Severe Toxicities From Definitive Chemoradiotherapy for Oropharyngeal Cancer in a Patient With Comorbid Sjögren's Syndrome.

Radiotherapy in patients with a collagen vascular disease (CVD) requires careful consideration due to the potential for exacerbated treatment-related toxicities. We report the case of a 43-year-old Japanese woman with human papillomavirus (HPV)-positive oropharyngeal cancer and a history of Sjögren's syndrome (SjS) who underwent definitive chemoradiotherapy with high-dose cisplatin (100 mg/m2 every three weeks) and three-dimensional conformal radiation therapy (3D-CRT) to a total dose of 70 Gy in 35 fractions. Beginning midway through treatment (around 30-40 Gy), she developed severe acute toxicities, including Grade 3 radiation dermatitis and confluent mucositis, per the Common Terminology Criteria for Adverse Events (CTCAE) v5.0. This was followed by significant late toxicities, including bilateral middle ear effusion associated with chronic otitis media and persistent xerostomia that continued to impact her oral intake. This patient's case highlights the potential for severe treatment-related toxicity in patients with SjS undergoing standard chemoradiotherapy for head and neck cancer, and it underscores the importance of careful pre-treatment evaluation and individualized planning.