Sensori-neural hearing loss after radiotherapy for nasopharyngeal carcinoma: individualized risk estimation.

Abstract

Sensori-neural hearing loss (SNHL) is a common complication to radiation therapy in the upper head and neck region. In this study, we estimated the dose response relationship for SNHL with adjustment for pre-therapeutic risk factors. The pre- and post-therapeutic hearing levels were recorded in a previously published study of 20 patients receiving radiotherapy for nasopharyngeal carcinoma. In the present study, the dose to the inner ear of these patients was estimated with a computed tomography (CT) based treatment planning system. CT data from a 'proxy patient' were used for patients with no available CT scan. SNHL was analyzed as a function of radiation dose and potential risk factors were tested. The incidence of SNHL increased significantly with increasing dose to the cochlea. Increasing patient's age, and decreasing pre-therapeutic hearing level were statistically significantly associated with an increased risk of SNHL. A nomogram is presented for estimating individualized dose constraints of potential use in treatment planning. The inner ear is a critical structure in patients with nasopharyngeal carcinoma and the dose to the inner ear should be carefully considered when planning radiation treatment in this region.