Two new studies indicate that about one in 100 Jewish women of Eastern European descent, or about four times as many as previously thought, harbors a specific genetic mutation that increases her risk of breast and ovarian cancer.
The unexpectedly high prevalence of the genetic error - and continuing uncertainty about how much added risk the mutation confers - has reignited a debate over whether all Ashkenazi Jewish women should be offered genetic tests that would tell them whether they’ve inherited the mutations. About 90 percent of American Jews are Ashkenazi.
The gene in question, called BRCA2, is almost never mutated in other ethnic groups and is unrelated to a better studied “breast cancer gene” called BRCA1.
Previous research had already found BRCA1 mutations in about 1 percent of Ashkenazi Jews. Since the two mutations are almost never inherited together, the new results indicate that fully one in 40 Ashkenazi Jewish women harbors one or the other of the genetic glitches.
“We were very much surprised that the actual carrier frequency of this mutation was so much higher than we expected,” said Kenneth Offit of Memorial Sloan-Kettering Cancer Center in New York, who led one of the two studies published Monday in Nature Genetics. “But practically speaking, when one goes into the clinic to counsel women, the value of all this is not so clear.”
The problem, Offit said, is that inherited mutations play a role in only about 10 percent of the nation’s 211,000 new cases of breast and ovarian cancer each year. And many women who inherit the mutations will never get either cancer anyway - although no one can predict who will and who won’t.
Moreover, there is still no proof that preventative treatments can reduce a woman’s odds of getting inherited breast or ovarian cancer.
Test advocates claim women have the right to know their genetic makeup - especially those in ethnic or family groups known to be at risk.
But other scientists Monday reiterated their opposition.
“Should we be offering mutation screening for all women of Jewish origin? My answer is still no, said Francis Collins, chief of the National Center for Human Genome Research in Bethesda, Md. “Even if you know they have a risk of breast or ovarian cancer, we’ll still be left unclear about what to recommend.”