Successful Multimodal Treatment of SMARCA4-Deficient Sinonasal Carcinoma

SMARCA4-deficient sinonasal carcinoma is a recently proposed tumor entity that is rare and associated with a poor prognosis. No standardized treatment strategy has been established. We report a case of SMARCA4-deficient sinonasal carcinoma treated at our department. A 47-year-old woman was referred for treatment of a tumor of the left nasal cavity. The biopsy at a previous institution suggested a neuroendocrine tumor, but it was finally diagnosed as olfactory neuroblastoma. Imaging revealed no lymph node or distant metastases. Endoscopic endonasal resection of the malignant sinonasal tumor was performed with resection and reconstruction of the anterior skull base, achieving complete removal of the tumor. Postoperative intensity modulated radiation therapy (IMRT, 60 Gy) was administered. During IMRT, the histopathological examination confirmed the diagnosis of SMARCA4-deficient carcinoma. Adjuvant chemotherapy following the protocol for undifferentiated carcinoma was administered using the FP regimen (5-fluorouracil 800 mg/m² and cisplatin 80 mg/m²) for 3 cycles. At 2 years and 1 month after surgery, the patient remains alive with no evidence of disease. SMARCA4-deficient carcinoma is an aggressive and poorly differentiated tumor with a poor prognosis, and our experience suggests that a multimodal approach combining surgery, radiation therapy, and chemotherapy following the treatment strategy for undifferentiated carcinoma is effective.