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Evidence record

Metformin × Breast Cancer

AMPK activation suppresses mTOR-mediated proliferation in breast epithelial cells.

Moderate Evidence
PublishedLast updated June 28, 2026Download evidence report

Why this drug?

Beyond glycemic control, metformin modulates AMPK/mTOR signaling and has demonstrated anti-proliferative effects in preclinical cancer models, with observational cohorts suggesting reduced cancer incidence in diabetic patients.

Known risks

  • Lactic acidosis (rare, especially with renal impairment)
  • GI upset
  • Vitamin B12 deficiency with long-term use
  • Contraindicated in severe renal dysfunction

Evidence behind this

Confidence score62%
Signal strength: LowLevel 2b–3 (observational + preclinical)
Evidence grade
Moderate Evidence

Observational studies suggest reduced cancer incidence; RCTs in adjuvant setting show mixed results.

Mechanism

AMPK activation suppresses mTOR-mediated proliferation in breast epithelial cells.

observationalmeta analysispreclinicalPhase II

Authoritative sources

  • PubMed · 22019127

    Metformin and cancer risk in diabetic patients

    Decensi A et al. (2012)

    View
  • PubMed · 23487376

    Metformin and breast cancer: a systematic review

    Coleman CB et al. (2013)

    View
  • ClinicalTrials.gov · NCT01101438

    Metformin in early breast cancer (MA.32)

    View

AI-generated summary

Generated March 15, 2026Last verified June 28, 2026

Metformin shows mechanistic plausibility and epidemiological support for breast cancer risk reduction, but prospective RCT evidence in treatment-naïve adjuvant settings remains inconclusive. Suitable for hypothesis generation and trial design, not clinical recommendation outside diabetes care.

Source papers
  • Decensi A et al., 2012
  • Coleman CB et al., 2013

This summary is AI-assisted and human-reviewed. It does not constitute medical advice. Always consult authoritative sources and qualified professionals.