Metformin use is associated with improved survival in women with type 2 diabetes mellitus (T2DM) and hormone-related cancers, according to research findings published in Gynecologic Oncology.

The survival benefit with metformin was observed in patients with breast, endometrial, and ovarian cancers, even after accounting for surrogates of diabetes progression, such as HbA1C level, body mass index, and duration of diabetes.

The study included 6225 women with T2DM and new diagnoses of ovarian (n=438), breast (n=4424), or endometrial (n=1420) cancer from January 1, 2010, through June 1, 2019, at an outpatient facility (57 patients had more than 1 diagnosis).

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The use of glycemic medications at the time of first cancer diagnosis was classified into different tiers, and the survival outcomes were compared for each of 4 categories:  

  • Metformin (tier 1) vs no glycemic medication
  • Metformin vs tier 2 medications (sulfonylureas, thiazolidinediones, SGLT2 inhibitors, DPP4 inhibitors, alpha glucosidase inhibitors, and GLP-1 agonists)
  • Metformin vs tier 3 medications (insulins and amylinomimetics)
  • Tier 2 vs tier 3 medications.

Metformin was the most frequently used glycemic medication (n=3232). Women taking metformin were younger and had a lower likelihood of comorbidities and hospitalizations after diagnosis. The women who were taking metformin or tier 2 medications had comparable body mass index, A1C levels, and duration of diabetes.

The crude death rates were highest in women treated with tier 3 medications only (37%), followed by tier 2 users (33%), patients on no medication (23%), and metformin users (18%).

There was a significant increase in the risk of death for women taking tier 2 or tier 3 medications, compared with women taking metformin. The risk of death was higher in tier 3 medication users (adjusted hazard ratio [aHR], 1.83; 95% CI, 1.58-2.13) than in tier 2 users (aHR, 1.32; 95% CI, 1.11-1.57).

In sensitivity analyses, the benefit of metformin remained consistent after accounting for the duration of diabetes.

“Our findings, consistent with prior studies, indicate metformin use improves survival in women with T2DM and hormonally mediated women’s cancers,” the researchers wrote. “[C]onducting a randomized controlled trial of metformin therapy in women with these cancer types is justified.”


Lemon LS, Orr B, Modugno F, et al. Metformin and survival: Is there benefit in a cohort limited to diabetic women with endometrial, breast, or ovarian cancer? Gynecol Oncol. Published online February 6, 2022. doi:10.1016/j.ygyno.2022.01.022