnx+rn) and gross cervical lymph nodes (GTVnd). Results: The median follow-up was 45 (range, 15-67) months. There was no recurrence in the omitted elective regions. The 36-month LRRFS, PFS, and OS were 95.4%, 44.6%, and 90.8%, respectively. The main grade 3/4 hematologic toxicities were neutropenia (42.2%), anemia (20.0%), and thrombocytopenia (13.3%). The incidence of acute grade 3/4 dermatitis, mucositis, and xerostomia were 4.4%, 8.9%, and 4.4%, respectively. Conclusions: Omitting CTV1 and CTV2 was well-tolerated and provided favorable clinical outcomes in the era of immunotherapy.