Supplementary Material for: Toripalimab in Metastatic Renal Collecting Duct Carcinoma: A Case Report

Introduction: Collecting duct carcinoma (CDC), a rare and highly aggressive subtype of renal cell carcinoma (RCC), is often associated with a dismal prognosis due to its resistance to conventional therapies. Although platinum-based chemotherapy is the standard-of-care first-line treatment for metastatic CDC, its clinical benefit is limited and transient. Case presentation: We present a case of postoperative metastatic CDC with a urothelial carcinoma-like immunophenotype (CK7+/P40+) that demonstrated a remarkable response to toripalimab, a programmed death protein 1 (PD-1) inhibitor developed in China. The patient achieved a complete response (CR) after six cycles of toripalimab administration (240 mg, Q3W), which was confirmed by the complete resolution of bilateral pulmonary metastases. To date, the patient has maintained progression-free survival (PFS) for 22 months. Conclusions: This case highlights the potential efficacy of PD-1 inhibition as a viable therapeutic strategy for this aggressive RCC subtype.