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Breast Cancer in Women with a Family History: Does OC Use Increase Risk?

To analyze the association between oral contraceptive (OC) use and breast cancer, these researchers obtained data on relatives of a cohort of 426 Minnesota patients (probands) with breast cancer diagnosed in the late 1940s and early 1950s. Follow-up data on sisters, daughters, granddaughters, nieces, and female in-laws were collected by telephone from 1991 to 1996. Each family member was asked about the presence of breast or ovarian cancer: Among families with these cancers, 132 had a history of 3 or more of these cancers, and 35 had a history of 5 or more.

Compared with nonuse, OC use before 1975 was significantly associated with an increased risk for breast cancer in sisters and daughters of probands (relative risk, 3.3) but not in granddaughters or nieces (RR, 1.2) or in-laws (RR, 1.2). Adjustments for age of menarche, smoking, parity, and age at first birth did not alter the results. OC use after 1975, when formulations contained significantly lower dosages of estrogen and progestins, was not associated with an elevated breast cancer risk; however, the data set was small and the confidence interval wide (RR, 0.9; CI, 0.2-4.5).

Comment: Although more data are needed on the effects of post-1975 OCs, this study provides important information for counseling average- and high-risk patients. Clinicians can report that OC use does not increase risk in women who are not first-degree relatives of breast-cancer patients and that it may further amplify risk in patients who are already at very high risk when they begin taking OCs. OC use significantly reduces the risk for endometrial and ovarian cancers, and this is true of women with a family history of ovarian cancer and women who are carriers of the BRCA1 or BRCA2 gene. Before prescribing OCs to patients at high risk for breast cancer, clinicians should factor in the baseline risk for ovarian and breast cancer, available cancer prevention strategies (including chemotherapy prevention with tamoxifen or participation in the STAR trial, and prophylactic mastectomy), and the likelihood of using reliable alternative contraceptive methods while prioritizing patient preference.

— AJ Davis

Published in Journal Watch Women's Health November 13, 2000

Citation(s):

Grabrick DM et al. Risk of breast cancer with oral contraceptive use in women with a family history of breast cancer. JAMA 2000 Oct 11 284 1791-1798.

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