Health Station

Mohsen Heidari : The Epidemiology student at Shahid Beheshti University of Medical Sciences and Health Services

 
Introduction to cancer
نویسنده : محسن حیدری - ساعت ٧:۳۸ ‎ب.ظ روز شنبه ۱٥ مهر ۱۳٩۱
 

 

 

 

Cancer Epidemiology
An Introduction

The Epidemiologic Perspective

Aims of Cancer Epidemiology

Methods of Epidemiology

Historical Perspective and Examples

Contemporary Studies

The Future

WHO Statistics

2020  , 15 million people will die from cancer

 

 


Causes

Ageing population

Obesity

Smoking

True or False?

Smoking  causes  lung  cancer

Cancer Epidemiology
Historical Perspective

1700s: tobacco and cancer

Reports of cancer risks associated with tobacco in the 18th century included snuff taking and nasal cancer, reported by Hill in 1761, and pipe smoking and lip cancer by von Soemmering in 1795.

True or False?

Large percentage of cancers are preventable

True or False?

In the past 20 years tremendous improvements in the treatment of all cancers have been achieved

True or False?

Preventing cancer is easier than treating cancer

True or False?

Screening tests are available for most cancers

Personal views of cancer

“in the popular imagination cancer equals death”

 

 

 

(Susan Sontag,1977)

 

 

“Cancer forces us to confront our lack of control over our own or others death”

 

 

 

Kleinman (1988)

Statistics

>9.7 million cases are detected each year

6.7 million people will die from cancer

Every day, around 1700 Americans die of the disease

20.4 million people living with cancer in the world today

1 in 3 people will  be diagnosed with cancer in the UK and 1 in 4 will die from their disease

What is Cancer?

Division – uncontrolled cell division

 

Growth – formation of a lump (tumour) or large numbers of abnormal white cells in the blood

 

Mutation – changes to how the cell is viewed by the immune system

 

Spread – ability to move within the body and survive in another part

 

What is cancer?

Abnormal cell growth (neoplasia)‏

Malignant as opposed to benign

Benign: slow growth, non-invasive, no metastasis

Malignant: rapid growth, invasive, potential for metastasis

Division – uncontrolled cell division

Oncogenes

 

Tumour suppressor genes – p53

 

Suicide genes – apoptosis

 

DNA repair genes

 

 

 

Growth

Tumour

Pressure on nerves

Blocking organs

Stopping normal function

Altering nerve signals

Fungating

 

Mutation and Spread

Invasion

 

Angiogenesis

Types of Cancer

Carcinomas

Sarcomas

Lymphomas

Leukaemias

Adenomas

 

Often prefixed by the specific cell

 

 

 

 

 

 

What causes cancer?

Five Criteria for a Cause è Effect Relationship

Carcinogenesis.
Some factors to consider…

Heredity

Immunity

Chemical

Physical

Viral

Bacterial

Lifestyle

 

 

Heredity

5-10% of Cancers

 

?15% of all cancers

 

Molecular biology and Human Genome Project

Heredity

Genes isolated for several classic familial cancer syndromes:

RB1 (retinoblastoma)

APC (familial polyposis)

Human Non Polyposis Colon Cancer (HNPCC)

BRCA 1&2 (breast cancer)

p53 (many cancers)

 

Immunity

 

 

HIV / AIDS

 

Immunosuppression

Virus’s

Hepatitis B

Human T-cell Leukaemia virus

Epstein Barr Virus

Human Papilloma Virus (HPV)

 

Bacterial

H. pylori

 

Other Parasites:

Schistosoma spp

Clonorchis sinensis

 

Chemical

Alcohol

Asbestos

Wood dust

Rubber, plastics, dyes

Tar / bitumen

Aflatoxin

Alkylating agents

 

Tobacco

Smoking

Single biggest cause of cancer

25-40% smokers die in middle age

9 in 10 lung cancers

Know to cause cancer in 1950

Smoking and alcohol

Industrial pollution

Physical causes

 

Ultraviolet radiation

Sunlight

Certain industrial sources

 

 

 

Radiation

Radon

Cancer treatment

 

 

 

 

Obesity

Lifestyle:

  - Highly caloric diet, rich in fat, refined carbohydrates and animal protein

  - Low physical activity

Consequences:

  - Cancer

  - Diabetes

  - Cardiovascular disease

  - Hypertension

 

 

Lifestyle

Age

 

Occupation

 

Ethnicity

 

Deprivation

 

Cancer Epidemiology
Historical Perspective

Tobacco and Lung Cancer

Asbestos and Lung Cancer

Leather Industry and Nasal Cancer

Dyes and Bladder Cancer

Ionizing Radiation and Many Cancers

DES and Vaginal Adenocarcinoma

EBV and Burkitt’s Lymphoma

HPV and Cervical Cancer

Survival variations

CONCORD Study (1.9 million survivors) demonstrated a clear relationship to income not only between countries but also between the ethnic groups in those countries

(Coleman et al Lancet Oncology 2008)

Diagnosis and staging

Clinical History

 

Normal diagnostic procedures

Scans, xrays

Blood tests

Biopsy

 

Pathological staging

Epidemiology

“Distribution and determinants of disease frequency in human populations”

 

 

 

Cancer Epidemiology
Historical Perspective

1775

British surgeon, Percival Pott reported probably the first description of occupational carcinogenesis in the form of scrotum cancer among chimney sweeps.

 

Aims of Cancer Epidemiology

Uncover new etiologic leads

study of the distribution of cancer

quantify the risk associated with different exposures and host factors

Promote insights into the mechanisms of carcinogenesis

Assess efficacy of preventive measures

Investigate predictors of survival

 

Types of Epidemiologic Studies

Cohort

Case-Control

Cross-Sectional (Prevalence)

Other

 

 

Methods of Cancer Epidemiology

Descriptive Studies

Incidence, mortality, survival

Time Trends

Geographic Patterns

Patterns by Age, Gender, SES, Ethnicity

Analytic Studies

Case-control

Cohort

 

Challenges to Interpretation

Observational vs. Experimental Design

Cancer “clusters”

Study Design and Conduct

Study Size

Biases:  Misclassification, confounding, selection

 

Exposure assessment important

Epidemiology and “strong” and “weak” effects

Impact on a population level

Replication critical

 

 

 

Cancer Epidemiology
Sources

US SEER Registry System

IARC International Registries

State/Hospital Registries

 

Etiologic Clues

“Alert” Clinician

Experimental Studies

 

 

 

Cancer Epidemiology
Current/Future Topics

Infectious Agents

Cancer and inflammation

Obesity

Physical Activity

Diet

Hormones

Immunologic Factors

Cancer disparities

Inherited Susceptibility (Polymorphisms)

 

Cancer Epidemiology
Current/Future Topics

Tumor (somatic) Alterations

Cancer Classification

Biomarkers of Exposure/Effect

Vaccines

Survivorship

Cancer and disability

Alternative therapy

 

 

The burden of cancer

6% of NHS hospital expenditure 

$/€/£ etc millions spent on research

Substantial financial burdens upon families and carers

Physical and emotional burden

 

 

 

 

 

 

 

2006 Estimated US Cancer Cases*

 

Is cancer a heritable disease?

There are heritable cancer syndromes

The majority of cancers, however, are not familial

Cancer is a genetic disease, but the majority of mutations that lead to cancer are somatic

What causes the mutations that lead to cancer?

Viruses: HPV --> cervical cancer

Bacteria: H. pylori --> gastric cancer

Chemicals --> B[a]P --> lung cancer

UV and ionizing radiation --> skin cancer

What do these agents have in common?

 

Summary

Cancer is a disease of Division, growth and spread

 

It has a number of causes many of them preventable

 

The survival of the patient is determined by the stage of the disease, the earlier the detection or the smaller the tumour the better the survival

 

 

 


 
 
 



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اوقات شرعی

شنبه, شهریور ۴, ۱۳91