|Mark your calendars for a CHE Cafe Call with CHE-cofounder Michael Lerner and Ted Schettler, discussing the themes that emerge in Ted’s analysis and opportunities for reducing the burden and impact of breast cancer. The call will be on Monday, December 16th at 10 am PST/1 pm EST. For more information and to RSVP for this call, please click here.
The Ecology of Breast Cancer About twenty-five years ago I began to think about breast cancer as an ecological disorder, after realizing that genetic susceptibility, other recognized risk factors, and life style simply do not explain why many people develop this disease. Nor do they fully explain breast cancer patterns in populations. I thought that insights from ecological science might lead to different study designs and interventions to help prevent this disease, then responsible for over 40,000 deaths annually in the United States.
Ecological science seemed worth considering. Migration studies show that breast cancer risk remains low in first-generation immigrants who move to a high-risk country after spending childhood and adolescence in a country with lower incidence. But the risk in second-generation immigrants increases when they live their entire lives in a high-risk country. What makes a country high-risk for breast cancer? That kind of question is familiar to ecologists. They often want to know what makes an ecosystem vulnerable. Why does ecosystem structure and function change, often rapidly and irreversibly?
Ecology is the study of complex, diverse interactions among organisms and their environments. Ecologists study multi-level nested systems of individuals, populations, and diverse communities. Ecosystems feature interactions within and across levels, feedback loops, thresholds, and shifting dynamics that together impart resilience or vulnerability. These concepts seemed relevant to breast cancer and other complex diseases that are stubbornly resistant to more complete understanding of their origins and response to treatment.
The Ecology of Breast Cancer: The Promise of Prevention and the Hope for Healing, explores these ideas more fully. It reviews and summarizes a large scientific literature and draws practical conclusions that I hope will stimulate more widespread efforts to prevent this disease and improve outcomes after diagnosis and treatment.
Historically, scientific studies of most human diseases, including breast cancer, have typically gathered and analyzed data using linear, reductionist models and methods. They have attempted to identify main effects of single variables while “controlling” for others using various statistical techniques and often studying relatively homogeneous populations. Dynamic interactions among variables have been either of secondary interest or ignored altogether. While this approach has led to important insights and medical therapies, it has limited ability to address the systemic causes and prevention of complex diseases.
In recent years eco-social models that include multi-level interactions and changing system dynamics have gained some traction in epidemiologic research. Systems biology is an emerging approach applied to basic biological research that focuses on complex interactions within biologic systems. But most breast cancer research uses older, more traditional methods. Decades of research into the effects of diet on breast cancer risk is limited by failure to account for confounding and modifying effects of physical activity levels. The unanticipated effects of combinations of early life chemical exposures and variable diets on mammary gland cancer risk in laboratory animals are dramatic, but this is difficult to study in people and we have no human data.
Several years ago, I began looking into lifestyle interventions that people who had been diagnosed and treated for breast cancer might undertake to complement their traditional therapy. I was curious after conversations with Michael Lerner, president of Commonweal, a nonprofit center in California, and co-founder of the Commonweal Cancer Help Program. Michael is author of Choices in Healing (MIT Press, 1994) and has co-led Cancer Help Program retreats for 28 years. Most of the participants in the Cancer Help Program are women with breast cancer who are committed to improving the quality of their lives and prognoses. Integrative therapies for breast cancer and integrative oncology more generally significantly improve outcomes, and we thought that a summary of the evidence addressing diet, exercise, weight control, stress reduction, and social support as elements of a comprehensive approach to breast cancer treatment would be useful. I soon decided to broaden the scope of this project to include breast cancer prevention, to explore the evidence linking these and other variables to development of the disease in the first place.
In addition to risk factors associated with hormone levels and reproductive development and history, many other, multi-level environmental variables also interact with human breast biology. This begins during fetal development and continues throughout life, influencing breast cancer risk and outcomes following diagnosis and treatment. None of these risk factors appears to increase breast cancer risk nearly as dramatically as cigarette smoking increases the risk of lung cancer. Instead breast cancer arises from a complex entanglement of many, multi-level variables. To be sure, some are more important than others, but most generally seem to contribute only modestly to risk, particularly when they are studied in isolation. But their dynamic interactions, over the life course, can be dramatic and profoundly important, as repeatedly demonstrated in laboratory studies and increasingly in epidemiologic studies as well. Breast cancer seems to fit well within the ecologic or eco-social framework.
The Ecology of Breast Cancer: The Promise of Prevention and the Hope for Healing concludes that breast cancer is generally a disease arising from diverse societal conditions. To be sure, in individual women or men, a genetic predisposition or specific environmental exposure may be predominantly responsible. But breast cancer patterns in populations cannot be explained by one or two culprits. Rather, dynamic interactions among numerous features woven into the fabric of our lives and communities collectively create conditions that make breast cancer more or less likely. Thinking about this as a design problem and an ecological challenge are likely to help us identify multi-level interventions that will reduce breast cancer incidence and improve outcomes after diagnosis. This cannot be done by individuals alone. Community planners, health care professionals, public health officials, businesses, schools, governments, and farmers also have opportunities to help reduce the burden of this disease.
Some people resist an ecological framing of breast cancer, preferring to see this all-too-common disease exclusively as one of abnormal cells, often unexplainable, in unfortunate women or men. And it’s undeniable that biomedical sciences have made great progress in breast cancer treatment, based on improved understanding of this cellular pathology. But, a public health perspective widens the lens to look at breast cancer patterns in populations and offers additional insights into prevention and treatment. An ecological framework accommodates both and adds new science. It expands the ways we can study and address this disease.
Finally, there may be considerable value in applying the ecological framework more widely to other complex disorders, including various kinds of cancer, diabetes, asthma, cardiovascular disease, learning disabilities, cognitive decline, and dementia. I strongly suspect that changes in diet and the food system, the built environment, social environment, and reductions in hazardous chemical exposures designed to address breast cancer will help to reduce the burden of many of these as well.
Science Director, Science & Environmental Health Network