Ethical issues and cancer screening

1. Ethical issues and cancer screening

2. Efficacy The extent to which a specific intervention, procedure, regimen, or service produces a beneficial result under ideal conditions. Ideally the determination of efficacy is based on the results of a randomised controlled trial. Last JM (ed). A Dictionary of Epidemiology. Third edition New York: Oxford University Press, 1995.

3. Effectiveness The extent to which a specific intervention, procedure, regimen, or service, when deployed in the field in routine circumstances, does what it is intended to do for a specified population. Last JM (ed). A Dictionary of Epidemiology. Third edition New York: Oxford University Press, 1995.

4. Assessing the Efficacy of Screening Lead-time bias Length bias Selection bias Overdiagnosis bias

5. Screened X X death Not screened X X death Disease begins Screen diagnosis Signs/symptoms

6. Screened X X death Not screened X X death Disease begins Screen diagnosis Signs/symptoms Survival time

8. __________ ____________________________ _______________ __________ ___________ ______ ________________________________ ________ _____________ ________ ____ _______ _________ ____________________ _____ _______ ___________ ___________ _________________________ _____________ Horizontal lines represent the pre-symptomatic screen-detectable phase in various individuals

9. screenscreen __________ ____________________________ _______________ __________ ___________ ______ ________________________________ ________ _____________ ________ ____ _______ _________ ____________________ _____ _______ ___________ ___________ _________________________ _____________

11. Cumulative breast cancer mortality (Deaths per 1,000 women entered after 7 years follow-up) Trial Non-attenders Controls HIP 2.7 4.3 Stockholm 1.8 1.5 S2C 4.5 2.1 Malmo 5.6 3.1

14. Design of RCT Study participants Intervention group Control group Outcome (breast cancer mortality)

15. Randomised controlled trial Population-based Appropriate outcome measure Intention to treat analysis

16. Population based screening differs from other medical interventions because it is offered to asymptomatic people with the understanding that they will benefit

19. Benefits and risks of screening for cancer Benefits: Risks: Improved prognosis for some Longer morbidity for those people diagnosed by screening. whose prognosis is unaltered. Less radical treatment which Over-treatment of questionable cures some people with early cancer. abnormalities. Reassurance for those with False reassurance for those with negative test results. false negative results. Anxiety and sometimes morbidity for people with false positive results. Adapted from Chamberlain JM. J Epid Com Hlth 1984; 38: 270-7.

20. Sensitivity and Specificity of FOBT Nottingham RCT: • Sensitivity 53.6% • Specificity 98% • PPV 10% Hardcastle JD, Chamberlain JO, Robinson MHE, et al. Randomised controlled trial of faecal-occult blood screening for colorectal cancer. Lancet 1996; 348: 1472-7.

21. Predicted outcome of 1,000 FOBTs • True positives 2 • False negatives 2 • False positives 18 • True negatives 978 • Number requiring colonoscopy 20 • Number diagnosed with CRC 2 • Number diagnosed with an adenoma > 10mm 6 • Number with no abnormality detected 12