Pathological Complete Response to Nivolumab Plus Ipilimumab Combination Therapy in Advanced Renal Cell Carcinoma With Inferior Vena Cava Tumor Thrombus

Introduction Nivolumab plus ipilimumab is a standard first‐line regimen for advanced renal cell carcinoma; however, primary tumors often respond less favorably to this combination than to immune checkpoint inhibitor–tyrosine kinase inhibitor regimens, and pathological complete response is rare. Case Presentation A 78‐year‐old man presented with abdominal pain. Computed tomography revealed a 91‐mm right renal mass with a Neves level 3 inferior vena cava tumor thrombus. Needle biopsy confirmed clear cell renal cell carcinoma with diffuse programmed death‐ligand 1 expression, and both the tumor proportion and combined positive scores were approximately 100%. Nivolumab plus ipilimumab was administered. After 21 months, the primary tumor decreased in size by 68.1% and tumor thrombus regressed from level 3 to 1. Histopathological examination following radical nephrectomy with tumor thrombectomy demonstrated a pathological complete response. Conclusion Diffuse programmed death‐ligand 1 expression on pretreatment biopsy may have been associated with a favorable response to nivolumab plus ipilimumab.