Single Isolated Sacral Metastasis From Clear Cell Renal Cell Carcinoma: A Case Report

This case report describes a rare occurrence of a single isolated sacral metastasis in a 59-year-old male with clear cell renal cell carcinoma (ccRCC). The patient presented with progressive lower back pain and sacral numbness following a fall. Initial imaging revealed a destructive lytic lesion in the S1-S2 region and a left renal mass. A CT-guided biopsy of the sacral lesion confirmed metastatic ccRCC. PET-CT confirmed no additional metastases. Multidisciplinary management included partial left nephrectomy for the primary renal tumor, stereotactic body radiotherapy (SBRT; 45 Gy/15 fractions) targeting the sacral metastasis, and immunotherapy with sunitinib. The patient experienced significant pain relief within 1-week post radiotherapy and demonstrated stable disease with near-resolution of the sacral lesion at 3-month follow-up. At 12 months, imaging confirmed sustained disease stability. This case highlights the importance of considering metastatic RCC in patients with isolated sacral lesions, even in the absence of disseminated disease, and underscores the efficacy of combining localized ablation, radiotherapy, and targeted systemic therapy. Early diagnosis and a tailored multidisciplinary approach are critical for optimizing outcomes in such rare presentations.