Breast Cancer

Metformin Not Effective in Treatment of Patients With Early Stage Breast Cancer

Metformin, a medication commonly used to treat patients with type 2 diabetes, does not improve invasive, disease-free survival of patients with breast cancer, according to findings in a recent study.

To determine whether adjuvant metformin use was effective in the treatment of patients with high-risk, operable breast cancer without diabetes, the researchers conducted a randomized, double-blind, placebo-controlled trial.

A total of 3469 (mean age, 52.4 years; 3643 women [99.8%]) patients were enrolled in the clinical study. The patients were randomly assigned to receive 850 mg of oral metformin twice per day (n = 1824) or a placebo twice per day (n = 1825) for 5 years.

Primary analysis was conducted for patients who were ER/PgR+ (n=2533) with a median duration of follow-up of 96.2 months (range, 0.2-121 months).

“Among patients with high-risk operable breast cancer without diabetes, the addition of metformin vs placebo to standard breast cancer treatment did not significantly improve invasive disease–free survival,” the researchers concluded.


—Jessica Ganga


Goodwin PJ, Chen BE, Gelmon KA, et al. Effect of metformin vs placebo on invasive disease-free survival in patients with breast cancer. The MA.32 randomized clinical trial.  JAMA. 2022;327(20):1963-1973. doi:10.1001/jama.2022.6147