Heredity and environment are the main contributing factors to the development of cancer. Epidemiologists focus on these two areas when studying cancer clusters. Behavior and lifestyle also contribute to cancer risks so they are also included when studying environment.
To establish a connection between an environmental risk factor and a genetic predisposition is difficult. Scientists must study large groups of people over the course of a long period of time to understand the process of carcinogenesis (the process of normal cells becoming cancer cells). This makes establishing the existence of cancer clusters a lengthy process.
The exposure to certain carcinogenics may also not affect health for many years. In the case of asbestos exposure, it often takes decades for mesothelioma to develop after exposure to the substance. Therefore, the cancer cluster was not identified until many years after the initial exposure began.
Researchers have made some discoveries in regards to heredity and cancer. They have determined that all cancers are caused by some form of gene mutation, which causes the gene to perform abnormally.
Some of these abnormalities are present in an individual at birth. These types of gene mutations are passed down from parent to child. Although this is an uncommon source of cancer it does create “inherited susceptibility” or a predisposition to cancer. Inherited susceptibility does not mean cancer will definitely occur in an individual, however it does indicate a condition where, if other exposures and factors exist, cancer may occur.
Cancer clusters can often be suspected within families due to a higher than expected rate of disease within the family. These cases can sometimes be attributed solely to coincidence. Other times these “familial clusters” can be due to inherited susceptibility coupled with environmental factors.
Somatic alterations are changes that occur to genes throughout an individuals lifetime. These alterations are more likely than inherited susceptibility to be the cause of cancer.
Environmental exposures have often been suspected by individuals to be the cause of cancer clusters. The environmental factors that are considered by epidemiologists include the air, water and earth surrounding an individual or group. Other environmental factors that influence cancer clusters are home and workplace conditions, tobacco use, drugs and alcohol, chemical exposures, and exposure to radiation or even sunlight.
Due to varying susceptibility in individuals and the vast array of chemical and other substances in our world identifying specific causes of cancer is extremely difficult.
Workplace discoveries in regards to chemical exposures have provided positive results in the study of dangerous exposures to certain substances. Certain occupational studies have proved the toxicity of chemical carcinogens and led researchers to develop ways of reducing exposure.
Causes of Cancer Clusters
There are many risk factors for cancer in the world today. Smoking, poor diet, lack of exercise and inactivity are some of the preventable cancer risks. Carcinogens in the environment can also cause cancer. Cancer clusters, once identified as such, often may not have an underlying cause.
There are often several explanations when considering cancer clusters including coincidence, external behaviors (smoking) and miscalculation of historic incidences. When these factors do not explain the cancer cluster, a deeper, more thorough study can be conducted. These often take many years and do not always provide a clear and definitive answer.