Article Text

PDF

Review: breast cancer is associated with a family history of the disease in first degree relatives
  1. Esther C Janowsky, MD, PhD
  1. University of North Carolina at Chapel Hill
 Chapel Hill, North Carolina, USA

    Statistics from Altmetric.com

    
 
 QUESTION: In women with a family history of breast cancer, how does the pattern of breast cancer in first degree relatives affect the risk for developing the disease?

    Data sources

    Studies were identified by searching computerised literature databases, reviewing bibliographies of review articles, and contacting experts in the field.

    Study selection

    Selected studies were cohort or nested case control studies that included ≥ 100 women with incident invasive breast cancer, and information about reproductive or hormonal factors was sought on each woman.

    Data extraction

    Principal investigators of the included studies were contacted for data on each woman regarding whether any of her first degree female relatives (mother, sisters, or daughters) had been diagnosed with breast cancer and, if so, their age when the diagnosis was made. Data were also collected on the numbers of sisters and daughters of each woman and the ages of each unaffected first degree female relative.

    Main results

    52 published and 2 unpublished studies included 58 209 women with breast cancer (mean age 52 y) and 101 986 women without breast cancer (mean age 53 y). 7496 women (12.9%) with breast cancer and 7438 women (7.3%) without had ≥ 1 first degree female relative with a history of breast cancer. The risk for breast cancer increased with an increasing number of affected relatives (table 1). Age specific risk ratios (RRs) were not affected by race, age at menarche, education, height, weight, or use of contraceptives or hormone treatment. 27 studies provided data on the age that breast cancer was diagnosed in each first degree relative. The risk for breast cancer increased as the age of relatives who had been diagnosed with breast cancer decreased (table 2). The estimates of probability that a woman 20 years of age would develop breast cancer by age 50 were 1.7%, 3.7%, and 8.0% for women with 0, 1, and 2 affected first degree relatives, respectively. The corresponding lifetime probability estimates (ie, age 20 to 80y) were 7.8%, 13%, and 21%. The probability estimates for death were 2.3%, 4.2%, and 7.6%.

    Table 1

    Relative risk (RR) for breast cancer by number of affected first degree female relatives

    Table 2

    Relative risk (RR) for breast cancer by age of affected first degree female relatives

    Conclusions

    Women with first degree relatives with a history of breast cancer are at increased risk for developing the disease. The risk increases with an increasing number of affected relatives and is higher for younger than for older women.

    
 
 QUESTION: In women with a family history of breast cancer, how does the pattern of breast cancer in first degree relatives affect the risk for developing the disease?

    Commentary

    The review by the Collaborative Group on Hormonal Factors in Breast Cancer (CGHFBC) reported an increased risk for breast cancer according to the number of affected first degree relatives (mother, sister, or daughter) and the age at which the relatives were diagnosed. This effect was pronounced in women below the age of 50 years and was highest when a relative was diagnosed below the age of 40 years (RR 13.5, 99% CI 3.4 to 53.9). The review did not discuss women with hereditary breast cancer (eg, carriers of BRCA1 or BRCA2 mutations) as a separate group who indeed have higher risks for the disease.1

    A family history of breast cancer is one of the few identified and most consistent determinants of breast cancer risk. Nevertheless, it is associated with relatively few cases in the population. In the CGHFBC study, approximately 13% of women with breast cancer had first degree relatives with the disease compared with 7% of women without the diagnosis. Clearly, a population-wide strategy of early detection aimed at women with a family history of the disease would miss most individuals with breast cancer because 87% would not have a positive family history.

    How well do these risks apply to individuals? Rockhill et al 2 found that the modified Gail model fits well in predicting numbers of breast cancer cases in specific categories of risk but did only slightly better than chance (concordance statistic 0.58, 95% CI 0.56 to 0.60) on the individual level.

    The CGHFBC study provides a useful ancillary guide in individual practices for identifying women at relatively high risk for breast cancer who can be counselled and monitored, while emphasising both the small numbers of women in these high risk categories and the reassuring fact that most women in these categories will not develop breast cancer.

    References

    View Abstract

    Footnotes

    • Sources of funding: Imperial Cancer Research Fund and UNDP/UNFPA/ WHO/World Bank Special Programme of Research, Development and Research Training in Human Reproduction.

    • For correspondence: ICRF Cancer Epidemiology Unit, Radcliffe Infirmary, Oxford, UK. Fax +44 (0)1865 310545.A modified version of this abstract also appears in Evidence-Based Nursing.

    Request permissions

    If you wish to reuse any or all of this article please use the link below which will take you to the Copyright Clearance Center’s RightsLink service. You will be able to get a quick price and instant permission to reuse the content in many different ways.