A Single-arm, Open-label, Single-center Prospective Study of Fruquintinib Combined With Envafolimab in the Treatment of Advanced or Unresectable Locally Advanced Bone and Soft Tissue Sarcoma

VEGF receptor tyrosine-kinase inhibitor：fruquintinib（4mg), Oral，qd, d1-d14, Q3w，Until disease progression or intolerable toxicity occurs.

anti-PD-1 immune checkpoint inhibitor：Envafolimab（400mg), subcutaneous injection, d1, Q3w，Until disease progression or intolerable toxicity occurs.