Tumor stage and treatment outcomes in external auditory canal SCC: a multicenter cohort study

External auditory canal squamous cell carcinoma (EAC SCC) is a rare malignancy with limited evidence guiding treatment strategies. This study sought to evaluate prognostic factors for overall survival (OS), cancer-specific survival (CSS), and time to progression (TTP), and to explore potential differences in outcomes between surgery-based and (chemo)radiotherapy [(C)RT]-based therapies.

This retrospective multicenter cohort study included 87 patients with histologically confirmed EAC SCC diagnosed between 2007 and 2022 at tertiary hospitals in Taiwan. Patients were grouped by treatment: (1) surgery plus adjuvant (C)RT; (2) (C)RT alone or (C)RT followed by salvage surgery. OS, CSS, and TTP were analyzed using Kaplan-Meier methods, Cox proportional hazards models, and inverse probability of treatment weighting (IPTW). Subgroup analyses were performed to explore treatment-effect modification by age, sex, and tumor stage.

The median age was 66 years, and 64.4% were male. The 5-year OS rate was 46%, with a median follow-up of 2.66 years. T4 tumors (HR 4.98, 95% CI: 1.71-14.5), nodal (HR 3.59, 95% CI: 1.58-8.18), and distant metastasis (HR 2.92, 95% CI: 1.14-7.49) were associated with worse OS, though only tumor stage remained significant after adjustment. Patients treated with (C)RT-based treatment showed poorer OS compared with surgery plus adjuvant (C)RT in crude and IPTW analyses, but these associations attenuated in fully adjusted models. Subgroup analyses suggested that outcome differences were more apparent in older patients, males, and those with advanced tumors although residual confounding effect and the small sample may have influenced these findings.

Tumor stage and treatment modality appeared to be important prognostic factors in this cohort of EAC SCC. While surgery combined with adjuvant (C)RT was associated with more favorable outcomes in several analyses, the observational design limited causal inference. These results should be viewed as hypothesis-generating and underscore the need for larger prospective studies with standardized treatment reporting to clarify optimal strategies.