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Original Investigation
April 2018

Family History and Breast Cancer Risk Among Older Women in the Breast Cancer Surveillance Consortium Cohort

Author Affiliations
  • 1Department of Oncology, Georgetown University Medical Center, Washington, DC
  • 2Department of Public Health Sciences, School of Medicine, University of California, Davis, Davis, California
  • 3Kaiser Permanente Washington Health Research Institute, Seattle, Washington
  • 4Department of Population Health Sciences, Carbone Cancer Center, School of Medicine and Public Health, University of Wisconsin–Madison, Madison
  • 5Department of Surgery, University of Vermont College of Medicine, Burlington
  • 6Department of Medicine, University of California, San Francisco
  • 7Department of Biomedical Data Science, Geisel School of Medicine at Dartmouth, Lebanon, New Hampshire
  • 8Department of Radiology, University of North Carolina at Chapel Hill, Chapel Hill
JAMA Intern Med. 2018;178(4):494-501. doi:10.1001/jamainternmed.2017.8642
Key Points

Question  Is family history associated with breast cancer risk among older women, and if so, do any associations vary by breast density?

Findings  In this cohort study of 403 268 women, first-degree family history was associated with an increased risk of breast cancer among women 65 years and older. Risk associated with family history was not significantly modified by breast density.

Meaning  Family history should be considered when weighing harms and benefits of screening mammography in older women.

Abstract

Importance  First-degree family history is a strong risk factor for breast cancer, but controversy exists about the magnitude of the association among older women.

Objective  To determine whether first-degree family history is associated with increased risk of breast cancer among older women, and identify whether the association varies by breast density.

Design, Setting, and Participants  Prospective cohort study between 1996 and 2012 from 7 Breast Cancer Surveillance Consortium (BCSC) registries located in New Hampshire, North Carolina, San Francisco Bay area, western Washington state, New Mexico, Colorado, and Vermont. During a mean (SD) follow-up of 6.3 (3.2) years, 10 929 invasive breast cancers were diagnosed in a cohort of 403 268 women 65 years and older with data from 472 220 mammography examinations. We estimated the 5-year cumulative incidence of invasive breast cancer by first-degree family history, breast density, and age groups. Cox proportional hazards models were fit to estimate the association of first-degree family history with risk of invasive breast cancer (after adjustment for breast density, BCSC registry, race/ethnicity, body mass index, postmenopausal hormone therapy use, and benign breast disease for age groups 65 to 74 years and 75 years and older, separately). Data analyses were performed between June 2016 and June 2017.

Exposure  First-degree family history of breast cancer.

Main Outcomes and Measures  Incident breast cancer.

Results  In 403 268 women 65 years and older, first-degree family history was associated with an increased risk of breast cancer among women ages 65 to 74 years (hazard ratio [HR], 1.48; 95% CI, 1.35-1.61) and 75 years and older (HR, 1.44; 95% CI, 1.28-1.62). Estimates were similar for women 65 to 74 years with first-degree relative’s diagnosis age younger than 50 years (HR, 1.47; 95% CI, 1.25-1.73) vs 50 years and older (HR, 1.33; 95% CI, 1.17-1.51) and for women ages 75 years and older with the relative’s diagnosis age younger than 50 years (HR, 1.31; 95% CI, 1.05-1.63) vs 50 years and older (HR, 1.55; 95% CI, 1.33-1.81). Among women ages 65 to 74 years, the risk associated with first-degree family history was highest among those with fatty breasts (HR, 1.67; 95% CI, 1.27-2.21), whereas in women 75 years and older the risk associated with family history was highest among those with dense breasts (HR, 1.55; 95% CI, 1.29-1.87).

Conclusions and Relevance  First-degree family history was associated with increased risk of invasive breast cancer in all subgroups of older women irrespective of a relative’s age at diagnosis.

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