Nicolaus Copernicus University in Torun Medical College in Bydgoszcz Family Doctor Department CANCER PREVENTION IN GENERAL PRACTICE
A key mission for family medicine is preserving health and maximizing function of patients throughout their lives. In all diseases, the goal is prevention. Prevention involves intervention in a healthy, asymptomatic patient. Any test should be firmly evidence-based, showing that the benefits of the intervention outweigh its potential harm. The evidence-based recommendations of the US - Preventive Service Task Force are considered the "gold standard" for clinical preventive services. (The Guide to Clinical Preventive Services in: Textbook of Family Medicine, Rakel R, Rakel D. Elsevier Saunders, 2011)
Primary prevention, prevention of disease occurrence - is defined as interventions that reduce the risk of disease in otherwise healthy individuals. E.g. - to avoid smoking and stop drinking too much alcohol, vaccination against HPV virus, prevention sun radiation. Secondary prevention, controlling disease in early form - screening to identify risk factors for disease or the early detection of a disease among asymptomatic and at risk individuals. E.g. - screening for colon cancer using colonoscopy to detect precancerous polyps and then removing the polyps, carcinoma in situ. Tertiary prevention, prevention of complications once the disease is present - individuals who clearly have a disease, and the goal is to prevent them from developing further complications. E.g. - within diabetes - retinal examination, psychotherapy for patients after chemo-therapy (anti-suicide prevention)
World Health Organization Criteria for a Screening Test (The Wilson-Jungner criteria): 1. The condition being screened for should be an important health problem 2. The natural history of the condition should be well understood 3. There should be a detectable early stage 4. Treatment at an early stage should be of more benefit than at later stage 5. A suitable test should be devised for the early stage 6. The test should be acceptable 7. Intervals for repeating the test should be determined 8. Adequate health service provision should be made for the extra clinical workload resulting from screening 9. The physical and psychological risk should be less than the benefits 10.The costs should be balanced against the benefits
Prevalence - is the proportion of a defined group of people who have a condition or disease at a given point in time. Prevalence can be expressed in cases per 1000, 10,000 or 100,000 people or as a percentage. Incidence - is the proportion of an initially disease-free group of people who develop the disease over a given period. Prevalence and incidence may describe the frequency and burden of disease in a population; however, incidence specifically communicates new cases of the disease over a specific period (e.g., new cases in a given year). Morbidity - is the impact of the disease on health and functioning and mortality is the degree to which the condition results in death. Some diseases may have high prevalence but cause low morbidity, and other diseases may be rare but life-threatening conditions. Performance of screening test Disease Present Absent Test Positive True positive (a) False positive (b) Negative False negative (c) True negative (d) SENSITIVITY = a/(a+c) SPECIFICITY = d/(b+d) Negative predictive values = d/(c+d) Positive predictive values = a/(a+b)
Screening Test Accuracy: the accuracy of test is its ability to measure the actual value of the quantity being measured (using sensitivity and specificity) sensitivity is defined as the proportion of people with the target disorder who have a positive test result specificity is the proportion of people without the target disorder who have a negative test result the positive predictive value is the proportion of people with a positive test result who have the target disorder the negative predictive values is the proportion of people with a negative test result who are free of the target disorder
Number needed to screen - is a concept used to express the number of individuals who would need to be screened for a disease to prevent a single complication (morbidity or mortality) of that disease Number needed to treat is a corollary concept that may be used for preventive medication (e.g., aspirin) - it is the number of individuals who would need to undergo the treatment or intervention to prevent a single case of disease (e.g., heart disease). Risk Factor - is a condition that is associated with an increased likelihood of a disease (e.g., smoking is a risk factor for and a proven cause of lung cancer; a smoker is many times more likely than a nonsmoker to develop lung cancer in his or her lifetime) Risk factors may be considered: - modifiable (can be changed) such as smoking, cholesterol level, body weight - non-modifiable, such as age, gender, family history, race
Performance of screening tests to be more effective: - adequate participation of the target population - few false-negative or false-positive results - screening intervals shorter than the time taken for the disease to develop to an untreatable stage - adequate follow-up of all abnormal results - effective treatment at the stage detected by screening There is NO ideal screening test. Always explain: likelihood of positive/negative findings and possibility of falsepositive/negative results uncertainties and risk attached to the screening process significant medical, social, or financial implications of screening for the particular condition or predisposition follow-up plans, including availability of counseling and support service (Oxford Handbook of General Practice, Oxford University Press, 2010)
Benefits and disadvantages of screening BENEFITS Improved prognosis for some cases detected by screening Less radical treatment for some early cases Reassurance for those with negative test results Increased information on natural history of disease and benefits of treatment at early stage DISADVANTAGES Longer morbidity in cases where prognosis is unaltered Overtreatment of questionable abnormalities False reassurance for those with false-negative results Anxiety and sometimes morbidity for those with false-positive results Unnecessary intervention for those with false-positive results Hazards of the screening test Diversion of resources to the screening programme
Cancer in general practice The most common cancers in men 1. lung cancer 2. colorectal cancer 3. ventricle cancer 4. prostate cancer The most common cancers in women 1. lung cancer 2. breast cancer 3. colorectal cancer 4. ovarian cancer
Colorectal Cancer: is the fourth most common cancer in the US and second leading cause of cancer deaths sensitivity and specificity of screening with fecal occult blood testing (FOBT) has been estimated at 40% and 96-98 %, respectively sigmoidoscopy visualizes only the lower half on the colon but is estimated to identify 80% of all patients with significant findings in the colon colonoscopy has a sensitivity of 90 % for large polyps and 75 % for small polyps double-contrast barium enema C T scan is advised Recommendations: screening for colorectal cancer in men and women 50 years to 75 years using FOBT, sigmoidoscopy or colonoscopy screening may be initiated earlier for those with risk factors (e.g., 10 years before earliest diagnosis of family member) screening average - risk adults beginning at age 50 with yearly FOBT or fecal immunochemical test annually, a flexible sigmoidoscopy every 5 years, an FOBT plus flexible sigmoidoscopy every 5 years, a double - contrast barium enema every 5 years, a CT colonography every 5 years, or a colonoscopy every 10 years
Cervical Cancer the incidence of cervical cancer is decreasing but it is still the 10th leading cause of cancer death screening prevents ca. 1000-4000 death/y in the UK from squamous cell cancer of the cervix risk factor for this disease are human papillomavirus (HPV - DNA), early sexual life, multiple sexual partners, smoking sensitivity of single conventional Papanicolaou (Pap) ranges from 60% to 80% tests: thin-layer cytology (e.g., ThinPrep, AutoCyte PREP) are available with higher sensitivity but lower specificity there are vaccines protecting against designed against of high risk HPV. I the US: the quadrivalent HPV vaccine (types 6, 11, 16, 18). Three injections should be administered before the first sexual experience. Pap screening still necessary. Recommendations women who are sexually active should have a cervix, screening within 3 years of onset of sexual activity or by the age of 21, whichever comes first, screening every 3 years EU: in women with risk factors (early sexual life, many partners, immunosupression, HPV infection, smoking) screening from 16 years of age every 1-2 years
Breast cancer in the US - the second leading cause of death from cancer in women the risk for breast cancer increases with age: the 10-years risk for breast cancer is 1 in 69 for women at the age of 40, 1 in 42 at the age of 50, and 1 in 29 at the age of 60. Accuracy of the Screening Test mammography: the sensitivity ranges from 77% to 95% for cancers diagnosed over the following year, and specificity ranges from 94% to 97%; sensitivity is lower in women younger than 50 and women taking hormone replacement due to increased breast tissue density clinical breast examination (CBE): the sensitivity ranges from 40% to 69% and specificity from 86% to 99% breast self-examination (BSE): does not reduce breast cancer mortality or significantly alter the stage at diagnosis, controversial method Recommendations in the US: biennial screening mammography before the age of 50 should be an individual decision biennial screening mammography for women aged 50 to 74 years after the age of 70: depends on the existence of risk factors ultrasound examination is not a proper screening test genetic counseling referral for women with a family history of breast cancer who may be at risk for BRCA mutation
Lung cancer the leading cause of all cancer deaths cigarette smoking is the main risk factor other risk factors: family history, passive smoking, exposure to asbestos Accuracy of the Screening Tests chest radiography with or without sputum cytology, low-dose computed tomography (LDCT) are being evaluated as good methods Recommendations there is insufficient evidence to recommend for or against screening asymptomatic individuals for lung cancer
Ovarian cancer is the fifth leading cause of cancer death in women in the US most women have non-localized disease at diagnosis risk factors for developing ovarian cancer include a first- or second-degree relative with ovarian cancer, being a carrier of the BRCA1 or BRCA2 gene mutation and taking estrogens after menopause oral contraceptive use and parity have a protective effect, reducing the risk of disease Accuracy of Screening Tests the sensitivity and specificity of CA 125 blood level, transvaginal ultrasound are difficult to determine because thresholds for abnormal findings differ among studies no evidence that any screening test reduces mortality Recommendation routine screening is not recommended
Prostate cancer is the second leading cause of cancer death in men incidence increases with age, and more than 75% of cases are in men older than 65 years other risk factors: being black and having a first-degree relative with prostate cancer Accuracy of the Screening Test the sensitivity and specificity of prostate-specific antigen (PSA) depend on the threshold set for a clinically significant abnormal values using the cutoff of 4 ng/ml sensitivity ranges from 63% to 83% and a specificity about 90% in the first screening specificity and sensitivity decreases with increasing age and hyperplasia Recommendation the US: the evidence is insufficient to recommend for or against routine screening for prostate cancer using PSA or DRE (digital rectal examination) in men younger than 75 Poland: men after 50: DRE and PSA levels in the blood to be checked every year
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