Download Cancer: A global concern The epidemiology of Cancer

Cancer: A global concern
The epidemiology of Cancer
Farid Najafi
School of Population Health
Kermanshah University of Medical Sciences
(KUMS)
2008
What is cancer?
•
•
•
A generic term for a group of more than
100 diseases
‘Malignant tumours’ and ‘Neoplasm’ are
other names
Charecterized by followings:
– Rapid creation
– Metastasis
Oncogenesis: The process whereby normal
cells become cancer cells
cancer...
• unrestrained cell division +
• disordered tissue growth

• local invasion
• distant spread
cancer...
• failure to control growth
• genetic imbalance:
• excess stimulus (oncogene activation)
• loss of tumour suppression
• act via various factors (eg loss of telomerase,
 angiogenesis)
DNA errors: may be inherited;
or acquired
Functional properties of tumor cells
1. Contact inhibition of cell movement
2. Immortality of cells
Primary vs. Secondary tumors
• The original tumor is called a primary
tumor and all cells derive from single
aberrant cell
• As tumors metastasize the new colonies
or foci are refferred to as secondary
tumors or metastatic centers
Malignant transformation
• Initiation: a change in the cell’s genetic material
primes the cell to become cancerous. Change
may be spontanous or by an agent that cause
cancer (carciongen)
• Promotion: Unlike carcinogens, promoters do
not cause cancer by themselves. They allow a
cell that has undergone initiation to become
cancerous
• Spread:
Biology of cancer
1. Healthy cells
2. Dysplasia: subtle morphological abnormalities
3. Carcinoma in Situ: abnormality in proliferation but no
invasion into the underlying basement membrane
4. Localize cancer (I): invasion to the local tissues
5. Regional spread (II & III): invasion to the regional or
extended regional lymph nodes
6. Generalized disease (IV): blood-borne metastasis
Cancer burden indicators
• Cancer control policies are based on the
availability of statistical measures of the impact of
cancer in a population
• Main epidemiological indicators are cancer
mortality, incidence, prevalence, and survival
• These four indicators describe different aspects of
the disease impact and of the efficacy of health
care system in controlling the disease
• They are related each other and overall they are
a complete set of indicators to describe cancer
burden
The disease process
Events
Pre-clinical phase
Onset of
disease
Clinical phase
Diagnosis
Treatment
Follow-up
Death
cancer
exposure
A
B
C
other
causes
Survival
Prevalence
Incidence
Mortality
Cancer burden indicators
Cancer burden indicators: Mortality
• Mortality - Number of cause-specific deaths
occurring in a defined population in the unit of
time. Usually expressed as rate per 100,000
persons/year
• Classification: ICD-9 or 10
• Availability: cause specific mortality data from
official statistics in almost all countries.
Local/regional/national geographical detail.
Cancer burden indicators: Incidence
• Incidence – Number of new cancer cases
diagnosed in a defined population in the unit of
time. Usually expressed as rate per 100,000
persons/year.
• Classification: ICD-O (3° revision) topography
and morphology
• Availability: in areas covered by populationbased Cancer Registries (CR). Good quality
data.
Cancer burden indicators: Survival
– Cause of death known Cancer Specific Survival
probability of surviving cancer after x years from
diagnosis in a cohort of patients diagnosed in a period of
time t
– Cause of death unknown Relative Survival (RS)
ratio of the observed survival in the patients group to the
expected survival in a similar group in the population
(same age, sex, year, area, socio-economic class etc…)
– RS measures the extra-risk of dying of cancer patients
by removing the competitive mortality due to causes other
than cancer.
Cancer burden indicators: Prevalence
• Prevalence
– The number of surviving cancer patients in a
population at a defined index date.
– Usually expressed as count or proportion x
100.000
– Total (or complete) prevalence involves all
survivors irrespectively of the date of diagnosis.
– Partial prevalence by years from diagnosis
represents the number of survivors by limited
disease duration.
Some facts about cancer
• A leading cause of death (13% of all
deaths in 2005 worldwide)
• >70% of cancer deaths in 2005 occurred
in developing countries
• Common types of cancers:
– Men: Lung, stomach, liver, colorectal,
oesophagus and prostate
– Women: Breast, lung, stomach, colorectal and
cervical
the cancer burden
2000:
10 million new cases (world)
2020:
20 million new cases
-70% in countries with < 5% cancer
control resources
Some facts about cancer
• 40% of cancer can be prevented
• Smoking is the single largest preventable cause
of cancer in the world
• 1/5 of cancers are due to chronic infections:
–
–
–
–
–
HBV: liver cancer
HPV: cancer of cervix
Helicobacter pylori: stomach cancer
Schistosomes: cancer of bladder
HIV infection: kaposi sarcoma and lymphomas
Cancers in developed and
developing countries
• Developed countries
– Cancer is the second-biggest cause of death after
CVD
– Prostate, breast and colon cancer are the most
common types
• Developing countries
– Death due to cancer is going to mimic developed
countries
– Stomach, lung and cervical cancer are more common
• World
– Lung cancer kills more people than any other cancer
Some other facts about cancer
The rule of Thirds
1/3 preventable; 1/3 curable (1/2 in developed
countries
The importance of screening
Earlier diagnosis means more curability
Cause of cancers
1. Physical agents
•
•
•
Ionizing radiation: X-rays & Radioactivity
Nonionizing radiation: Sunlight
Physical substances: Asbestos & pollution
2. Chemical agents
•
•
Promotion and initiation
Industrial exposure
•
Benzene, benzidine, cadmium, nickel or vinyl
choloride
Cause of cancers
 Biological agents
•
•
Viruses
Parasites
 Diet
•
•
•
Dietary fat
Food preservation
Protective substances in the diet
Cause of cancers
Social factors
• Social class
• Occupation
• Industrial hazard
• Medical Services and care
• Radiation and medications
• Lifestyle
• Habits and food hadling
• Air and water pollution
avoidable cancer causes
• smoking (30%)
• diet (20-50%)
•
•
•
•
•
infection (10-20%)
radiation (6%)
alcohol (5%)
occupation (3%)
pollution (1-5%)
• (reproductive hormones 10-20%)
Global action against cancer, WHO, 2005
Causes of cancer
• Tobacco consumption is the world’s most
avoidable cause of cancer
• 30% of all cancer deaths in developed
countries
• The contribution of diet and inactive
lifestyle to cancer is similar to smoking in
developed countries
• One-fifth of cancers worldwide are due to
chronic infections
smoking and cancer
•
•
•
•
•
•
•
•
mouth
pharynx
oesophagus
larynx
lung
pancreas
kidney
bladder
lip, nose, stomach.
myeloid leukaemia
(liver, large bowel,
cervix)
infection and cancer
• parasites:
bladder, bowel, liver, bile
ducts (Asia, Africa)
• bacteria:
stomach (? bladder, bowel)
• viruses:
numerous
viruses and cancer
• Hepatitis B,C
• Human papilloma
• EBV
• Human herpes (8)
• various
liver
cervix, vulva, vagina,
penis, anus
Burkitt’s lymphoma,
Hodgkin’s lymphoma,
naso-pharyngeal ca
Kaposi’s sarcoma
T-cell leukaemia,
mesothelioma..
diet and cancer
aflatoxin
‘salted fish”


liver cancer
NPC
(salted foods

stomach cancer)
overeating/
obesity
 vegetables/
fruit

gall bladder, uterus,
breast (post-menopause)
lung, stomach,
oesophagus, mouth,

pharynx, colon, breast,
pancreas, bladder
treatment strategies (i)
screening:
breast 
large bowel 
cervix 
prostate 
lung 
treatment strategies (ii)
•  cures (chemoRx, hormone Rx, XRx)
• extend life (as above + lifestyle change)
• palliate always
The role of epidemiological knowledge in disease control: a case of two cancers
Intervntion
Accepted utility for widescale use
Lung cancer
Breast cancer
Prevention
YES. Smoking cigarettes is
the strong risk factor; and
exposure is modifiable by
actions at personal and
community levels
NO. Many weak risk factors,
most not readily modifiable
Screening
NO. Even the newest tests
(CT lung scans) yield very
limited survival benefits
YES. Substantial good
evidence (RCTs) of lower
mortality due to population
screening programs for over
50s
Improved
treatment
NO. Minor survival
improvements only with
newer treatments
YES. RCT results show
survival advantage with
appropriate
chemotherapy/radiotherapy
Cancer in Iran
Causes of deaths
Iran (2005, 2030)
WHO, 2007
Some facts about cancer in Iran
• In 2005 cancer killed 47,000 people in
Iran, 27,000 of those people were under
the age of 70
• In 2002 stomach cancer was the most
common cancer found in men in Iran
• In 2005 stomach cancer was the leading
cause of cancer deaths in women and
men
Incidence of cancer
(Iran, 2002)
Cancer deaths
(Iran, 2005)
Incidence of cancer
(Iran, United States)
Incidence of cancer
(Iran, United State)
Gastric Cancer
Biology
• Several Hystological types of gastric
cancer of which adenocarcinoma is by the
most frequent
• Sarcomas and lymphomas are other types
• This lecture mainly focous on
adenocarcinoma
Epidemiology
• Infrequent before 40 years of age
• Twice as frequent in men than in women
• Leading cause of death from cancer
worldwide and in Iran
• Highest incidence in Japan, South
America and Eastern Europe
• Adjusted rate worldwide is 15.62% per
100,000
EUROCARE-4
STOMACH
Age standardized 5-year relative survival, by country (both sexes)
Colon and Rectum
Stomach
Incidence ASRx100,000
Tehran M 20
Tehran F 10
Europe M
W <5
E 30
N <5
S 18
Denmark
Denmark
Finland
Finland
Iceland
Iceland
Norway
Norway
Sweden
Sweden
Ireland
Ireland
UK England
UK England
UK Northern Ireland
UK Northern Ireland
UK Scotland
UK Scotland
UK Wales
UK Wales
Austria
Austria
Belgium
Belgium
France
France
Germany
Germany
Netherlands
Netherlands
Switzerland
Switzerland
5-year survival 25%
Range= 14-32%
Italy
Italy
Malta
Malta
Portugal
Portugal
Slovenia
Slovenia
Spain
Spain
Czech Republic
Czech Republic
Poland
Poland
EUROCARE-4 POOL
EUROCARE-4 POOL
0
20
40
60
80
5-year relative survival (%)
100
Northern Europe
UK and Ireland
Central Europe
Southern Europe
Eastern Europe
0
20
40
60
80
100
5-year relative survival (%)
Sant et al EJC, 2009
Risk factor of gastric cancer
• Chronic Atrophic Gasteritis is the first step
in the development of most gastric cancer,
associated with:
– Tobacco
– H.pylori infection
– Diet with high level of nitrites, nitrates, salt
and smoked food
– Previous gastric surgery
– Pernicious anemia (B12 deficiency due to
absence of interinsic factor+atrophic gastritis
tobacco
• Increases the risk of gastric cancer by
50%
• Responsible for 11% of all Stomach
Cancer
• Decreases the level of carotenoids and
Vitamin c
• Increases the risk of H.pylori
Helycobacter pylori
• Associated with a two to sixfold increase in
the risk of developing Gastric Cancer
• In 1994 the WHO designated H.pylori a
group 1 carcinogen
Dietary factors
• Consumption of fruit, vegetables and fiber
have a protective effect against Gastric
Cancer
• Their effect is probably associated with
Vitamin C or carotenes
• Nitrates and nitrites are usually found in
salted, smoked and dried foods
Genetic factors
• Blood type A
• A first degree relative with Gastric Cancer
• Hereditary non-polyposis colorectal cancer
Secondary prevention
• Early detection: difficult due to lack of
symptoms
• Screening might be effective where the
disease is a major health problem (such
as Japan)
– Gas-contrast Stomach Fluorography
– Further paraclinical tests (endoscopy and
biopsy) if the result is abnormal
Conclusion
• High mortality rate
• The best primary prevention strategies
are:
– Smoking cessation
– Healthy diet
– Avoidence of salted, smoked and poorly
preserved foods
– Erradication of H.pylori
Lung cancer
Some facts about lung cancer
• Lung cancer is the third most common
cancer in the western world, after prostate
and breast cancer
• One of the most preventable kinds of
cancer
• Four out of five cases are associated with
smoking
EUROCARE-4
LUNG CANCER
Age-standardized 5-year relative survival by country
Incidence ASRx100,000
Tehran M 15
Tehran F 7
Europe M
between 42-65
Denmark
Finland
Iceland
Norway
Sweden
Ireland
UK England
UK Northern Ireland
UK Scotland
UK Wales
Austria
Belgium
5-year survival 12%
Range = 8-15%
France
Germany
Netherlands
Switzerland
Italy
Malta
Portugal
Slovenia
Spain
Czech Republic
Poland
EUROCARE-4 POOL
0
20
40
60
80
5-year relative survivalSant
(%)
Northern Europe
UK and Ireland
Central Europe
Southern Europe
100 Eastern Europe
et al. EJC 2009
Risk factors
• Tobacco and passive smoking
– Smokers have a 10-25 times higher risk compared to
non-smokers
– 10%-20% of all lung cancers in non smokers are due
to passive smoking
• Air pollution
– Exposure to air pollution increase the risk of lung
cancer by 100%
• Chronic obstructive lung disease (COPD)
• Occupational exposure
– Asbestos, glass-wool and ceramic fibres
• Genetic factors
Taylor R et al 2007
Prevention of lung cancer
• 80%-85% of lung cancers are associated
with smoking
• 10% are associated with occupational
carcinogens
• 1% are associated with passive smoking
Histological types of lung cancer
• Two major types:
– Small-cell lung cancer
– Nonsmall-cell lung cancer
• Squamous cell carcinoma
• Adenocarcinoma
• Large-cell carcinoma
• Squamous cell carcinoma is the most
commonest type in males and adenocarcinoma
is the most commonest type in females
Early detection of lung cancer
• Low cure rate (13%)
• Low cure rate is related to lack of early
detection measures
• There is no successful screening test
Actual survival curves of 647 patients >= 60
Minami, H. et al. Chest 2000;118:1603-1609
Conclusion
• NO currently established means for the
screening or early detection of lung cancer
• 85-88% of all lung cancer are caused by
active or passive smoking
• Reduction of tobacco consumption still is
the most important strategy