title: Pre-existing diabetes and breast cancer prognosis among elderly women.
abstract: BACKGROUND
  The objective of this study was to assess the impact of pre-existing diabetes on breast cancer prognosis.
  
  
  METHODS
  Women (n=2833) with centrally confirmed invasive breast cancer in the Women's Health Initiative, who were linked to Medicare claims data (CMS) were followed from the date of breast cancer diagnosis to date of death or 20 September 2013. Information on diabetes was identified through the CMS Chronic Condition Warehouse algorithm. Cox proportional hazard regression was used to estimate adjusted hazard ratios for overall mortality. A competing risks model (proportional subdistribution) model was used to estimate hazard ratios for breast cancer-specific mortality.
  
  
  RESULTS
  Women with diabetes were more likely to have factors related to delayed diagnosis (less recent mammograms, and more advanced cancer stage) and were less likely to receive radiation therapy. Compared with women without diabetes, women with diabetes had significantly increased risk of overall mortality (HR=1.57, 95% CI: 1.23-2.01) and had nonsignificantly increased risk for breast cancer-specific mortality (HR=1.36, 95% CI: 0.86-2.15) before adjustment for factors related to delayed diagnosis and treatment. Adjustment for these factors resulted in a little change in the association of diabetes with overall mortality risk, but further attenuated the point estimate for breast cancer-specific mortality.
  
  
  CONCLUSIONS
  Our study provides additional evidence that pre-existing diabetes increases the risk of total mortality among women with breast cancer. Very large studies with data on breast cancer risk factors, screening and diagnostic delays, treatment choices, and the biological influence of diabetes on breast cancer will be needed to determine whether diabetes also increases the risk for breast cancer-specific mortality.
authors.affiliation: Department of Epidemiology and Biostatistics, School of Public Health, Indiana University Bloomington, Bloomington, IN, USA.
authors.forename: J
authors.initials: J
authors.lastname: Luo
authors.affiliation: Department of Applied Health Science, School of Public Health, Indiana University Bloomington, Bloomington, IN, USA.
authors.forename: M
authors.initials: M
authors.lastname: Hendryx
authors.affiliation: Division of Health policy & Management, School of Public Health, University of Minnesota, Minneapolis, MN, USA.
authors.forename: B
authors.initials: B
authors.lastname: Virnig
authors.affiliation: Department of Biostatistics, School of Public Health, West Virginian University, Morgantown, WV, USA.
authors.forename: S
authors.initials: S
authors.lastname: Wen
authors.affiliation: Los Angeles Biomedical Research Institute at Harbor-University of California, Los Angeles Medical Center, Torrance, CA, USA.
authors.forename: R
authors.initials: R
authors.lastname: Chlebowski
authors.affiliation: Program in Epidemiology, Division of Public Health Sciences, Fred Hutchinson Cancer Research Center, Seattle, WA, USA.
authors.forename: C
authors.initials: C
authors.lastname: Chen
authors.affiliation: Department of Epidemiology & Population Health, Albert Einstein College of Medicine, Bronx, NY, USA.
authors.forename: T
authors.initials: T
authors.lastname: Rohan
authors.affiliation: Fred Hutchinson Cancer Research Center, Seattle, WA, USA.
authors.forename: L
authors.initials: L
authors.lastname: Tinker
authors.affiliation: Department of Social and Preventive Medicine, University at Buffalo, Buffalo, NY, USA.
authors.forename: J
authors.initials: J
authors.lastname: Wactawski-Wende
authors.affiliation: George Washington University Medical Center, Washington, DC, USA.
authors.forename: L
authors.initials: L
authors.lastname: Lessin
authors.affiliation: HealthPartners Institute for Education and Research, Box 1524, Mailstop, 21111R, Minneapolis, MN, USA.
authors.forename: K L
authors.initials: KL
authors.lastname: Margolis
mesh_terms: D000368:Aged; D001943:Breast Neoplasms / Q000401:mortality / Q000473:pathology*; D018270:Carcinoma, Ductal, Breast / Q000401:mortality / Q000473:pathology*; D003924:Diabetes Mellitus, Type 2 / Q000401:mortality / Q000473:pathology*; D005260:Female; D006801:Humans; D053208:Kaplan-Meier Estimate; D011379:Prognosis; D016016:Proportional Hazards Models; D012307:Risk Factors