Comparative effect of initiating metformin versus sulfonylureas on breast cancer risk in older women

Jin Liern Hong, Michele Jonsson Funk, John B. Buse, Louise M. Henderson, Jennifer L. Lund, Virginia Pate, Til Stürmer

Research output: Contribution to journalArticle

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Abstract

Background: Several observational studies have reported that metformin may be associated with reduced risk of breast cancer; however, many of these studies were affected by time-related biases such as immortal time bias and time-window bias. This study aimed to examine the relative risk of breast cancer for older women initiating metformin versus sulfonylureas while avoiding such biases. Methods: The study cohort consisted of women aged 65+ who initiated monotherapy with metformin (n = 45,900) or sulfonylureas (n = 13,904) and were free of cancer and renal disease within 6 months before treatment initiation using 2007-2012 US Medicare claims data. We followed treatment initiators for incident breast cancer, and estimated hazard ratios using weighted Cox models. Unmeasured confounding by body mass index and smoking was further adjusted by propensity score calibration using external information from Medicare Current Beneficiary Survey 2006-2009 panels. Results: During 58,835 and 16,366 person-years of follow-up, 385 initiators of metformin treatment and 95 of sulfonylurea were diagnosed with breast cancer. Metformin initiators did not have a reduced risk of breast cancer compared with sulfonylurea initiators (hazard ratio: 1.2; 95% confidence interval: 0.94, 1.6). Externally controlling for body mass index and smoking did not affect the estimates. Conclusion: The findings of this study provide no support for a reduced risk of breast cancer after initiation of metformin compared with a clinical alternative in older women. This study is limited by the relatively short follow-up time and we cannot exclude the possible benefits of long-Time metformin use on breast cancer risk.

LanguageEnglish (US)
Pages446-454
Number of pages9
JournalEpidemiology
Volume28
Issue number3
DOIs
StatePublished - May 1 2017

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Metformin
Breast Neoplasms
Medicare
Body Mass Index
Smoking
Propensity Score
Kidney Neoplasms
Proportional Hazards Models
Calibration
Observational Studies
Cohort Studies
Therapeutics
Confidence Intervals

ASJC Scopus subject areas

  • Epidemiology

Cite this

Hong, J. L., Funk, M. J., Buse, J. B., Henderson, L. M., Lund, J. L., Pate, V., & Stürmer, T. (2017). Comparative effect of initiating metformin versus sulfonylureas on breast cancer risk in older women. Epidemiology, 28(3), 446-454. DOI: 10.1097/EDE.0000000000000635

Comparative effect of initiating metformin versus sulfonylureas on breast cancer risk in older women. / Hong, Jin Liern; Funk, Michele Jonsson; Buse, John B.; Henderson, Louise M.; Lund, Jennifer L.; Pate, Virginia; Stürmer, Til.

In: Epidemiology, Vol. 28, No. 3, 01.05.2017, p. 446-454.

Research output: Contribution to journalArticle

Hong, JL, Funk, MJ, Buse, JB, Henderson, LM, Lund, JL, Pate, V & Stürmer, T 2017, 'Comparative effect of initiating metformin versus sulfonylureas on breast cancer risk in older women' Epidemiology, vol. 28, no. 3, pp. 446-454. DOI: 10.1097/EDE.0000000000000635
Hong JL, Funk MJ, Buse JB, Henderson LM, Lund JL, Pate V et al. Comparative effect of initiating metformin versus sulfonylureas on breast cancer risk in older women. Epidemiology. 2017 May 1;28(3):446-454. Available from, DOI: 10.1097/EDE.0000000000000635
Hong, Jin Liern ; Funk, Michele Jonsson ; Buse, John B. ; Henderson, Louise M. ; Lund, Jennifer L. ; Pate, Virginia ; Stürmer, Til. / Comparative effect of initiating metformin versus sulfonylureas on breast cancer risk in older women. In: Epidemiology. 2017 ; Vol. 28, No. 3. pp. 446-454
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