Two studies in last week's New England Journal of Medicine carry significant implications for women who may be at risk for breast cancer.
A Canadian study produced strong new evidence that the benefits of mammography for detecting breast cancer outweigh any risks posed by radiation from the exams.
"This study indicates that a woman should have no concern about the risk of radiation from mammography," said Geoffrey Howe of the National Cancer Institute of Canada in Toronto, who led the study.
"The risk is negligible compared to the benefits," Howe said.
The study involved more than 31,000 women.
In another study, Dr. Nancy G. Hildreth of the University of Rochester School of Medicine and Dentistry found that exposure to medical X-rays during infancy can significantly increase women's chances of breast cancer when they reach their 30s.
The research was based on a long-term follow-up of women who were given X-ray therapy shortly after birth for treatment of enlarged thymus glands. Such treatment was common until the late 1950s, when doctors realized that seemingly enlarged thymuses were actually normal.
By age 36, the study found, those who had received the treatment were nearly four times more likely to get breast cancer than were sisters who did not receive the radiation.