Treatment outcomes of 73 cases of external auditory canal squamous cell carcinoma: A single-center six-year analysis in Japan

Objectives: External auditory canal cancer (EAC) is a rare type among head and neck cancers, predominantly composed of squamous cell carcinoma (SCC) pathologically. Various comprehensive treatments including surgery, radiation therapy, and chemotherapy are conducted in many facilities for squamous cell carcinoma of the external auditory canal. However, due to its rarity, there is no established standard treatment. This study aimed to report the treatment outcomes at our single facility and prognostic factors post-surgery for EAC-SCC. Methods: We conducted a retrospective analysis of 73 cases of EAC-SCC, which underwent initial treatment at our facility from July 2015 to November 2022. We utilized the modified Pittsburgh classification for TNM and staging. Results: There were 37 male and 36 female cases, with a median age of 65 (ranging from 40 to 93). T1: 32 cases, T2: 5 cases, T3: 14 cases, T4: 10 cases. Stage I: 28 cases, stage II: 5 cases, stage III: 12 cases, stage IV: 16 cases. The median follow-up period was 23.8 months (ranging from 2.8 to 93.6 months). There were 61 cases in the surgery group and 12 cases in the chemoradiotherapy (CRT) group. In survival analysis, the overall 3-year recurrence-free survival (RFS) rate was 81.9 %, and the 3-year disease-specific survival (DSS) rate was 89.1 %. For stage III/IV advanced cancers, the 3-year RFS rate was 78.3 % and DSS rate was 79.1 % in the surgery group, and in the CRT group, they were 66.7 % and 91.7 %, respectively. For T4 cases, the 3-year RFS rate was 58.3 % and DSS rate was 61.0 % in the surgery group, and in the primary CRT group, they were 75.0 % and 87.5 %, respectively. While there were no significant differences in treatment outcomes between the surgery and CRT groups overall, there was a trend suggesting better outcomes in the CRT group for T4 cases. In advanced cases (Stage III/IV, T3/4), younger females tended to be treated with CRT. Positive resection margins (HR: 11.97, 95 % CI: 1.80-79.70, p = 0.010) revealed to be a significant prognostic factor based on RFS. Conclusion: We reported the treatment outcomes at a single facility and post-surgery prognostic factors. The treatment outcomes at our facility are comparable to other institutions, and in advanced cancers, the CRT group showed a tendency for better treatment outcomes. Post-surgery prognostic factor was positive resection margins.