- BACKGROUND: Mucosal head and neck squamous cell cancers are often managed with multimodality treatment which can be associated with significant toxicity. The objective of this study was to assess emergency department visits and unplanned hospitalizations for these patients during and immediately after their treatment. METHODS: A cohort of patients treated for head and neck squamous cell carcinoma was developed using administrative data. Emergency department visits and hospitalizations in the 90-day post-treatment period was determined. If a second treatment was initiated prior to the completion of 90 days, the attributable risk period was changed to the second treatment. RESULTS: Cohort of 3898 patients (1312 larynx/hypopharynx; 2586 oral cavity/oropharynx) from 2008 to 2012. The number of unplanned hospitalizations or ED visits (per 100 patient days) were 0.69 for surgery, 0.78 for surgery followed by concurrent chemoradiotherapy (CCRT), 0.55 for surgery followed by radiotherapy, 0.86 for CCRT, and 0.50 for radiation. Patients receiving CCRT had a statistically higher likelihood of treatment period events. The larynx/hypopharynx cancer subsite, higher comorbidity and more advanced stage of disease were all independent predictors of events. CONCLUSIONS: Patients undergoing treatment for head and neck cancer have significant unplanned hospitalizations and visits to the emergency department in the treatment period. Rates are higher in patients receiving CCRT. Quality improvement interventions should be used to improve these rates.