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Cancer risks in individuals referred to a breast/ovarian cancer risk evaluation clinic
The penetrance of mutations in the BRCA1 and BRCA2 genes depends on the population surveyed. Original penetrance estimates based on highly selected families with multiple affected members are substantially higher than estimates based on mutation carriers identified from populations of unselected breast cancer cases. What are the appropriate figures to use when counselling women? Most BRCA1/2 testing is done after referral to genetics services on the basis of concerns about a family history of breast cancer. Brose et al argue that penetrance estimates for mutations identified in this context are likely to be the most clinically relevant [Brose, MS et al (2002) J Natl Cancer Inst 94, 1365-1372 (Abstract). They analysed cancer incidence over 10-year age intervals in 483 BRCA1 mutation carriers from 147 families referred to a breast/ovarian cancer risk evaluation clinic. The cumulative female breast cancer risk to age 70 was approximately 70% and the ovarian cancer risk was 40%. They also found evidence for increased risk of other cancers in BRCA1 mutation carriers. However, Thompson and Easton, reporting the results of a much larger study, found that only female BRCA1 mutation carriers were at significantly increased risk of primary cancers other than breast or ovarian; they calculate a relative risk of 2.3 for other gynaecological cancers and for cancers at some other abdominal sites [Thompson, D and Easton, DF (2002) J Natl Cancer Inst 94, 1358-1365 (Abstract).