Question Does the addition of metformin to standard breast cancer treatment improve invasive disease–free survival?
Findings This randomized clinical trial included 3649 patients with high-risk operable breast cancer without diabetes. Treatment with metformin vs placebo resulted in a hazard ratio for an invasive disease–free survival event of 1.01; this was not statistically significant.
Meaning Addition of metformin to standard breast cancer treatment did not significantly improve invasive disease–free survival.
Effect of Metformin vs Placebo on Invasive Disease–Free Survival in Patients With Breast Cancer: The MA.32 Randomized Clinical Trial via JAMA.