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Cancer epidemiology, prevention and screening
Epidemiology-Lausanne Cancer epidemiology, prevention and screening R. Sankaranarayanan MD Head, Early Detection and Prevention Section (EDP) Head, Screening Group (SCR)
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Cancer epidemiology Distribution – burden, pattern
Determinants – causes, risk factors Application – prevention, control
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Cancer epidemiology studies
Descriptive studies Observational studies Experimental studies
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Major causes of cancer Tobacco use Alcohol
Infection – HBV, HCV, HPV, EBV, Helicobacter pylori, liver fluke, among others Dietary factors Physical activity (lack of!) Radiation Chemical exposures Genetic factors (list incomplete . . !)
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Breast cancer risk factors
Estrogen exposure: early menarche (<12), late menopause (>55), never breast fed, hormone therapy Late child beating: >30 years Breast density Obesity after menopause Physical inactivity Alcohol consumption Radiation exposure Genetic alterations: BRCA1, BRCA2 genes Family history
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Cancer – worldwide burden
7 million Deaths 11 million New Cases 25 million Living with Cancer
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WPRO Population (2000): 1.681,000,000 Males Females
Epidemiology-Lausanne Stomach Lung Liver Colon/Rectum Oesophagus Breast Leukaemia Cervix uteri Pancreas Non-Hodgkin lymphoma Brain nervous system Bladder Prostate Nasopharynx Ovary etc. Kidney etc. Males 858,000,000 population 1.782,000 cases 1.299,000 deaths Females 823,000,000 population 1.229,000 cases 778,000 deaths Incidence Mortality (Thousands) Population (2000): 1.681,000,000 : Regional Office for the Western Pacific
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SEARO Population (2000): 1,535,000,000 Females Males
Epidemiology-Lausanne SEARO Cervix uteri Breast Oral cavity Lung Colon/Rectum Oesophagus Other pharynx Stomach Liver Larynx Leukaemia Non-Hodgkin lymphoma Ovary etc. Brain nervous system Prostate Bladder Males 786,000,000 population 605,000 cases 442,000 deaths Females 749,000,000 population 660,000 cases 408,000 deaths Incidence Mortality (Thousands) Population (2000): 1,535,000,000
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EMRO Population (2000): 480,000,000 Females Males
Epidemiology-Lausanne EMRO Breast Bladder Lung Oral cavity Colon/Rectum Stomach Oesophagus Leukaemia Non-Hodgkin lymphoma Cervix uteri Liver Brain nervous system Larynx Thyroid Ovary etc. Prostate Males 246,000,000 population 181,000 cases 134,000 deaths Females 234,000,000 population 187,000 cases 119,000 deaths Incidence Mortality (Thousands) Population (2000): 480,000,000 :: Regional Office for the Eastern Mediterranean
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AFRO Population (2000): 640,000,000 Females Males
Epidemiology-Lausanne Cervix uteri Kaposi sarcoma Breast Liver Prostate Non-Hodgkin lymphoma Stomach Oesophagus Colon/Rectum Oral cavity Lung Leukaemia Bladder Ovary etc. Melanoma of skin Larynx Males 319,000,000 Population 244,000 cases 196,000 deaths Females 321,000,000 population 271,000 cases 204,000 deaths (Thousands) Population (2000): 640,000,000 Incidence Mortality
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EURO Population (2000): 874,000,000 Females Males
Epidemiology-Lausanne Lung Breast Colon/Rectum Prostate Stomach Bladder Kidney etc. Corpus uteri Pancreas Leukaemia Non-Hodgkin lymphoma Ovary etc. Cervix uteri Melanoma of skin Oral cavity Liver Males 424,000,000 population 1.560,000 cases 1.004,000 deaths Females 450,000,000 population 1.392,000 cases 783,000 deaths (Thousands) Population (2000): 874,000,000 Incidence Mortality :: Regional Office for Europe
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PAHO Population (2000): 831,000,000 Females Males
Epidemiology-Lausanne PAHO Males 411,000,000 population 1.180,000 cases 551,000 deaths Females 420,000,000 Population 1.120,000 cases 512,000 deaths (Thousands) Prostate Breast Lung Colon/Rectum Stomach Bladder Non-Hodgkin lymphoma Cervix uteri Melanoma of skin Corpus uteri Leukaemia Kidney etc. Pancreas Ovary etc. Brain nervous system Oral cavity Population (2000): 831,000,000 Incidence Mortality
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Prevention aims to reduce the frequency of new invasive cancers
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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)
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Evaluation of prevention of cancer
Trends in: the prevalence of risk factors incidence of cancer mortality
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Adult per capita consumption of tobacco
Epidemiology-Lausanne Adult per capita consumption of tobacco products in the 20th Century in Australia Year 0.0000 0.5000 1.0000 1.5000 2.0000 2.5000 3.0000 3.5000 4.0000 1903 1906 1909 1912 1915 1918 1921 1924 1927 1930 1933 1936 1939 1942 1945 1948 1951 1954 1957 1960 1963 1966 1969 1972 1975 1978 1981 1984 1987 1990 1993 1996 Annual amount of tobacco dutied per adult over 15 years ( kg) Depression World War II Uptake by women Early research on health effects of smoking Report of the US Surgeon General Broadcast of tobacco advertising phased out Commencement of Quit Campaigns Tobacco Taxation Workplace smoking bans introduced New health warnings Introduction of manufactured cigarettes Almost all of the major changes in tobacco consumption in Australia have come about as a result of government action, even the increases. Free distribution of cigarettes to the troops in WWII. The declines have come about because governments were persuaded to act by NGOs who could demonstrate strong public support.
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Trends in lung cancer mortality and smoking prevalence in Australia 1940-2004
Epidemiology-Lausanne 17
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Trends in incidence of lung cancer in Asia
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Impact of Hepatitis B vaccination on liver cancer incidence: Taiwan
Vaccination for infants born to HBsAg carriers during Vaccination extended for all infants aged <12 months in 1986, 1-4 year old infants in 1987 5-9 year old infants during , years and to adults 20 years and above during 64 liver cancers among vaccinated subjects in Pyrs Vs. 444 cancers among unvaccinated subjects in Pyrs 69% reduction in liver cancer among vaccinated cohort Chang et al., JNCI. 2009;101:
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Time trends in age-standardized cancer incidence rate of breast in 13 cancer registries in Asia, females
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Trends in cervical cancer incidence in Singapore, 1960-2000
Epidemiology-Lausanne Trends in cervical cancer incidence in Singapore, Singapore: Chinese Singapore:Indian Singapore: Malay Singapore: Mortality Years Time D.M. Parkin, S. Whelan, J. Ferlay and H. Storm. Cancer Incidence in Five Continents, Vol. I to VII. IARC CancerBase No. 7, Lyon, 2005
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Cervical cancer mortality rates in Chile 1985-1999
Adjusted death rate/ women Courtesy Dr Catterina Ferreccio Cancer Unit/ Health Ministry/M. Prieto
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Early detection approaches
Epidemiology-Lausanne 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 precancer or early invasive cancer in symptomatic or asymptomatic individuals in opportunistic settings. Improved awareness and access to health services promote early clinical diagnosis.
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Early detection is associated with:
Benefits/?harm 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.
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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
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Objective of screening
To achieve reduction in incidence and/ or mortality from the disease in question among the persons screened at a reasonable cost
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Screening Suitable disease Requirements a) Important problem
b) Can be detected in preclinical stage c) Effective treatment available d) End result improved by early diagnosis
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Total pre-clinical phase (TPCP) 30 to 55 25 years
Age Birth Death symptoms screening Cells exfoliate exposure Cancer begins Interval Age Duration Total pre-clinical phase (TPCP) 30 to years 2. Detectable pre-clinical phase (DPCP) 45 to years
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Short and long natural histories of disease: relationship of length of preclinical phase
Short Natural History Preclinical Phase Clinical Phase Long Natural History
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Screening 2. Suitable test a) Affordable and easy to apply
Requirements 2. Suitable test a) Affordable and easy to apply b) Valid: sensitivity specificity positive predictive value c) Safe and acceptable
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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
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Disease Affected Positive Teat Results Free Possible normal limit Number of People Teat value A Disease Affected Positive Teat Results Free Possible normal limit Teat value Number of People B A, Ideal distribution of test results in disease-free and affected individual. B, The inevitable tradeoff of sensitivity and specificity. Moving the possible normal limits to the left increases sensitivity and decreases specificity, whereas moving the possible normal limit to the right increases specificity and decreases sensitivity. (adapted from Friedman GD: Epidemiology and patient care. In Laufer RS, Hrieger A (eds): Primer of Epidemiology. New York, McGraw-Hill, 1974; with permission)
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Screening 3. Suitable programme settings
Requirements 3. Suitable programme settings a) Adequate infrastructure for diagnosis and treatment in health services b) Adequate trained manpower c) Adequate financial resources
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Evaluation of screening Programme
Process measures Outcome measures
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Outcome evaluation of screening Programmes
Early outcome Stage distribution Case fatality and survival Final outcome Reduction in incidence (if precancerous lesions are detected); mortality (if invasive disease is detected); quality of life; cost- effectiveness
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Suitable cancers for screening
Cervical cancer Breast cancer Colorectal cancer Oral cancer
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Screening methods Cervical Cancer Colorectal cancer Breast 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
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Organised and opportunistic screening programmes exist for
Cervical cancer Breast cancer Colorectal cancer
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