epidemiology overview 1

8/14/2019 Epidemiology Overview 1

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Cancer

Epidemiology: anoverview


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A Global Concern

1990 2000 2010

60 million deaths 80 million deaths

2/3 in developing countries

With 5% of the resources to deal with theproblem

40 million of these deaths are preventable


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A Global Concern

9 Million new diagnoses each year

5 million deaths each year

10% of all deaths in the world each year

Usually regarded as a problem of developedcountries

More than half of of all cancers are seen in of the worlds population who live indeveloping countries


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Epidemiology of Cancer

Studies on the epidemiology of cancerbreak down into two basic areas.

The biology/molecular genetics of cancer.

The sociology of cancer.

Understanding both of these areas incritical for cancer control.


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Basic biology of cancer

Many diseases One disease process.

A disorder of cellular growth and differentiation.

100 different cancers

Affects any cell in the body that can undergomitosis/cell division.

Cancer has links to other disease processes


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Biology of Cancer

Some infections cause cancer Schistosomiasis: bladder cancer

Liver fluke (Clonorchis sinensis): gall bladder cancer

Toxic causes and cancer Lung cancer (mesothelioma) exposure to asbestos

Despite all this cancer is fundamentally agenetic disorder.

Cancers are only a problem because theyspread or metastasise


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Biology of Cancer

HOST RESISTANCE TUMOUR GROWTH

OUTCOME


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Biology of Cancer

Tumours do not grow freely in the human host.

There is a defence or host resistance.

Resembles a defence against an infection.

Transformation, invasiveness, metastasismalignancy, will all depend upon interaction with

the host defences.

This balance will change during the life history ofthe tumour.


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Biology of CancerImplications

Regard cancer as a Rule of thirds.

1/3 are preventable

1/3 are curable (1/2 in developed countries)

These numbers depend on Effective and comprehensive screening

Early diagnosis

Leads to greater curability


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The Rule of Thirds

This is the case because most cancers areacquired (somatic).

Only about 5% of all cancers are inherited.

If cancers are acquired (from externalinfluences) they are potentially avoidable.


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The Sociology of Cancer

Cancer is a lifestyle disease

Carcinogens arise as a consequence of

lifestyle. Conditions of living Conditions of work

Carcinogen exposures arise from twosituations Where people live

Changes people make in the world


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Sociology of Cancer

Where people live.

Geographic and temporal variability

Habits Smoking ----- Lung cancer.

Diet ------------ Stomach and colon cancer.

Food preservatives --------- Stomach and liver cancer.

Environmental hazards Viruses and liver cancer.


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Sociology of Cancer

Changes people make in the world (Industrialisation)

Ionising radiation

Chemicals from manufacturing processes.

For example (Ionising Radiation):

Latter part of 19th century half of certaingroups of mine workers in central Europe diedof lung cancer

Also occurred in early 20th century USA

Radioactivity in the bedrock of these minescaused the cancer


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Sociology of Cancer

Example (manufacturing)

Dyestuffs (betanaphthylamine) caused bladdercancer in Europe and USA until occupational

health initiatives stooped its use.

Reoccurring in Southern Asia whereindustrialisation has exported this technologyto new areas.

New cases of mesothelioma in turkey due touse of asbestos like products


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Sociology Implications forCancer Control

Importance of lifestyle changes.

Importance of prevention and screening.

The need for a public health strategy frocancer control At a national level

Balanced programme of Prevention, Screening,Early diagnosis, treatment, palliation


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Implications for cancercontrol

These factors mainly depend on changesin the behaviour patterns of humans. Addictions to drugs, smoking, alcohol, food.

Sexual behaviour

Examples: Oral cancer and tobacco chewing

Lung cancer and smoking

Cervical cancer and sexual promiscuity

Major area of research is how to changebehavioural patterns to promote healthand prevent disease and cancer.


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Biological Factors and canceraetiology

Four classes of external agents incarcinogenesis. Physical

Chemical

Biological

Diet

Physical Agents

Ionising radiation: Cosmic and earth sources(energy production).

Cumulative exposure from medical medical anddiagnostic procedures.


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Ionising radiation Breast, leukaemia, lung, thyroid, stomach, colon,

bladder are common radiation induced tumours.

Non-Ionising radiation: Solar UV light andtanning industry All forms of skin cancer.

Particles: Air Pollution and other factors

Asbestos dust and mesothelioma


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Chemical Agents are very important incarcinogenesis.

Concepts of Promotion and Initiation havebeen developed in chemical exposure.

Industrial exposure.

Chemical exposure due to habits.


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Chemical exposure is perhaps one of theareas that provides a mechanism of control.

Many chemical exposures are as a result of; Habits (smoking): lung cancer Industrial processes: Many cancers

Medicinal practices (diethylstilbestrol to preventabortion (can cause vaginal cancer)

Alcohol: head and neck cancer


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Chemical Agents

Exposure Chemical Site of Cancer

Insecticide spraying Arsenic Skin

Nickel refining Nickel Paranasal Sinuses

Chromium plating Chromium Lung

Shale oil productionPolynuclear Aromatic

HydrocarbonsScrotum

Vinyl chloride production Vinyl Chloride Liver

Gas retort work naphthylamine Bladder

Tyre manufacturing Benzene Leukaemia


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Biological Agents are central to thedevelopment of many cancer:

Hepatitis B virus: Liver cancer

Epstein Barr virus: Lymphomas and somenasal/pharyngeal cancer

Human Papilloma virus 16: Cervical cancer

Schistosomiasis: Bladder cancer

Liver fluke: Gall bladder cancer


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Dietary factors Dietary fat

Food preservatives

Protective substances in food and diet.

These factors mainly relate to lifestyle and habits. High fat /low fibre diet associated with colorectal cancer

Food preservative (nitrites) associated stomach cancer

Many food are associated with health andprotection against cancer Cruciferous vegetables, whole grain (fibre), citrus fruits


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Social Factors and CancerCausation

Social class

Socioeconomic gradient

Occupation

Industrial hazards

Medical Services and care

Radiation and medications

Lifestyle

Habits and food handling

Air and water pollution


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Summary - Risk factors

Smoking

Dietary factors

Obesity

Exercise

Occupation

Genetic susceptibility

Infectious agents

Reproductivefactors

Socioeconomicfactors

Environmentalpollution

Ultraviolet light

Ionising radiation

Prescription drugs

Electromagneticfields

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