Successful Treatment of Paranasal Sinus Metastasis From Renal Cell Carcinoma With Immune Checkpoint Inhibitors and Radiotherapy: A Case Report

Introduction Renal cell carcinoma (RCC) metastasis to the paranasal sinuses is rare and lacks standard treatment, particularly for unresectable tumors. We report a case of sphenoid sinus metastasis with sarcomatoid differentiation successfully managed with radiation therapy and immunotherapy. Case Presentation A 59‐year‐old male who had undergone left radical nephrectomy for RCC 13 years prior presented with acute left eye pain and tinnitus. Contrast‐enhanced computed tomography (CT) revealed a hyper vascular sphenoid sinus mass with osseous destruction. Biopsy confirmed metastatic RCC with sarcomatoid differentiation. Given rapid symptom progression, intensity‐modulated radiation therapy (39 Gy in 13 fractions) was initiated, followed by immunotherapy with nivolumab and ipilimumab. The patient developed complete blindness, which gradually improved during treatment. Serial CT showed a partial response sustained through four cycles. Subsequent 37 cycles of maintenance nivolumab showed persisting tumor reduction. Conclusion Radiation with nivolumab and ipilimumab may be effective for unresectable paranasal sinus metastases of RCC.