BRCA Genetic Mutations Sharply Raise Risks of Breast and Ovarian Cancers, Study Finds
Women who have inherited mutated versions of either of two genes linked to breast and ovarian cancer have "extremely high odds" of getting one of the cancers even if they do not have a family history of the diseases, according to the New York Breast Cancer Study, the results of which were published in Friday's issue of the journal Science, the Washington Post reports (Weiss, Washington Post, 10/24). Between 1996 and 2001, researchers studied 1,008 Ashkenazi Jewish women being treated at 12 New York medical centers for breast or ovarian cancer, the Wall Street Journal reports. Researchers extracted genetic material from blood samples of the women and found that 104 had a mutation in either the BRCA1 or BRCA2 gene (Waldholz, Wall Street Journal, 10/24). The mutations are believed to account for 5% to 10% of the more than 200,000 new cases of breast cancer each year, the New York Times reports (Grady, New York Times, 10/24). About one in 400 people carry one of the gene mutations, but about one in 40 Ashkenazi Jews carry the mutation (Wall Street Journal, 10/24). Researchers found that the risk of developing breast cancer for women with one of the mutations was 20% by age 40, 55% by age 60 and 82% by age 80; the average U.S. woman has about a 10% chance of developing breast cancer in her lifetime. For ovarian cancer, the lifetime risk was 54% for mutations in BRCA1 and 23% for mutations in BRCA2, compared with less than 2% for the average U.S. woman (Washington Post, 10/24).
The study "should settle a simmering controversy over how dangerous the genes are, and help clarify a difficult set of treatment choices for the women who carry them," the Journal reports. According to the Journal, several previous studies have concluded that the breast cancer risk from the mutated genes was "much lower" than the current study found. The confirmation of the higher risk rate "helps clarify treatment options," report co-author Dr. Mary-Claire King, a geneticist at the University of Washington, said. Jessica Mandell, a genetics counselor who helped run the study, said, "Armed with the new study, counselors can help women and their families decide if they should be tested for the gene" (Wall Street Journal, 10/24). Those with the mutations are already urged to have regular mammograms, MRIs and ultrasound scans to detect the cancer early and to consider taking tamoxifen, which can reduce breast cancer risk (New York Times, 10/24). In light of the study results, several researchers and doctors said that those with the mutations should "seriously consider" having their ovaries surgically removed -- which brings the risk of ovarian cancer down to almost zero and reduces the incidence of breast cancer by about 50% -- when they are done having children, the Post reports (Washington Post, 10/24).
The study also found that 52 of the 104 women with one of the genetic mutations did not have a known family history of breast cancer in their immediate families; in almost all of the 52 cases, the mutation had come "silently" from the women's fathers. While male carriers of the mutations have a low risk of developing breast cancer, they have a 50% chance of passing the gene to their children, the Journal reports (Wall Street Journal, 10/24). In addition, the study found that women who exercised and maintained a healthy weight during their teens and early twenties delayed the onset of breast cancer by "many years," the Post reports (Washington Post, 10/24). "The possibility that lifestyle changes such as increased exercise and weight control could modify the impact of genetic risk has very intriguing implications, not only for BRCA-related cancers but for other breast cancers as well,'' Dr. Larry Norton, head of the division of solid tumor oncology at Memorial Sloan-Kettering Cancer Center, said (Recer, AP/Akron Beacon Journal, 10/24). King added, "You can't make the risk go away, but a healthy lifestyle does ameliorate it to some degree" (New York Times, 10/24). The study also found that breast cancer could be delayed by pregnancy early in life and late onset of first menstruation. However, the largest non-genetic factor affecting breast cancer risk was year of birth, with those born in 1940 having a 24% change of developing breast cancer by age 50, while those born after 1940 had a 67% chance. The decades after 1940 have seen earlier menstruation, later first births, increased rates of obesity, more sedentary lifestyles and dietary changes, which are "difficult to disentangle," King said (Washington Post, 10/24).
The Wall Street Journal Friday examined how a "random genetic quirk" from "hundreds of years ago in Eastern Europe" caused Ashkenazi Jews to develop increased incidences of BRCA gene mutations. The Journal reports that ethnic attacks caused "millions of Eastern European Jews [to be] contracted to a group numbering in the thousands," creating a "genetic bottleneck" of random mutations in a small group being passed down to many descendents as the population expanded back into the millions (Waldholz, Wall Street Journal, 10/24).
The following broadcast programs reported on the breast cancer study:
- NPR's "All Things Considered" includes comments from King (Palca, "All Things Considered," NPR, 10/24). The full segment is available online in RealPlayer.
- CBS' "Evening News" reports on the importance of genetic testing for breast and ovarian cancer. Included are comments by Dr. Kenneth Offit of Memorial Sloan-Kettering Cancer Center (Kaledin, "Evening News," CBS, 10/24). The segment is available online in RealPlayer.
- NBC's "Nightly News" reports on the genetic and non-genetic factors that affect breast cancer (Bazell, "Nightly News," NBC, 10/24). The segment in available online in WindowsMedia.
- NPR's "Science Friday" reports on the ramifications of the research and includes comments by Elizabeth Swisher, Director of the Breast and Ovarian Cancer Prevention Program at the University of Washington School of Medicine (Flatow, "Science Friday", NPR, 10/24). The segment is available online in RealPlayer.