While cartography and oncology sounds like an odd mix, two projects made public in December have put cancer on the map.
The projects, the National Cancer Institute's Atlas of Cancer Mortality in the
United States: 1950-1994, and New York State's Cancer Surveillance Improvement
Initiative, use intensive graphing software to map cancer rates at a county level. The technology is
called geographic information systems, and its use has blossomed in the past 20 years as public
health and medical researchers discover graphing software's value as a tool to focus in on
smaller geographic areas that need attention.
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The Atlas of Cancer Mortality in the United States: 1950-1994 presents 254 color-coded maps that show cancer deaths in more than 3,000 counties by race and gender for 1950-69 and 1970-94. The atlas is the product of several years' worth of labor; work on the project began in the early 1990s.
"The maps are designed to provide us with clues to etiologic and prognostic factors involved in cancer," Joseph F. Fraumeni, Jr., M.D., director of NCI's Division of Cancer Epidemiology and Genetics, told the National Cancer Advisory Board at a recent meeting.
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Patterns of cancer mortality are the same for some cancers such as colon and breast for the most recent time period compared with the earlier data. However, striking differences can be seen in lung cancer, said Susan Devesa, Ph.D., also from NCI's Division of Cancer Epidemiology and Genetics, and the lead author of the most recent atlas.
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Devesa and her colleagues took an in-depth look at these changing patterns in a paper published in the Journal of the National Cancer Institute last year (June 16, 1999, p. 1040). They concluded that "the changing mortality patterns for lung cancer generally coincide with regional trends in cigarette smoking, indicating that public health measures aimed at smoking prevention and cessation should have a dramatic effect in reducing lung cancer rates."
These changing patterns and other more subtle shifts can be seen on the maps in the atlas. In addition to the printed version, an interactive and more comprehensive version of the maps are available on the Internet at http://www.nci.nih.gov/atlas. This "dynamic" version allows researchers to access the data to do independent analyses, Devesa said. Users will be able to select a specific type of cancer, geographic region, and population, and will be able to create the map with their own custom colors.
Cancer in New York
The day after NCI presented its newest atlas, the New York State Department of Health released county maps of the incidence of breast, lung and bronchus, and colorectal cancers. The maps are part of New York's Cancer Surveillance Improvement Initiative, and they are based on data from the state's cancer registry from 1992 to 1996.
"These maps are a powerful tool to examine where in the state we have a higher burden of disease," Robert Smith, Ph.D., director of cancer screening for the American Cancer Society, said at a press conference.
The incidence maps for colorectal cancer show that all counties except one fall within 20% of the state's incidence rate. The lung and bronchus cancer maps show a pattern of high incidence along the Canadian border.
The breast cancer map shows that 22 of New York's 62 counties have an incidence rate that is higher than the state average of 101.6 cases per 100,000 women. Two counties in particular, Nassau and Suffolk counties, had rates that were 16% and 11% above the state rate.
These two counties as well as Schoharie County and Tolland County, Conn., have been the focus of an ongoing Long Island Breast Cancer Study Project, a joint effort that includes NCI, the National Institute for Environmental Health Sciences, and the New York Department of Health. It comprises more than 10 projects that focus on environmental factors as possible causes for the abnormally high rates.
What Do They Say?
Although the maps provide provocative visuals, they don't tell the whole story.
"When you see the rates, they are telling you what happened, but not why," NCI's Devesa said. "To determine why, additional studies need to be done."
And, in fact, from the beginning that has been the purpose of mapping cancer, said Thomas J. Mason, Ph.D., professor and chairman of the department of epidemiology and biostatistics at the University of South Florida, Tampa. Mason was the author of the first NCI cancer atlas, Atlas of Cancer Mortality for U.S. Counties: 1950-1969.
"We felt very comfortable that [mapping cancer mortality] would lead us in the right direction - that from the maps we would be able to identify areas where additional study was likely, which would lead to a better understanding of local determinants of malignancy," Mason said. "And in every instance, that's been the case."
The U.S. maps have already prompted two follow-up studies: an investigation of the high rates of bladder cancer in northern New England, and a study of the increase in incidence and mortality rates for non-Hodgkin's lymphoma.
And New York State has more studies planned as well. The state's department of health expects to release maps for eight additional cancer sites as well as ZIP code-level incidence maps for 1993-1997 in the next few months. High-incidence areas will be the target of future research studies and educational campaigns on risk factors for cancer.
Such a visual interpretation of incidence and mortality patterns leaves itself open for the public to misinterpret the maps as definitions of healthy and unhealthy communities. When New York's incidence maps were released, New York State Health Commissioner Antonia C. Novello, M.D., cautioned that the maps in no way should be a factor in deciding where to live or whether to move.
Also, in responding to criticism that the state health department had taken too long to release its maps, she said, "It has taken a long time because we want it accurately. It has taken a long time because we don't want panic. It has taken a long time because we want to make sure that the public understands so the people can help me protect them."
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