Breast and Colon Cancer Screening

Question 1

What makes good screening? 2

Screening principles
the Disease 3
the Test 3
the programme

Answer 1

• detect true positive
• reject true negative

The disease

• Recognise early
• Treatment available early
• Must be sufficiently common in general public

The test

• Sensitive and specific
• Safe and accessible
• Inexpensive

Question 2

Screening bias
Length-time bias
3

Lead time bias
3

Answer 2

Length-time bias
- screening detects more indolent disease
- still same amount of aggressive tumours detected
- but improved outcome to the indolent tumours detected
which would have been picked up later when symptomatic

Lead- time bias
- screening detects earlier disease/ pre-symptomatic
- compared to symptomatic individuals survival can appear prolonged even though treatment doesn’t change
due to length of time between diagnosis and death increasing

Question 3

Breast Cancer Screening 
who
age 
test 
how often 

Colorectal Cancer Screening
who 
age
test
how often
- one off can have...at age...
- mortality of...
- what if they refuse....

FOB vs FIT

If you have …. or …. then …..

Answer 3

History, Exam, Mammogram

F, Age 50-69/70yo annual, 2 or 3 yearly mammogram

Men and Women 50-74yo
FOB test every 2 years
If +ve required to 2 more tests and then diagnosis on colonoscopy
- a one off flexi-sigmoidoscopy is offered at 55yo (but colonscopy has higher sensitivity)
- mortality of colonoscopy is 1-1000
- Flexi-sig every 5-10 years in those who refuse colonscopy with yearly faecal occult blood test

FOB vs FIT
FOB is 3 diff samples on 3 diff days
FIT is 1 on 1 day
FIT is superior, more sensitive and not triggered by animal blood in diet etc.

If FAP or HNPCC
- Surveillance colonoscopy every 1-3 years