Megestrol Acetate with or without Pterostilbene in Treating Patients with Endometrial Cancer Undergoing Hysterectomy

Inclusion Criteria

• Documented informed consent of the participant and/or legally authorized representative
• Willing to undergo an intraoperative biopsy/or standard of care tissue collection during surgery, following completion of treatment with MA +/- PTE
• Age >= 18 years
• Eastern Cooperative Oncology Group (ECOG) performance status of 0‐2
• Histologically confirmed EC or complex atypical hyperplasia of the endometrium
• Candidate for a total hysterectomy with or without bilateral salpingo‐oophorectomy
• About to initiate preoperative window period, with planned hysterectomy scheduled
• Platelets >= 100,000/mm^3 * NOTE: Platelet transfusions are not permitted within 14 days of platelet assessment unless cytopenia is secondary to disease involvement
• Total bilirubin =< 1.5 X upper limit of normal (ULN)
• Aspartate aminotransferase (AST) =< 1.5 x ULN
• Alanine aminotransferase (ALT) =< 1.5 x ULN
• Creatinine clearance of >= 60 mL/min per 24 hour urine test or the Cockcroft‐Gault formula
• Women of childbearing potential: negative urine or serum pregnancy test in premenopausal women. Postmenopausal women do not need to undergo a pregnancy test. If the urine test is positive or cannot be confirmed as negative, a serum pregnancy test will be required

Exclusion Criteria

• Pterostilbene supplements within 30 days prior to day 1 of protocol therapy
• Any of the following phytochemical‐based supplements within 30 days prior to day 1 of protocol therapy: resveratrol, genistein, and quercetin
• Chemotherapy for EC
• Allergic reaction/hypersensitivity to similar agents, excipients
• Unstable cardiac disease as defined by one of the following: * Cardiac events such as myocardial infarction (MI) within the past 6 months * NYHA (New York Heart Association) heart failure class III‐IV * Uncontrolled atrial fibrillation or hypertensive emergency/urgency (defined as systolic blood pressure >= 180 mmHg and/or diastolic blood pressure >= 120 mmHg)
• Active or history of recent thromboembolism or stroke, within the past 6 months
• Cushing’s syndrome
• Acute infection requiring systemic (intravenous) treatment
• Known history of human immunodeficiency virus (HIV) infection
• Known active hepatitis B or C infection
• Inability to swallow tablets/capsules
• Any other condition that would, in the investigator’s judgment, contraindicate the patient’s participation in the clinical study due to safety concerns or compliance with clinical study procedures, e.g., infection/inflammation, intestinal obstruction, unable to swallow medication, social/ psychological issues, etc
• Prospective participants who, in the opinion of the investigator, may not be able to comply with all study procedures (including compliance issues related to feasibility/logistics)