Oral Contraceptives and Premenopausal Bilateral Breast... : Epidemiology (original) (raw)

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Oral Contraceptives and Premenopausal Bilateral Breast Cancer: A Case-Control Study

Ursin, Giske1; Aragaki, Corinne C.1; Paganini-Hill, Annlia2; Siemiatycki, Jack3; Thompson, W Douglas4; Haile, Robert W.1

1From the Department of Epidemiologv, School of Public Health, Center for the Health Sciences, University of California, Los Angeles, CA

2From the Department of Preventive Medicine, University of Southern California, Los Angeles, CA

3From the Department of Epidemiology. Institut Armand Frappier, Quebec, Canada

4From the Applied Medical Sciences, University of Southern Maine, Portland, ME

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Abstract

We estimated the effect of oral contraceptive (OC) use on premenopausal bilateral breast cancer in a matched case-control study. One hundred forty-four cases were identified from population-based registries of Los Angeles County, California, and of Connecticut and from the major hospitals in Montreal and Quebec City. Matched controls were the unaffected sisters of the cases. When age \vas included in the model, ever-use of OCs for 1 year or more was associated with an odds ratio of 1.7 (95% confidence interval = 1.0–2.9). The odds ratios associated with 1–2, 3–6, and 7 years of use were 1.2 (0.61–2.4), 2.5 (1.2–5.3), and 2.0 (0.93–4.2), respectively. Too few women had used OCs before their first full-term pregnancy or before age 25 for these estimates to be informative. Restricting the analyses to women who had ever given birth yielded an odds ratio for ever-use of OCs of 2.1 (1.0–4.4). The results indicate an increased risk of premenopausal bilateral breast cancer associated with OC use. (Epidemiology 1992;3:414–419)