Oral Contraceptive Use and Risk of Early-Onset Breast Cancer in Carriers and Noncarriers of BRCA1 and BRCA2 Mutations

Milne RL, Knight JA, John EM, Dite GS, Balbuena R, Ziogas A, Andrulis IL, West DW, Li FP, Southey MC, Giles GG, McCredie MR, Hopper JL, Whittemore AS (2005) Oral Contraceptive Use and Risk of Early-Onset Breast Cancer in Carriers and Noncarriers of BRCA1 and BRCA2 Mutations. Cancer Epidemiol Biomarkers Prev 14:350-356

BACKGROUND: Recent oral contraceptive use has been associated with a small increase in breast cancer risk and a substantial decrease in ovarian cancer risk. The effects on risks for women with germ line mutations in BRCA1 or BRCA2 are unclear.METHODS: Subjects were population-based samples of Caucasian women that comprised 1,156 incident cases of invasive breast cancer diagnosed before age 40 (including 47 BRCA1 and 36 BRCA2 mutation carriers) and 815 controls from the San Francisco Bay area, California, Ontario, Canada, and Melbourne and Sydney, Australia. Relative risks by carrier status were estimated using unconditional logistic regression, comparing oral contraceptive use in case groups defined by mutation status with that in controls.RESULTS: After adjustment for potential confounders, oral contraceptive use for at least 12 months was associated with decreased breast cancer risk for BRCA1 mutation carriers [odds ratio (OR), 0.22; 95% confidence interval (CI), 0.10-0.49; P < 0.001],="" but="" not="" for="" brca2="" mutation="" carriers="" (or,="" 1.02;="" 95%="" ci,="" 0.34-3.09)="" or="" noncarriers="" (or,="" 0.93;="" 95%="" ci,="" 0.69-1.24).="" first="" use="" during="" or="" before="" 1975="" was="" associated="" with="" increased="" risk="" for="" noncarriers="" (or,="" 1.52="" per="" year="" of="" use="" before="" 1976;="" 95%="" ci,="" 1.22-1.91;="" p="">< 0.001).conclusions:="" there="" was="" no="" evidence="" that="" use="" of="" current="" low-dose="" oral="" contraceptive="" formulations="" increases="" risk="" of="" early-onset="" breast="" cancer="" for="" mutation="" carriers,="" and="" there="" may="" be="" a="" reduced="" risk="" for="" brca1="" mutation="" carriers.="" because="" current="" formulations="" of="" oral="" contraceptives="" may="" reduce,="" or="" at="" least="" not="" exacerbate,="" ovarian="" cancer="" risk="" for="" mutation="" carriers,="" they="" should="" not="" be="" contraindicated="" for="" a="" woman="" with="" a="" germ="" line="" mutation="" in="" brca1="" or="">