title: Differential Use of Screening Mammography in Older Women Initiating Metformin versus Sulfonylurea.
abstract: OBJECTIVE
  Differential use of screening mammography may lead to biased detection of breast cancer. This study aimed to compare receipt of screening mammography and the incidence of screen-detected breast cancer between metformin and sulfonylurea initiators.
  
  
  METHODS
  We used 2006-2014 US Medicare claims to identify initiators of metformin or sulfonylurea aged 65+ years continuously enrolled in Parts A/B for ≥2 years pre-initiation and ≥2 years post-initiation. We reported frequencies of screening mammograms and screen-detected breast cancer in 1 year pre-initiation among all cohort members and in 1 year post-initiation among cancer-free cohort members. Weighted screening risk differences (RDs) were estimated comparing metformin to sulfonylurea group.
  
  
  RESULTS
  We identified 41,436 and 13,367 initiators of metformin and sulfonylurea, 35% and 24% of which had ≥1 screening mammogram in 1 year pre-initiation (weighted RD: 6 percentage points; 95% CI: 5 to 7), respectively. The weighted RD for screen-detected breast cancer associated with metformin was 0.00 percentage points (95% CI: -0.09 to 0.09). Among cancer-free cohort members, metformin initiators had 5 percentage points (95% CI: 4 to 6) and 0.11 percentage points (95% CI: -0.02 to 0.23) absolute risk excess of screening mammography and screen-detected breast cancer in 1 year post-initiation, compared with sulfonylurea initiators, respectively.
  
  
  CONCLUSIONS
  Metformin initiators were more likely to receive screening mammograms than sulfonylurea initiators pre- and post-initiation, indicating possible detection bias due to differential screening mammography. Researchers should be aware of the potential for more screening mammograms pre- and post-initiation when interpreting the findings of metformin on breast cancer incidence. Copyright © 2017 John Wiley & Sons, Ltd.
authors.affiliation: Department of Epidemiology, Gillings School of Global Public Health, University of North Carolina at Chapel Hill, Chapel Hill, NC, USA.
authors.forename: Jin-Liern
authors.identifier: http://orcid.org/0000-0001-9483-6316
authors.initials: JL
authors.lastname: Hong
authors.affiliation: Department of Epidemiology, Gillings School of Global Public Health, University of North Carolina at Chapel Hill, Chapel Hill, NC, USA.|Department of Radiology, School of Medicine, University of North Carolina at Chapel Hill, Chapel Hill, NC, USA.
authors.forename: Louise M
authors.initials: LM
authors.lastname: Henderson
authors.affiliation: Department of Epidemiology, Gillings School of Global Public Health, University of North Carolina at Chapel Hill, Chapel Hill, NC, USA.
authors.forename: Michele
authors.initials: M
authors.lastname: Jonsson Funk
authors.affiliation: Department of Epidemiology, Gillings School of Global Public Health, University of North Carolina at Chapel Hill, Chapel Hill, NC, USA.
authors.forename: Jennifer L
authors.initials: JL
authors.lastname: Lund
authors.affiliation: Department of Medicine, School of Medicine, University of North Carolina at Chapel Hill, Chapel Hill, NC, USA.
authors.forename: John B
authors.initials: JB
authors.lastname: Buse
authors.affiliation: Department of Epidemiology, Gillings School of Global Public Health, University of North Carolina at Chapel Hill, Chapel Hill, NC, USA.
authors.forename: Virginia
authors.initials: V
authors.lastname: Pate
authors.affiliation: Department of Epidemiology, Gillings School of Global Public Health, University of North Carolina at Chapel Hill, Chapel Hill, NC, USA.
authors.forename: Til
authors.initials: T
authors.lastname: Stürmer
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D001943:Breast Neoplasms / Q000175:diagnosis* / Q000453:epidemiology; D015331:Cohort Studies; D055088:Early Detection of Cancer / Q000379:methods*; D005260:Female; D006801:Humans; D007004:Hypoglycemic Agents / Q000008:administration & dosage; D008327:Mammography / Q000379:methods*; D008403:Mass Screening / Q000379:methods; D008687:Metformin / Q000008:administration & dosage*; D013453:Sulfonylurea Compounds / Q000008:administration & dosage*
chemical_list: D007004:Hypoglycemic Agents; D013453:Sulfonylurea Compounds; D008687:Metformin
keywords: Breast Cancer; Diabetes; Metformin; Screening mammography