1. Cancer prevention and early detection
Lausanne-Part2-2010
Cancer prevention and early detection
C. Sauvaget MD Screening Group (SCR)

2. Prevention aims to reduce the frequency of new invasive cancers
Lausanne-Part2-2010
Prevention aims to reduce the frequency of new invasive cancers

3. Prevention is achieved by
Lausanne-Part2-2010
Prevention is achieved by
Modulating exposure of individuals to cancer risk factors by
Awareness
Elimination of risk factors
Supplementation
Vaccination
Legislation
Early detection ad treatment of potentially malignant precancerous lesions (e.g. CIN, polyps)

4. Evaluation of prevention of cancer
Lausanne-Part2-2010
Evaluation of prevention of cancer
Trends in:
the prevalence of risk factors
incidence of cancer
mortality

5. Natural history of cancer and levels of prevention
Lausanne-Part2-2010
Natural history of cancer and levels of prevention
Pre-clinical phase
Clinical phase
Exposure
Onset of disease
Early detection
Onset of symptoms and/or signs
D1 Cure A B C
D2 Disability
Primary prevention
Secondary prevention
Tertiary prevention
D3 Death

6. Lausanne-Part2-2010
Time trends in age-standardized cancer incidence rate of breast in 13 cancer registries in Asia, females
Hirabayashi and Zhang, Jpn J Clin Oncol 2009;39(6)411–412

7. Early detection approaches
Lausanne-Part2-2010
1. Screening: Systematic, routine application of a suitable early detection test at specified intervals in a systematically invited asymptomatic population.
2. Early clinical diagnosis: Searching for precancerous or early invasive cancer in symptomatic or asymptomatic individuals in opportunistic settings. Improved awareness and access to health services promote early clinical diagnosis.

8. Cancer early detection options
Lausanne-Part2-2010
Cancer early detection options
Screening programs
Clinical early diagnosis
Screened +
Sick
Population
Screening target
Clinical early diagnosis target

9. Early detection is associated with:
Lausanne-Part2-2010
Early detection is associated with:
Benefits/harms
Costs to Individual and the Health Services
It is important to establish that benefits of early detection, particularly screening, outweigh harms and it is cost-effective in reducing incidence/mortality.

10. Lausanne-Part2-2010
Screening
Presumptive identification of unrecognised disease by tests which can be applied rapidly
Involves application of a simple, inexpensive test to a large number of persons to classify them as likely (screen positive) or unlikely (screen negative) to have the disease which is the object of screen
It is the whole system to improve health: identification of risk and intervention

11. Objective of screening
Lausanne-Part2-2010
Objective of screening
To achieve reduction in incidence and/ or mortality from the disease in question among the persons screened at a reasonable cost

12. Screening Requirements
Lausanne-Part2-2010
Screening Requirements
Suitable disease
Suitable test
Suitable screening settings

13. Screening Suitable disease Requirements a) Important problem
Lausanne-Part2-2010
Screening
Requirements
Suitable disease
a) Important problem
b) Can be detected in preclinical stage
c) Effective treatment available
d) End result improved by early diagnosis

14. Screening Requirements
Lausanne-Part2-2010
Screening Requirements
A suitable screening test
2.1 Adequate validity
Sensitivity
Specificity
2.2 Acceptability and cost

15. 2.1 Accuracy of diagnostic tool = Validity
Lausanne-Part2-2010
2.1 Accuracy of diagnostic tool = Validity
SENSITIVITY: likelihood that the test will detect disease when it is present
SPECIFICITY: likelihood that the test is negative when the disease is absent
POSITIVE PREDICTIVE VALUE: likelihood that a positive test has detected the disease of interest

16. Ideal situation for a screening test
Lausanne-Part2-2010
Ideal situation for a screening test
No overlap of distributions among healthy and diseased A
Cut-off
Value
Number of
People
Negative
Test
Results
Disease
Free
Positive
Test
Results
Disease
Affected
Screening Test
The test is 100% sensitive and 100% specific.
The distribution of the screening test results among the subjects with the disease is completely separated from the distribution among the subjects without the disease.

17. Real situation for a screening test
Lausanne-Part2-2010
Real situation for a screening test
Overlap of distributions among healthy and diseased B
Disease
Affected
Free
Screening Test
Number of
People
Cut-off
Value
Moving the cut-off value to the right (increasing the screening test value) decreases sensitivity (detection of disease) but increases specificity (exclusion of healthy). More false negative will be missed at screening.
Positive
Test
Results
Negative
False
Negative
Positive
The screening test tends to give higher values for subjects with the disease than those without the disease. Moving the cut-off value to the left (lowering the screening test value) increases sensitivity (detection of disease) and decreases specificity (exclusion of healthy).

18. 2.2 Acceptability and cost
Lausanne-Part2-2010
2.2 Acceptability and cost
In addition to adequate validity, a screening test should be:
Low cost
Convenient
Simple
As painless as possible
Does not cause complications

19. Screening 3. Suitable programme settings Requirements
Lausanne-Part2-2010
Screening
Requirements
3. Suitable programme settings
Adequate infrastructure for diagnosis and treatment in health services
Adequate trained manpower
Adequate financial resources

20. Successful cervical cancer prevention key elements
Lausanne-Part2-2010
Successful cervical cancer prevention key elements
Link Screening
and Treatment
Effectiveness
of Treatment
Screening
Coverage

21. Evaluation of screening programmes
Lausanne-Part2-2010
Evaluation of screening programmes
Process measures
Outcome measures

22. Evaluation of screening Programmes Outcome
Lausanne-Part2-2010
Evaluation of screening Programmes Outcome
Early outcome
Stage distribution
Case fatality and survival
Final outcome
Reduction in incidence (if precancerous lesions are detected); mortality (if invasive disease is detected)

23. Lausanne-Part2-2010
Mortality rates from invasive cervical cancer and screening coverage rate, Mexico,
Courtesy Dr Eduardo Lazcano

24. Effectiveness of cervical cancer screening in Taiwan
Lausanne-Part2-2010
Effectiveness of cervical cancer screening in Taiwan
Chen et al, Br J Cancer 2009

25. Suitable cancers for screening
Lausanne-Part2-2010
Suitable cancers for screening
Cervical cancer
Breast cancer
Colorectal cancer
Oral cancer

26. Screening methods Cervical Cancer Colorectal cancer Breast cancer
Lausanne-Part2-2010
Screening methods
Cervical Cancer
Pap smear
Liquid based cytology
HVP DNA testing
Visual screening
Breast cancer
Mammography
Clinical breast examination
Colorectal cancer
Faecal occult blood tests (FOBT)
Sigmoidoscopy
Colonoscopy
Oral cancer
Visual inspection

27. Organised and opportunistic screening programmes exist for
Lausanne-Part2-2010
Organised and opportunistic screening programmes exist for
Cervical cancer
Breast cancer
Colorectal cancer

28. Lausanne-Part2-2010