Risk from susceptibility gene may be exaggerated in most studies.(Brief Article)

2002 SEP 19 - (NewsRx.com & NewsRx.net) -- An analysis of past studies on mutations in the breast cancer susceptibility genes BRCA1 and BRCA2 suggests that estimates of penetrance (or the likelihood that mutation carriers will develop breast cancer during their lifetime) have been exaggerated.

This can happen because a woman's risk of developing breast cancer is likely to be associated not only with the specific genetic mutation but also with many other risk factors, concluded a study in the August 21, 2002, issue of the Journal of the National Cancer Institute.

Accurately estimating penetrance is important for genetic counseling because the estimates may influence decisions about cancer prevention, such as whether to undergo a prophylactic mastectomy. Early studies examined families that had multiple cases of breast cancer and resulted very in very high penetrance estimates - in the range of 71-85% by 70 years of age.

To avoid this problem, more recent studies have used women with breast cancer who do not necessarily have a strong family history of the disease. These studies have resulted in considerably lower estimates. But this strategy, too, is biased and can still lead to inflated penetrance estimates, according to study author Colin B. Begg, PhD, of the Memorial Sloan-Kettering Cancer Center, New York.

He argued that all risk factors for breast cancer are over-represented in incident cases of breast cancer. This means that a sample of women who have been diagnosed with breast cancer who are identified as mutation carriers are more likely to also have other breast cancer risk factors than similar mutation carriers who are disease-free. The current strategy for estimating risk is unbiased only if all carriers share an identical risk of ...