Women with a BRCA1 or BRCA 2 gene mutation have a 5- to 20-fold higher risk of getting breast or ovarian cancer, the Stanford researchers wrote. That means a lifetime probability of up to 65 percent for breast cancer, and up to 40 percent for ovarian cancer. Women who have the BRCA1 and BRCA2 mutations and are cancer-free are urged to step up their screening and to begin it early, by age 25, among other measures. They may also consider a preventive mastectomy or ovary removal after childbearing is done.

However, the 2007 study, Whittemore said, ???sent an alarm signal to the medical community??? as it suggested a high risk even in BRCA-negative relatives. ???What we thought to be the flaw was that they were comparing these relatives of women with breast cancer to the general population. A better comparison group would have been women who have relatives with breast cancer but no mutation,??? Whittemore said. ???That's what we did.???

The new study looked at 3,047 families from the United States, Australia and Canada. It included 160 families with BRCA1 and 132 with BRCA 2. The researchers compared cancer risk in women who tested negative but had relatives with BRCA-related breast cancer with a group of cancer-free women who had relatives with cancer that wasn't BRCA-related. They found no increased risk for the women who were BRCA-negative and had close relatives with BRCA-related cancer.

Besides BRCA1 and BRCA2 mutations, other risk factors, not totally understood, that can run in families also drive breast cancer risk, experts say. One example is drinking habits. The findings suggest that BRCA-negative women can follow the same breast cancer screening routine as the general population, if they have no other strong risk factors, Whittemore said.

The findings should be reassuring to women without the mutation, agreed Dr. Patricia Ganz, director of cancer prevention and control research at the University of California's Jonsson Comprehensive Cancer Center. ???The main message,??? she said, ???is that these women (without the mutation) don't need all that extra surveillance.???