AB161. SOH25_AB_185. Outcomes of elective neck radiation in adenoid cystic carcinoma: a systematic review and meta-analysis

Background: Adenoid cystic carcinoma (ACC) is a rare head and neck malignancy primarily located in the salivary glands. Management of node-negative (N0) disease in ACC remains contentious, with conflicting evidence and limited guidelines on elective nodal irradiation (ENI). This systematic review and meta-analysis assessed the effect of ENI on clinical outcomes in patients with head and neck ACC.

Methods: Searches were conducted in PubMed/MEDLINE, Scopus, Web of Science, Embase, and Cochrane Library from inception until the 18th of October 2024. Eligibility criteria included head and neck ACC studies comparing ENI with neck observation. Statistical analysis utilised random-effects models to generate pooled risk ratios (RRs) and hazard ratios (HRs) for recurrence and survival outcomes, respectively.

Results: This study included eight non-randomised studies involving 553 patients. Over half, 51.2% (n=283), received ENI, and 48.8% (n=270) were in the observation group. The ENI group had reduced rates of cervical nodal recurrence [RR 0.17; 95% confidence interval (CI): 0.05–0.51; P=0.002] but no difference in overall survival (HR 0.94; 95% CI: 0.52–1.68; P=0.83). Subgroup analysis demonstrated a reduction in cervical nodal recurrence in ACC of major salivary gland origin (RR 0.09; 95% CI: 0.01–0.69; P=0.02) but not sinonasal primary sites (RR 0.47; 95% CI: 0.10–2.42; P=0.38). Complications of ENI were poorly reported, with documented adverse effects including fibrosis and desquamation.

Conclusions: ENI reduces cervical nodal recurrence in selected subgroups but does not improve overall survival. These findings suggest ENI is not appropriate for widespread use but may benefit carefully selected N0 patients.

Keywords: Adenoid cystic; elective nodal irradiation (ENI); head and neck cancer; salivary cancer; node negative neck