Durable remission of metastatic myxoid liposarcoma following the cautious addition of pembrolizumab to ongoing pazopanib treatment: A case report.

Responses to conventional treatments, like chemotherapy and targeted agents, are generally infrequent, and of brief duration in patients with metastatic soft tissue sarcomas. We present a case of metastatic myxoid liposarcoma that achieved biopsy-proven complete remission with minimal toxicity following the addition of pembrolizumab to pazopanib as fourth-line treatment. This regimen resulted in significant tumor regression following just five doses. After 15 doses of pembrolizumab, radiographs demonstrated an ongoing response, with stable residual lesions, and a biopsy of a sacral lesion confirmed a pathologic complete remission. The patient subsequently discontinued all therapies and remains in an ongoing unmaintained remission. The combination of pembrolizumab and pazopanib demonstrated unexpected clinical benefit with minimal toxicity, suggesting that it may be worthy of further investigation in myxoid liposarcoma and possibly other histologic subtypes of STS.