Testing for the breast cancer predisposition gene, BRCA1

BMJ 1996; 313 doi: https://doi.org/10.1136/bmj.313.7057.572 (Published 07 September 1996) Cite this as: BMJ 1996;313:572
  1. Rosalind Eeles
  1. Senior lecturer in cancer genetics and clinical oncology Institute of Cancer Research and Royal Marsden Hospital, Sutton, Surrey SM2 5PT

    Documenting the outcome in gene carriers is essential

    Each year there are 27 768 cases of breast cancer and 5100 cases of ovarian cancer in Britain.1 Most of these cases will be sporadic, in which genetic changes occur only within cancer cells. However, in rare instances a genetic change will have been inherited. This means that it is present in every cell and can be passed down through the generations. Carriers have a 50% chance of passing the cancer predisposition gene to each of their children. The presence of a cancer predisposition gene increases the risk of cancer but does not mean that cancer will definitely develop. About 5% of breast and ovarian cancers occur as a result of highly penetrant germ line mutations in cancer predisposition genes.2 One of these genes, BRCA1, which predisposes to breast and ovarian cancer, was mapped to the long arm of chromosome 17 in 19903 and has now been cloned.4 It probably accounts for about 2% of all cases of breast cancer. Collaborative studies by the Breast Cancer Linkage Consortium (BCLC) on over 200 families worldwide have shown that BRCA1 is responsible for about 50% of families with at least four members with breast cancer at under 60 years of age and over 80% of families with histories of both breast and ovarian cancer.5

    Studies by the consortium have provided estimates of the risks of cancer in BRCA1 carriers, and these figures can be used in genetic counselling. …

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