Avoiding Certain Environmental Factors May Reduce Breast Cancer Risk

Women may be able to lower their risk of developing breast cancer by avoiding certain environmental factors, suggests a new report from the Institute of Medicine, or IOM.

According to a Dec. 7 IOM news release, the report -- Breast Cancer and the Environment: A Life Course Approach -- suggests that "women may be able to reduce their risk for breast cancer by avoiding unnecessary medical radiation; forgoing use of combination estrogen-progestin menopausal hormone therapy, if possible; limiting alcohol consumption; maintaining a healthy weight; exercising regularly; and avoiding tobacco use."

Family physician Michael LeFevre, M.D., M.S.P.H, of Columbia, Mo., who is co-vice chair of the U.S. Preventive Services Task Force, said that although there is a lot of information reported on screening for breast cancer, very little is heard regarding primary prevention. The IOM report is interesting, he noted, because it looks at potentially modifiable risk factors and makes recommendations that might reduce incidence, rather than trying to improve disease outcomes after diagnosis.

The report's authors found the strongest evidence of increased breast cancer risk lies with hormone replacement therapy, or HRT, that combines estrogen and a progestin. In addition, exposure to ionizing radiation in diagnostic procedures, such as CT scans; excess weight among postmenopausal women; and alcohol consumption also showed cancer-causing potential.

"Of special interest to family physicians should be the risks associated with combined hormone replacement therapy and radiation," LeFevre told AAFP News Now. "The former has been reduced significantly in the U.S. since the publication of the results of the Women's Health Initiative, but only recently have we seen much concern expressed about the effects of radiation exposure associated with medical imaging."

LeFevre said the dramatic and documented increases in radiation exposure seen in the past several years, particularly in regard to cardiac imaging, also add weight to the recommendations.

"Obviously, the breast gets significant exposure when radiation is used to image the heart," he said. "Family physicians may wish to consider the potential risks of radiation when deciding to recommend cardiac imaging that involves radiation."

Overall, the IOM report acknowledges the data gap that exists regarding breast cancer prevention and points out the need for further research.

"The committee notes a growing appreciation among researchers of the important role of the precise timing of environmental exposures in increasing or reducing later breast cancer risks. Research will need to factor in such evolving knowledge in order to yield an accurate picture of a woman's breast cancer risk status over time and how she may be affected by specific environmental risk factors at different points in her lifetime," say the report's authors.

"Familiar advice about healthy lifestyles appears relevant, but it remains difficult to discern the contribution of other environmental factors," the authors add. "By learning more about the significance of a woman's age and her physical maturity when she encounters environmental risk factors, as well as which preventive actions can be most effective and when they should be taken, it may be increasingly possible to identify, develop and implement ways to effectively prevent various forms of breast cancer."

The report offers a list of "opportunities for action" that family physicians may find helpful.

Those opportunities include

"Limiting alcohol consumption, maintaining a healthy weight, exercising regularly, and avoiding tobacco use will usually be part of any (checkup)," said LeFevre. "As to forgoing the use of combination estrogen-progestin menopausal hormone therapy -- that will be a part of any discussion about the use of HRT for menopausal symptoms that includes risks and benefits."

Avoiding unnecessary medical radiation, however, will likely be the hardest opportunity to make use of, LeFevre added.

"It rarely comes up," he said. "But when considering use of a diagnostic test that involves radiation, there are many circumstances in which a physician may need to point out that there are hazards of the cumulative exposure to radiation that accrue with diagnostic imaging, and that we need to consider how important or useful the results of a particular test might be relative to the risks of radiation.

"There may be times where I might have to say, 'A (stress test using sestamibi as an imaging agent) might give us some interesting information about your heart, but the likelihood that we learn something important is too low to justify the exposure to radiation.'"