December 26, 2007
Breast Cancer’s Genetic Marker: Mutation Associated With Jewish Women
A gene mutation strongly identified with Jewish breast cancer patients has also turned up in a small but significant percentage of Hispanic patients, scientists are reporting today.
In their study of more than 3,000 women with the disease, scientists also found a surprisingly high prevalence among young black women with breast cancer.
Those inheriting the mutation have a relatively high risk of developing breast or ovarian cancer over their lifetimes, but they can take measures to forestall the disease or reduce its impact.
"From other studies, we know that minority women are less likely to be referred for genetic counseling or testing," said Esther M. John, an epidemiologist with the Northern California Cancer Center and lead author of an article appearing in today's Journal of the American Medical Association.
"The message to doctors is that these mutations don't only occur in white women, they occur in other ethnic groups."
Researchers in the San Francisco area tested patients under age 65 for mutations of the BRCA1 gene, discovered years ago to run in families of Eastern European -- also known as Ashkenazi -- Jewish ancestry.
The scientists, who included researchers from Stanford University in California and the Dana-Farber Cancer Institute in Boston, are also looking for mutations of the BRCA2 gene, another cancer gene identified with Jewish women.
The genes normally perform a helpful function -- suppressing cancer just as it's developing. But defects in those genes negate that ability, thereby raising a woman's risk of getting the disease.
The mutations are not very common in any population. But women who inherit it have a 65 percent risk of developing breast cancer and a 39 percent chance of developing ovarian cancer before age 70.
An estimated 8.3 percent of Ashkenazi Jewish women with breast cancer have the defective BRCA1 gene, according to the California study. Scientists also found the mutation in 3.5 percent of Hispanic patients, 2.2 percent of non-Hispanic white patients, 1.3 percent of black patients, and half of 1 percent of Asian-American patients.
Doctors who read the study said they were somewhat surprised by the relatively high prevalence of the gene -- 16.7 percent -- among black patients diagnosed with breast cancer before age 35. John cautioned, however, that the study did not include a large number of women in that demographic, so further studies would be needed to confirm the result.
Dr. Katherine Tkaczuk, director of the breast evaluation and treatment program at the University of Maryland Medical Center, said she already recommends testing for patients who meet certain conditions, regardless of their ethnicity.
Women who have a strong family history of breast cancer, or who developed the disease at a young age, have a relatively high risk of having an inherited form of breast cancer, she said.
Such women might want to consider testing because a positive finding can influence the way the disease is managed -- and persuade daughters to be on the lookout for early signs of cancer.
"Knowledge is power," Tkaczuk said. "Knowing that one has the gene can be very helpful in terms of management of breast cancer, especially surgical management."
Because patients carrying the gene stand a higher chance of a recurrence, some might choose a mastectomy over a lumpectomy -- or even surgical removal of the unaffected breast. Their daughters have a 50 percent chance of inheriting the gene, so they may want more frequent mammograms or other diagnostic tests.
Unfortunately, the high cost of genetic testing is frequently a barrier, doctors said. The test can cost more than $3,000 for the patient, but much less -- perhaps one-tenth as much -- for daughters or siblings. That's because much of the ground was covered in the original patient's screening. Some insurance policies pay for testing.
But doctors remind carriers of the mutations that lifestyle -- not just genetics -- can influence whether people ultimately develop cancer.
"We know from general studies that if a woman is physically active, that reduces risk," Tkaczuk said. "If she avoids weight gain, that reduces risk."
These principles apply generally to women with breast cancer. Researchers are studying whether they specifically apply to women with BRCA mutations, she said.
Dr. Deborah Armstrong, a specialist in ovarian and breast cancer at the Johns Hopkins Kimmel Cancer Center, said doctors should present the option of genetic testing to women with risk factors.
"My perspective is that for people at high risk, there should at least be a discussion about genetic testing," said Armstrong. The discussion should begin with an oncologist and continue with a genetic counselor, she said.