Limited Toxicity of Hypofractionated Intensity Modulated Radiation Therapy (H-IMRT) for Head and Neck Cancer.

Purpose/objective(s) Hypofractionated intensity modulated radiation therapy (H-IMRT) is uncommonly used in head and neck cancers due to concern for toxicity. This study reviews our experience using H-IMRT for head and neck cancers and explores its tolerability and efficacy. Materials/methods This single institution IRB approved retrospective study includes patients with head and neck cancers treated with definitive or post-operative H-IMRT from 2011-2020. Patients treated with ≥50Gy in 20 fractions to the primary tumor site and/or neck with at least 3 months of follow up were included. Patients treated to a superficial target only without proximity to mucosal surfaces or coverage of the elective neck (e.g., scalp; skin only targets) were excluded. Patients undergoing re-irradiation were excluded. Toxicity was scored using CTCAE v4.0. Acute toxicity included events occurring within 90 days of H-IMRT completion. Late toxicities occurred any time thereafter. Multiple toxicities in the same patient were scored separately. Results Fifty-nine patients with a median follow up of 10.9 months (range 3.0-111.5) were included. The majority of patients were white (93%) and male (78%) with a median age of 79.1. The most common primary tumor sites were skin (42%), major salivary glands (22%), and oral cavity (9%). The most frequent histologies included squamous cell carcinoma (66%) followed by thyroid cancer (7%), melanoma (5%), and Merkel cell carcinoma (5%). Treatment was delivered post-operatively in 80% and definitively in 20% of patients. All patients were treated with ≥50 Gy in 20 fractions, with the most common dose being 50 Gy (53%) followed by 55 Gy (44%). In 64% of patients a secondary elective dose of 45-50 Gy was used. Site treated included primary tumor site/bed with unilateral neck (54%), primary tumor site/bed with bilateral neck (19%), primary tumor site/bed alone (14%), unilateral neck (8%), and bilateral neck (5%). Five patients (8%) experienced a locoregional failure at a median time of 5.4 months (range 2.8-13.9). There were no grade 4 or 5 toxicities. Ten patients (17%) experienced acute grade 3 toxicity including mucositis (12%) and dermatitis (5%). Forty-six patients (78%) had an acute grade 2 toxicity, most commonly dermatitis (41%), pain (32%), fatigue (32%), dysgeusia (31%) and xerostomia (22%). Five patients (8%) experienced grade 2 late complications including neck fibrosis in three patients and trismus, aspiration pneumonia, and osteoradionecrosis in one patient each. No patient experienced grade 3 or higher late toxicity. No patients required the placement of a feeding tube or tracheostomy. Conclusion Hypofractionated IMRT in the definitive or post-operative treatment of head and neck cancers using ≥50Gy in 20 fractions appears safe and well tolerated with modest toxicity. Prospective studies comparing the safety and efficacy of H-IMRT to conventionally fractionated IMRT are warranted.