The efficacy of computed tomography imaging-based radiotherapy for external auditory canal squamous cell carcinoma

Background: External auditory canal (EAC) cancer is a rare disease for which there are no adequate evidence-based treatment strategies. Radical radiotherapy is often used as the initial treatment for EAC cancer from the viewpoint of organ preservation. This study aimed to elucidate the efficacy of radiotherapy for squamous cell carcinoma (SCC) of the EAC. Methods: : Fifteen consecutive patients with SCC of the EAC who were treated with radical radiotherapy were retrospectively analyzed. The fractional dose was 2.0 or 3.0, and the total dose ranged from 66 to 70 Gy. Three-dimensional conformal radiation therapy was performed on seven patients. Intensity-modulated radiation therapy was performed on eight patients. Patients with T1 disease were treated with radiotherapy alone. Patients with T2-4 disease were treated with chemoradiotherapy. Results: : The median follow-up period was 30.4 months. The 3 year local control (LC) rate for all patients was 51%, the disease-free survival (DFS) rate was 44%, and the overall survival (OS) rate was 73%. For T1-3 disease, the 3 year LC rate was 74%, DFS was 62%, and OS was 89%. However, for T4 disease, the 3 year LC rate was 17%, DFS was 17%, and OS was 50%. In a univariate analysis, only the T-category was a significant factor for predicting LC and DFS ( p = 0.006 and 0.02, respectively). All local recurrences were within the high-dose irradiated area. Conclusions: : The results of this study suggest that chemoradiotherapy is a reasonable first-line treatment for T1-3 SCC of the EAC. However, the efficacy of chemoradiotherapy in T4 cases was inadequate. Further research is warranted to elucidate the efficacy of treatments with more intensive antitumor effects for locally advanced EAC cancers.