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On June 4, 2004 BCERF held its Spring Cancer and Environment Forum on the Cornell campus in Ithaca, in its new home in the College of Veterinary Medicine. The agenda carried the diverse but interrelated themes of how nutrition, body type characteristics, and genetic-environment interaction affect breast cancer risk. At least 65 people from academia, NYS agencies, county health departments, breast clinics, members of the Ithaca Breast Cancer Alliance, and other individuals participated in the day. Evaluation results suggest that the Forum offered participants new (and sometimes challenging!) material to add to their knowledge of the emerging science of breast cancer risk factors.
Dr. Rodney Dietert facilitated his last Forum as Director of BCERF, as he will be stepping down from this position this summer. BCERF staff and the Sprecher Institute presented Rod with a plaque in honor of his years of service to the program. We were happy to have the following people welcome participants to the Forum: Dean Donald F. Smith, Professor of Surgery and Dean of the College of Veterinary Medicine at Cornell; Dr. Helene Dillard, Director of Cornell Cooperative Extension and Professor of Plant Pathology; Assemblywoman Barbara Lifton representing the 125th Assembly District; and Dr. Rodney Page, Professor of Medicine and Director of the Sprecher Institute for Comparative Cancer Research.
Mammographic Density and the Incidence of Breast Cancer: A Modifiable Example of Gene-Environment Interaction
Dr. Norman Boyd, the Head of the Division of Epidemiology, Statistics and Behavioural Research at the Ontario Cancer in Toronto, joined us to discuss a marker of breast cancer risk, mammographic density (the appearance of dense breast tissue on mammograms). Although this relationship has been documented using less precise methods, Dr. Boyd has worked with a group to develop a quantitative and reproducible method for measuring breast density. Dr. Boyd and is colleagues have generated an abundance of data documenting the positive correlation between increased breast density and increased breast cancer risk. Though this relationship may not be causal, he described the many ways that this correlation tells us more about breast cancer risk than any other method we currently have.
Dr. Boyd posed the question: how is it that a risk factor that gets less common as people age is related to a disease that is more common as people age? He then explained: it is breast tissue age, not chronological age, which most influences changing levels of susceptibility. Mammographic density parallels breast tissue age. Both breast tissue age and mammographic density act as ‘cumulative exposures’ and are affected by reproductive events such as the ages at menarche, first child’s birth and menopause. He noted that reproductive variables explain 20% of mammographic density in the population. Dr. Boyd then provided fascinating data on where genetics fits into the larger research picture. In a large study of 1000 pairs of female twins in North America and Australia, there was approximately 65% agreement in the level of breast density in identical twins and 28% in nonidentical twins. He concludes that genes for mammographic “density-for-age” exist and that: these may be important determinants of age-specific incidence of breast cancer; they may likely explain some proportion of familial breast cancer risk; and failure to take this into account may lead to a misrepresentation of the role of environmental risk factors.
In examining data from Chinese populations, it appears that their much shorter average period of exposure to density (i.e. the population tends to have a higher level of breast dense tissue for a much shorter period) may be related to potentially modifiable factors, such as fat intake. Dr. Boyd cited data showing a lowfat diet over two years reducing the area of breast dense tissue. We look forward to more information as Dr. Boyd’s studies continue to yield results.
Folate, Cancer, Genetic Variation and the Food Supply
Another angle on genetics and cancer was provided by Dr. Patrick Stover, an Associate Professor here at Cornell in the Division of Nutritional Sciences. Dr. Stover began his talk describing the effect that the Human Genome Project has on the expectation of change in the worlds of pharmocogenomics and nutritional genomics. In other words, is the way being paved toward personalized medicine and nutrition, according to genotype? Dr. Stover’s expertise in the area of the nutrient folate, a water-soluble B-vitamin, and its relationship to birth defects and disease outcome demonstrates that the answer is not simple.
Folate plays a role in two metabolic pathways related to cancer risk: DNA synthesis and cellular methylation. These pathways may explain the relationship between folate deficiency and cancer risk. More widely known is the relationship of impaired folate status and neural tube defects in offspring – the rationale behind the fortification of the food supply with folic acid since 1998. Data describing the rates of neural tube defects, however, also points to a genetic component. Dr. Stover presented information on a common polymorphism (variant in gene sequence) which is associated with risk for neural tube defects; however, this polymorphism is also protective against cancer, demonstrating that a genotype can be simultaneously advantageous and disadvantageous for health outcomes.
Epidemiologically, high folate status has been shown to be associated with decreased cancer risk. The Physicians’ Health Study showed a seven-fold difference in colon cancer risk between individuals with low folate and high (supplement-level) folate status. Several studies have also shown that folate may mitigate the relationship of high alcohol intake and breast cancer risk.
Dr. Stover and colleagues have also done work in both tumors and cancer cells that is defining the specific metabolic pathways which are important to the connection between folate and cancer. We look forward to learning the ongoing results of studies from Dr. Stover’s laboratory.
Obesity, Environment and Breast Cancer Risk
Dr. Barbour Warren, Research Associate for BCERF, presented on “Obesity, Environment and Breast Cancer Risk.” This provided the scientific premises for a BCERF community intervention and research project, currently in the planning stages. He described the data demonstrating that obesity is an important breast cancer risk factor, and explained that:
• it is consistently associated with about a doubling of breast cancer risk;
• it can be changed, albeit with some difficulty;
• it has adverse effects on breast cancer diagnosis, recurrence and survival.
He defined obesity, and the obesity epidemic, including the fact that genetics are unlikely to explain the recent increases in obesity. He very effectively showed how we are experiencing a “mismatch” of genes and environment, having developed to efficiently store energy and yet being a sedentary society with an abundant food supply (compared to historically requiring a large amount of physical work and having an unpredictable food supply). Dr. Warren’s data characterizing our food supply included plenty of examples of the “super-sizing” of soft drink portions and commercial baked goods, a 200% increase in meals and snacks eaten out from 1977 to 1995, and the current relative low-pricing of food as compared to the earlier part of the last century. In describing an environmental approach to addressing obesity, Dr. Warren emphasized that these food environment issues need to be addressed, as well as the design of our community environments and the structure of our leisure time. These issues greatly effect how sedentary our society is on whole. Stay tuned for more information about the BCERF community intervention and research project on this theme.
Organizational and programmatic updates
Due to illness, we were not able to hear from the representative of the Healthy Living Partnership of Tompkins County, and will hope to do so in the future. We were happy to hear from Heather Clark on the Agriculture and Environmental Program Committee for Cornell Cooperative Extension of Tompkins County, Suzanne Snedeker on recent activities within BCERF’s environmental chemicals projects, and Joyce Rodler on the pest management program of Cornell Cooperative Extension of Suffolk County.
Breast Cancer Advocacy: History and Context
Bob Riter, Associate Director of the Ithaca Breast Cancer Alliance (IBCA) and breast cancer survivor, brought the group a completely different perspective on breast cancer: a discussion of the major events and approaches of the breast cancer movement. It was not until the mid-1970s when major public figures, such as Betty Ford, announced openly that they had breast cancer that the disease came fully into public view. This seemed to open the way for the accomplishments that followed, changing the environment within which many women (and men, Bob reminds us) navigated their way through the breast cancer experience. Bob reflected on accomplishments such as the availability and acceptability of peer support and the pursuit of second opinions, quicker turnaround on pathology reports, and acceptance that more aggressive treatment does not always mean better treatment. He also touched on the major accomplishment of the institutional role that advocates play in allocating federal research dollars. Looking toward the future he sees a continued focus on prevention in the breast cancer movement, more attention to the 2.1 million survivors and their needs, access to care issues, and coalition building. Bob ended by sharing with the group the recently produced documentary on the founding of IBCA, which won the National Award in the Documentary Public Awareness category, from the 2004 Hometown Video Festival. This video was produced by Baseema Banoo and Ward Krkuska.
Program on Breast Cancer and Environmental Risk Factors
Cornell University, College of Veterinary Medicine
Vet Box 31, Ithaca, NY 14853-6401
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