Using metformin to treat insulin resistance in women with early-stage breast cancer after chemotherapy

Metformin (Dimethylbiguanide) and Insulin Resistance in Women Completing Neoadjuvant and/or Adjuvant Cytotoxic Treatment of Stage I-III Breast Cancer

Phase 3 Interventional City of Hope Medical Center · NCT06763328

This study is testing if metformin can help women with early-stage breast cancer who have finished chemotherapy and are struggling with insulin resistance to improve their health.

Quick facts

PhasePhase 3
Study typeInterventional
Enrollment200 (estimated)
Ages18 Years and up
SexFemale
SponsorCity of Hope Medical Center Academic / other
Drugs / interventionschemotherapy
Locations3 sites (Duarte, California and 2 other locations)
Trial IDNCT06763328 on ClinicalTrials.gov

What this trial studies

This phase III trial investigates the effectiveness of extended release metformin hydrochloride in normalizing glycosylated hemoglobin levels in women who have completed chemotherapy for stage I-III breast cancer and are experiencing insulin resistance. Participants are randomized into two groups: one receiving metformin along with standard dietary and exercise guidance, and the other receiving only standard care. The study aims to determine if metformin can prevent or reverse insulin resistance, which is a risk factor for diabetes and heart disease. Blood samples will be collected throughout the study to monitor health outcomes and potential epigenetic changes.

Who should consider this trial

Good fit: Ideal candidates are women aged 18 and older who have completed treatment for stage I-III breast cancer within the last 30 days to 3 years and are currently disease-free.

Not a fit: Patients who are not female assigned at birth or those with active breast cancer may not benefit from this study.

Why it matters

Potential benefit: If successful, this approach could help prevent diabetes and improve overall health in breast cancer survivors.

How similar studies have performed: Other studies have shown promise in using metformin for metabolic issues in cancer survivors, suggesting potential for success in this approach.

Eligibility criteria

Show full inclusion / exclusion criteria
Inclusion Criteria:

* Documented informed consent of the participant and/or legally authorized representative
* Agreement to allow lab draw of approximately 26 mL of blood (less than 3 tablespoons)

  * To check blood counts, organ function and disease at baseline and 12 months
  * Clinical labs at baseline, 3 months, 6 months,12 months, and 24 months
  * Research labs at baseline, 6 months,12 months, and 24 months
* Age: ≥ 18 years
* Female sex assigned at birth
* Ability to read and understand English or Spanish for questionnaires
* Diagnosis of estrogen receptor (ER)-negative /HER2-wild type or -amplified invasive mammary carcinoma stages I-III
* Receive systemic treatment for breast cancer treatment
* Completed treatment for stage 1-3 breast cancer within 90 days to 5 years and are disease free
* Women who receive drugs for weight loss - e.g. semaglutide - prior to diagnosis are eligible for this protocol and can continue the drug during the intervention

Exclusion Criteria:

* 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 \[GFR\] \< 30 mL/min/1.73m\^2) or those with acute renal insufficiency of any severity due to hepato-renal syndrome or in the peri-operative liver transplantation period
* Previously diagnosed type 1 or type 2 diabetes
* Patients pregnant or within 1 year of pregnancy and completion of lactation (pregnancy tests are standard of care \[SOC\] for initiation of chemotherapy)
* Other active malignancy. Patients with a prior or concurrent malignancy whose natural history or treatment does not have the potential to interfere with the safety or efficacy assessment of the investigational regimen are eligible for this trial
* Any other condition that would, in the investigator's judgment, contraindicate the patient's participation in the clinical study due to safety concerns with clinical study procedures
* An employee who is under the direct/indirect supervision of the principal investigator (PI)/a co-investigator/the study manager and/or a direct study team member
* 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)

Where this trial is running

Duarte, California and 2 other locations

Study contacts

How to participate

  1. Review the eligibility criteria above with your treating physician.
  2. Visit the official trial page on ClinicalTrials.gov for the most current contact information and recruitment status.
  3. Contact the listed study coordinator or principal investigator to request pre-screening. Pre-screening is free and never obligates you to enroll.
Conditions Anatomic Stage I Breast Cancer AJCC v8Anatomic Stage II Breast Cancer AJCC v8Anatomic Stage III Breast Cancer AJCC v8Invasive Breast Carcinoma
Last reviewed 2026-06-13 by the Find a Trial editorial team. Information on this page is for educational purposes and is not medical advice. Always consult qualified healthcare professionals about clinical trial participation.