Cancer cluster
Encyclopedia
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 time.
Historical examples of work-related cancer clusters are well documented in the medical literature. Notable examples include: scrotal cancer among chimney sweep
s 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 benzene
.
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 filed. 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 justified.
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. Given the number of inquiries it is likely that even some of these are due to chance alone.
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 significant
.
The same article noted that "the Division of Public Health is unlikely to study the matter further. The Department cited a lack of resources" as well as the difficulty of "pinning down"a precise environmental cause. The findings were reported elsewhere.
Epidemiology
Epidemiology is the study of health-event, health-characteristic, or health-determinant patterns in a population. It is the cornerstone method of public health research, and helps inform policy decisions and evidence-based medicine by identifying risk factors for disease and targets for preventive...
, statisticians
Statistics
Statistics is the study of the collection, organization, analysis, and interpretation of data. It deals with all aspects of this, including the planning of data collection in terms of the design of surveys and experiments....
, and public health workers to define an occurrence of a greater-than-expected number of cancer
Cancer
Cancer , known medically as a malignant neoplasm, is a large group of different diseases, all involving unregulated cell growth. In cancer, cells divide and grow uncontrollably, forming malignant tumors, and invade nearby parts of the body. The cancer may also spread to more distant parts of the...
cases within a group of people in a geographic area over a period of time.
Historical examples of work-related cancer clusters are well documented in the medical literature. Notable examples include: scrotal cancer among chimney sweep
Chimney sweep
A chimney sweep is a worker who clears ash and soot from chimneys. The chimney uses the pressure difference caused by a hot column of gas to create a draught and draw air over the hot coals or wood enabling continued combustion. Chimneys may be straight or contain many changes of direction. During...
s in 18th century London
London
London is the capital city of :England and the :United Kingdom, the largest metropolitan area in the United Kingdom, and the largest urban zone in the European Union by most measures. Located on the River Thames, London has been a major settlement for two millennia, its history going back to its...
, osteosarcoma
Osteosarcoma
Osteosarcoma is an aggressive cancerous neoplasm arising from primitive transformed cells of mesenchymal origin that exhibit osteoblastic differentiation and produce malignant osteoid...
among female watch dial painters
Radium Girls
The Radium Girls were female factory workers who contracted radiation poisoning from painting watch dials with glow-in-the-dark paint at the United States Radium factory in Orange, New Jersey around 1917....
in the 20th century, skin cancer
Skin cancer
Skin neoplasms are skin growths with differing causes and varying degrees of malignancy. The three most common malignant skin cancers are basal cell cancer, squamous cell cancer, and melanoma, each of which is named after the type of skin cell from which it arises...
in farmers, bladder cancer
Bladder cancer
Bladder cancer is any of several types of malignant growths of the urinary bladder. It is a disease in which abnormal cells multiply without control in the bladder. The bladder is a hollow, muscular organ that stores urine; it is located in the pelvis...
in dye workers exposed to aniline
Aniline
Aniline, phenylamine or aminobenzene is an organic compound with the formula C6H5NH2. Consisting of a phenyl group attached to an amino group, aniline is the prototypical aromatic amine. Being a precursor to many industrial chemicals, its main use is in the manufacture of precursors to polyurethane...
compounds, and leukemia
Leukemia
Leukemia or leukaemia is a type of cancer of the blood or bone marrow characterized by an abnormal increase of immature white blood cells called "blasts". Leukemia is a broad term covering a spectrum of diseases...
and lymphoma
Lymphoma
Lymphoma is a cancer in the lymphatic cells of the immune system. Typically, lymphomas present as a solid tumor of lymphoid cells. Treatment might involve chemotherapy and in some cases radiotherapy and/or bone marrow transplantation, and can be curable depending on the histology, type, and stage...
in chemical workers exposed to benzene
Benzene
Benzene is an organic chemical compound. It is composed of 6 carbon atoms in a ring, with 1 hydrogen atom attached to each carbon atom, with the molecular formula C6H6....
.
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 filed. 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 justified.
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. Given the number of inquiries it is likely that even some of these are due to chance alone.
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 significant
Statistical significance
In statistics, a result is called statistically significant if it is unlikely to have occurred by chance. The phrase test of significance was coined by Ronald Fisher....
.
Examples
In 2007 the Associated Press reported a confirmed cancer cluster in Delaware,Delaware health officials have confirmed what residents near a coal-fired power plant long suspected: there is a cluster of cancer cases near the Indian River Power Plant. The News Journal reported Sunday that the rate of cancer cases in the area is 7 percent higher than the national average...The state study was released last month to Lt. Gov. John Carney, who requested the report.."
The same article noted that "the Division of Public Health is unlikely to study the matter further. The Department cited a lack of resources" as well as the difficulty of "pinning down"a precise environmental cause. The findings were reported elsewhere.
See also
- Cancer epidemiology
- BiostatisticsBiostatisticsBiostatistics is the application of statistics to a wide range of topics in biology...
- IncidenceIncidence (epidemiology)Incidence is a measure of the risk of developing some new condition within a specified period of time. Although sometimes loosely expressed simply as the number of new cases during some time period, it is better expressed as a proportion or a rate with a denominator.Incidence proportion is the...
- List of cancer clusters
- Risk assessmentRisk assessmentRisk assessment is a step in a risk management procedure. Risk assessment is the determination of quantitative or qualitative value of risk related to a concrete situation and a recognized threat...
- ToxicologyToxicologyToxicology is a branch of biology, chemistry, and medicine concerned with the study of the adverse effects of chemicals on living organisms...
- Cuzick–Edwards test
External links
- Pub Med - latest standards for evaluating cancer clusters
- Cancer Mortality Maps & Graphs: U.S., 1950-94
- National Institute of Environmental Health Sciences (NIEHS)
- U.S. Centers for Disease Control
- U.S. Environmental Protection Agency
- List of known cancer clusters in the U.S.A.
- Australian Story about a cluster of breast cancer cases in the workplace