Impact of metformin on biomarkers linked to breast cancer

Takeaway

• This meta-analysis suggests that metformin intervention significantly reduces insulin, fasting glucose, C-reactive protein (CRP), homeostatic model assessment for insulin-resistance (HOMA-IR), leptin, body mass indices (BMI) and Ki-67 among diabetic patients with breast cancer.

Why this matters

• Previous reviews evaluating the effects of metformin among diabetic patients with breast cancer have shown conflicting results.

Study design

• 9 studies involving 1363 participants (intervention: n=665 and control: n=698) met eligibility criteria after a search on MEDLINE/PubMed, SCOPUS and Cochrane library.
• Funding: None.

Key results

• Compared with the control group, metformin intervention was associated with significant reduction in:
  • insulin (weighted mean difference [WMD], −0.99 U/mL; 95% CI, −1.66 to −0.33; P=.01; I²=59.8),
  • blood glucose levels (WMD, −1.78 mL/dL; 95% CI −2.96 to −0.60; P=.09; I²=42.9),
  • CRP (WMD, −0.60 mg/L; 95% CI −0.88 to −0.33; P=.73; I²=0.00),
  • HOMA-IR (WMD, −0.45; 95% CI, −0.73 to −0.13; P=.20; I²=33.9),
  • leptin (WMD, −2.44 ng/mL; 95% CI, −3.28 to −1.61; P=.61; I²=0.00),
  • BMI (WMD, −0.55 kg/m²; 95% CI, −1.00 to −0.11; P=.17; I²=41.2) and
  • Ki-67 (WMD, −4.06; 95% CI, −7.59 to −0.54; P=.01; I²=79.1).
• Subgroup analyses showed that reduction in insulin, glucose and BMI were more significant with metformin intervention duration of >4 weeks compared with trials of <4 weeks.
• Cholesterol levels (WMD, −13.03 mg/dL; 95% CI, −19.35 to −6.71) decreased significantly with metformin intervention duration of <4 weeks.

Limitations

• Heterogeneity among included studies.