What Is a Cancer Cluster?
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A cancer cluster is defined as a greater than expected number of cancer cases that occurs within a group of people, in a geographic area, or over a period of time. A person may suspect that a cancer cluster exists when several loved ones, neighbors, or coworkers are diagnosed with cancer. However, what appears to be a cluster may actually reflect the expected number of cancer cases within the group or area. When considering the possible existence of a cancer cluster in your area, it is important to remember a few key facts: 1) cancer is a common disease, affecting about one in four people in their lifetime; 2) the term cancer refers not to a single disease, but instead to a group of related yet different diseases; 3) a cancer cluster may be due to chance alone, like the clustering of balls on a pool table; and 4) an apparent cancer cluster is more likely to be genuine if the cases consist of one type of cancer, a rare type of cancer, or a type of cancer that is not usually found in an
A cancer “cluster” is a situation in which there are more cancer cases in a group of people, in a location, or in a time period than would be expected based upon usual patterns (see Cancer Clusters Fact Sheet). A cancer “cluster” usually refers to an excess of one particular type of cancer. A grouping of several different types of cancers is not usually considered to be a “cluster”. Public health officials and researchers who respond to questions about clusters from the public think of “clusters” in two distinct ways. The first is a suspected cluster (a concern has been reported but not yet evaluated). The second is a confirmed cluster (where officials have confirmed that the number of cases is in fact higher than expected). Public health officials nationwide receive hundreds of inquiries every year about suspected clusters. However, after an evaluation only a small fraction of these suspected clusters are actually confirmed. Many people assume that if a cluster is statistically confir
