Cytoreductive Nephrectomy Following Immunotherapy for Metastatic Renal Cell Carcinoma and IVC Tumor Thrombus Arising from a Horseshoe Kidney.

Introduction: Performing surgery for renal cell carcinoma (RCC) in patients with horseshoe kidneys presents unique anatomic challenges. The complexities of clinical decision-making and technical challenges are further compounded by the presence of both IVC tumor thrombus extension and metastatic disease.

Case presentation: We encountered the unique case of a 66-year-old woman with a horseshoe kidney who presented with a 14cm mass in her right kidney with level II tumor thrombus extension into the IVC, retroperitoneal lymphadenopathy, and pulmonary nodules that were biopsy-proven to be consistent with metastatic clear cell RCC (cT3aN1M1). She was treated with combination immune checkpoint inhibition (ICI) and targeted therapy upfront. Given her durable response to systemic therapy, we elected to perform a consolidative cytoreductive nephrectomy for residual ypT3aN0 disease, and she has since remained disease-free radiographically. Using step-by-step illustrative photographs obtained intraoperatively, we detail our surgical approach and highlight technical pearls to manage similar cases of advanced RCC arising from horseshoe kidneys.

Conclusion: We present a complex case of metastatic RCC with IVC tumor thrombus arising from a horseshoe kidney. We share our clinical and technical approach to overcoming the medical and surgical challenges inherent to her case. The optimal role and timing of cytoreductive nephrectomy relative to ICI administration continue to evolve based on both tumor- and patient-related factors. Indeed, we favor a multidisciplinary approach to optimize patient outcomes.