Clinical outcomes in a cohort of head and neck adenoid cystic carcinoma patients treated with carbon ion radiotherapy: initial outcomes from Gansu Wuwei Tumor Hospital, China

This study aimed to evaluate the clinical outcomes and identify prognostic factors in a cohort of Head and neck adenoid cystic carcinoma (ACC) patients treated with carbon-ion radiotherapy (CIRT) at our center. Between June 2020 and January 2025, 41 patients with histologically confirmed head and neck ACC were treated with CIRT at our center, including 32 patients who underwent surgery before CIRT and 9 who received definitive CIRT without prior resection. Survival outcomes, therapeutic responses, and toxicities were evaluated. The median follow-up was 27.0 months (interquartile range, 18.0–36.0 months). The estimated 1-, 2-, 3-, and 5-year RFS rates were 85.4%, 75.9%, 65.4%, and 51.8%, respectively. The corresponding OS rates were 97.6%, 94.4%, 90.3%, and 90.3%, respectively. The 1-, 2-, 3-, and 5-year LC rates were 97.4%, 85.3%, 85.3%, and 71.1%, respectively. Multivariate analysis identified recurrent disease, solid histological subtype, and ECOG performance status 2 as independent adverse prognostic factors for RFS. For LC, recurrent disease and ECOG performance status 2 were independently associated with a higher risk of local failure. Notably, no significant difference in survival or local control was observed between patients who underwent prior surgery and those who received definitive CIRT. The treatment was well tolerated, with no grade 3 or higher acute or late toxicities observed. Early outcomes suggest that CIRT is a safe and promising treatment modality for head and neck ACC patients with locally advanced disease, predominantly located in minor salivary glands and sinonasal sites. In this small cohort, preliminary data suggest that definitive CIRT yielded survival and local control trends comparable to surgery followed by CIRT, supporting its potential as a function-sparing alternative for patients unsuitable for radical surgery. Given the indolent clinical course of ACC and the limited follow-up of this cohort, these early findings require confirmation in larger prospective studies with extended follow-up.