Family history of breast cancer is an established risk factor for breast cancer. In addition, there is evidence that oral contraceptive use may be associated with a moderate increase in breast cancer risk. The three cohort studies that have investigated the relationship between oral contraceptive use and breast cancer risk among women with a family history of breast cancer have yielded mixed results, possibly due to the relatively small sample sizes employed and/or differences in the selection of covariates for inclusion in multivariate models. Therefore, we examined the association between oral contraceptive use and breast cancer risk in a large cohort study in Canada. The cohort consisted of the 27,318 women in the Canadian National Breast Screening Study who reported a family history of breast cancer on enrollment into the study. Linkages to national mortality and cancer databases yielded data on deaths and cancer incidence, with follow-up ending between 1998 and 2000, depending upon the province. During a mean of 16.0 years of follow-up, we observed 1707 incident cases of breast cancer among women with any history of breast cancer of which 795 cases occurred among women with a mother, sister, and/or daughter with breast cancer. Among women with any family history of breast cancer, ever use of oral contraceptives was associated with a 12% reduction in risk of breast cancer (95% confidence interval [CI]=0.73-1.07), and there was an inverse trend with increasing duration of use of borderline statistical significance (p(trend)=0.03). Although we also observed a 25% lower risk of breast cancer associated with oral contraceptive use of greater than 84 months versus never use among women with a first degree relative with breast cancer, this finding was not statistically significant (95% CI=0.47-1.19, p(trend)=0.48). Our data raise the possibility that relatively long duration of oral contraceptive use may be inversely associated with risk among women with a family history of breast cancer.
oral contraceptives breast cancer risk family history prospective cohort, Silvera oral contraceptive use breast cancer family history Canada, OCP duration breast cancer risk first degree relative, hormonal contraception breast cancer hereditary risk cohort study, Canadian National Breast Screening Study oral contraceptives, oral contraceptive protective effect familial breast cancer, breast cancer incidence oral contraceptive duration women, family history breast cancer hormonal contraception interaction, oral contraceptive long-term use breast cancer inverse association, hereditary breast cancer risk modifiers oral contraceptives prospective
PMID 16184471 16184471 DOI 10.1007/s10552-005-0343-1 10.1007/s10552-005-0343-1
Cite this article
Silvera, S. A. N., Miller, A. B., & Rohan, T. E. (2005). Oral contraceptive use and risk of breast cancer among women with a family history of breast cancer: a prospective cohort study. Cancer causes & control : CCC, 16(9), 1059-1063. https://doi.org/10.1007/s10552-005-0343-1
Silvera SAN, Miller AB, Rohan TE. Oral contraceptive use and risk of breast cancer among women with a family history of breast cancer: a prospective cohort study. Cancer Causes Control. 2005;16(9):1059-1063. doi:10.1007/s10552-005-0343-1
Silvera, S. A. N., et al. "Oral contraceptive use and risk of breast cancer among women with a family history of breast cancer: a prospective cohort study." Cancer causes & control : CCC, vol. 16, no. 9, 2005, pp. 1059-1063.
Keywords
Contraceptives, Oral
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