A Retrospective Analysis of 22 Cases with Carcinomas of the External Auditory Canal

Carcinoma of the external auditory canal is a rare tumor, accounting for about 1% of all head and neck cancers. Although no treatment method has been established yet, surgical treatment is the primary treatment method in cases where resection is possible. At our institution, we adopt surgical treatment, mainly lateral temporal bone resection （LTBR）, for cases with T1―T3 disease, and chemoradiation therapy（CCRT）for cases with T4 disease, as the treatment of first choice. We have adopted cartilage conduction hearing aids（CC―HAs）in some cases following LTBR. We examined the short―term outcomes, at two years, in the patients treated at our department. This study was a retrospective case review of 22 ears with carcinoma of the external auditory canal in 21 patients who underwent initial treatment at our institution between January 2012 and June 2018. The observation period was 2 to 81 months（median 26 months）. The tumors were analyzed using the modified Pittsburgh tumor staging system. The tumor T stage was T1 in four ears, T2 in nine ears, T3 in six ears, and T4 in three ears. CCRT was performed in three ears with T4 disease and one ear with T2 disease, heavy ion radiotherapy was performed in one ear with T2 disease, and surgery（LTBR in 16 ears and partial external auditory meatus resection in one ear）was performed for all the other cases. The surgical margin after LTBR was positive in three out of six cases with T3 disease and negative in all of the cases with T1 and T2 disease. The positive surgical margin was mainly found in the medial wall of the tympanic cavity or cartilaginous portion of the external acoustic meatus. The overall 2―year survival rate was 87.4%; the rate was 100% in the T1 cases, 87.5% in the T2 cases, 75.0% in the T3 cases, and 100% in the T4 cases. Four out of five patients who tried CC―HAs continued to use them after the LTBR. The indication for LTBR should be carefully judged in cases with T3 disease. The appropriate indication for LTBR in cases with T3 disease are: 1）a small amount of soft tissue shadow beyond the tympanum in the preoperative CT, and/ or 2）a clear boundary between the tumor and the soft tissue around the external acoustic meatus in the preoperative enhanced MRI. In cases with T3 disease not fulfilling these criteria, CCRT should be selected as the treatment of first choice. However, considering the side effects after CCRT, including sensorineural hearing loss and persistent otorrhea in some cases, LTBR with postoperative CC―HAs is one of the optimal treatment options that would allow the remaining hearing ability to be utilized.