PH: Cancer Screening

Question 1

What is meant by ‘lead-time bias’?

Answer 1

The length of time between the detection of a disease and its usual clinical presentation and diagnosis

Question 2

What is meant by ‘length-time bias’?

Answer 2

The apparent increase in survival due to the tendency to selectively detect slowly growing cancers at screening examinations instead of typical cancers

Question 3

Define ‘survival’

Answer 3

Measures the average time from diagnosis to death, not the number of deaths. Example: how long someone will live after being diagnosed with breast cancer is their survival

Question 4

Define ‘mortality’

Answer 4

Measures the number of deaths in a given population. Example: mortality is when in 1,000 women of 50-54 ages, the number of women who will die from breast cancer each year

Question 5

How can you avoid length-time and lead-time bias in cancer screening results?

Answer 5

By using mortality from the cancer in question as an end-point instead of survival

Question 6

Describe the screening programme for breast cancer

Answer 6

2 view mammography every 3 years women aged 50-69

Question 7

Describe the screening programme for cervical cancer

Answer 7

Cervical smear every 3-5 years for women aged 25-64

Question 8

Describe the screening programme for colorectal cancer

Answer 8

Faecal occult blood examination every 2 years for those aged 50-69

Question 9

What’s the biggest risk factor for breast cancer?

Answer 9

Age