Expert Panel Pinpoints Environmental Culprits in Breast Cancer
Source : Pubdate : 2012/4/16 15:32:00 Author :
Women can lower their risk of developing breast cancer by avoiding unnecessary medical radiation, forgoing menopausal hormone therapy and limiting alcohol use, but they don't need to worry about using hair dyes or cellphones, a broad new national report says.
Reviewing the body of research on environmental factors that may affect breast cancer risk, the nonprofit, independent Institute of Medicine (IOM) also said that the scientific jury is still out on whether exposure to some chemicals -- including bisphenol A (BPA), pesticides and ingredients in cosmetics and dietary supplements -- alter women's odds of the disease.
"It does a number of things: identifies elements of the environment we think are important in breast cancer causation, tells researchers and public health people what we can do to move forward on the issue, and provides opportunities for individual women to modify their lifestyle or behavior to diminish the impact," said Hiatt, a professor and chair of epidemiology and biostatistics at the University of California, San Francisco.
The report, funded by Susan G. Komen for the Cure, was unveiled Wednesday at the San Antonio Breast Cancer Symposium.
The committee, interpreting "environment" to include all factors not inherited through DNA, noted that many breast cancer risk factors can't be modified, including age, family history, and age at first menstruation and menopause. Another barrier is that breast cancer research cannot center on the strongest types of studies -- randomized controlled clinical trials -- because of the ethical challenges of intentionally exposing women to potentially harmful substances.
Of the environmental factors reviewed, those with the most consistent evidence of a link to higher breast cancer risk are:
· Use of hormone therapy combining estrogen and progestin.
· Exposure to ionizing radiation, which occurs during diagnostic tests such as CT scans.
· Excess weight among postmenopausal women.
· Alcohol consumption.
The connection between smoking and breast cancer is more nebulous, the report said, because of mixed evidence. For several other factors -- including secondhand smoke exposure, nighttime shift work and exposure to the workplace chemicals benzene, ethylene oxide or 1,3-butadiene -- the evidence is less persuasive but suggests a possible link to higher risks.
A breast cancer association with bisphenol A (BPA), which is widely used in plastic containers and food packaging, is biologically plausible, the committee said, but research assessing the risk in humans is lacking. The same is true of pesticides and ingredients in cosmetics and dietary supplements, most of which aren't tested before going to market.
However, research doesn't support a link between the use of hair dyes and non-ionizing radiation -- which is emitted from electronic devices such as cellphones and microwaves -- and breast cancer, the study said.
Advocating a "life-course approach," the report called for future research to focus on the many stages of breast development, which begins in utero and undergoes substantial changes through puberty, pregnancy, breast-feeding and menopause. Most research has concentrated on the several years before women develop breast cancer, but environmental exposures during their other life stages may have a profound influence on chances of developing the malignancy, which is diagnosed in about 230,000 American women each year.
SOURCES: Robert J. Schneider, Ph.D., co-director, Breast Cancer Research Program and associate director, translational cancer research, NYU Langone Medical Center, New York City; Stephanie Bernik, M.D., chief, surgical oncology, Lenox Hill Hospital, New York City; David J. Hunter, M.B.B.S., M.P.H., Sc.D., dean, academic affairs, and professor of cancer prevention, departments of epidemiology and nutrition, Harvard School of Public Health, Boston; Iuliana Shapira, M.D., director, cancer genetics service, Monter Cancer Center, Lake Success, N.Y.; Robert A. Hiatt, M.D., Ph.D., professor and chair, department of epidemiology and biostatistics, and director of population sciences, Helen Diller Family Comprehensive Cancer Center, University of California, San Francisco; U.S. Institute of Medicine presentation, "Breast Cancer and the Environment: A Life Course Approach," Dec. 7, 2011, San Antonio Breast Cancer Symposium, Texas.
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