The Role of Parotid Gland Invasion in Adenoid Cystic Carcinoma of the External Auditory Canal.

OBJECTIVE

This study aimed to investigate the significance of parotid gland invasion in predicting distant metastasis of adenoid cystic carcinoma in the external auditory canal.

STUDY

DESIGN

Single-institution retrospective cohort study.

METHODS

A retrospective review of patients with adenoid cystic carcinoma of the external auditory canal who underwent surgery was performed. Information on patient demographics, parotid gland invasion, tumor stage, perineural invasion, lymphovascular invasion, and follow-up data were collected and analyzed.

RESULTS

One hundred twenty-nine patients were identified for review. Parotid gland invasion was noted in 45 patients (34.9%). Parotid gland invasion was significantly associated with tumor stage, perineural invasion, distant metastasis, and postoperative adjuvant therapy. Distant metastasis was noted in 30 patients (23.3%). Multivariate Cox proportional hazards analysis identified parotid gland invasion as an independent risk factor for predicting distant metastasis. The 5-year distant metastasis-free survival rate was 83.6% for patients without parotid gland invasion and 61.8% for patients with parotid gland invasion (p = 0.010).

CONCLUSIONS

The parotid gland invasion rate is relatively high in adenoid cystic carcinoma of the external auditory canal and is significantly related to tumor stage. Parotid gland invasion is associated with worse distant metastasis-free survival.

LEVEL OF EVIDENCE: 4 Laryngoscope, 134:419-425, 2024.