Expanding role of radiotherapy in adenoid cystic carcinoma of the tracheobronchial tree: a new horizon.

BACKGROUND Primary adenoid cystic carcinomas (ACCs) of central trachea-bronchi system are rare and heterogeneous tumors. Definitive radiotherapy (RT) is the recommended treatment in surgically unresectable or incomplete resection or in the presence of severe comorbidities. OBJECTIVE To evaluate the clinical features and outcomes of patients with ACC of trachea-bronchi treated with radiotherapy. METHODS Retrospective medical records review was done in all patients with histologically confirmed ACC of trachea-bronchi between January 2010 and December 2019. Patient disease and treatment characteristics and toxicity data were analyzed. Overall survival (OS), local recurrence-free survival (LRFS), and distant metastasis-free survival (DMFS) were computed using Kaplan-Meier method (log-rank test). RESULTS Nineteen patients (10 women and 9 men) were included in this analysis with median age of 40 years (range, 14-70). Of these patients, 63.2% (n = 12) presented in stage IV disease. Twelve and three patients received definitive (median dose 67.8 Gy) and adjuvant (median dose 50 Gy) RT, respectively. The median follow-up was 42.5 months (range, 4-120); 15 patients were alive and 4 were dead at that time. Local recurrence or progression was observed in 52.6% and distant metastasis found in 47.3% of patients. The 5-year OS, LRFS, and DMFS for all patients were 81.2%, 52.8%, and 39.6%, respectively. Baseline lymph node involvement showed significant impact on OS (56.3% vs 100%, p = 0.011). Among patients receiving definitive RT, patients with higher RT dose (⩾66 Gy) had significantly better survival outcomes (5-year LRFS: 75% vs 16.7%, p = 0.013). CONCLUSION Definitive RT is an exemplary treatment for unresectable disease. Higher dose is recommended to improve long-term outcomes.