Complete response to combination therapy with nivolumab and ipilimumab for metastatic collecting duct carcinoma of the kidney

Collecting duct carcinoma (CDC) of the kidney is a rare subtype of renal cell carcinoma (RCC) arising from the distal collecting tubules, characterized by an aggressive phenotype, unfavorable response to several types of systemic agent and a poor prognosis. Recently, treatments with immune checkpoint inhibitors have been widely performed for patients with metastatic RCC; however, no data are available regarding the impact of first-line combination therapy with nivolumab and ipilimumab on metastatic CDC. Here, we report a CDC patient with multiple lymph node metastases who underwent cytoreductive open nephrectomy and subsequently, received nivolumab and ipilimumab therapy. Following four courses of this combined therapy, all nodal metastases had shrunk to < 1 cm in diameter, and thus this patient was judged to show a complete response (CR). To our knowledge, this is the first reported case of a patient with metastatic CDC achieving a CR to combined treatment with nivolumab and ipilimumab, which could be a promising first-line therapy against metastatic CDC.