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Jun. 27--Exposure to diagnostic chest X-rays may increase the risk of breast cancer for women with either of two genes that predispose them to the disease, according to medical research reported today.
For decades, doctors have assured patients that ionizing radiation emitted in brief exposures in an X-ray pose no long-term health risks. Most doctors still offer that assurance.
But a team of European researchers writing in today's Journal of Clinical Oncology says exposure to diagnostic chest X-rays before age 20 appears to pose a risk to carriers of the genes known as BRCA1 and BRCA2. The investigation is the first to analyze the impact of low-level X-ray exposure among women at genetically high risk for the disease.
"Exposure at a young age seems to be important, especially having had chest X-rays before the age of 20," said David E. Goldgar, the study's lead investigator and the former chief of genetic research at the International Agency for Research on Cancer in Lyon, France.
BRCA1 and BRCA2, when healthy, protect against breast cancer. About 10 percent of people who develop breast cancer possess mutated forms of the genes.
Goldgar added that BRCA genes produce proteins that play a vital role in repairing DNA damage caused by X-rays. Goldgar said anyone with BRCA mutations would be handicapped because "breaking the double helix, as it turns out, is exactly the kind of damage caused by ionizing radiation," Goldgar said.
Speaking in a telephone interview yesterday from Lyon, Goldgar said women with BRCA mutations may be more susceptible to low-dose ionizing radiation than women in the general population. In the study, routine chest X-rays, he said, may have been performed for diagnosis of pulmonary infections, or any other condition in which an image of both lungs was required.
Dr. Len Horovitz, a specialist in pulmonary disease at Lenox Hill Hospital in Manhattan, said he doubts that low-dose chest X-rays cause breast cancer, even in a vulnerable population.
"A chest X-ray is a 1- to 2-millirem radiation exposure," Horovitz said yesterday. "In an average year, a woman is exposed to about 350 millirems of radiation as part of daily living."
Goldgar said his findings are not definitive. The study, which was based on responses to questionnaires, did not investigate the impact of mammography, another form of low-dose X-ray, and one that women with BRCA mutations are recommended to undergo at least a decade or more before other women in the population.
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Copyright (c) 2006, Newsday, Melville, N.Y.
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