Module: Epidemiology and Statistics

Topic 5


Topic 5: Should we screen for breast cancer and what do we tell women about the effectiveness of screening?

Objectives

When you have completed the reading and participated in the taught components for this week, we hope you will be able to

  • Describe the advantages and limitations of the UK Cancer registration systems in the UK, and apply these to other registries
  • Explain what is meant by incidence, prevalence, lead time and lead time bias 
  • Explain what is meant by sensitivity, specificity, and positive and negative predictive value and how these relate to the prevalence of the condition
  • Explain the Wilson and Jungner criteria and give examples of how they have led to screening decisions

 

Lecture: Should we screen for breast cancer?

There has been considerable debate about the effectiveness of breast screening in recent years. Starting with the article by Howard Wainer published in a Royal Statistical Society magazine, the lecture will explain the statistical concepts behind the reporting of information about breast screening: incidence, prevalence, lead time and lead time bias, sensitivity, specificity, and positive and negative predictive values and explain the Jungner and Wilson criteria for making decisions about screening with reference to breast cancer and prostate cancer. 

Seminar: What should we tell women about the effectiveness of breast screening?

In this seminar, you will compare two leaflets that explain the effectiveness of breast screening, thinking about the information that you think women would like to see in such a leaflet, and how to explain some of the figures and concepts covered in the lecture in as straightforward a way as possible.

In part of the seminar you will have a chance explore the effect of the sensitivity and specificity of a test combined with prevalence on positive and negative predictive values, and relate these to some real examples of different cancers.

You will also begin to think about how to design a study to answer some of the questions that are difficult to answer with present data and whether this would be either feasible or ethical; this will link to the next two weeks when you will be thinking in more detail about different study designs. 

Preparation for this week

Before the lecture

Read the article by Howard Wainer from Significance. In this article he attempts to explicate some of the statistical issues involved in the often fierce debate about whether and how to screen for breast cancer. How do you and some of your colleagues, family and friends feel about this issue and screening for other cancers? Does reading Wainer’s article change your mind? What other information do you feel you would like to have? You should do all of this before the lecture. This will help you to get the most out of the lecture.

 Between the lecture and the seminar you should familiarise yourself with the two breast screening leaflets that we are going to look at and compare in the seminar. Copies of the leaflets will be given out at the seminar but you may wish to download your own hard copies between the lecture and seminar if you want to annotate them in any way before the seminar.  

Lecture Notes and Powerpoints

Set Reading

  • Barker D, Cooper C, Rose G. Epidemiology in medical practice. (1998) Churchill Livingstone; 5th edition Chapters 7 and 8

ACADEMIC PAPERS

  • McPherson K: Screening for breast cancer - balancing the debate. BMJ 2010, 340:c3106 (Read it here)
  • McPherson K How we got it wrong with breast screening BMJ 2012;344doi: 10.1136/bmj.e3450 (Published 17 May 2012) (Read it here)
  • Wainer H. How should we screen for breast cancer. Significance 2011:March:28-30 (Read it here)

 

WEBPAGES

Additional reading