First-In-The-Nation Small Area Breast Cancer Maps Issued

ZIP Code Level Maps Also Detail "Areas of Elevated Incidence"

Albany, April 11, 2000 – As the next step in New York's $4 million Cancer Surveillance Improvement Initiative (CSII), the State Health Department today issued multi– colored maps – the first of its kind in the nation – that show the incidence of breast cancer by ZIP Code across the State. The Health Department produced the maps using the most recent Cancer Registry data available.

Governor George E. Pataki directed the Health Department to produce cancer maps as part of the (CSII)–a comprehensive project that has enhanced the State's ability to track the occurrence of cancer by improving the New York State Cancer Registry, and through the use of maps, charts and other graphic representations of the geographic pattern of cancer cases. The initiative also is designed to increase public understanding of cancer, its known or suspected causes and risk factors, and to promote prevention and early detection.

"These maps demonstrate our commitment to providing the women of New York State with helpful information about where breast cancer is occurring in their communities," State Health Commissioner Antonia C. Novello, M.D., M.P.H. said. "Remember, information leads to knowledge and knowledge leads to power. Thanks to Governor Pataki and his support for this important project, we will empower the health community and private citizens, alike, to know more about the risk factors for breast cancer and make decisions that may reduce their risk of contracting the disease or improve their chances of survival."

Breast cancer was mapped because it is one of the most common cancers among women in New York State. About 12,000 women are diagnosed with breast cancer every year in the State, and more than 3,500 die from the disease. Nationally, it is estimated that one in eight women will develop breast cancer in their lifetime.

Next Steps:

The ZIP Code level breast cancer maps will be followed by small area maps detailing the incidence of colorectal, prostate and lung cancer. The Health Department, in conjunction with the Cancer Surveillance Improvement Initiative Advisory Committee–an expert panel of nationally known scientists, academicians, physicians and cancer and environmental activists– also is prioritizing cancer risk factors for mapping. Based on the breast cancer map, the Health Department also plans to evaluate locations for additional breast cancer screening services for uninsured or under–insured women.

"Cancer maps can do many things. They can show us the pattern of cancer incidence across the State, help health officials plan services and suggest areas for further research. They cannot, by themselves, tell us what is causing cancer, but they can help us ask the right questions," Dr. Novello said. "These maps are another important step in the process. We have met with breast cancer activists and we have heard their concerns. Those concerns will be addressed."

Health Department staff are developing a follow–up plan to further investigate areas of elevated incidence and as appropriate, to evaluate them along with known and suspected risk factors. The proposed protocol begins by selecting areas for further study based on the strength of the evidence that an unusual disease pattern has occurred.

Working with the affected community, Health Department scientists will then conduct in– depth studies to examine various possibilities for the increased cancer incidence using the Department's Division of Epidemiology, Center for Environmental Health, Wadsworth Laboratory and other State agency resources.

The ZIP Code level maps released today:

The maps released today show breast cancer incidence by ZIP Code across the State and in each county. They are color–coded to indicate how the actual incidence of breast cancer within a particular ZIP Code compares to the expected incidence–that is, how many women living in that ZIP Code would be predicted to contract the disease within a given time period. The prediction is calculated based on the size of the age–specific population at risk.

Specifically, the ZIP Code level maps use shades of purple, green and gray to show whether the number of new cases of breast cancer diagnosed within each particular ZIP Code during the years 1993–1997 is higher, lower or about the same as the expected incidence.

The various colors represent different categories; for instance, light purple represents 15 to 49 percent above the expected incidence. Medium purple represents 50 to 100 percent above the expected incidence and dark purple shows ZIP Codes that are more than 100 percent above what was expected. Gray indicates ZIP Codes that were about the same as expected; green indicates lower than the expected incidence.

The categories were determined using a statistical technique that finds natural breaks in the data. These breaks were then rounded off to be easily understandable and meaningful. For example, "more than 100 percent above expected" means more than twice as many cases occurred as were expected.

The maps also use slanted or crossed lines, called cross–hatching, to identify groups of ZIP Codes which comprise areas where cancer incidence is believed to be elevated. Not all individual ZIP Codes within the cross–hatched areas have higher than expected incidence. Despite these variations, the overall cancer pattern for an "area of elevated incidence" (identified by cross hatching) is considered to be statistically significant.

The maps are accompanied by an index which lists ZIP Codes in numerical order by county and which provides the actual as well as expected incidence of breast cancer for each ZIP Code shown. In order to protect patient confidentiality, as is required by State law, some ZIP Codes (those with very few total cancer cases) were combined with a neighboring ZIP Code before being mapped.

ZIP Code level maps do not show carcinogens or details such as personal habits and lifestyle that may increase the chances of a person getting cancer. Such "risk factor" maps will be produced during the next phase of the Cancer Surveillance Improvement Initiative.

Areas of elevated incidence:

As is described above, the "areas of elevated incidence" identified on the maps are groups of ZIP Codes in which the combined incidence of breast cancer is higher than the rate of breast cancer for the State as a whole. Using a formula called the spatial scan statistic, Health Department scientists have determined that the higher than expected incidence of breast cancer in "areas of elevated incidence" appears less likely to be due to chance or a random occurrence.

In basic terms, the spatial scan statistic is a method developed by Dr. Martin Kulldorff– a member of the Cancer Surveillance Improvement Initiative Advisory Committee–that calculates for each ZIP Code the likelihood of an excess in cancer incidence and then combines neighboring ZIP Codes to achieve higher statistical power. (To understand the concept of statistical power, think of how political polls are conducted. Pollsters would not try to predict the outcome of an election based on the opinion of just a few people. When more people are polled, the findings are more reliable.)

The groups of combined ZIP Codes are subsequently ranked and computer models are used to test whether the elevated cancer incidence in the highest areas is statistically significant or is likely to be due to chance. This explains why a particular ZIP Code within a group of ZIP Codes that has been identified as an "area of elevated incidence" may be color–coded as having a lower than expected incidence. Even though the observed number of new cases of breast cancer in the ZIP Code is lower than expected, there is a chance it was a random occurrence.

Nonetheless, while the pattern of breast cancer in some individual ZIP Codes may not be statistically important, the overall pattern in the larger "area of elevated incidence" they comprise is considered to be significant.

Using the spatial scan statistic, the following regions have been identified as having an elevated incidence of breast cancer:

  • Northwestern Erie/Southwestern Niagara counties
  • Eastern Monroe/Western Wayne counties
  • Mid/Southern Rockland and Western Westchester counties
  • Southern Westchester County
  • Southeastern Staten Island
  • Manhattan (Eastern side of Central Park area)
  • Southern Brooklyn
  • Northern Nassau County
  • Southwestern Nassau County
  • Southeastern Nassau County/Southwestern Suffolk County
  • East end of Suffolk County (Mount Sinai, Port Jefferson and Coram)

Because so many things contribute to cancer risk including age, heredity, lifestyle factors, and exposures to cancer–causing agents, the reasons for the increased number of breast cancer cases in areas of elevated incidence are not known. Like other areas of the northeastern United States with a high breast cancer incidence, these areas may share similarities in demographic make up of the population that research has shown to be associated with increased rates of breast cancer in the community. These factors include higher median income level, higher education levels, smaller family size, later age at first childbirth, race and ethnicity.

Limitations of cancer maps:

Health officials stress that neither the cancer maps released today nor those to be produced in the future will be able to demonstrate a cause and effect relationship between cancer risk factors, including suspected environmental carcinogens, and incidence of disease. This is partly because cancers develop slowly, usually appearing many years after exposure to a carcinogen, as well as the fact that people often move many times during their lives. Where a person currently lives, and where their cancer is diagnosed, may be completely different from where they lived when the cancer started.

In the case of environmental factors, the presence of a known or suspected cancer–causing agent, by itself, does not prove whether any individuals were exposed. Without exposure, there is no increased risk. Also, even if there is a known exposure to a carcinogen, the maps do not show whether the people who got cancer are the people who were exposed.

Exposure assessment, as well as other critical individual details, such as family history of cancer, residential and occupational histories, and behavioral factors such as smoking, diet and amount of physical activity, are determined through in–depth studies by epidemiologists, who study disease. An example of this is the $25 million breast cancer case–control study the National Cancer Institute currently is conducting on Long Island. It is likely that the findings of the study will have important implications for women throughout New York State.

Maps available on Web:

The maps currently are posted on the State Health Department's web site (www.health.state.ny.us) along with information about the purposes of the CSII; general facts about cancer, its known causes and prevention; facts about breast cancer; and how to read the maps and accompanying ZIP Code index. A hard copy version of the ZIP Code level breast cancer map book will be available in the future.

Previous cancer maps issued:

Cancer maps issued previously by the Department as part of the CSII showed the incidence, by county, of the following types of cancer:

  • Bladder cancer
  • Brain and central nervous system cancer
  • Breast cancer
  • Colorectal cancer
  • Kidney cancer
  • Leukemia
  • Liver cancer
  • Lung cancer
  • Non–Hodgkin's lymphoma
  • Prostate cancer
  • Thyroid cancer

County level maps also are available on the Department's web site or by calling 1–800–458–1158.

4/11/00 – 49 OPA