Prospective longitudinal patient-reported outcomes of swallowing following intensity modulated proton therapy for oropharyngeal cancer

Background and purpose: With an enlarging population of long-term oropharyngeal cancer survivors, dysphagia is an increasingly important toxicity following oropharynx cancer treatment. While lower doses to normal surrounding structures may be achieved with intensity modulated proton therapy (IMPT) compared to photon-based radiation, the clinical benefit is uncertain. Methods and materials: Seventy-one patients with stage III/IV oropharyngeal cancer (AJCC 7th edition) undergoing definitive IMPT on a longitudinal prospective cohort study who had completed the MD Anderson Dysphagia Inventory (MDADI) at pre-specified time points were included. Results: The majority of patients had HPV-positive tumors (85.9%) and received bilateral neck radiation (81.4%) with concurrent systemic therapy (61.8%). Mean composite MDADI scores decreased from 88.2 at baseline to 59.6 at treatment week 6, and then increased to 74.4 by follow up week 10, 77.0 by 6 months follow up, 80.5 by 12 months follow up, and 80.1 by 24 months follow up. At baseline, only 5.6% of patients recording a poor composite score (lower than 60), compared to 61.2% at treatment week 6, 19.1% at follow up week 10, 13.0% at 6 months follow up, 13.5% at 1 year follow up, and 11.1% at 2 years follow up. Conclusions: Patient reported outcomes following IMPT for oropharyngeal cancer demonstrates decreased swallowing function at completion of treatment with relatively rapid recovery by 10 weeks follow up and steady improvement through 2 years. The results are comparable to similar longitudinal studies of photon-based radiotherapy for oropharynx cancer, and suggest that IMPT confers no additional excess toxicity related to swallowing.