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Oral contraceptives and breast cancer risk among younger women.

Abstract

BACKGROUND

Several studies have suggested a link between oral contraceptive use and breast cancer in younger women, but it is possible that chance or bias, including selective screening of contraceptive users, contributed to the putative association.

PURPOSE

Given that oral contraceptives were first marketed in the United States in the early 1960s, we conducted a population-based case-control study to examine the relationship between use of oral contraceptives and breast cancer among women in a recently assembled cohort, focusing on women younger than 45 years of age who had the opportunity for exposure throughout their entire reproductive years.

METHODS

Breast cancer patients and healthy control subjects were identified, the latter group by random-digit dialing, in Atlanta, Ga., Seattle/Puget Sound, Wash., and central New Jersey. In Seattle and New Jersey, the study was confined to women 20 through 44 years of age; in Atlanta the age range was extended through 54 years. Patients included women with in situ or invasive breast cancer newly diagnosed during the period of May 1, 1990, through December 31, 1992. In-person interviews were completed by 2203 (86.4%) of 2551 eligible patients and 2009 (78.1%) of 2571 eligible control subjects. Analyses focused on women younger than 45 years of age (1648 patients and 1505 control subjects) to maximize opportunities for extended exposure. Logistic regression analyses were used to obtain maximum likelihood estimates of relative risks (RRs) and their 95% confidence intervals (CIs).

RESULTS

Among women younger than 45 years, oral contraceptive use for 6 months or longer was associated with an RR for breast cancer of 1.3 (95% CI = 1.1-1.5). Risks were enhanced for breast cancers occurring prior to age 35 years (RR = 1.7; 95% CI = 1.2-2.6), with the RR rising to 2.2 (95% CI = 1.2-4.1) for users of 10 or more years. The RR for breast cancer for those whose oral contraceptive use began early (before age 18 years) and continued long-term (> 10 years) was even higher (RR = 3.1; 95% CI = 1.4-6.7). The RRs observed for those who used oral contraceptives within 5 years of cancer diagnosis were higher than for those who had not, with the effect most marked for women younger than age 35 years (RR = 2.0; 95% CI = 1.3-3.1). Oral contraceptive associations were also strongest for cancers diagnosed at advanced stages. Evaluation of screening histories and methods of diagnosis failed to support the speculation that associations could be due to selective screening. Among women 45 years of age and older, no associations of risk with use of oral contraceptives were noted.

CONCLUSIONS

The relationship between oral contraceptives and breast cancer in young women appears to have a biologic basis rather than to be an artifact or the result of bias.

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  • Publisher Full Text
  • Authors+Show Affiliations

    ,

    Environmental Epidemiology Branch, National Cancer Institute, Bethesda, MD 20892, USA.

    , , , , , , , ,

    Source

    Journal of the National Cancer Institute 87:11 1995 Jun 07 pg 827-35

    MeSH

    Adult
    Breast Neoplasms
    Carcinoma in Situ
    Case-Control Studies
    Contraceptives, Oral, Hormonal
    Female
    Humans
    Logistic Models
    Neoplasm Invasiveness
    Risk
    Risk Factors
    Time Factors

    Pub Type(s)

    Journal Article

    Language

    eng

    PubMed ID

    7791232

    Citation

    Brinton, L A., et al. "Oral Contraceptives and Breast Cancer Risk Among Younger Women." Journal of the National Cancer Institute, vol. 87, no. 11, 1995, pp. 827-35.
    Brinton LA, Daling JR, Liff JM, et al. Oral contraceptives and breast cancer risk among younger women. J Natl Cancer Inst. 1995;87(11):827-35.
    Brinton, L. A., Daling, J. R., Liff, J. M., Schoenberg, J. B., Malone, K. E., Stanford, J. L., ... Hoover, R. N. (1995). Oral contraceptives and breast cancer risk among younger women. Journal of the National Cancer Institute, 87(11), pp. 827-35.
    Brinton LA, et al. Oral Contraceptives and Breast Cancer Risk Among Younger Women. J Natl Cancer Inst. 1995 Jun 7;87(11):827-35. PubMed PMID: 7791232.
    * Article titles in AMA citation format should be in sentence-case
    TY - JOUR T1 - Oral contraceptives and breast cancer risk among younger women. AU - Brinton,L A, AU - Daling,J R, AU - Liff,J M, AU - Schoenberg,J B, AU - Malone,K E, AU - Stanford,J L, AU - Coates,R J, AU - Gammon,M D, AU - Hanson,L, AU - Hoover,R N, PY - 1995/6/7/pubmed PY - 1995/6/7/medline PY - 1995/6/7/entrez KW - Age Factors KW - Americas KW - Breast Cancer KW - Cancer KW - Case Control Studies KW - Contraception KW - Contraceptive Methods KW - Correlation Studies KW - Demographic Factors KW - Developed Countries KW - Diseases KW - Evaluation KW - Family Planning KW - Neoplasms KW - North America KW - Northern America KW - Oral Contraceptives KW - Population KW - Population Characteristics KW - Research Methodology KW - Risk Assessment KW - Statistical Studies KW - Studies KW - United States SP - 827 EP - 35 JF - Journal of the National Cancer Institute JO - J. Natl. Cancer Inst. VL - 87 IS - 11 N2 - BACKGROUND: Several studies have suggested a link between oral contraceptive use and breast cancer in younger women, but it is possible that chance or bias, including selective screening of contraceptive users, contributed to the putative association. PURPOSE: Given that oral contraceptives were first marketed in the United States in the early 1960s, we conducted a population-based case-control study to examine the relationship between use of oral contraceptives and breast cancer among women in a recently assembled cohort, focusing on women younger than 45 years of age who had the opportunity for exposure throughout their entire reproductive years. METHODS: Breast cancer patients and healthy control subjects were identified, the latter group by random-digit dialing, in Atlanta, Ga., Seattle/Puget Sound, Wash., and central New Jersey. In Seattle and New Jersey, the study was confined to women 20 through 44 years of age; in Atlanta the age range was extended through 54 years. Patients included women with in situ or invasive breast cancer newly diagnosed during the period of May 1, 1990, through December 31, 1992. In-person interviews were completed by 2203 (86.4%) of 2551 eligible patients and 2009 (78.1%) of 2571 eligible control subjects. Analyses focused on women younger than 45 years of age (1648 patients and 1505 control subjects) to maximize opportunities for extended exposure. Logistic regression analyses were used to obtain maximum likelihood estimates of relative risks (RRs) and their 95% confidence intervals (CIs). RESULTS: Among women younger than 45 years, oral contraceptive use for 6 months or longer was associated with an RR for breast cancer of 1.3 (95% CI = 1.1-1.5). Risks were enhanced for breast cancers occurring prior to age 35 years (RR = 1.7; 95% CI = 1.2-2.6), with the RR rising to 2.2 (95% CI = 1.2-4.1) for users of 10 or more years. The RR for breast cancer for those whose oral contraceptive use began early (before age 18 years) and continued long-term (> 10 years) was even higher (RR = 3.1; 95% CI = 1.4-6.7). The RRs observed for those who used oral contraceptives within 5 years of cancer diagnosis were higher than for those who had not, with the effect most marked for women younger than age 35 years (RR = 2.0; 95% CI = 1.3-3.1). Oral contraceptive associations were also strongest for cancers diagnosed at advanced stages. Evaluation of screening histories and methods of diagnosis failed to support the speculation that associations could be due to selective screening. Among women 45 years of age and older, no associations of risk with use of oral contraceptives were noted. CONCLUSIONS: The relationship between oral contraceptives and breast cancer in young women appears to have a biologic basis rather than to be an artifact or the result of bias. SN - 0027-8874 UR - https://www.unboundmedicine.com/medline/citation/7791232/Oral_contraceptives_and_breast_cancer_risk_among_younger_women_ L2 - https://academic.oup.com/jnci/article-lookup/doi/10.1093/jnci/87.11.827 DB - PRIME DP - Unbound Medicine ER -