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Beaber EF, Buist DSM, Barlow WE, Malone KE, Reed SD, Li CI. Recent oral contraceptive use by formulation and breast cancer risk among women 20 to 49 years of age. Cancer Res 2015; 74:4078-89. [PMID: 25085875 DOI: 10.1158/0008-5472.can-13-3400] [Citation(s) in RCA: 58] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
Previous studies of oral contraceptives and breast cancer indicate that recent use slightly increases risk, but most studies relied on self-reported use and did not examine contemporary oral contraceptive formulations. This nested case-control study was among female enrollees in a large U.S. integrated health care delivery system. Cases were 1,102 women ages 20 to 49 years diagnosed with invasive breast cancer from 1990 to 2009. Controls were randomly sampled from enrollment records (n = 21,952) and matched to cases on age, year, enrollment length, and medical chart availability. Detailed oral contraceptive use information was ascertained from electronic pharmacy records and analyzed using conditional logistic regression, ORs, and 95% confidence intervals (CI). Recent oral contraceptive use (within the prior year) was associated with an increased breast cancer risk (OR, 1.5; 95% CI, 1.3-1.9) relative to never or former OC use. The association was stronger for estrogen receptor-positive (ER(+); OR, 1.7; 95% CI, 1.3-2.1) than estrogen receptor-negative (ER(-)) disease (OR, 1.2, 95% CI, 0.8-1.8), although not statistically significantly different (P = 0.15). Recent use of oral contraceptives involving high-dose estrogen (OR, 2.7; 95% CI, 1.1-6.2), ethynodiol diacetate (OR, 2.6; 95% CI, 1.4-4.7), or triphasic dosing with an average of 0.75 mg of norethindrone (OR, 3.1; 95% CI, 1.9-5.1; Pheterogeneity compared with using other oral contraceptives = 0.004) was associated with particularly elevated risks, whereas other types, including low-dose estrogen oral contraceptives, were not (OR, 1.0; 95% CI, 0.6-1.7). Our results suggest that recent use of contemporary oral contraceptives is associated with an increased breast cancer risk, which may vary by formulation. If confirmed, consideration of the breast cancer risk associated with different oral contraceptive types could impact discussions weighing recognized health benefits and potential risks.
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Affiliation(s)
- Elisabeth F Beaber
- Group Health Research Institute, Group Health Cooperative, Seattle, Washington. Division of Public Health Sciences, Fred Hutchinson Cancer Research Center, Seattle, Washington. Department of Epidemiology, University of Washington, Seattle, Washington.
| | - Diana S M Buist
- Group Health Research Institute, Group Health Cooperative, Seattle, Washington. Department of Epidemiology, University of Washington, Seattle, Washington
| | - William E Barlow
- Department of Biostatistics, University of Washington, Seattle, Washington
| | - Kathleen E Malone
- Division of Public Health Sciences, Fred Hutchinson Cancer Research Center, Seattle, Washington. Department of Epidemiology, University of Washington, Seattle, Washington
| | - Susan D Reed
- Group Health Research Institute, Group Health Cooperative, Seattle, Washington. Division of Public Health Sciences, Fred Hutchinson Cancer Research Center, Seattle, Washington. Department of Epidemiology, University of Washington, Seattle, Washington. Department of Obstetrics and Gynecology, University of Washington, Seattle, Washington
| | - Christopher I Li
- Division of Public Health Sciences, Fred Hutchinson Cancer Research Center, Seattle, Washington. Department of Epidemiology, University of Washington, Seattle, Washington
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Beaber EF, Malone KE, Tang MTC, Barlow WE, Porter PL, Daling JR, Li CI. Oral contraceptives and breast cancer risk overall and by molecular subtype among young women. Cancer Epidemiol Biomarkers Prev 2014; 23:755-64. [PMID: 24633144 DOI: 10.1158/1055-9965.epi-13-0944] [Citation(s) in RCA: 47] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022] Open
Abstract
BACKGROUND Evidence suggests that recent oral contraceptive (OC) use is associated with a small increased breast cancer risk; yet risks associated with contemporary OC preparations and by molecular subtype are not well characterized. METHODS We conducted a population-based case-control study of invasive breast cancer among women ages 20 to 44 residing in the Seattle-Puget Sound area from 2004 to 2010 (985 cases and 882 controls). We collected information on contraceptive use and participant characteristics via an in-person interview. Multivariable-adjusted logistic regression was used to calculate odds ratios (OR) and 95% confidence intervals (CI). RESULTS Lifetime duration of OC use for ≥ 15 years was associated with an increased breast cancer risk (OR, 1.5; 95% CI, 1.1-2.2). Current OC use (within 1 year of reference date) for ≥ 5 years was associated with an increased risk (OR, 1.6; 95% CI, 1.1-2.5) and there were no statistically significant differences in risk by OC preparation. Risk magnitudes were generally greater among women ages 20 to 39, and for estrogen receptor-negative (ER(-)) and triple-negative breast cancer (current use for ≥ 5 years among ages 20-39: ER(-) OR, 3.5; 95% CI, 1.3-9.0; triple-negative OR, 3.7; 95% CI, 1.2-11.8), although differences between groups were not statistically significant. CONCLUSIONS Long-term use of contemporary OCs and current use for ≥ 5 years was associated with an increased breast cancer risk among women ages 20 to 44. Risk may be greater among younger women and for ER(-) and triple-negative breast cancer, but these findings require confirmation. IMPACT Continued surveillance and pooled analyses of OC use and breast cancer risk by molecular subtype are needed as OC preparations evolve.
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Affiliation(s)
- Elisabeth F Beaber
- Authors' Affiliations: Division of Public Health Sciences, Division of Human Biology, Fred Hutchinson Cancer Research Center; Departments of Epidemiology, Biostatistics, and Pathology, University of Washington, Seattle, Washington
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