Predictors of aspiration pneumonia in oral cavity cancer patients undergoing radiation therapy: A focus on skeletal muscle index

PURPOSE: Aspiration pneumonia is a life-threatening adverse event of radiotherapy in patients with oral cavity cancer. This study aimed to evaluate the association between muscle mass changes and aspiration pneumonia after radiotherapy. MATERIALS AND METHODS: This study comprised 1,122 patients with oral cavity cancer who underwent surgery and post-operative radiotherapy between 2010 and 2021 at two tertiary centers. Changes in skeletal muscle index (SMI) were measured using pre- and mid-radiotherapy computed tomography scans at the C3 vertebral level. The primary and secondary outcomes were aspiration pneumonia and overall survival, respectively. RESULTS: With a median follow-up of 5.6 (interquartile range: 2.9-9.2) years, 125 (11.1%) patients developed aspiration pneumonia. Patients with aspiration pneumonia tended to have older age, poorer performance status, smoking, and higher mean dose to swallowing organs. Patients with aspiration pneumonia lost more SMI during radiotherapy than those without it (-3.4% vs. -1.0%; p < 0.001). After adjusting for clinical and dosimetric factors, an increase in SMI change during radiotherapy was independently associated with a lower risk of aspiration pneumonia in the overall population (hazard ratio: 0.78 per 1% increase, p < 0.001) or subgroups stratified by pre-radiotherapy SMI tertile. The occurrence of aspiration pneumonia was independently associated with poorer overall survival (hazard ratio: 2.81, p < 0.001). A 1% increase in SMI change during radiotherapy was independently associated with better overall survival (hazard ratio: 0.78, p < 0.001). CONCLUSIONS: Increased muscle mass during radiotherapy was associated with a lower risk of aspiration pneumonia, which in turn was associated with overall survival.