A cancer cluster is a term used by public health officials to describe a higher-than-usual number of cancer cases within a specific geographical area or town. Cancer clusters may be suspected when several loved ones, neighbors, friends, or co-workers in the same community fall ill with the same, and sometimes rare, type of cancer within the same time frame. Types of cancers that are commonly documented in a cluster include lymphoma or leukemia, and cancers of the brain, skin, lung and bladder. Epidemiologists and public health workers receive and investigate the reports of possible cancer clusters. Overall, a cancer cluster may exist if the cancer itself is rare, there is one type of cancer involved, and it is a cancer that does not normally occur in a certain age group.
People who suspect a cancer cluster in their communities may report the problem to the local or state health department. From there, the agency compiles information about the possible cancer cluster such as the type, cause, timing, geographical location, and the number of people affected. Specific demographic information about the individuals affected is also analyzed. Other information that investigators consider include when the cancer was diagnosed and where it has spread.
Scientists who investigate cancer clusters, known as epidemiologists, study the causes and frequency of diseases and their impact on human populations. Epidemiologists research their findings based on genetics, environmental factors, and biostatistics, i.e., the collection, analysis, and interpretation of public health data. Biostatistics help to determine factors such as whether the cancer occurred by chance and the population at risk. Epidemiologists also evaluate genetic changes related to a cancer cluster or clusters that occur in families. Environmental factors generally include diet and exposure to potentially hazardous substances in the home or workplace.
After preliminary research, epidemiologists sometimes determine there is no cancer cluster if patients were exposed to a carcinogen, or diagnosed at different time periods, or if not everyone is affected by the disease. If research shows a suspected cancer cluster, epidemiologists investigate further by contacting patients, examining medical records, and studying whether the cancer in question is tied to long-term exposure to a carcinogen or substance. Epidemiologists also compare their findings to state cancer registries and census data to determine whether a link exists between the specific cancer cases. Additional epidemiological studies with federal officials may be necessary to confirm a cancer cluster.
Understanding what cancer clusters are and where they come from begins with understanding the disease itself. Cancer, as defined by the National Cancer Institute, involves growing and spreading abnormal cells throughout the body. Cancer is actually a group of related yet different diseases instead of just one disease. Cancer generally comes from constant exposure to a carcinogen such as smoke or chemicals. An example of a cancer cluster could be a group of co-workers diagnosed with mesothelioma, which affects the abdomen and the chest lining. According to research by epidemiologists, long-term exposure to asbestos material used in industrial settings may cause mesothelioma.