PDCD1 and telomere syndrome: Pembrolizumab (anti-PD-1) monotherapy demonstrated an objective response in 18% of the patients with metastatic or locally unresectable STS and who had received at least three lines of prior systemic treatment. The highest rates were seen in UPS (40%) and liposarcoma (20%). The median progression-free survival was 18 weeks, although it was 30 weeks for patients with UPS [38]. Pembrolizumab was also examined in rare and ultra-rare sarcomas that were advanced stage or refractory to other treatment.