Proton Beam Therapy for the Treatment of Recurrent Human Papillomavirus-Related Multiphenotypic Sinonasal Carcinoma: A Case Report.

Human papillomavirus-related multiphenotypic sinonasal carcinoma (HMSC) is a rare sinonasal tract tumor. Although HMSC has a favorable prognosis, patients tend to experience local recurrence after the initial therapy; therefore, careful follow-up is required after surgical dissection. Proton beam therapy is one of the therapeutic modalities used to treat sinonasal cancer. This is the first report on the use of proton beam therapy for definitive irradiation in HMSC. Herein, we report the case of a 30-year-old woman with HMSC. The right nasal tumor was surgically resected by endoscopy, and HMSC was diagnosed using pathology. The diagnosis of HMSC was made. Nine months after surgery, a recurrent invasive tumor was found in the right nasal cavity, and surgical treatment was not feasible. Proton beam therapy was administered to the recurrent lesion, resulting in radiographic complete response maintained for nine months. This case suggests that postoperative recurrence must be noted and that proton beam therapy is an option to treat locally advanced lesions.