Cadonilimab in the treatment of advanced metastatic soft tissue clear cell sarcoma achieved complete remission: a case report.

Soft tissue sarcoma is highly heterogeneous, and clear cell sarcoma (CCS) is a rare, aggressive subtype prone to recurrence and lymph node or lung metastasis. This report describes a patient with upper-limb CCS who developed postoperative recurrence and pulmonary metastasis. After transient benefit from first-line doxorubicin plus ifosfamide chemotherapy, the disease progressed despite second-line PD-1 inhibitor combined with anlotinib. Treatment was subsequently switched to cadonilimab, a PD-1/CTLA-4 bispecific antibody, in combination therapy, resulting in a progression-free survival of more than 24 months. This outcome appears encouraging compared with previously reported CCS benchmarks; however, given the single-case nature and combined treatment strategy, the specific contribution of cadonilimab should be interpreted with caution.