Long Duration Pembrolizumab for Metastatic Undifferentiated Pleomorphic Soft Tissue Sarcoma With Multimodality Therapy.

Patients with undifferentiated pleomorphic sarcoma (UPS) of soft tissue have responsiveness to immunotherapy treatment. Since few patients with soft tissue sarcoma respond to immunotherapy, guidelines for its management are lacking. Specifically, the optimal duration of immunotherapy is unclear. This report is unique owing to the probable longest reporting of successful continuous immunotherapy for metastatic UPS over 6.5 years and 109 cycles. Here a patient who developed metastatic UPS is presented. The patient required systemic therapy for metastatic sarcoma, eventually with immunotherapy. A prolonged treatment over many years is elaborated. A robust response was seen but occasionally augmented by adding external beam radiation therapy (XRT). Treatment was tolerated without adverse effects. A brief review of current treatment practice and known risks of prolonged immunotherapy is presented. For similar patients, a lengthy treatment course, beyond that utilized for other malignancies, can be considered. This is likely to be safe if it is tolerated and without early adverse effects. Other treatment modalities such as palliative surgery and XRT are described which may also be required for management of mixed responses.