Adjuvant Radiotherapy and Survival in Parotid Gland Adenoid Cystic Carcinoma: A National Cancer Database Analysis

OBJECTIVE: To determine the association of positive margins and adjuvant radiotherapy on overall survival in parotid gland adenoid cystic carcinoma. STUDY DESIGN: Retrospective cohort analysis. SETTING: National Cancer Database from 2004 to 2021. METHODS: The National Cancer Database was queried for patients diagnosed with adenoid cystic carcinoma of the parotid who underwent upfront definitive surgical excision. Kaplan-Meier and Cox proportional hazard modeling were used for data analysis. RESULTS: Of 1360 included subjects, the mean age was 56.1 years (range 18-90), 61.6% were female, and 80.4% were white. Negative margins were reported in 52.0%, with microscopic positive margins present in 29.4% of patients. Total parotidectomy was performed in 52.4%, with facial nerve sacrifice in 36.0%. Adjuvant radiotherapy was given to 78.2% and chemotherapy to 8.7%. Median follow-up was 83.4 months; 10-year overall survival was 63.1%. Patients with positive margins, older age, male sex, and advancing stage were associated with worse overall survival. Adjuvant radiotherapy did not improve overall survival in the entire cohort (P = .8) or in early-stage disease (pT1N0-pT2N0) (P = .15) or microscopically positive margin subgroups (P = .8). CONCLUSION: Surgically resected adenoid cystic carcinoma of the parotid gland frequently exhibits positive margins, with adjuvant radiotherapy given in the majority of cases. With the inherent limitations of retrospective analyses of the National Cancer Database, radiotherapy had no significant difference in 10-year overall survival.