BOSTON -- More than 1 million American women who carry a single copy of a defective gene are believed to be at five to six times the normal risk of breast cancer, say researchers. The gene appears to make carriers -- men as well as women -- at increased risk for cancer from medical X-rays.
It has long been known that having two copies of this "bad" gene puts a person at 100 times the normal risk of developing cancer.
Since most carriers of the gene do not know they have it, the researchers told the Associated Press yesterday, their work suggests that doctors should cover all women's breasts with lead shields during X-rays and use non-X-ray tests whenever possible.
The new study, published today in the New England Journal of Medicine, shows that having just one copy of the bad gene significantly increases the risk of breast cancer, which this year will strike 175,000 women. It also raises a man's overall risk of cancer 3.8 times and a woman's overall risk 3.5 times. Overall, about 2 million to 3 million Americans -- about 1.4 percent of the population -- are believed to carry one copy of the bad gene.
Whether mammograms, which use X-rays, specifically increase the risk of breast cancer in women carrying this gene has not yet been shown, the researchers said.
But the link between radiation and breast cancer is so striking in women carrying this gene, they said, that any woman who is a carrier should consider skipping mammograms and instead have periodic breast exams performed by a highly trained examiner, the researchers said.