Screening for Cancer and Other Diseases
there is a lower need for screening everyone
If the disease is rare (low incidence),
Burden of Cervical Disease
In the United States • 13,060 new cases and 4,310 deaths expected in 2023 • Low-income and minority women • ~3.5 million low grade lesions detected each year • Annual cost of colposcopic biopsy and management: $6 billion Marked declines in areas with organized Pap screening • ½ of cases occur in women screened with existing techniques
Approaches to Colorectal Cancer Screening
Population-Based in Europe, UK: stool-based tests, flexible sigmoidoscopy, sometimes colonoscopy Opportunistic in USA: Variety of methods; colonoscopy often recommended
Difference between population-based and opportunistic screening?
Population-based screening is a systematic approach targeting entire populations or specific groups, aiming to identify and treat conditions at the population level. Opportunistic screening, in contrast, occurs during routine healthcare encounters based on individual risk factors, symptoms, or specific clinical situations.
Validity of Screening Tests
The ability of a test to distinguish between who has the disease and who does not. • Two components - Sensitivity -- Ability of the test to identify correctly those who have the disease. - Specificity -- Ability of the test to identify correctly those who do not have the disease.
Research does not account for every single person in the country; some treatment will be more favored for certain individuals
What is bad about population heterogeneity?
Disease will affect the population differently; whole population will not get wiped out
What is good about population heterogeneity?
Difficulties in Early Detection
• Anatomy • Access to the organ • Histopathological features • Diagnosis and confirmation
Colorectal Cancer Screening Guidelines
• Beginning at age 50, both men and women should follow one of the schedules • Flexible sigmoidoscopy every 5 years, or • Colonoscopy every 10 years, or • Double-contrast barium enema every 5 years, or • CT colonography (virtual colonoscopy) every 5 years
Screening
• CRC charts • Breast sceening • Genetic screening • Sensitivity and specificity • Population-based versus opportunitistic • Screening for other diseases (infectious, diabetes, strokes, heart disease). • Screening for cancer • Factors influencing screening (cost, incidence, test sensitivity, what do do after identifying ill people, ect)
Efficacy of Screening
• Early detection • Public view: favorable • Medical view: no harm, do benefit, ↓ mortality • Screening for average risk • Screening for high risk • Recurrence (e.g., cancer) or new
Importance of Screening Tests
• False positives' impact on the health care system and anxiety (PSA testing) and impact on employment, insurance, and labeling. • False negatives and early-stage cancer for cure and prognosis.
Ethical, legal, and social issues
• Implications for other family members who may not be involved or interested in the receipt of genetic risk information • Consequence of labeling healthy individuals with a disease predisposition • Profound social and cultural significance of genetic testing
Symptoms and Diagnosis of Breast Cancer
• Mass • Tumor spread • Mammography changed clinical picture • Pathologic confirmation by cytologic or histopathologic examination
Genetic Screening Rationale
• Potential to reduce burden of cancer by early detection or primary prevention to at-risk individuals • Spare those who receive true negative results the burden of unnecessary screening and prevention procedures
Breast Cancer Screening
• Screening tests: BCE, BSE, Film screen mammography, digital mammography • 16% of cancers found at screening as DCIS • DCIS -> invasive cancer • Biologic markers e.g. low grade nuclear changes -> DCIS
The screening process
• The evidence for screening • Available resources • Bias (more observations after screening, selected cancers not entire population) • Randomized trials • Intervention and control groups should be comparable • Epidemiology and natur
Prevention and Screening
• The need for disease control & prevention - Framework for disease control & prevention • Chronic disease epidemiology - Genetic factors - Environmental factors - Risk assessment • Strategy for prevention - Early detection - Chemoprevention
Sensitivity
• The proportion of people with the disease who will have a positive result. A highly sensitive test correctly identifies patients with a disease. • A test with 85% sensitivity will identify 85% of patients who have the disease, but will miss 15% of patients who have the disease. • Also called the true positive rate • A highly sensitive test can be useful for ruling out a disease if a person has a negative result. For example, a negative result on a pap smear probably means the person does not have cervical cancer.
Specificity
• The specificity is the proportion of people without the disease who will have a negative result. • In other words, the specificity of a test refers to how well a test identifies patients who do not have a disease. A test that is 95% specific will identify 95% of patients who do not have the disease. • also called the True Negative Rate • Tests with a high specificity (a high true negative rate) are most useful when the result is positive. A highly specific test can be useful for ruling in patients who have a certain disease.
Breast Cancer Screening Guidelines (ACS, 2010)
• Yearly mammograms recommended starting at age 40 • CBE every 3 years for women in the 20s-30s and every year for women 40+ • BSE is an option starting in their 20s. • Family history and genetic tendency-- be screened with MRI in addition to mammograms.
Types of Breast Cancer
•Majority ductal •Invasive ductal carcinoma* •Invasive lobular carcinoma •Tubular carcinoma •Medullary carcinoma •Mucinous carcinoma •Inflammatory breast carcinoma (IBC) •Ductal carcinoma in situ •Lobular carcinoma
Objectives of Colorectal Cancer Screening
•Prevent cancers by detection and resection of adenomatous polyps •Detection of surgically curable colorectal cancers (Stages 1, 2)