BRCA genes get help in causing breast cancer-study

By Andrew Stern

CHICAGO, Jan 8 (Reuters) - The risk of breast cancer among women carrying the well-known BRCA mutations is also affected by other genes, researchers said on Tuesday.

The study of close relatives of breast cancer patients who had one of the BRCA mutations showed the risk of the disease varied greatly between families, indicating that other genes must be involved.

So a woman who knows she has a BRCA1 or BRCA2 mutation still cannot know precisely what her risk of breast cancer is, the researchers reported in the Journal of the American Medical Association. "The implications of that are that there must be other genetic factors involved here," Dr. Colin Begg of Memorial Sloan-Kettering Cancer Center in New York, who led the study, said in a telephone interview.

"Because if some carrier families have higher risks than other carrier families presumably there are other genes being passed through these families that elevate or lower the risks," Begg said.

Begg's team studied 2,000 women diagnosed with breast cancer, and the families of the 181 patients who had BRCA mutations. They found that 5 percent of those with cancer in one breast had a BRCA1 or BRCA2 mutation and 15 percent of those with cancer in both breasts did.

All had been diagnosed early, before the age of 55.

But only 25 percent of all the patients had a close relative with breast cancer.