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

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

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)

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

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

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

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.

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

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.

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

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

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

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

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

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

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.

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).

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

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

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

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

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)

Lausanne-Part2-2010 Mortality rates from invasive cervical cancer and screening coverage rate, Mexico, 1979-2004 Courtesy Dr Eduardo Lazcano

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

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

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

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

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