Screening + Tumour Marker + cancer biology🏹🪁

Question 1

Biases in screening

Answer 1

Question 2

What is screening?

Answer 2

A strategy to detect potential health diseases in an asymptomatic population.

Question 3

Principle of screening

Answer 3

1. The condition should be an important health problem.
2. There should be a latent stage of the disease.
3. There should be a test or examination for the condition.
4. The natural history of the disease should be adequately understood.
5. There should be a treatment for the condition.
6. The test should be acceptable to the population.
7. The total cost of finding a case should be economically balanced in relation to medical expenditure as a whole. (Cost-effective)
8. Facilities for diagnosis and treatment should be available.
9. There should be an agreed policy on whom to treat.
10. Case-finding should be a continuous process, not just a “once and for all” project.

Question 4

Features of screening ( disease, test and screened population)

Answer 4

Features of the disease

• Significant impact on public health
• Asymptomatic phase during which detection is possible
• Outcomes improved by treatment during asymptomatic phase

Features of the test

• Sufficiently sensitive to detect disease during asymptomatic phase
• Sufficiently specific to minimize false positive results
• Acceptable to patients

Features of the screened population

• Sufficiently high prevalence of the disease to justify screening
• Relevant medical care is accessible
• Patients willing to comply with further work-up and treatment

Question 5

Types of Screening

Answer 5

1. Mass screening - entire population or subgroup irrespective of risk status
2. Selective screening- high risk group
3. Opportunistic screening - done as part of a clinical encounter for some other health condition
4. Multi-phasic screening - more than one test is applied for more than one condition

Question 6

Tools of screening ( example)

Answer 6

Tools for screening

1. Physical examination – DRE
2. Stool occult blood
3. Tumour markers – blood
4. Imaging - PET scan, MRI, MMG

Question 7

Types of Bias in Screening

Answer 7

1. Types of bias in screening
   a. Selection bias
   - screens high risk or low risk patients
   1. Volunteers are healthier, with lower mortality from all causes
   2. Observed benefit may be due to self-selection of volunteers
   3. Detection of disease that would never have become clinically evident during the time of the trial and follow-up

b. Lead Time Bias

- *early detection is confused with increased survival*
1. Lead time is that period of time between detection of condition by screening and when it ordinarily would be diagnosed d/t symptoms
2. Lead time depends on rate of disease progression and ability of screening test to detect

c. Length time bias (tumour)

• occurs when screening detects a disease that has long latency period
  1. Occurs due to heterogeneity of diseases (some long latency period, some short)
  2. Faster growing tumours generally have shorter asymptomatic phase than slower-growing tumours and so are less likely to be detected.
  3. However, faster growing tumours have poorer prognosis

Question 8

Screening issues in Malaysia

Answer 8

1. No structured mass population screening
2. Screening on targeted population
3. Based on most common cancer in Malaysia
   
   1. Breast cancer, CRC
4. Issues in Malaysia
   
   1. Poor data base
   2. Poor public awareness
   3. Cost
   4. Political issues
   5. Counselling not available
   6. Inadequate resources

Question 9

Example of Question, screening for colorectal cancer

Answer 9

Screening need to adjusted based on risk - high risk ( FAP, HNPCC, Lynch etc) should have colonoscope or sigmoidoscopy done

Question 10

Example of Question :
Screening for breast ca.

Answer 10

Gail Model (Breast Cancer Risk Assessment Tool)

The Gail Model is a statistical model used to estimate a woman’s risk of developing invasive breast cancer over:
* The next 5 years, and
* Lifetime risk up to age 90

Parameters:
- age
- age at first menstrual period
- age at first live birth
- family history of breast cancer
- numbers of previous breast biopsies
- atypical hyperplasia in breast biopsies

Question 11

Tumour Markers

Answer 11

Question 12

Cancer Biology

Answer 12

Question 13

Important termionology

Answer 13

Dysplasia is a premalignant condition characterised by increased cell growth, cellular atypia and decreased differentiation.
Disordered cell growth

Hypertrophy: increase in cell size without cell
replication.

Hyperplasia: increase in cell number due to cell division.

Metaplasia is the reversible replacement of one differentiated (mature) cell type by another differentiated cell type, usually as an adaptive response to chronic irritation or stress

Question 14

Basic of Chemotherapy

Answer 14