Impact of radiotherapy for head and neck cancer on obstructive sleep apnea: a prospective study

Background: In recent years, a relatively high prevalence of obstructive sleep apnea (OSA) in patients following radiotherapy (RT) for head and neck cancer (HNC) has been reported; however, little is known regarding the impact of RT on sleep disorders and the underlying mechanisms. This aim of this study was to elucidate the pathogenesis of OSA by comparing the clinical and sleep test parameters and magnetic resonance imaging (MRI) findings before and after HNC treatment with radiation. Methods: This prospective study included patients scheduled for RT with or without chemotherapy or bioradiotherapy for HNC. Patients diagnosed with HNC between May 2017 and August 2020 were consecutively recruited. The results of the sleep tests were analyzed both before and after treatment. The clinical characteristics of the patients and cephalometric and MRI parameters were also measured. Results: First, a total of 32 patients (64.8 +/- 11.8 years old; BMI, 22.7 +/- 3.6 kg/m2) underwent pre-treatment sleep tests. The prevalence of OSA [ apnea hypopnea index (AHI) =5] in these patients was 81.3% (26 patients) before treatment, and the mean AHI was 20.8 +/- 19.0 events/hr. Next, 21 patients performed a sleep test both before and after treatment. Regarding subjective symptoms, there were no significant differences in the Epworth Sleepiness Scale ( ESS) (P=0.142) or Pittsburgh Sleep Quality Index (PSQI) (P=0.935) after treatment; however, the BMI and neck circumference significantly decreased after treatment (P<0.0001 and P=0.0001, respectively). The incidence of OSA in these patients was 81.0% (17 patients) before treatment and 85.7% (19 patients) after treatment (P=1.0). Overall, the AHI was not significantly different, changing only from 14.5 to 14.9 after treatment (P=0.147). The MRI parameters showed that the retroglossal pharyngeal area increased significantly after treatment (P=0.007). Conclusions: This study found that the prevalence of OSA before and after RT for HNC was higher than that in the normal population, despite a significant decrease in BMI and increase in the retroglossal pharyngeal area after treatment. We suggest that physicians who manage patients with HNC should consider the occurrence of OSA before and after treatment.