The Cancer Chronicles: The Elusive Connection Between the Environment and Breast Cancer

By George Johnson | May 27, 2013 8:08 pm

Barbara Brenner, 1951-2013. Anita Bowen Photography

An obituary last week in the New York Times announced the death of Barbara Brenner, a powerful advocate for women with breast cancer. She had been diagnosed with the disease at age 41, but that is not what killed her. The cause of death, 20 years later, was a neurological condition, amyotrophic lateral sclerosis.

Her organization, Breast Cancer Action, is one of many plaintiffs in a Supreme Court case opposing the right of a biotech company called Myriad Genetics to hold a patent on the BRCA genes, which has given it a monopoly on the test for whether a woman has inherited a mutation like Angelie Jolie’s. The question of whether isolating a gene outside of a living cell involves “sufficient inventiveness” to warrant a patent is a subject I hope to explore here later. For now, what caught my attention in the obituary were these words:

Dr. Otis W. Brawley, the chief medical and scientific officer of the American Cancer Society, called Ms. Brenner “a dear friend,” but added, “I didn’t agree with her, probably 40 or 50 percent of the time.”

One point of difference was over whether environmental factors play a major role in cancer. Ms. Brenner thought they did; Dr. Brawley is skeptical.

His position is shared by most researchers who study the disease — an example of how the public perception of cancer is so often at odds with the science. While I was writing The Cancer Chronicles and discussing it with friends, I found that many took it for granted that a large amount of breast cancer is caused by artificially produced chemicals in the atmosphere and in processed foods. But the evidence is just not there.

Some of the misunderstanding comes from announcements like this by The Breast Cancer Fund (a different organization from Ms. Brenner’s), which is holding a conference this week in San Francisco called “Pioneering Prevention.”

For the last decade, the Breast Cancer Fund and our community have been working to usher in this new era by focusing on identifying and eliminating our exposure to toxic chemicals and radiation linked to the disease. We’ve analyzed the science, won passage of landmark public health legislation, and convinced industry giants to make safer, less toxic products.

Validating our work, a recent federal advisory committee report, Breast Cancer and the Environment: Prioritizing Prevention, concludes that prevention is the key to reducing the burden of breast cancer.

Elsewhere on the organization’s web site we read that this same study “concludes that preventing exposure to environmental risk factors is the most promising path to decreas[ing] incidence of the disease.”

While no single sentence quoted above is factually incorrect, the overall impression is misleading. Only some of the organization’s followers will know that “environment” is defined by epidemiologists to mean anything that is not genetically inherited. In other words, almost everything. Diet, personal habits, professional occupation, geographical locale — human behavior in all of its manifestations — are considered environmental.

The definition is so expansive that it includes not only artificially manufactured chemicals but also fluctuations in a woman’s naturally produced estrogen, which can vary according to the choices she makes. The decision to have fewer or no children, or to begin conceiving later in life, exposes her body to more menstrual cycles — monthly doses of estrogen — and that increases cancer risk. One of the roles of estrogen is to accelerate the production of new breast cells. That is done through cellular division — and every time a cell divides into two cells, copying all of its DNA, there is a chance of a random mutation. The right combination can turn a healthy cell into a malignant one, giving rise to a tumor.

These subtleties will be lost to many visitors of the Breast Cancer Fund’s website, unless they download the government report and go to Chapter 6 for a discussion of the “Accepted Risk Factors for Breast Cancer Based on Human and Animal Data.” The first two are genetic — family history of breast cancer and rare mutations like those of the BRCA genes (often these two factors overlap). Then come physical characteristics like breast density (more fat can be beneficial) and a history of benign breast disorders. Next on the list is exposure to a woman’s own estrogen. That is followed by lack of exercise, alcohol consumption (several drinks a day throughout life might increase breast cancer risk from 12 to 18 percent), exposure to ionizing radiation, adult body mass, weight gain, and height. (The Million Women Study has found that every four inches over five feet raised overall cancer risk by 16 percent.)

That is the end of the “accepted” list. Next come “Risk Factors With Some Evidence”: diet, inflammation, disruption of the body’s circadian rhythms by working at night, growth hormones that are connected with obesity, psychosocial factors — and, at the very end, chemical exposures. These include artificial endocrine disrupters, like bisphenol A used in plastic water bottles, and the many carcinogens in tobacco smoke.

It is possible that, as both the Breast Cancer Fund and Breast Cancer Action contend, more research may reveal a greater role for the chemicals introduced into air, water, and food by the onslaught of civilization. It’s frequently said that some 85,000 synthetic substances have been unleashed on the world, only a fraction of which have been tested to see if they might be carcinogenic.

In the face of that, it is consoling to learn from the National Cancer Institute that since 1999 the incidence of breast cancer in the United States has declined year by year and has now leveled off. As with all these things, the reasons are complex — more to write about later.

Note: This is the first of a series of posts that will be tied to my book The Cancer Chronicles: Unlocking Medicines’s Deepest Mystery, which is scheduled for publication in August.

Related Post: Angelina Jolie’s State of the Art Cancer Treatment

  • JonFrum

    The fact that the connection between cancer and environmental ‘toxins’ is elusive tells you all you need to know. If you’ve looked for a connection (and people have) and you haven’t found a certain connection, then either the connection is very weak, or it doesn’t exist. More study isn’t going to find a strong connection.

    Simple minds want simple answers.By definition.

    • Felix Tejeda

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      • Buddy199

        moron troll

  • Kuze81

    “While this article is well written and persuasively argued, I will continue to stick to my intuitions about ‘chemicals are causing cancer’ because my brain prefers intuitive narratives of good and evil rather than objective evidence.” -People

  • Ben

    Combining what we know (genetics or environment) doesn’t explain the whole story of why some women get breast cancer and some don’t. Thus the possibility remains that unknown environmental and genetic factors still contribute to this disease. It is irresponsible to imply that contaminants or genetics is not playing a role… Many studies have looked at both possibilities and still our knowledge is incomplete– Suggesting that one isn’t a contributing factor is outrageous and does more harm than good. Discover magazine must do better in clearly labeling these speculative articles “editorials” if it is to maintain any credibility…

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Fire in the Mind

Whether a subtle new pattern shows up in an experiment on the Higgs boson, an epidemiological report about a suspected cancer cluster, or a double-blind trial purporting to demonstrate ESP, it can be maddeningly difficult to distinguish between what we see and what we think we see. "Fire in the Mind" takes a look at the big questions behind today’s science news.

About George Johnson

George Johnson writes about science for the New York Times, National Geographic Magazine, Slate, and other publications. His nine books include The Cancer Chronicles: Unlocking Medicine's Deepest Mystery (August 2013), The Ten Most Beautiful Experiments, A Shortcut Through Time, and Fire in the Mind. He is a winner of the AAAS Science Journalism Award and has twice been a finalist for the Royal Society science book prize. Co-founder and director of the Santa Fe Science Writing Workshop, he can be found on the Web at talaya.net. Twitter @byGeorgeJohnson.

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