Could a common diabetes drug and fasting shrink breast tumors before surgery?

NCT ID NCT05023967

First seen Jun 25, 2026 · Last updated Jun 27, 2026 · Updated 1 time

Summary

This phase IIb trial is testing whether combining a nightly fast (time-restricted eating) with the diabetes drug metformin can slow the growth of breast cancer cells before surgery. The study includes 120 women with early-stage breast cancer or a precancerous condition called DCIS. Participants will take metformin and follow a fasting schedule for a few weeks before their planned surgery, and researchers will measure changes in tumor cell growth and other biomarkers.

What this could mean

Our plain-language read of the trial. This is informational only — not medical advice or a prediction.

Active substance
Metformin extended-release (a diabetes drug) plus time-restricted eating (nightly fasting)
What this could lead to
If it works, this could point toward a simple, low-cost way to slow breast cancer growth before surgery, possibly reducing the need for more aggressive treatments.
What could go wrong
This is a small, early-phase trial (phase IIb) with only 120 participants. The results may not apply to all breast cancer types, and metformin can cause side effects like low blood sugar or digestive issues.

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Conditions

The condition(s) this trial relates to.

As listed by the trial registrant

The condition terms exactly as the trial's registrant entered them.

Contacts and locations

Locations

  • European Institute of Oncology

    Milan, 20141, Italy

  • Galliera Hospital

    Genoa, 16128, Italy

  • M D Anderson Cancer Center

    Houston, Texas, 77030, United States

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