Good response with nivolumab and cabozantinib combination therapy in patients with metastatic collecting duct carcinoma with high expression of PD-L1, c-MET, and AXL.

Collecting duct carcinoma (CDC) is a rare subtype of renal cell carcinoma with a poor prognosis. Moreover, despite various chemotherapeutic strategies and administration of several tyrosine kinase inhibitors for metastatic CDC, the outcomes remain unfavorable, with no established treatment. Herein, we report the cases of two patients with CDC who exhibited a good response to nivolumab and cabozantinib combination therapy. Both patients were diagnosed with CDC via a needle biopsy of the renal tumor, revealing high expression levels of programmed death ligand 1 (PD-L1), c-MET, and AXL. After 10 and 12 courses of combination therapy for Cases 1 and 2, respectively, significant response was observed against the primary and metastatic lesions. Subsequently, the patients underwent laparoscopic nephrectomy. To the best of our knowledge, this is the first report documenting the favorable therapeutic response of nivolumab and cabozantinib combination therapy against metastatic CDC in patients with high expression of the corresponding molecular targets. These findings may have a strong implication in the selection of first-line systemic therapies for metastatic CDC.