Cancer cluster is a term used by epidemiologists, statisticians, and public health workers to define an occurrence of a greater-than-expected number of cancer cases within a group of people in a geographic area over a period of time¹.

Historical examples of work-related cancer clusters are well documented in the medical literature. Notable examples include: scrotal cancer among chimney sweeps in 18th century London, osteosarcoma among female watch dial painters in the 20th century, skin cancer in farmers, bladder cancer in dye workers exposed to aniline compounds, and leukemia and lymphoma in chemical workers exposed to benzene².

Cancer cluster suspicions usually arise when members of the general public report that their family members, friends, neighbors, or coworkers have been diagnosed with the same or related cancers. State or local health departments will investigate the possibility of a cancer cluster when a claim is filed³. In order to justify investigating such claims, health departments conduct a preliminary review. Data will be collected and verified regarding: the types of cancer reported, numbers of cases, geographic area of the cases, and the patients clinical history. At this point, a committee of medical professionals will examine the data and determine whether or not an investigation (often lengthy and expensive) is justified⁴.

In the U.S., state and local health departments respond to more than 1,000 inquiries about suspected cancer clusters each year. It is possible that a suspected cancer cluster may be due to chance alone, however, only clusters that have a disease rate that is statistically significantly greater than the disease rate of the general population are investigated.

A cluster is more likely to be "genuine" if the case consists of one type of cancer, a rare type of cancer, or a type of cancer that is not usually found in a certain age group. Between 5% to 15% of suspected cancer clusters are statistically significant⁵.

See also

• Biostatistics
• Incidence
• List of cancer clusters
• Risk assessment
• Toxicology

Notes

• Note 1: Cancer Cluster FAQ (http://www.cdc.gov/nceh/clusters/faq.htm). Centers for Disease Control and Prevention, National Center for Environmental Health, Division of Environmental Hazards and Health Effects.
• Note 2: Cancer Facts (http://cis.nci.nih.gov/fact/3_58.htm). National Cancer Institute. U.S. National Institutes of Health.
• Note 3: M. J. Thun and T. Sinks. Understanding Cancer Clusters. CA Cancer J Clin 2004; 54:273-280 (http://caonline.amcancersoc.org/cgi/content/full/54/5/273#SEC2)
• Note 4: J.R. Devier, R.C. Brownson, J.R. Bagby Jr., G.M. Carlson, J.R. Crellin. A public health response to cancer clusters in Missouri. Am J Epidemiol 1990; Jul; 132:S23-31.

External links

• Cancer Mortality Maps & Graphs: U.S., 1950-94 (http://www3.cancer.gov/atlasplus/new.html)
• National Institute of Environmental Health Sciences (NIEHS) (http://www.niehs.nih.gov/)
• U.S. Centers for Disease Control (http://www.cdc.gov/nceh/clusters/default.htm)
• U.S. Environmental Protection Agency (http://www.epa.gov/region02/health/cancer_clusters.htm)