More than 230,000 new cases of breast cancer expected to be diagnosed in the United States in 2011, many wonder about the role that environmental exposures may be playing.
Written by Catharine Paddock PhD
A new Institute of Medicine (IOM) report released on Wednesday concludes there are some evidence-based steps women can take to reduce their risk of developing breast cancer associated with environmental factors. These include avoiding unnecessary medical radiation (such as unessential X-rays and CT-scans), not smoking, avoiding use of estrogen-progestin menopausal hormone replacement therapy(HRT) if possible, limiting alcohol intake, keeping to a healthy weight (especially after the menopause), and exercising regularly.
The report, which was released at the San Antonio Breast Cancer Symposium, and is also available to view online, points out that these are preventive steps that focus on those environmental risk factors (including lifestyle choices) where there is consistent scientific evidence of a link with breast cancer. It also suggests there is evidence, although this is less clear, of a link between breast cancer and exposure to certain chemicals, such as those found in some workplace settings, gasoline fumes, vehicle exhaust, and tobacco smoke. These include benzene, 1,3-butadiene, and ethylene oxide.
The IOM says there are other areas where evidence is “provocative” and inconclusive, but sufficient to warrant “priority attention” such as overnight shift work and other ways that disrupt the sleep cycle; chemicals that mutate genes or alter their expression, or affect hormones such as estrogen; plus interactions between genetic and environmental factors. Contrary to some popularly held beliefs, avoiding personal use of hair dyes, and non-ionizing radiation emitted by technological devices like mobile phones, will not affect a woman’s risk of breast cancer, says the IOM report, as several studies now have shown no link between these factors and the disease.
Overall, the report find there have been some major advances in our understanding of breast cancer and the things that raise the risk of developing it, but we need to do more research to find out exactly what causes the disease and how to prevent it. Over the course of a lifetime, many changes happen to a woman’s body, including her breasts. New information suggests women and girls may be susceptible to different risk factors at different life stages, so the IOM recommends that future research takes a “life-course approach” to studying the effects of exposure throughout the lifespan, including at specific stages of breast development. It needs to look at cumulative exposure as well as multiple exposure over the lifespan.
Too much of our knowledge is based on studies that focus on the few years before diagnosis, but more recent research suggests we also need to look at exposure that happens much earlier in life, even in childhood, as well as key stages in physiological development and change, such as adolescence, pregnancy, and menopause. The report uses the term “environment” in a broad sense, and reviews evidence on a range of factors that women encounter in their day to day lives. These factors include: ionizing radiation, combination estrogen-progestin hormone therapy, body weight after the menopause, and physical exercise. But for many other factors, the evidence from human studies is either limited, contradictory, or absent, says the report.
Susan G. Komen for the Cure, an organization that describes itself as the “largest grassroots network of breast cancer survivors and activists”, commissioned the IOM report. The brief was to review the current evidence on breast cancer and the environment, including gene-environment interactions, look at the research challenges, explore any actions that women might take to reduce their risk where there is good evidence to support this, and recommend directions for future research.
Since its inception in 1982, the organization has invested more than $1.9 billion in non-profit funds to fight breast cancer around the world. Their President, Elizabeth Thompson, said in a statement that: “Understanding the role that environmental factors play in the development of breast cancer is hugely complex and the IOM has done a good job laying out the challenges. We intend to use these findings to guide our decisions about research to fund, so that women and their families have the best science to guide them in making important lifestyle choices. We believe our efforts going forward will be made even more effective through the guidance provided by this study.”
Thompson drew attention to the fact the IOM stressed more research is needed before we can get a clear picture of which substances can definitely be tied to breast cancer. She said the organization is now: “… issuing a challenge to other agencies working in the environmental area to join with Susan G. Komen to create a fund to begin work on these very important initiatives.”
Estimates suggest more than 230,000 American women will receive a diagnosis for breast cancer in 2011.