The toll of breast cancer in terms of worldwide mortality has reached a stunning 521,000 deaths annually, according to the World Health Organization.
With this level of mortality, breast cancer is the leading cause of cancer death for women globally.
Yet, we still don’t know very much about what actually causes breast cancer. And knowing that it is the leading cause of cancer death for women seems to beg the question: what is it about breasts that make them so susceptible to cancer?
In “Breasts: A Natural and Unnatural History,” Florence Williams attempts to provide some insights into that question.
Williams is a science journalist and also a mother. She describes how, while nursing her second child, she happened to read a news report which said that “scientists were finding industrial chemicals in the tissues of land and marine mammals as well as human breast milk.” Troubled by this information, and also aware of the rising incidence of breast cancer globally, she set out to understand what the impact of modern life means for our breasts and for our health.
In the early chapters of the book, Williams introduces us to some of the theories of how the human mammary gland evolved and how it may have led to our larger brain size relative to other mammals and, eventually, to the development of speech. She also writes about the work of scientists who study the biology of the breast and how it develops. Williams notes that there are some interesting parallels between the growth of the normal breast during puberty–through massive proliferation of ductal cells–and the processes that occur in cancer.
Our breasts evolved with a finely tuned ability to respond to signals from our environment, Williams explains. Our mammary glands contain estrogen receptors, and Williams notes that our bodies inherited an “eons-old” ability to absorb estrogen from our surroundings, even after we learned how to make it ourselves. This sensitivity conferred an important advantage from an evolutionary standpoint, but now it puts us at risk. That is because synthetic compounds that mimic estrogen have become increasingly prevalent in our environment.
Our breasts, for better or worse, have more varied and more sensitive hormone receptors than other organs. If anything their receptors veer toward oversensitivity. They need to sense the environment to store fat and grow at the optimal time and feed an infant in an uncertain world. What might have been handy once upon a time now looks increasingly like a liability.
The book goes on to describe the many changes that breasts go through over the course of a woman’s lifetime and what research is telling us about the risks associated with these changes. At each of these stages — from puberty to pregnancy, nursing and menopause, breasts develop and interact with the environment. The hormonal fluctuations surrounding these events in some circumstances protect the breast and in others increase the risk of cancer developing later. But the nature of our lives and our world today confers much greater risk as we go through these stages than we evolved to handle, Williams argues.
It all adds up to a new ecology of the breast. Here’s the basic cheat sheet for how the risk of breast cancer has changed over the ages. Old days: We did not have so much exposure to cycling estrogens and progesterones (we were thinner, hit puberty later, had more children, dropped dead earlier). Modern times: We’re awash in steroidal hormones. We’re fat and sexually precocious, but have babies late if at all. We take the pill and “bio-identicals,” slather novel, untested chemicals on our bodies, and consume them through food and water. We’re pretty much marinating in hormones and toxins.
Williams tells us about an evolution in her own thinking as she met with many experts and learned more about the factors that influence the likelihood that a woman may develop breast cancer, including genes, childhood exposures, reproductive history and later exposures such as hormone therapy.
I was increasingly learning that the whole blame-your-lifestyle approach to understanding breast cancer is problematic. In a way, it presents an excuse not to probe into the deeper reasons for disease. As environmental historian Nancy Langston put it, ‘Traditional medicine and public health practices have been reductive, focused on individual risk factors for disease.’ Instead, she argues, we need a more ecological understanding that explores how genes and the environment interact to compromise our immune system in the first place.
In her concluding chapter, Williams notes that treatment of women with breast cancer has improved and more women are living longer after a breast cancer diagnosis. But she points out, “ultimately, though, diagnostics and treatments are already measures of defeat: the tumor has arrived.” She believes that to spare women the agonies of breast cancer and its treatment, as a society we need to focus more on the big picture of health and on prevention.
Call me a dreamer, but I’d rather have healthy pipes to begin with. This is where prevention gets trickier. On a personal level, it means making vexing choices: drinking less alcohol, seeking alternative menopause treatments, exercising (a lot), scrutinizing labels, and reducing exposures to toxins and endocrine disruptors. These measures only take us so far. A better and more successful approach would be a societal one in which industries have incentives to design safer products and make healthier foods, and governments adopt a commonsense and rigorous approach to testing and regulating chemicals. Social policies could encourage more breast-feeding and less obesity.
The book is an easy read and quite fascinating. After reading this book, I appreciate even more than I did before the extent to which our breasts are a highly communicative organ, primed to respond to signals both internal and external. The trait is important, at least from an evolutionary standpoint, but makes us more vulnerable to the development of cancer in the world we live in now.
I’d like to think there is cause for hope in this story. But there is only so much we can do as individuals to reduce our risk. As Williams describes, we’re going to need changes in incentives and in public policy in order to address exposures that are beyond our ability to alter as individuals. It is hard to see how the rising toll of global deaths from breast cancer can be reduced without these kinds of changes.