بسم الله الرحمن الرحيم. introduction cancer deaths seven million half a million ...
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بسم الله بسم الله الرحمن الرحمن الرحيمالرحيم
INTRODUCTIONINTRODUCTION
Cancer deaths Cancer deaths seven millionseven millionhalf a million half a million die from cancer each year in die from cancer each year in the United States (US) alone the United States (US) alone It is estimated that 50 percent of cancer is It is estimated that 50 percent of cancer is preventable preventable
INTRODUCTIONINTRODUCTION risk factors (account for two-thirds of risk factors (account for two-thirds of all cancers in the US all cancers in the US
–tobacco use, tobacco use, –excess weight, excess weight, –poor diet, poor diet, –inactivityinactivity
INTRODUCTIONINTRODUCTION nine modifiable risks were identified as the nine modifiable risks were identified as the cause of 35 percent of cancer deaths cause of 35 percent of cancer deaths worldwide: worldwide:
–smoking, smoking, –alcohol use, alcohol use, –diet low in fruit and vegetables, diet low in fruit and vegetables, –excess weight, excess weight, –inactivity, inactivity, –unsafe sex, unsafe sex, –urban air pollution, urban air pollution, –use of solid fuels, and use of solid fuels, and –contaminated injections in health-care settings contaminated injections in health-care settings
Harvard Report on Cancer Prevention
Volume 2: Prevention of
Human Cancer. Cancer Causes
and Control 1997; 8:S1.
INTRODUCTIONINTRODUCTIONLifestyle issues which promote Lifestyle issues which promote cancer are also risk factors for cancer are also risk factors for other diseases, such as stroke, other diseases, such as stroke, heart disease, and diabetes.heart disease, and diabetes.
TOBACCO USETOBACCO USE –kills approximately 5 million people each kills approximately 5 million people each yearyear–mostly through mostly through
malignancy, malignancy, cardiovascular, andcardiovascular, andrespiratory diseaserespiratory disease
–Approximately one-half of all smokers die of Approximately one-half of all smokers die of a tobacco-related disease, and a tobacco-related disease, and –adult smokers lose an average of 13 years adult smokers lose an average of 13 years of life due to this addictionof life due to this addiction
–What Is Cancer Screening?–Evaluation of a Screening Test–Breast Cancer Screening–Cervical Cancer Screening–Colorectal Cancer Screening–Skin Cancer Screening–Prostate Cancer Screening–Lung Cancer Screening–Adherence to Cancer Screening–Future of Screening
The goal of cancer screening The goal of cancer screening –detect cancer at an early stage detect cancer at an early stage
when it is treatable and curable when it is treatable and curable
For a screening test to be useful:For a screening test to be useful:–should detect cancer earlier than would should detect cancer earlier than would occur otherwise, occur otherwise, –should be evidence that earlier diagnosis should be evidence that earlier diagnosis results in improved outcomes results in improved outcomes
Advances in genetics and molecular Advances in genetics and molecular biologybiology
–will make it possible to detect cancer at will make it possible to detect cancer at earlier and earlier stages along the earlier and earlier stages along the carcinogenesis pathway carcinogenesis pathway –the line between prevention and screening the line between prevention and screening may narrow further, as it has for colorectal may narrow further, as it has for colorectal and cervical cancers and cervical cancers
The National Cancer Policy Board The National Cancer Policy Board estimated that appropriate use of estimated that appropriate use of screening among screening among
–persons aged 50 and older could reduce persons aged 50 and older could reduce the mortality from colorectal cancer by 30% the mortality from colorectal cancer by 30% to 80%; to 80%; –women aged 50 and older could reduce women aged 50 and older could reduce mortality from breast cancer by 25% to mortality from breast cancer by 25% to 30%, 30%, –women aged 18 and older could reduce women aged 18 and older could reduce the rate of cervical cancer mortality by 20% the rate of cervical cancer mortality by 20% to 60%. to 60%.
What Is Cancer Screening?What Is Cancer Screening? lead to early detection of asymptomatic or lead to early detection of asymptomatic or unrecognized disease unrecognized disease acceptable acceptable inexpensive tests or examinations inexpensive tests or examinations in a large number of persons in a large number of persons expeditiously to separate apparently well expeditiously to separate apparently well persons who probably have disease from persons who probably have disease from those who probably do not. those who probably do not.
What Is Cancer Screening?What Is Cancer Screening? The main objective of cancer screening is to:The main objective of cancer screening is to:
– reduce morbidity and mortality from a particular reduce morbidity and mortality from a particular cancer among persons screenedcancer among persons screened
What Is Cancer Screening?What Is Cancer Screening?
Characteristics of Screening Tests versus Diagnostic Tests
Screening Diagnosis
Applied to asymptomatic Applied to asymptomatic groupsgroups
Applied to symptomatic individuals
Lower cost per testLower cost per test Higher cost; all necessary tests applied to identify disease
Lower yield per testLower yield per test Higher probability of case detection
Lower adverse Lower adverse consequences of errorconsequences of error
Failure to identify true positives can delay treatment and worsen prognosis
What Is Cancer Screening?What Is Cancer Screening? cancers suitable for screening cancers suitable for screening
–High morbidity and mortality, High morbidity and mortality, –high prevalence in a detectable high prevalence in a detectable preclinical state,preclinical state,–possibility of effective and improved possibility of effective and improved treatment because of early detection, treatment because of early detection, and and –availability of a good screening test availability of a good screening test with high sensitivity and specificity, with high sensitivity and specificity, –low cost, and low cost, and –little inconvenience and discomfort little inconvenience and discomfort
What Is Cancer Screening?What Is Cancer Screening? cancers suitable for screening cancers suitable for screening
–Breast CABreast CA–Cervical CA Cervical CA –colorectal CAcolorectal CA–Skin cancerSkin cancer
Evaluation of a Screening TestEvaluation of a Screening Test
If the test is If the test is abnormalabnormal, , –what are the chances that disease is what are the chances that disease is present? present?
If the test result is If the test result is normalnormal, , –what are the chances that disease is what are the chances that disease is absent? absent?
Evaluation of a Screening TestEvaluation of a Screening Test The validity of a screening test The validity of a screening test
–SensitivitySensitivity and and specificityspecificity address the address the validity of screening tests validity of screening tests
Sensitivity is the probability of testing positive Sensitivity is the probability of testing positive if the disease is truly present. if the disease is truly present.
–As sensitivity increases, As sensitivity increases, false-negative decreases false-negative decreases Specificity is the probability of screening Specificity is the probability of screening negative if the disease is truly absent. negative if the disease is truly absent.
–A highly specific test A highly specific test false-positive decreases false-positive decreases
Evaluation of a Screening TestEvaluation of a Screening Test The validity of a screening test The validity of a screening test
–Predictive value Predictive value is a function of sensitivity, specificity, and is a function of sensitivity, specificity, and prevalence of disease prevalence of disease PV+ is an estimate of test accuracy in PV+ is an estimate of test accuracy in predicting presence of disease; predicting presence of disease; PV– is an estimate of the accuracy of the test PV– is an estimate of the accuracy of the test in predicting absence of disease in predicting absence of disease
Definitions of Criteria for Evaluating a Screening Test
Truth (Diagnostic Classification)
Screening Test Results Cancer Present Cancer Absent
Positive TP FP
Negative FN TN
Sensitivity = TP/TP + FN x 100
Specificity = TN/FP + TN x 100
PV+ = TP/TP + FP x 100
PV– = TN/TN + FN x 100
Accuracy = TP + TN/TP + TN + FP + FN x 100
FN, false-negative (number of subjects with cancer who are incorrectly classified as cancer-free by the test); FP, false-positive (number of cancer-free subjects who are incorrectly classified as having cancer by the test); PV, predictive value; TN, true-negative (number of cancer-free subjects who are correctly classified by the test); TP, true-positive (number of subjects with cancer who are correctly classified by the test).
Evaluation of a Screening TestEvaluation of a Screening Test
–The optimal outcome is a reduction in The optimal outcome is a reduction in cancer mortality cancer mortality
Evaluation of a Screening TestEvaluation of a Screening Test Measures of Effectiveness Measures of Effectiveness
–Potential negative effects of screening Potential negative effects of screening
includeinclude
physical, economic, and psychological physical, economic, and psychological
consequences of false-positives and false-consequences of false-positives and false-
negatives, negatives,
the potential for overdiagnosis, the potential for overdiagnosis,
the potential carcinogenic effects of screening,the potential carcinogenic effects of screening,
the labeling phenomenon. the labeling phenomenon.
Evaluation of a Screening TestEvaluation of a Screening Test Measures of Effectiveness Measures of Effectiveness
–Potential negative effects of screening Potential negative effects of screening includeinclude
physical, economic, and psychological physical, economic, and psychological consequences of false-positives and false-consequences of false-positives and false-negatives, negatives, the potential for overdiagnosis, the potential for overdiagnosis, the potential carcinogenic effects of screening,the potential carcinogenic effects of screening,the labeling phenomenon. the labeling phenomenon.
Evaluation of a Screening TestEvaluation of a Screening Test Measures of Effectiveness Measures of Effectiveness
–Physicians should engage patients in Physicians should engage patients in discussions of the risks and benefits of discussions of the risks and benefits of cancer screening cancer screening
Table 22-5: Screening Guidelines for Breast, Colorectal, Prostate, and Cervical Cancers for Selected Health Care Organizations
Type of Cancer
American Cancer Society20 U.S. Preventive Services Task Force3 National Cancer Institute's Physician Data Query (PDQ) System1
Breast cancer
Annual mammography for women aged 40–69 y. No age cutoff. To the extent possible, a CBE should be performed at the time of mammography. Monthly BSE.136 Women aged 20–39 y should have a CBE from a health professional every 3 y and should perform BSE monthly.20
Recommends screening mammogram, with or without CBE, every 1–2 y.
Mammography every 1–2 y for women age 40 y and older. Women at higher risk should talk with their physicians about schedule.
Cervical cancer
For all women who are, or have been, sexually active or who have reached age 21 y, Pap test and pelvic examination yearly with Pap tests or every 3 y with liquid-based tests. At or after age 30 y, women who have had 3 normal tests can be screened every 2–3 y. Women with risk factors (e.g., HPV infection) may require more frequent screening. Screening is not necessary for women who have had total hysterectomies unless the surgery was for treatment of cervical cancer.
Pap test every 1–3 y for all women who are sexually active and/or have a cervix. No evidence to support an upper limit, but age 65 y can be defended in women with a history of normal and regular Pap tests.
Evidence strongly suggests a decrease in mortality for regular screening with Pap tests in women who are sexually active or who have reached age 18 y. The upper limit at which such screening ceases to be effective is unknown.
Colorectal cancer
One of the following schedules for men and women aged 50 y and over at average risk: FOBT yearly; sigmoidoscopy every 5 y; FOBT + sigmoidoscopy every 5 y; colonoscopy every 10 y; DCBE every 5 y. Those at high risk for colorectal cancer should begin screening earlier and/or more frequently.
Screening for colorectal cancer is strongly recommended for men and women aged 50 y and over. Several screening modalities are effective. Good evidence has been shown that periodic FOBT reduces mortality from colorectal cancer, and there is fair evidence that sigmoidoscopy alone or in combination with FOBT reduces mortality. No direct evidence has been shown for either colonoscopy or DCBE.
FOBT either annually or biennially using rehydrated or nonrehydrated stool specimens in people aged 50 y and over decreases mortality for colorectal cancer. Regular screening by sigmoidoscopy in people over age 50 y may decrease mortality from colorectal cancer. Evidence is insufficient to determine the optimal interval for such screening.
Prostate cancer
PSA test and DRE should be offered annually, beginning at age 50 y, to men who have a life expectancy of at least 10 y. Men at high risk for cancer should start screening at 45 y. Men should be given the information needed to make informed decisions about prostate cancer screening.
Evidence is insufficient to recommend for or against routine screening for prostate cancer using PSA testing or DRE.
Evidence is insufficient to establish that a decrease in mortality occurs with screening by DRE, transrectal ultrasound, or PSA.
Screening Guidelines for Breast, Colorectal, Prostate, and Cervical Cancers for Selected Health Care Organizations
Type of Cancer
American Cancer Society
U.S. Preventive Services Task Force
National Cancer Institute's Physician Data Query (PDQ) System
Breast cancer
Annual mammography for women aged 40–69 y. No age cutoff. To the extent possible, a CBE should be performed at the time of mammography. Monthly BSE.Women aged 20–39 y should have a CBE from a health professional every 3 y and should perform BSE monthly.20
Recommends screening mammogram, with or without CBE, every 1–2 y.
Mammography every 1–2 y for women age 40 y and older. Women at higher risk should talk with their physicians about schedule.
Table 22-5: Screening Guidelines for Breast, Colorectal, Prostate, and Cervical Cancers for Selected Health Care Organizations
Type of Cancer
American Cancer Society20
U.S. Preventive Services Task Force3
National Cancer Institute's Physician Data Query (PDQ) System1
Cervical cancer
For all women who are, or have been, sexually active or who have reached age 21 y, Pap test and pelvic examination yearly with Pap tests or every 3 y with liquid-based tests. At or after age 30 y, women who have had 3 normal tests can be screened every 2–3 y. Women with risk factors (e.g., HPV infection) may require more frequent screening. Screening is not necessary for women who have had total hysterectomies unless the surgery was for treatment of cervical cancer.
Pap test every 1–3 y for all women who are sexually active and/or have a cervix. No evidence to support an upper limit, but age 65 y can be defended in women with a history of normal and regular Pap tests.
Evidence strongly suggests a decrease in mortality for regular screening with Pap tests in women who are sexually active or who have reached age 18 y. The upper limit at which such screening ceases to be effective is unknown.
Type of Cancer
American Cancer Society20
U.S. Preventive Services Task Force3
National Cancer Institute's Physician Data Query (PDQ) System1
Colorectal cancer
One of the following schedules for men and women aged 50 y and over at average risk: FOBT yearly; sigmoidoscopy every 5 y; FOBT + sigmoidoscopy every 5 y; colonoscopy every 10 y; DCBE every 5 y. Those at high risk for colorectal cancer should begin screening earlier and/or more frequently.
Screening for colorectal cancer is strongly recommended for men and women aged 50 y and over. Several screening modalities are effective. Good evidence has been shown that periodic FOBT reduces mortality from colorectal cancer, and there is fair evidence that sigmoidoscopy alone or in combination with FOBT reduces mortality. No direct evidence has been shown for either colonoscopy or DCBE.
FOBT either annually or biennially using rehydrated or nonrehydrated stool specimens in people aged 50 y and over decreases mortality for colorectal cancer. Regular screening by sigmoidoscopy in people over age 50 y may decrease mortality from colorectal cancer. Evidence is insufficient to determine the optimal interval for such screening.
Type of Cancer
American Cancer Society20
U.S. Preventive Services Task Force3
National Cancer Institute's Physician Data Query (PDQ) System1
Prostate cancer
PSA test and DRE should be offered annually, beginning at age 50 y, to men who have a life expectancy of at least 10 y. Men at high risk for cancer should start screening at 45 y. Men should be given the information needed to make informed decisions about prostate cancer screening.
Evidence is insufficient to recommend for or against routine screening for prostate cancer using PSA testing or DRE.
Evidence is insufficient to establish that a decrease in mortality occurs with screening by DRE, transrectal ultrasound, or PSA.
Breast Cancer ScreeningBreast Cancer Screening lifetime breast cancer incidence is lifetime breast cancer incidence is 7.8%, 7.8%, Widely accepted techniques for breast Widely accepted techniques for breast cancer screening, cancer screening,
–mammography,mammography,–clinical breast examination (CBE), and clinical breast examination (CBE), and –breast self-examination (BSE). breast self-examination (BSE).
–No cancer screening test has been studied more No cancer screening test has been studied more than mammography (with or without CBE). than mammography (with or without CBE).
Breast Cancer ScreeningBreast Cancer Screening
Most trials have included women in their 40s, Most trials have included women in their 40s, two trials began accrual at age 45. two trials began accrual at age 45. One of the Canadian trials [the first National One of the Canadian trials [the first National Breast Cancer Screening Study (NBSS1)] was Breast Cancer Screening Study (NBSS1)] was designed to examine mammography and CBE designed to examine mammography and CBE versus usual care for women in their 40s versus usual care for women in their 40s
