Immunotherapy for Soft Tissue Sarcomas: Anti-PD1/PDL1 and Beyond

Simple Summary Although immunotherapy has revolutionized the standard of care of many cancers, its efficacy in soft tissue sarcomas has been disappointing so far. Nevertheless, some recent studies have reported meaningful activity in a few selected histotypes, especially alveolar soft part sarcoma (ASPS). Furthermore, emerging biomarkers, such as the presence of tertiary lymphoid structures, seem to be predictive of the efficacy of immune checkpoint inhibitors. Finally, innovative therapeutic agents (especially adoptive T-cell therapies) and the combination of immunotherapeutic agents with other therapies such as tyrosine kinase inhibitors represent promising prospects. Sarcomas gather a heterogeneous group of mesenchymal malignant tumors including more than 150 different subtypes. Most of them represent aggressive tumors with poor prognosis at the advanced stage, despite the better molecular characterization of these tumors and the development of molecular-driven therapeutic strategies. During the last decade, immunotherapy has been developed to treat advanced cancers, mainly thanks to immune checkpoint inhibitors (ICI) such as anti-PD1/PDL1 and later to adoptive immune cell therapies. In this review, we aim to summarize the state of the art of immunotherapy in soft tissue sarcomas (STS). Overall, the clinical trials of ICI that included a wide diversity of STS subtypes reported limited efficacy with some outlying responders. Both emerging biomarkers are of interest in selecting good candidates and in the development of combination therapies. Finally, the recent breakthroughs of innovative adoptive therapies in STS seem highly promising.