CDC Releases Draft Guidelines for Identifying Cancer Clusters

Agency would no longer rely on statistical significance for identifying new cancer clusters that emerge in communities throughout the U.S.

Multiple reports of cancer clusters across the U.S. have prompted federal disease experts to update the guidelines for identifying and investigating the cases.

The U.S. Centers for Disease Control and Prevention (CDC) issued a draft guidance this week, titled “Guidelines for Examining Unusual Patterns of Cancer and Environmental Concerns”, following reports of cancer clusters in New Jersey, Texas and even one affecting baseball players on the Philadelphia Phillies in recent years.

The guideline is focused on helping community and state agencies identify groups of people within the same geographic location who are diagnosed with the same type of cancer.

Rates of cancer among cancer cluster patients are much higher than seen in the general population. For example, rates of brain cancer are about three out of every 100,000 people. Among Phillies players, the rate of brain cancer is nearly four times that rate.

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Cancer clusters are often associated with an environmental factor, such as polluted drinking water or toxic emissions. However, it can be difficult to both confirm that a cancer cluster is an actual related group of cases that are not just a statistical abnormality, and it can be difficult to determine the underlying cause.

The CDC says the proposed draft guidelines were established after extensive scientific literature review. Officials focused on placing a greater emphasis on engaging and communicating with community members about the issue.

Additionally, the CDC recommends local health departments consider proactive evaluation of cancer registry data at regular intervals to look for unusual patterns of cancer before a cluster may be identified.

The new guidelines replace steps in the 2013 Guidelines with criteria to address environmental factors, such as chemical and pollutant exposure, more broadly. Prior guidelines used statistical significance to determine whether to move forward with an investigation. The new guidelines instead aim to evaluate potential exposures and cancer rates regardless of statistical significance.

Furthermore, the CDC is identifying and developing tools and templates to support public health partners when conducting cancer cluster investigations.

The CDC is taking public comments on the draft guidance through the Federal Register until July 25, 2022. Comments can be submitted using Docket No. CDC-2022-0070 via the Federal eRulemaking Portal or by mail at:

Division of Environmental Health Science and Practice
National Center for Environmental Health
Centers for Disease Control and Prevention
Attn: Docket No. CDC-2022-0070
4770 Buford Highway NE
Mailstop S-106-6
Atlanta, GA 30341


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