The researchers are doing this study to improve their knowledge about immunotherapy use and how effective it is as a treatment for people with sarcoma by collecting information from participants' medical records who have been treated with immune checkpoint blockade or T-cell receptor-based therapy.

Inclusion Criteria:

• Participants must have a histologic diagnosis of sarcoma confirmed by an MSK pathologist.
• Any prospectively identified patient being treated or to be treated with an immune checkpoint inhibitor, such as anti-PD-1, anti-PD-L1, anti-CTLA-4, or anti-LAG3 inhibitor, either as monotherapy or in combination with additional systemic therapy OR any prospectively identified patient being treated or to be treated with ACT-based treatment including but not limited to lifileucil, Afamitresgene autoleucel, and letetresgene autoleuce o Novel immune checkpoints inhibitors that are developed after submission of this protocol will also be included) Please Note: there is no age requirement. Patients of all ages are eligible to enroll

Exclusion Criteria:

• Patient unwilling to consent to collection of historical and longitudinal clinicopathologic data in the patient medical record from baseline (the period prior to ICB or ACT initiation), during, and after ICB or ACT treatment

All sarcoma patients who will undergo or are undergoing ICB-based or ACT-based treatment at MSK will be approached for participation in this observational study.

Memorial Sloan Kettering Cancer Center supports the international committee of medical journal editors (ICMJE) and the ethical obligation of responsible sharing of data from clinical trials. The protocol summary, a statistical summary, and informed consent form will be made available on clinicaltrials.gov when required as a condition of Federal awards, other agreements supporting the research and/or as otherwise required. Requests for deidentified individual participant data can be made beginning 12 months after publication and for up to 36 months post publication. Deidentified individual participant data reported in the manuscript will be shared under the terms of a Data Use Agreement and may only be used for approved proposals. Requests may be made to: crdatashare@mskcc.org.