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Original Contribution
January 9/16, 2008

Variation of Breast Cancer Risk Among BRCA1/2 Carriers

Author Affiliations

Author Affiliations: Department of Epidemiology and Biostatistics, Memorial Sloan-Kettering Cancer Center, New York, New York (Drs Begg, Capanu, Liang, Sima, and J. Bernstein and Ms Hummer); Department of Preventive Medicine, University of Southern California, Los Angeles (Drs Haile, Thomas, Langholz, and L. Bernstein); Department of Oncology, University Hospital, Lund, Sweden (Dr Borg); Division of Public Health Sciences, Fred Hutchinson Cancer Research Center, Seattle, Washington (Dr Malone); Department of Biochemistry and Molecular Genetics, University of Virginia, Charlottesville (Dr Concannon); Institute of Cancer Epidemiology, Danish Cancer Society, Copenhagen, Denmark (Dr Olsen); Department of Epidemiology, University of Iowa, Iowa City (Dr Lynch); and Department of Medicine, University of California, Irvine (Dr Anton-Culver).

JAMA. 2008;299(2):194-201. doi:10.1001/jama.2007.55-a

Context  The risk of breast cancer in BRCA1 and BRCA2 mutation carriers has been examined in many studies, but relatively little attention has been paid to the degree to which the risk may vary among carriers.

Objectives  To determine the extent to which risks for BRCA1 and BRCA2 carriers vary with respect to observable and unobservable characteristics.

Design, Setting, and Participants  Probands were identified from a population-based, case-control study (Women’s Environmental Cancer and Radiation Epidemiology [WECARE]) of asynchronous contralateral breast cancer conducted during the period of January 2000 to July 2004. Participants previously diagnosed with contralateral breast cancer or unilateral breast cancer were genotyped for mutations in BRCA1 and BRCA2. All participants had their initial breast cancer diagnosed during the period of January 1985 to December 2000, before the age of 55 years.

Main Outcome Measure Incidence of breast cancer in first-degree female relatives of the probands was examined and compared on the basis of proband characteristics and on the basis of variation between families.

Results  Among the 1394 participants with unilateral breast cancer, 73 (5.2%) were identified as carriers of deleterious mutations (42 with BRCA1 and 31 with BRCA2). Among the 704 participants with contralateral breast cancer, 108 (15.3%) were identified as carriers of deleterious mutations (67 with BRCA1 and 41 with BRCA2). Among relatives of carriers, risk was significantly associated with younger age at diagnosis in the proband (P = .04), and there was a trend toward higher risk for relatives of contralateral breast cancer vs unilateral breast cancer participants (odds ratio, 1.4 [95% confidence interval, 0.8-2.4]; P = .28). In addition, there were significant differences in risk between carrier families after adjusting for these observed characteristics.

Conclusion  There exists broad variation in breast cancer risk among carriers of BRCA1 and BRCA2 mutations.