Use of metformin and survival of diabetic women with breast cancer

Paul J H L Peeters, Marloes T Bazelier, Peter Vestergaard, Hubert G M Leufkens, Marjanka K Schmidt, Frank de Vries, Marie L De Bruin*

*Corresponding author for this work

Research output: Contribution to journalArticleAcademicpeer-review


OBJECTIVE: This study was set out to determine whether metformin use influences survival in breast cancer patients treated with antidiabetic drugs as compared to non-users.

RESEARCH DESIGN AND METHODS: We used data from the Danish national registries (1996-2008) to identify adult female patients diagnosed with breast cancer who were prescribed antidiabetic medication. We performed multivariate Coxproportional hazard regression to assess all-cause and breast cancer-specific mortality risks associated with metformin exposure. In a secondary analysis, we stratified use of metformin according to the cumulative number of prescriptions.

RESULTS: Of the 1058 breast cancer patients 349 died during follow-up, with breast cancer listed as the primary cause of death for 152 cases. Compared to non-use, current metformin treatment was associated with a significant reduction in overall mortality (adjusted HR 0.74, 95% CI, 0.58-0.96). For breast cancer-specific mortality, a non-significant risk reduction (adjusted HR 0.88, 95% CI, 0.59-1.29) was observed, which became significant after stratification according to cumulative number of prescriptions. An increased risk of both overall and breast cancer-specific mortality was observed in the first 12 months after discontinuation of metformin.

CONCLUSIONS: We observed a nonsignificant reduction in breast cancer-specific mortality associated with metformin exposure among breast cancer patients treated with antidiabetic drugs. However, our findings suggest that long-term metformin use may have a beneficial effect on survival in patients with breast cancer. Further confirmation of these findings is needed.

Original languageEnglish
Pages (from-to)357-63
Number of pages7
JournalCurrent Drug Safety
Issue number5
Publication statusPublished - Nov 2013
Externally publishedYes


  • Adolescent
  • Adult
  • Aged
  • Aged, 80 and over
  • Breast Neoplasms/complications
  • Cohort Studies
  • Comorbidity
  • Denmark/epidemiology
  • Diabetes Mellitus/drug therapy
  • Female
  • Follow-Up Studies
  • Humans
  • Hypoglycemic Agents/therapeutic use
  • Metformin/therapeutic use
  • Middle Aged
  • Registries
  • Risk Factors
  • Survival
  • Treatment Outcome
  • Young Adult


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