ALPINE: Maintenance Letrozole/Abemaciclib

This study is testing whether letrozole (a hormone therapy) combined with abemaciclib (a targeted drug that slows cell growth) can be used as maintenance therapy to prevent recurrence in people with a specific type of uterine cancer after completing initial treatment. **You may be eligible if...** - You have been diagnosed with endometrioid endometrial cancer or endometrial carcinosarcoma with an endometrioid component - Your tumor tests positive for estrogen receptors (ER-positive) - You have completed initial treatment (such as chemotherapy) with no evidence of disease **You may NOT be eligible if...** - Your cancer has progressed or spread - You have had prior treatment with a CDK4/6 inhibitor or certain hormone therapies for this cancer - You have significant heart, liver, or bone marrow problems - You are pregnant or breastfeeding Talk to your doctor to see if this trial is right for you.