Updated June 2026 · ClinicalTrials.gov

RECRUITINGPhase 3INTERVENTIONAL

Metformin for the Treatment of Insulin Resistance in Women With Stage I-III Breast Cancer Completing Chemotherapy

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

Metformin for the Treatment of Insulin Resistance in Women With Stage I-III Breast Cancer Completing Chemotherapy (NCT06763328) is a Phase 3 interventional studying Anatomic Stage I Breast Cancer AJCC v8 and Anatomic Stage II Breast Cancer AJCC v8, sponsored by City of Hope Medical Center. RECRUITING as of the most recent ClinicalTrials.gov update. Talk to your doctor before contacting the trial site.

About This Trial

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.

What Stage of Research Is This?

Phase 3 trials confirm efficacy and safety in large patient groups (often 300–3,000+) and form the evidence base for an FDA approval submission. For Anatomic Stage I Breast Cancer AJCC v8, Phase 3 studies typically randomize participants between the investigational treatment and either a placebo or current standard of care. A successful Phase 3 result is the threshold most treatments need to clear before regulatory approval.

This trial is currently recruiting participants. The sponsor has registered the study with ClinicalTrials.gov as actively enrolling, which means new applicants who meet the eligibility criteria can be considered for screening. Trial status can change between updates — confirm current recruiting status with the study contact before traveling for a screening visit.

Target enrollment of 80 participants puts this in the typical range for a Phase 2-style efficacy study or a moderate Phase 3 trial in a focused Anatomic Stage I Breast Cancer AJCC v8 subpopulation. At this scale, the study has enough statistical power to detect a clear treatment effect but is not the largest cohort in the field.

Who May Be Eligible (Plain English)

Who May Qualify: - Documented willing to sign a consent form 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 - 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 invasive breast cancer stages I-III - Completed adjuvant treatment for Stage 1-3 breast cancer within 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. Who Should NOT Join This Trial: - 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/1.73m\^2) or those with acute renal insufficiency of any severity due to hepato-renal syndrome or in the peri-operative liver transplantation period - Bilirubin of \>2.5 mg/dL (normal range 0.1-1.2 mg/dL). - Previously diagnosed type 1 or type 2 diabetes - Patients pregnant or within 1 year of pregnancy and completion of lactation (to be determined at randomization). - 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 ...See full criteria on ClinicalTrials.gov Always talk to your doctor about whether this trial is right for you.

These are translations of the protocol\'s inclusion and exclusion criteria, simplified for patients and caregivers. The original clinical text appears below. Eligibility is ultimately confirmed by the trial site\'s screening process — this summary is a starting point for a conversation with your doctor, not a final determination.

Original Eligibility Criteria

View original clinical language

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 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 * 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 invasive breast cancer stages I-III * Completed adjuvant treatment for Stage 1-3 breast cancer within 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 \[GFR\] \< 60 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 * Bilirubin of \>2.5 mg/dL (normal range 0.1-1.2 mg/dL). * Previously diagnosed type 1 or type 2 diabetes * Patients pregnant or within 1 year of pregnancy and completion of lactation (to be determined at randomization). * 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)

Treatments Being Tested

PROCEDURE

Biospecimen Collection

Undergo blood sample collection

OTHER

Educational Intervention

Receive standard of care healthy diet and exercise handouts

DRUG

Extended Release Metformin Hydrochloride

Given PO

OTHER

Questionnaire Administration

Ancillary studies

Locations (3)

Trial sites listed on ClinicalTrials.gov for this study. Site activation status can vary — confirm with the specific site before traveling for a screening visit.

City of Hope Medical Center

Duarte, California, United States

UC San Diego Moores Cancer Center

La Jolla, California, United States

University of California-Riverside

Riverside, California, United States

How to Talk to Your Doctor About This Trial

Bring the printable summary of this trial — including the NCT ID (NCT06763328), the sponsor (City of Hope Medical Center), and the key eligibility criteria — to your next appointment. Your doctor can review the inclusion and exclusion criteria against your medical history, lab values, and current treatments to assess whether you are likely to qualify. They can also help you weigh whether trial participation makes sense alongside your existing care plan.

Useful questions to walk through together: What does the trial protocol require beyond standard care? How long is the active treatment phase, and how long is follow-up? Are there study visits at sites I can reach? Who pays for the trial-specific procedures, and who pays for standard-of-care portions? See our 25 questions to ask about clinical trials guide for a more complete checklist.

Authoritative Sources

The official record for this trial lives on ClinicalTrials.gov — the federal registry maintained by the National Library of Medicine at NIH. For background on how this trial fits into the FDA approval pathway, see the FDA drug approval process. For oncology-specific guidance for patients considering trials, the National Cancer Institute publishes patient-oriented overviews. International trial registries are aggregated by the WHO ICTRP.

Frequently Asked Questions

What is the NCT06763328 clinical trial studying?

Who can participate in NCT06763328?

Eligibility for this trial depends on the specific inclusion and exclusion criteria set by the sponsor. The plain-English summary above translates the most important criteria into accessible language; the official clinical text is preserved in the collapsible section underneath. Whether you fit any specific trial is a medical decision your doctor needs to confirm — bring the trial information to your treating physician for a full review against your medical history.

How do I contact the trial site for NCT06763328?

Contact information registered with ClinicalTrials.gov is shown in the sidebar of this page. Before reaching out, confirm with your treating physician that this trial is appropriate for your situation. The trial site will then walk you through the screening process to determine final eligibility.

Is participating in a clinical trial safe?

Clinical trials in the United States are regulated by the FDA and overseen by Institutional Review Boards (IRBs) that review the protocol for safety. Risk varies by trial — Phase 1 studies test new treatments in humans for the first time, while Phase 3 trials use treatments that have already passed earlier safety screening. The informed consent document for any specific trial details the known risks and what to expect. Discuss those risks with your physician before deciding whether to participate.

Where can I verify the data on this page?

Every detail on this page comes directly from the ClinicalTrials.gov API. Click "View on ClinicalTrials.gov" in the sidebar to see the official, unmodified record. The federal record is always authoritative; this page is a structured presentation with a plain-English eligibility translation. For background on how clinical trials are regulated, see the FDA drug approval process documentation.

How This Page Is Built

Every field on this page is pulled directly from the ClinicalTrials.gov API v2 — no estimates, no proxies. The plain-English eligibility translation is generated from the original protocol text and reviewed for fidelity to the underlying clinical criteria. The original clinical text remains visible in the collapsible section above so users and clinicians can verify the translation. Read the full methodology for the data pipeline and known limitations.

Source: ClinicalTrials.gov API v2 record for NCT06763328. Maintained by the National Library of Medicine at NIH. Public domain. Cite as: "TrialFinderData. NCT06763328. Data: ClinicalTrials.gov."

Medical disclaimer: This page is informational, not medical advice. Talk to your doctor about whether a clinical trial is right for you.

Last updated 2026-06-26 · Data from ClinicalTrials.gov.