Multimodal management of PD-L1 positive sinonasal inverted papilloma with malignant transformation

Inverted papillomas (IP) are rare sinonasal tumors (Schneiderian papillomas) characterized by local invasion, with high recurrence rates and potential for malignant transformation into squamous cell carcinoma (SCC ex-IP). Traditionally, the mainstay of treatment has been surgical resection, often challenging due to invasion of the skull base or vital neurovascular structures. In advanced cases, prognosis is poorer and radiation therapy is the current standard of care with limited role of systemic therapy. We present a case of unresectable SCC ex-IP treated with sequential chemoradiation and PD-1 immunotherapy (pembrolizumab) and achieving complete response at 1 year. This case suggests that immunotherapy can effectively treat SCC ex-IP and we propose that programmed death ligand-1 (PD-L1) testing should be performed in all advanced cases. Prospective studies are needed to validate immunotherapy in adjuvant or frontline treatments for advanced SCC ex-IP, and the role of PD-L1 as a predictive biomarker.