Definitive Radiotherapy for Locally Advanced Adenoid Cystic Carcinoma of the Maxillary Sinus: A Case Report

Adenoid cystic carcinoma (ACC) is a rare malignant tumor of the salivary glands, characterized by slow growth, marked local aggressiveness, and a strong tendency for perineural invasion. Due to nonspecific symptoms, diagnosis is often delayed, and tumors are frequently locally advanced at presentation. While surgery is the standard treatment for resectable disease, definitive radiotherapy is a valid alternative for inoperable cases. We report a case of ACC of the maxillary sinus, staged T4bN2bM0, treated with definitive volumetric modulated arc therapy (VMAT) radiotherapy, with sustained locoregional control at one year. A 56-year-old chronic smoker was diagnosed with ACC of the right maxillary sinus, staged T4bN2bM0, and considered inoperable. The patient was treated with definitive radiotherapy (69.96 Gy; VMAT technique). A partial response was observed on early post-treatment assessment, with sustained locoregional control after one year of follow-up. Definitive radiotherapy can provide effective locoregional control in inoperable cases of ACC, although long-term follow-up remains essential because of the risk of late recurrence.