Primary Objectives:~The primary objective of this study is to describe the safety and toxicity of chemoradiation with concurrent immunotherapy, followed by chemotherapy plus concurrent immunotherapy, followed by immunotherapy maintenence in patients with stage IIIC endometrial cancer.~Secondary Objectives:~The secondary objectives are listed below.~To estimate progression free survival~To describe the time to recurence and the recurrence patterns including extent and location (i.e. isolated versus multi-focal, pelvic versus distant)~To estimate disease specific survival and overall survival~Exploratory:~To determine if the presence of deficient mismatch repair (dMMR) or microsatellite instability correlates with progression free survival, disease free survival and 5-year overall survival~To assess patient reported outcomes (PROs) during the course of treatment and follow up
To learn if chemotherapy given in combination with radiation therapy, followed by maintenance therapy, can help to control endometrial cancer. The safety and effects of this study treatment will also be studied