Cancer epidemiology is the study of factors affecting cancer in order to determine causes and trends of the disease. Students of cancer epidemiology employ epidemiological methods, which consider all factors resulting in the presence or absence of a disease, in order to identify the causes of cancer and ways to treat and control incidents. Organizations, known as cancer registries, collect clinical data from medical records and provide the information to local and regional groups for cancer epidemiology studies.
Epidemiologists study relationships between specific cancers and their risk factors in order to form hypotheses for possible interventions or treatments that may reduce the onset of cancer or the morbidity of the disease. This method is known as an observational epidemiological study. Randomized controlled tests are then used to determine the validity of the hypotheses.
Often, data for cancer epidemiology studies is collected by several agencies throughout the world, but the largest organization is The Surveillance Epidemiology and End Results Program (SEER). It is the authoritative cancer epidemiology organization in the US. Since 1973, SEER has tracked information regarding cancer and its causes in major population centers throughout the United States. The organization follows very detailed information including but not limited to ethnicity, tumor site, and treatment effectiveness.
Through careful study, cancer epidemiology has discovered several risk factors that contribute to the causes of cancer. Over one third of cancer cases worldwide are caused by modifiable factors. These factors include, tobacco use, alcohol abuse, and diets lacking fruits and vegetables. Obesity serves as a leading cause of cancer in developed countries, as does the contraction of the papillomavirus, usually through sexual transmission.
Cancer epidemiology studies have shown the majority of cancers are caused by environmental factors. On average, 200,000 cancer deaths worldwide are caused by risk factors associated with their workplace. Inhaling asbestos and exposure to benzene remain the highest causes for occupational-related cancers.
In the UK, cancer is the leading cause of death. The US ranks cancer second, with heart disease as the most common. In third world countries, cancer is usually not as common due to deaths caused by infectious diseases that shorten life spans, such as AIDS in parts of Africa. Incidence of cancer is expected to rise in developing countries as life expectancy increases and other diseases are controlled. Cancer is considered a major health problem in many parts of the world. It is estimated that those living in developed areas have a one in three chance of developing the disease in their lifetime.