Use of metformin and survival of diabetic women with breast cancer.
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.


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.
Paul J H L
PJ
Peeters
Marloes T
MT
Bazelier
Peter
P
Vestergaard
Hubert G M
HG
Leufkens
Marjanka K
MK
Schmidt
Frank
F
de Vries
Department of Pharmacoepidemiology and Clinical Pharmacology, Utrecht Institute of Pharmaceutical Sciences, Utrecht University, Universiteitsweg 99, 3584 CG Utrecht, The Netherlands. m.l.debruin@uu.nl.
Marie L
ML
De Bruin
D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D001943:Breast Neoplasms / Q000150:complications / Q000401:mortality / Q000628:therapy*; D015331:Cohort Studies; D015897:Comorbidity; D003718:Denmark / Q000453:epidemiology; D003920:Diabetes Mellitus / Q000188:drug therapy*; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D007004:Hypoglycemic Agents / Q000627:therapeutic use*; D008687:Metformin / Q000627:therapeutic use*; D008875:Middle Aged; D012042:Registries; D012307:Risk Factors; D013534:Survival; D016896:Treatment Outcome; D055815:Young Adult
D007004:Hypoglycemic Agents; D008687:Metformin