Cancer Research UK : Screening and cancer: the evidence

Screening and cancer: the evidence

Screening saves lives.

This page contains information about the links between screening and cancer. Click on the links below to read about specific topics.

Cervical screening
Breast screening
Bowel screening
PSA testing

You can find out more about the evidence behind other health topics in our other How do we know? pages.

Cervical cancer screening saves lives

In the 1950s, the death rates for cervical cancer began to fall by about 1% a year. But since 1988, when the NHS Cervical Screening Programme was set up, rates have decreased more rapidly by around 7% a year 1.

A Cancer Research UK study estimated that cervical screening has prevented an epidemic that would have killed about 6000 UK women every year 2.

Breast cancer screening saves lives

Many studies have shown that breast cancers are much easier to treat if they are detected early 3.

A Scottish research team found that survival from breast cancer improved by 11% between 1987 and 1993. They estimated that about half of this improvement was due to screening programmes 5. And studies from the International Agency of Cancer Research (IARC) and Cancer Research UK have found that screening has reduced breast cancer death rates by about 20-25% in women within the screening age range 6,7.

Bowel cancer screening will save lives

Most bowel cancers start off as harmless growths called adenomas. Only a small proportion of adenomas become cancers and this process takes a long time. Doctors can easily remove the vast majority of adenomas without the need for surgery. So if adenomas can be spotted before they become cancerous, many cases of bowel cancer could be prevented 8. Adenomas don’t usually produce symptoms so screening is an important way of spotting these cancer precursors.

The NHS has announced the rollout of a national bowel cancer screening programme by April 2006. Experts estimate that this programme could prevent about 1200 deaths every year in the UK from bowel cancer 9.

This screening programme will initially use a technique called faecal occult blood test (FOBT) to test for early signs of bowel cancer. Many studies have already shown that FOBT can reduce deaths from bowel cancer by about 20% 10-12. A clinical trial funded by Cancer Research UK will determine if a second technique, flexible sigmoidoscopy would be effective in preventing bowel cancer 13.

Screening for prostate cancer is not clear cut

Raised levels of prostate-specific antigen (PSA) in the blood can indicate prostate cancer. PSA levels can be measured by a GP using a PSA test. But PSA levels can rise because of many other reasons. So the PSA test is not foolproof. On its own, it cannot confirm a diagnosis of prostate cancer.

The use of PSA testing as a screening test is still controversial 14. All men have slightly different ‘normal’ levels of PSA. So not all men with high PSA levels have prostate cancer, and not all men with prostate cancer have high PSA levels 15.

Furthermore, not all prostate cancers are life-threatening. Half of men over 80 have cancer cells in their prostate but only 1 in 25 will die from prostate cancer. Presently, there is no way of distinguishing these slow-growing tumours from more aggressive ones. Because of a positive PSA test, men could therefore have unnecessary treatment for tumours that might have posed them no problems 14.

Doctors must provide men who are concerned about prostate cancer with full information about the pros and cons of PSA testing. You can find out more information about PSA testing in our CancerHelp UK website.

References

Sasieni, P., J. Cuzick, and E. Farmery, Accelerated decline in cervical cancer mortality in England and Wales. Lancet, 1995. 346: p. 1566-7.PubMed
Peto, J., et al., The cervical cancer epidemic that screening has prevented in the UK. Lancet, 2004. 364: p. 249-56.PubMed
Etzioni, R., et al., The case for early detection. Nat Rev Cancer, 2003. 3: p. 243-52.PubMed
Ugnat, A., et al., Survival of women with breast cancer in Ottawa, Canada: variation with age, stage, histology, grade and treatment. Br J Cancer, 2004. 90: p. 1138-43.PubMed
Thomson, C., et al., Improvements in survival for women with breast cancer in Scotland between 1987 and 1993: impact of earlier diagnosis and changes in treatment. Eur J Cancer, 2004. 40: p. 743-53.PubMed
Tabar, L., et al., Mammography service screening and mortality in breast cancer patients: 20-year follow-up before and after introduction of screening. Lancet, 2003. 361: p. 1405-10.PubMed
IARC, Breast Cancer Screening. IARC Handbooks of Cancer Prevention, ed. H. Vainio and F. Bianchini. Vol. 7. 2002, Lyon: IARCPress.
Scholefield, J., ABC of colorectal cancer. BMJ, 2000. 321: p. 1004-1006.PubMed
Atkin, W., Implementing screening for colorectal cancer. BMJ, 1999. 319: p. 1212-3.PubMed
Towler, B., et al., Screening for colorectal cancer using the faecal occult blood test, hemoccult. Cochrane Database Syst Rev, 2000. CD001216.PubMed
Hardcastle, J., et al., Randomised controlled trial of faecal-occult-blood screening for colorectal cancer. Lancet, 1996. 348: p. 1472-7.PubMed
Mandel, J., et al., Colorectal cancer mortality: effectiveness of biennial screening for fecal occult blood. J Natl Cancer Inst, 1999. 91: p. 434-7.PubMed
UK Flexible Sigmoidoscopy Screening Trial Investigators, Single flexible sigmoidoscopy screening to prevent colorectal cancer: baseline findings of a UK multicentre randomised trial. Lancet, 2002. 359: p. 1291-300.PubMed
Frankel, S., et al., Screening for prostate cancer. Lancet, 2003. 361: p. 1122-8.PubMed
Punglia, R., et al., Effect of verification bias on screening for prostate cancer by measurement of prostate-specific antigen. N Engl J Med, 2003. 349: p. 335-42.PubMed