Adjuvant Radiotherapy in pT1-2N0M0 Head and Neck Adenoid Cystic Carcinoma

Evidence regarding the indications and survival benefit of adjuvant radiotherapy (aRT) in pT1-2N0M0 head and neck adenoid cystic carcinoma (HNAdCC) is inconclusive. Lower-staged, node-negative HNAdCC therefore represents a rare, moderate-risk disease category with high variation in adjuvant management depending on patient and physician preferences. Our study investigates the impact of aRT on overall survival (OS) in this rare, moderate-risk disease category.

The 2006 to 2018 National Cancer Database was retrospectively reviewed for patients with pT1-2N0M0 HNAdCC. Multivariable binary logistic and Cox regression models were implemented.

Of 738 patients satisfying inclusion criteria, 379 (51.4%) underwent aRT. Oral cavity primary site (aOR 0.64, 95% CI 0.43-0.96) was associated with lower odds of undergoing aRT (p < 0.05); neck dissection (aOR 1.58, 95% CI 1.09-2.28) and PSM (aOR 1.84, 95% CI 1.30-2.60) were associated with higher odds of undergoing aRT (p < 0.025). Patients undergoing aRT had higher 5-year (94% vs. 86%) and 10-year OS (85% vs. 73%) than those not undergoing aRT (p < 0.001). Adjusting for patient demographics, pathologic features, and treatment, age at diagnosis (aHR 1.05, 95% CI 1.02-1.08, p < 0.001) was associated with worse OS; aRT (aHR 0.30, 95% CI 0.13-0.69, p = 0.005) was associated with higher OS.

Approximately half of patients with pT1-2N0M0 HNAdCC did not undergo aRT, highlighting a possible deviation from evidence-based recommendations and an opportunity for quality improvement in the multidisciplinary care of patients. aRT was associated with higher 5-year and 10-year OS, suggesting that patients with lower-staged, node-negative HNAdCC should be offered aRT to optimize long-term survival.