Endometrial Neoplasms

This clinical trial is looking at a drug called atezolizumab. Atezolizumab is approved as standard of care treatment for adult patients with urothelial cancer, non-small cell lung cancer, extensive-stage small cell lung cancer, hepatocellular carcinoma and triple negative breast cancer. This means it has gone through clinical trials and been approved by the Medicines and Healthcare products Regulatory Agency (MHRA) in the UK. Atezolizumab works in patients with these types of cancers which have certain changes in the cancer cells called high tumour mutational burden (TMB) or high microsatellite instability (MSI) or proven (previously diagnosed) constitutional mismatch repair deficiency (CMMRD). Investigators now wish to find out if it will be useful in treating patients with other cancer types which are also TMB/MSH-high or show CMMRD. If the results are positive, the study team will work with the NHS and the Cancer Drugs Fund to see if these drugs can be routinely accessed for patients in the future. This trial is part of a trial programme called DETERMINE. The programme will also look at other anti-cancer drugs in the same way, through matching the drug to rare cancer types or