INNV-30. Intracranial Metastasis of Renal Cell Carcinoma Exhibiting Mullerian Differentiation: A Case Report

Brain metastases outnumber all other brain tumors combined. Despite the frequency of brain metastases, a thorough PubMed search revealed no reported cases of brain metastasis secondary to renal cell carcinoma with gynecologic/mullerian origin. We believe this is the first reported case of such tumor. A 52-year-old male with no remarkable neurologic history developed left-sided weakness, altered personality, slurred speech, drooling from left facial droop, and flat affect. Imaging found brain metastases. He underwent right frontal craniotomy and resection of the right frontal mass lesion. Final pathologic diagnosis favored metastatic carcinoma of gynecologic/mullerian origin. He later started 240 mg nivolumab in 2 week cycles and 40 mg cabozantinib daily. During the second cycle, he started whole brain radiotherapy with simultaneous integrated stereotactic boost to the larger lesions. The P-GTV was defined as a 3-mm margin to the gross tumor volume, the clinical target volume encompassed the whole brain, and the planning target volume was defined as a 3-mm margin to the clinical target volume. The prescribed dose to the planning target volume was 30 Gy in 10 fractions, and the simultaneous boost to the P-GTV was 15 Gy in 10 fractions, for a total of 45 Gy in 10 fractions. Unfortunately, PET scan ten months after initial presentation found his hypermetabolic right kidney malignancy slightly increased in size along with redemonstrated hypermetabolic retroperitoneal metastatic lymph node activity. This is the last scan to date. The new plan is to stop nivolumab and cabozantinib and to start belzutifan 120 mg daily based on results from a recent clinical trial involving advanced renal cell carcinoma patients. Despite the uniqueness of the pathology of this patient’s malignancy, nivolumab, cabozantinib, and radiotherapy appear to reduce the burden of advanced renal cell carcinoma and associated brain metastases, even if from gynecologic/mullerian origin.