Medline ® Abstracts for References 1,2
of 'Prevalence of BRCA1 and BRCA2 mutations and associated cancer risks'
Familial breast cancer: collaborative reanalysis of individual data from 52 epidemiological studies including 58,209 women with breast cancer and 101,986 women without the disease.
Collaborative Group on Hormonal Factors in Breast Cancer
BACKGROUND: Women with a family history of breast cancer are at increased risk of the disease, but no study has been large enough to characterise reliably how, over women's lives, this risk is influenced by particular familial patterns of breast cancer. This report, on the relevance of breast cancer in first-degree relatives, is based on combined data from 52 epidemiological studies.
METHODS: Individual data on breast cancer in first-degree relatives (mothers, sisters, and daughters) of 58209 women with breast cancer and of 101986 controls were collected, checked, and analysed centrally. Risk ratios for breast cancer were calculated by conditional logistic regression, stratified by study, age, menopausal status, number of sisters, parity, and age when the first child was born. Breast-cancer incidence and mortality rates for particular family histories were calculated by applying age-specific risk ratios to breast-cancer rates typical for more-developed countries.
FINDINGS: Altogether 7496 (12.9%) women with breast cancer and 7438 (7.3%) controls reported that one or more first-degree relatives had a history of breast cancer: 12% of women with breast cancer had one affected relative and 1% had two or more. Risk ratios for breast cancer increased with increasing numbers of affected first-degree relatives: compared with women who had no affected relative, the ratios were 1.80 (99% CI 1.69-1.91), 2.93 (2.36-3.64), and 3.90 (2.03-7.49), respectively, for one, two, and three or more affected first-degree relatives (p<0.0001 each). The risk ratios were greatest at young ages, and for women of a given age, were greater the younger the relative was when diagnosed. The results did not differ substantially between women reporting an affected mother (9104) or sister (6386). Other factors, such as childbearing history, did not significantly alter the risk ratios associated with a family history of breast cancer. For women in more-developed countries with zero, one, or two affected first-degree relatives, the estimated cumulative incidence of breast cancer up to age 50 was 1.7%, 3.7%, and 8.0%, respectively; corresponding estimates for incidence up to age 80 were 7.8%, 13.3%, and 21.1%. Corresponding estimates for death from breast cancer up to age 80 were 2.3%, 4.2%, and 7.6%. The age when the relative was diagnosed had only a moderate effect on these estimates.
INTERPRETATION: Eight out of nine women who develop breast cancer do not have an affected mother, sister, or daughter. Although women who have first-degree relatives with a history of breast cancer are at increased risk of the disease, most will never develop breast cancer, and most who do will be aged over 50 when their cancer is diagnosed. In countries where breast cancer is common, the lifetime excess incidence of breast cancer is 5.5% for women with one affected first-degree relative and 13.3% for women with two.
A comprehensive evaluation of family history and breast cancer risk. The Utah Population Database.
Slattery ML, Kerber RA
OBJECTIVE: The purpose of this study is to assess the impact of family history on the risk of developing breast cancer.
DESIGN: A case-control study design was used.
SETTING: To provide a comprehensive assessment of family history risk, we used the Utah Population Database, a linked database compiled of genealogy data of the descendants of Mormon pioneer families, cancer data from the Utah Cancer Registry, and mortality data from the Utah Department of Vital Statistics.
PATIENTS: All women diagnosed with breast cancer who were in the genealogy database and the Utah Cancer Registry were included. Controls were women selected from the genealogy, who like cases had no record of previous cancer. They were matched to the cases by age and place of birth.
OUTCOME: Several definitions of family history were used. The total familial risk variable, developed to work effectively in theUtah Genealogy Database, accounts for all family members, their degree of relatedness to the case, and the amount of time they were observed for possible cancer diagnosis.
RESULTS: A threefold increase in risk, estimated by the odds ratio (OR), of breast cancer among those with the highest family history score (6% of cases) was observed when compared with those with the lowest family history score. The OR for women with a first-degree relative with breast cancer was 2.45 (95% confidence interval [CI], 1.84 to 3.06). If the nearest relative was a second-degree relative, the OR was 1.82 (95% CI, 1.39 to 2.24); if the nearest relative was a third-degree relative, the OR was 1.35 (95% CI, 1.07 to 1.64). A slightly greater risk was observed if the first-degree relative was a woman's mother (OR, 2.44; 95% CI, 1.77 to 3.42) rather than a sister (OR, 2.01; 95% CI, 1.66 to 2.43). Among subjects diagnosed before the age of 50 years, the disease experience of relatives prior to age 50 was most important, while for older subjects the experience of relatives of all ages was of roughly equal importance. Women who developed contralateral breast cancer within 3 years of initial diagnosis were nearly 10 times as likely as women without breast cancer to have a first-degree relative with breast cancer. Based on the risk estimates in this study, we have estimated that approximately 17% to 19% of breast cancer in the population could be attributed to family history. Women who had a first-degree relative with colon cancer had a 30% increased risk of breast cancer.
CONCLUSIONS: In this study population, women with a family history of breast cancer, even if the nearest relative with breast cancer is a third-degree relative, are at increased risk of the disease.
Department of Family and Preventive Medicine, University of Utah School of Medicine, Salt Lake City 84132.