107th Congress

Cancer Clusters --- Hearing Before the Senate Cancer Coalition -- June 5, 2001

Members Present

Senator Dianne Feinstein (D-CA) and Senator Sam Brownback (R-KS) Co-chairs; Senator Hillary Rodham Clinton (D-NY).

Witnesses

Robert N. Hoover, M.D., Sc.D., Director, Epidemiology and Biostatistics Program, Division of Cancer Epidemiology, National Cancer Institute (NCI); Susan Shaw Devesa, M.H.S., Ph.D., Chief Descriptive Studies Section, Division of Cancer Epidemiology, NCI; David W. Fleming, M.D., Deputy Director for Science and Public Health, Centers for Disease Control and Prevention (CDC); David A. Savitz, Ph.D., Professor and Chair in Epidemiology, School of Public Health, University of North Carolina; Sue-Min Lai, Ph.D., Associate Professor for Preventive Medicine, University Medical Center, University of Kansas; William Wright, Ph.D., Chief, Cancer Surveillance Section, California Department of Health Services.

Summary:

Purpose of Hearing:

The Senate Cancer Coalition convened the hearing to discuss cancer clusters.

Opening Remarks:

Senator Dianne Feinstein welcomed the witnesses and outlined the following issues she would like to examine regarding cancer clusters:

What are cancer clusters?
Why are cancer rates higher in some areas?
Are environmental risk factors the cause?
Do we know the causes? Can they be determined?
Why do some scientists discount cancer "hotspots"?
How should government respond?

She also welcomed Senator Sam Brownback, who has replaced former Senator Connie Mack (R-FL), as the new co-chair of the Senate Cancer Coalition.

In his introductory remarks, Senator Brownback greeted the witnesses with a special welcome to Dr. Sue-Min Lai, who was from the Senator's home state of Kansas. He expressed his pleasure about being the new co-chair of the coalition.

Senator Clinton welcomed the panel and stated that she was eager to hear their testimony because "the environment is one of the black holes of scientific research that needs to be illuminated." She expressed her dismay that we are "woefully behind" in prevention efforts. She also mentioned the hearing before the Senate Environmental and Public Works Committee that will be held June 11th on potential links between environmental contamination and chronic diseases and disease clusters, including high rates of breast cancer.

Statements of Witnesses:

Robert N. Hoover, M.D., Sc.D., accompanied by Susan Devesa, Ph.D.

Dr. Hoover defined "disease cluster" and addressed what government might do about cancer clusters. His testimony included the following main points:

• A disease cluster is the "occurrence of a greater than expected number of cases of a particular disease within a group of people, a geographic area, or a period of time."
• The term "environment" refers not only to air, water, and soil, but also to substances and conditions in the home and workplace; diet; the use of tobacco, alcohol, or drugs; exposure to chemicals, sunlight and radiation; lifestyle, economic and behavioral factors. When investigating a potential disease cluster, all of these factors are included in the analysis.
• Investigating small disease clusters usually does not yield definitive results because cancer resulting from an environmental exposure may take many years to appear and populations in a particular geographic setting are often in flux.
• State health departments and federal agencies including CDC, ATSDR, and the Environmental Protection Agency all respond to reports of cancer clusters.
• NCI plays a critical role in documenting evidence on cancer incidence and survival via its Surveillance, Epidemiology, and End Results (SEER) Program, and contributes to the funding of the National Program of Cancer Registries along with CDC and the states.
• NCI has studied geographic patterns of cancer mortality for over 30 years, and has published an Atlas of Cancer Mortality in the United States.
• A new tool, the Geographic Information System for Health (GIS-H) was especially created by NCI for the study of breast cancer, and it will be ready for pilot studies this year.
• NCI has identified the study of the interaction of genes and the environment as a high priority research area with great potential for discovery.
• NCI is creating Centers of Excellence in Cancer Communications Research to accelerate advances in cancer communications knowledge.

David W. Fleming, M.D.:

Although cancer clusters are relatively common, even under optimum circumstances, investigations of these clusters are not likely to lead to new insights into the causes or treatment of cancer.

• 85-90 per cent of cancer cluster investigations do not find evidence of increased cancer risk.
• Among the small proportion of reported clusters that do reveal an increased cancer risk, only rarely is there a common cause.
• Purely random events also cluster by chance, and statistical tests cannot separate observed clusters caused by chance from those due to an unrecognized common cause.
• State and local agencies should have the ability to mobilize quickly to respond to a cancer cluster concern; to analyze information regarding the incidence of cancer in a community; and to link and integrate information about environmental exposures with information about cancer cases and registry data.
• CDC supports state-based cancer registries; assessment and epidemiologic studies to evaluate how people are exposed to environmental hazards; studies of exposures to cancer-causing agents in the workplace; and studies of cancer clusters near hazardous waste sites, among others.
• CDC is considering establishing a single point of contact through which cancer cluster inquires might flow, as well as guidelines for responding to cancer cluster concerns.

David A. Savitz, Ph.D.:

Dr. Savitz made the distinction between 1) studying an unusual number of diagnosed cancers at a given place over a brief time period and 2) studying patterns of cancer occurrence over long periods across wide geographic areas. His testimony concluded that:

• Cancer registries are critical to understanding of cancer over time and by location.
• Studying cancer over longer periods of time and by geographic location are cost-effective, yield better results; increase the ability to detect the unexpected, and make it easier to evaluate potential causes that may lead to preventive measures.
• Studying cancer clusters over short periods of time and by locations have not been successful because 1) most environmental exposures happen very slowly, often over decades, and thus, an elevated cancer rate for 6 months or 1 year is not likely to point to some specific, identifiable cause, 2) causes of cancer operate over many years, so that clustering at the time of diagnosis does not correspond to clustering at the time when they were actually caused, 3) exposures that tend to cluster in time and space may well not be the dominant causes of cancer.
• Where there are known pollutants from waste sites or pesticides in the air or water, the focus should be on reducing exposures and improving the environment, whether or not it contributed directly to the reported cancer cluster. A balance between protecting the right to privacy of medical information and allowing the needed access for research must be found to ensure that important cancer research may continue.

Sue-Min Lai, Ph.D., M.S., M.B.A.:

Dr. Sue-Min Lai summarized CDC's four-stage approach to evaluating a reported disease cluster, including gathering information from the informer, evaluating whether there is an excess of disease, conducting a feasibility study, and developing a epidemiological investigation. She stated that most cancer cluster investigations conducted to date have not reached the feasibility stage. She also emphasized the following points that make disease cluster investigations problematic:

• Geographic boundaries for a cluster study are influenced by the observed result and may be in error.
• The effect of population emigration and immigration will dilute disease clusters with a specific localized cause and diminish their detection by geographical studies.
• Most statewide registries do not include information about length of residence and place of birth.
• The under-reporting of cancer cases in many regions, particularly in rural America, make an accurate assessment of cancer burden less likely.
• Rural medically underserved areas remain less likely to be targeted for cancer control and prevention.

William E. Wright, Ph.D.:

Dr. Wright oversees the development and implementation of cancer cluster protocols in California. His testimony addressed 1) the existence of cancer clusters, 2) how California responds to citizen concerns about cancer in their neighborhoods, and 3) how environmental causes of cancer should be investigated. His main points included:

• Cancer clusters do exist, some because people with certain risk factors tend to cluster, some because of environmental factors, especially in occupational settings, and many because of statistical chance.
• The term "environment" is often defined differently by the public and by scientists. The public refers to the environment as the air we breathe, the water we drink, and the soil in which we garden and our children play. Using this definition of environment, most scientists believe that the environment causes a relatively small proportion of all cancers.
• Scientists have a much broader definition of "environment," including the influence of smoking, diet, alcohol use and other lifestyle factors.
• Films such as "Erin Brockovich" and "A Civil Action" lead the public to believe erroneously that the environment, defined as contaminated water, pesticides, toxic dumps, air borne pollutants, etc., is largely to blame for most cancer.
• Studies of cancer clusters to identify an environmental cause of cancer in a selected neighborhood are almost certainly doomed to failure because: 1) Neighborhood cancer clusters are defined by place of residence at time of diagnosis, not as place of exposure. Given the assumed 20-30 years time lag between exposure and diagnosis of most cancers and the mobility of the U.S. population, it is unlikely that neighborhood cancers are due to exposures in that same neighborhood. 2) Neighborhood cancer cluster studies have very limited methods for measuring exposure to known and suspected carcinogens. 3) Neighborhood cancer cluster studies usually include too few cases to allow for a useful study or adequate control for confounding variables such as tobacco smoke exposure and other lifestyle variables. There is only one study where a neighborhood cluster investigation led to the discovery of an environmental carcinogen. Citizens in California usually express their concern about cancer in their neighborhood in two ways: 1) they become aware of an unusual number of cancer cases and need reassurance that it is not due to something in their neighborhood, and 2) they identify a real or perceived environmental hazard in their neighborhood and want it eliminated.
• Most people are not aware of the pervasiveness of cancer in our population.
• Although investigating cancer causes on a neighborhood cluster basis is very unlikely to yield critical answers, it is important to continue population-based surveillance efforts, and to respond with more definitive research when possible.
• Tobacco and diet are responsible for 60 per cent of all cancer mortality.

Questions:

Senator Feinstein:

How do you account for the low incidence of breast cancer in Asia?
What is the reason for the high incidence of prostate cancer among minority men in North Carolina?
Is there a correlation between strong agricultural portions of the United States and cancer? Are women contaminated with pesticides?
None of you have commented on Erin Brockovich.

Senator Brownback:

What is the reason for the high rates of breast cancer among white females?
What are the public education steps that you take when you see a high area of cancer incidence on a map?

Senator Clinton:

Please tell us about the Geographic Information System.

Follow-up Question for NCI:

Senator Feinstein said that she has received complaints from her constituents regarding the fact that NCI is not spending any of the Breast Stamp funding for research on environmental factors and breast cancer. She would like data on the grants being awarded from Breast Stamp funds. She would also like to know if there is DoD money devoted to environmental research.

Prepared by Susan Persons/OLPA