A Study of Cochlear Sparing in Intensity-modulated Radiotherapy in Head-and-Neck Cancer Patients

Background: Head-and-neck cancers are malignant tumors that include tumors located in the skin; lips; oral cavity; nasal cavity; paranasal sinuses; external, middle, and inner ear; and upper aerodigestive system. A single-modality treatment or adjuvant to chemotherapy or surgery is radiotherapy (RT). Hearing loss is the major side effect of RT. The aim of this study is to evaluate the cochlear-sparing efficacy of intensity-modulated RT based on pure-tone audiometry (PTA) reports and compare it with the previous article, where conventional RT was used in the same institution. Materials and Methods: A total of 44 patients were enrolled in this study. Informed consent was taken from all patients for participation in the study. When necessary, weekly chemotherapy was administered concurrently to all patients with head-and-neck cancer. All patients were treated with computed tomography-based plans. Inner ear contouring was done according to guidelines by Heather D. Pacholke. Planned treatment was executed by intensity-modulated RT on the linear accelerator. PTA was performed for both air conduction and bone conduction until 8000 Hz at baseline, at completion of treatment, and at 3-month and 6-month follow-up after completion of treatment. The difference of PTA thresholds was correlated with cochlea dose, and this study was compared with the previous study done with conventional RT on 2012 in the same institution. Results: The mean age was 56.73 ± 12.32 years, and the mean cochlear dose was 16.47 Gy. There was a statistically significant difference found between age groups and on comparing audiometric values with respect to mean PTA at baseline, 1 month, 3 months, and 6 months. On comparing those who underwent chemoradiation to those who underwent radiation only, there was no statistically significant difference found with respect to mean PTA at baseline and 1 month. However, there was a statistically significant difference found with respect to mean PTA at 3 months and 6 months. The result of statistical modeling showed a positive relationship with the severity of hearing loss in both groups, with a higher significance noted in the chemoradiation group ( P < 0.001). The incidence of severe hearing loss was 22.72%, and the degree of hearing loss was reduced with IMRT when compared with conventional type of RT. Conclusion: In this study, the significance of the cochlea as an organ at risk during IMRT is well established. Patients have shown to suffer from clinically significant sensorineural hearing loss (SNHL) post radiation. Therefore, we recommend cochlea dose restraint (<10 Gy) for patients undergoing chemoradiation. In addition to this, as per literature review, Vitamin E and steroids can be supplemented to prevent SNHL.