Cancer Clusters
Possible cancer clusters tend to get a lot of attention in the news and other forms of media. About 1,000 suspected cancer clusters are reported to state health departments each year. But just what is a cancer cluster?
People may become concerned that there’s a cancer cluster in their community if they believe there is a higher than normal number of cancers in the area. Often there’s a concern that the cancers might be caused by some type of carcinogen (cancer-causing agent) in the environment.
What is a cancer cluster?
Scientists have a specific definition of a cancer cluster. The US Centers for Disease Control and Prevention (CDC) and the National Cancer Institute (NCI) define a cancer cluster as a greater-than-expected number of cancer cases that occurs within a group of people in a defined geographic area over a specific period of time. Each part of this definition is important.
A greater-than-expected number of cancer cases…
To see if there is a greater number of cancers than expected, the number of cases seen needs to be compared to what would typically be seen in a similar group of people – such as a group with the same age, sex, and ethnicity.
The type(s) of cancer seen is also important. The cancers should either be all of the same type or types of cancer that are known to have the same cause.
Cancer is a group of more than 100 different diseases. Each type of cancer has its own risk factors and causes. True cancer clusters rarely involve more than one type of cancer. For it to be considered a true cluster, it usually must have one of the following characteristics:
- There is a larger than expected number of a specific type of cancer (or types of cancer that are known to have a common cause).