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Cancer epidemiology & prevention (Screening programmes (Effective…
Cancer epidemiology & prevention
Epidemiology:
science
describing the incidence and geographical distribution
of particular diseases
Adresses following questions:
what is the cause
of disease in an individual?
why do populations differ in terms of risk
of a particular disease?
Incidence – number of
new cases arising in a given period
in a specified population*
Prevalence - number of
persons in a defined population who have been diagnosed with that type of cancer, and who are still alive
at a given point in time*
Mortality -
number of deaths occurring in a given period
in a specified population*
Lethality –
mortality/incidence ratio
*per 100,000 persons
Causes of increasing cancer mortality
Ageing
of populations
Better
diagnosis
More reliable
statistics
Changes in
life style and environmental factors
Cancer prevention
Primary –
reduction of exposure
to carcinogenic factors
Secondary –
early detection and treatment
of precancerous lesions
detection
Clinically apparent disease:
noticed by a patient
Asymptomatic disease:
detected at
routine physical examination
detected by
mass screening programs
early warning signs
lump, sore which dos not heal (including in the mouth), mole which changes in shape, size and colour, new skin lesion which appears and continues to grow, Abnormal bleeding
persistent
cough
persistent
hoarsness
change in
bowel or urinary habits
unexplained weight loss
Screening programmes
Include populations without symptoms
of a particular disease
Aim at decreasing mortality caused by a particular disease
Including large populations: mass screening
Effective screening methods
Cervix: Cervical
cytology
Breast:
Mammography
Colon-rectum:
Faecal occult blood
Screening
methods of unknown value
Prostate:
Prostate specific antigen
Stomach:
H. pylori testing and/or radiographic
examination
Ovary:
Ca125 and/or ultrasound
Breast:
Mammography <50 years
Skin: Examination of
moles
Oral: Examination of
mouth
Ineffective
screening methods
Lung cancer:
Chest X ray
Breast:
Breast self-examination
Testis:
Self-examination
Neuroblastoma:
Urinary homovalinic acid
Cervix cancer
One of the most common cancers
in developing countries
(about
25% of all female cancers)
Less common in developed populations due to mass screening programmes
Efficacy of screening using a cervical smear (Pap) test performed every 3 years
HPV test more sensitive
Mammography screening
Mammography can
detect breast tumours at a clinically undetectable stage
Mammography screening
reduces breast cancer mortality by 25% in women over 50 years
Colorectal screening
Colorectal cancer is
one of the most common malignancies in the developed countries
Annual screening with faecal occult blood testing reduces colorectal cancer mortality by 16-27%
Colonoscopy is more effective, can be performed every 10 years
Lung cancer screening
Low dose CT performed anually in heavy smokers 55-74 years of age reduces mortality, cannot be the alternative for smoking cessation