About Cancer Clusters


Confirmation of a cancer cluster does not necessarily mean that there is any single, external cause or hazard that can be addressed. A confirmed cancer cluster could be the result of any of the following:

  • chance
  • miscalculation of the expected number of cancer cases (e.g., not considering a risk factor within the population at risk)
  • differences in the case definition between observed cases and expected cases
  • known causes of cancer (e.g., smoking)
  • unknown cause(s) of cancer.

Follow-up investigations can be done, but can take years to complete and the results are generally inconclusive (i.e., usually, no cause is found).

Complex nature of cancer

The complex nature of cancer makes it inherently challenging to identify, interpret, and address cancer clusters.

Cancer is a term describing different diseases that share a similar characteristic: uncontrollable cell growth and division. As a group, cancers are very common. Cancers are the second leading cause of death in the United States, exceeded only by diseases of the heart and circulatory system. One of every four deaths in the United States is due to some form of cancer. It has been estimated that in 2010 alone, over 1.5 million Americans will be diagnosed with a cancer, and more than half a million will lose their lives as a result of cancer.

Reporting a suspected cluster

If you suspect a cancer cluster in your community or workplace, or if you’d like information such as cancer statistics or trends in your area, first contact your local or state health department or state cancer registry. A local or state health department provides the first response to a suspected cancer cluster. The local or state health department gathers information about the suspected cancer cluster (e.g., types of cancer, number of cases, addresses and occupations of those people with cancer, possible causes), develops and applies the case definition, and determines whether there is a greater-than-expected number of cases. For information about how to contact your state or local health department, go to https://www.cdc.gov/other.htm#states. For state cancer registry contact information, go to https://nccd.cdc.gov/dcpc_Programs/index.aspx#/3.

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Additional Information
  • Question_01

    Cancer Cluster FAQ

    • Questions and answers about cancer clusters: how to report one, who responds, how they are investigated, how to reduce risk.
  • Book_03


    • Selected publications that relate directly to cancer clusters or provide useful information in conducting an investigation.
  • Clipboard_01


    • Useful information about cancer clusters that may be found online.

Page last reviewed: February 15, 2012