Cancer epidemiology
is the study of the incidence of cancer as a way to infer
possible trends and causes. The first such cause of cancer was
identified by British surgeon Percivall Pott, who discovered in
1775 that cancer of the scrotum was a common disease among
chimney sweeps. The work of other individual physicians led to
various insights, but when physicians started working together
they could make firmer conclusions.
A founding paper of this discipline was the work of Janet Lane-Claypon,
who published a comparative study in 1926 of 500 breast cancer
cases and 500 control patients of the same background and
lifestyle for the British Ministry of Health. Her
ground-breaking work on cancer epidemiology was carried on by
Richard Doll and Austin Bradford Hill, who published "Lung
Cancer and Other Causes of Death In Relation to Smoking. A
Second Report on the Mortality of British Doctors" followed in
1956 (otherwise known as the British doctors study). Richard
Doll left the London Medical Research Center (MRC), to start the
Oxford unit for Cancer epidemiology in 1968. With the use of
computers, the unit was the first to compile large amounts of
cancer data. Modern epidemiological methods are closely linked
to current concepts of disease and public health policy. Over
the past 50 years, great efforts have been spent on gathering
data across medical practise, hospital, provincial, state, and
even country boundaries, as a way to study the interdependence
of environmental and cultural factors on cancer incidence.
Cancer epidemiology must contend with problems of lead time bias
and length time bias. Lead time bias is the concept that early
diagnosis may artificially inflate the survival statistics of a
cancer, without really improving the natural history of the
disease. Length time bias is the concept that slower growing,
more indolent tumors are more likely to be diagnosed by
screening tests, but improvements in diagnosing more cases of
indolent cancer may not translate into better patient outcomes
after the implementation of screening programs. A similar
epidemiological concern is overdiagnosis, the tendency of
screening tests to diagnose diseases that may not actually
impact the patient's longevity. This problem especially applies
to prostate cancer and PSA screening.
Some cancer researchers have argued that negative cancer
clinical trials lack sufficient statistical power to discover a
benefit to treatment. This may be due to fewer patients enrolled
in the study than originally planned.
State and regional cancer registries are organizations that
abstract clinical data about cancer from patient medical
records. These institutions provide information to state and
national public health groups to help track trends in cancer
diagnosis and treatment. One of the largest and most important
cancer registries is SEER, administered by the US Federal
government. Health information privacy concerns have led to the
restricted use of cancer registry data in the United States
Department of Veterans Affairs and other institutions.
In some Western countries, such as the USA, and the UK cancer is
overtaking cardiovascular disease as the leading cause of death.
In many Third World countries cancer incidence (insofar as this
can be measured) appears much lower, most likely because of the
higher death rates due to infectious disease or injury. With the
increased control over malaria and tuberculosis in some Third
World countries, incidence of cancer is expected to rise; this
is termed the epidemiologic transition in epidemiological
terminology.
Cancer epidemiology closely mirrors risk factor spread in
various countries. Hepatocellular carcinoma (liver cancer) is
rare in the West but is the main cancer in China and
neighbouring countries, most likely due to the endemic presence
of hepatitis B and aflatoxin in that population. Similarly, with
tobacco smoking becoming more common in various Third World
countries, lung cancer incidence has increased in a parallel
fashion.
History >>
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Cancer
Classification
1. Nomenclature
2. Adult cancers
3. Childhood cancers
Signs and symptoms
Diagnosis
1. Investigation
2. Biopsy
Treatment
1. Surgery
2. Radiation therapy
3. Chemotherapy
4. Targeted therapies
5. Immunotherapy
6. Hormonal therapy
7. Symptom control
8. Complementary and alternative
9. Treatment trials
Prognosis
1. Emotional impact
Causes
1. Chemical carcinogens
2. Ionizing radiation &
Infectious diseases
3. Hormonal imbalances
& Immune system dysfunction
4. Heredity & Other causes
Pathophysiology
1. Epigenetics
2. Oncogenes
3. Tumor suppressor genes
4. Cancer cell biology
4.1 Clonal evolution
4.2 Biological properties of cancer cells
Prevention
1. Modifiable ("lifestyle") risk factors
2. Diet
3. Vitamins
4. Chemoprevention
5. Genetic testing
6. Vaccination
7. Screening
Epidemiology
History
Research |
