pReOperative Dostarlimab and Novel Therapies in EndOmetrial Cancer

Background Endometrial cancer is the most common invasive gynaecological malignancy and its incidence is predicted to double by 2030. Surgery remains the most effective treatment modality to cure operable early-stage and high-risk cancers but despite the use of adjuvant therapies, a proportion of patients will relapse due to the presence of micrometastases that cannot be detected at the time of primary treatment. Immune checkpoint inhibitors have been evaluated in endometrial cancer, for example, the GARNET trial demonstrated the benefit of dostarlimab (anti-PD1) in women with relapsed/advanced endometrial cancer. Pre-operative immunotherapy is an evolving strategy that consists of administering an ICI, either as monotherapy or in combination before surgical resection in high-risk resectable disease, in the window between diagnosis and primary surgery

Aims RODEO is a proposed window trial using dostarlimab in patients with newly diagnosed high-risk (stage 2-4)endometrial cancer who are suitable for primary surgery. The primary objective is to assess the pathological response rate to pre-operative dostarlimab and the secondary objectives are to assess the feasibility, toxicity, safety and efficacy of pre-operative dostarlimab.

Methods Patients will receive 2 doses of dostarlimab (500mg IV day 1 and day 22) prior to surgery.

How the results of this research will be used. This trial will investigate the efficacy and safety of dostarlimab in this setting and multiple translational and clinical endpoints will be explored. It will provide a unique opportunity to study the immune microenvironment in treatment naïve tumours and help determine key mechanisms involved in the response and resistance to therapy, with the potential to develop biomarkers which may elucidate response beyond MMR status, so widening the potential benefit of this agent and assisting in future patient selection.