Abstract
Renal cell carcinoma with level IV inferior vena cava tumor thrombus is rare and associated with high recurrence risk despite complete resection. We report an 80-year-old man who underwent radical nephrectomy and inferior vena cava thrombectomy with initial negative postoperative imaging. One year later, imaging findings were equivocal, but tumor-informed circulating tumor DNA was detectable, prompting early surgical resection of recurrent disease. Postoperatively, circulating tumor DNA became undetectable. This case highlights the potential role of tumor-informed circulating tumor DNA surveillance in detecting molecular residual disease and guiding management in high-risk renal cell carcinoma.