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Cancer Clusters

What is a cancer cluster?

A real or meaningful cancer cluster is a number of the same type of cancers occurring during a short period of time among people who may live or work in the same area.

Are cancer clusters common?

No. Real cancer clusters are extremely rare. There have been no proven cancer clusters in North Carolina, and only a few around the United States.

There are five people on my street with cancer; is this a meaningful cluster?

Not necessarily. We would have to study the situation to determine if it is a real cancer cluster. Remember, cancer is very common, especially among older people, and each type of cancer has a different cause. By chance, a group of people on your block could have a number of different cancers, but it would not be a meaningful cluster.

How is a cancer cluster studied?

We ask several questions: are they all the same type of cancer; during what period of time did these cancers appear; how old are the people with cancer; is it a rare cancer? Next we confirm that the cases are cancer. We see if the number of observed cases is higher than the number of expected cases.

Finally, we prepare a report with one of three recommendations:

  1. No further study because we see no evidence of a cancer problem
  2. We will monitor the area because there may be a problem, but the evidence is weak
  3. The area will be studied in detail because there seems to be a problem. If the number of cancer cases was higher than expected, we then study the relationship between the cancer and its possible causes in the area. A team would come and study the cancer patients, their lifestyles, work and home environments.

Cancer and the Environment (PDF, 2.3MB)

Investigating Suspected Cancer Clusters and Responding to Community Concerns External link

Cancer Cluster Communication Toolkit External link

Information from the National Cancer Institute about Cancer Clusters External link

Contact the Central Cancer Registry with questions about these or other cancer data in North Carolina.