This phase III trial evaluates how often women develop insulin resistance and type-2 diabetes and compares metformin with usual care to usual care alone in treating insulin resistance in women with stage I-III breast cancer after chemotherapy. Insulin resistance occurs when cells stop responding to insulin and is a risk factor for developing diabetes and heart disease. Higher levels of insulin have been shown to be associated with aggressive breast cancer. Metformin hydrochloride decreases the amount of glucose (a type of sugar) released into the bloodstream from the liver and increases the body's use of the glucose. Metformin as well as standard of care diet and exercise education is known to lower blood sugar. However, chemotherapy may accelerate metabolic disorders, such as high blood sugar, and the impact of metformin in these breast cancer survivors is not known. Giving metformin with usual care may be more effective than usual care alone in preventing or reversing insulin resistance in women with stage I-III breast cancer after chemotherapy.
Documented informed consent of the participant and/or legally authorized representative
Agreement to allow lab draw of approximately 26 mL of blood (less than 2 tablespoons)
To check blood counts, organ function and disease at baseline and 12 months
Review of clinical charts at pre-registration* (refer to Study Calendar), baseline, 3 months, 6 months,12 months, and 24 months
Currently taking metformin or any other oral antidiabetic medications. Weight loss medications are permitted - e.g. semaglutide
Taking tamoxifen or aromatase inhibitor
Contraindication to metformin prevention such as acute hypersensitivity or allergic reaction to metformin
Participants with acute or chronic renal insufficiency (a glomerular filtration rate [GFR] < 60 mL/min/1.73m²) or those with acute renal insufficiency of any severity due to hepato-renal syndrome or in the peri-operative liver transplantation period
City of Hope Medical Center
Lead sponsor
National Cancer Institute (NCI)
Collaborator