Colorectal cancer screening

The goal of cancer screening is to detect cancer or pre-cancerous changes at an early stage. The benefits of early detection include increased survival, increased treatment options and improved quality of life.1

Australia currently has three national screening programs for the early detection of various cancers.2

Population-wide testing for all early signs of various cancers can lead to overdiagnosis which may cause more harm than benefit.3 However, these particular programs have demonstrated an acceptable benefit in detecting cancer without a significant cost of overdiagnosis.2
Read more about which tests make a difference to patient outcomes
.

Population screening for colorectal cancer

Screening for colorectal cancer using the faecal occult blood test has a mortality benefit between 15% and 33% in randomised controlled trials.4-9  Since the introduction of screening in Australia, the number of cancers identified at the earliest and most treatable stage has tripled from 15% to 40%.10,11

Colorectal cancer screening – the FOBT

Faecal occult blood tests are used to detect the presence of blood in the faeces. The presence of blood in the faeces may indicate bowel abnormalities including precancerous adenomas or colorectal cancer. This blood may be present in microscopic quantities, referred to as 'occult blood'.4

The Australian screening program favours the use of immunochemical FOBT tests over older guaiac FOBTs. The guaiac FOBT involves a biochemical test that can be confounded by ingesting meat products and requires dietary restriction prior to the test. The immunochemical test is more specific and does not require dietary restriction.

Two or three serial stools should be tested depending on the brand and type of test. Follow the manufacturer's instructions.1

It is essential that any positive FOBT is followed up.1

The positive predictive value of the immunochemical FOBT seen in the Australian CRC screening program was: 4

  • 5.1% - suspected cancer
  • 20.1% - suspected cancer or advanced adenoma.
  • 26.3% - all cancers including small adenomas.

For a comparison, family history and/or symptoms alone has a positive predictive value of 0.5% for cancer, 4.3% for advanced adenoma and 7.5% for cancer or any adenoma.4

For more information

References
  1. The Royal Australian College of General Practitioners. Guidelines for preventive activities in general practice (The Red Book) 8th Edition. Melbourne: RACGP, 2012. http://www.racgp.org.au/your-practice/guidelines/redbook/ (accessed 11 February 2013).
  2. Australian Institute of Health and Welfare. Cancer in Australia an overview 2012. 2012. http://www.aihw.gov.au/publication-detail/?id=60129542359 (accessed 4 March 2013).
  3. Welch HG, Black WC. Overdiagnosis in cancer. J Natl Cancer Inst 2010;102:605–13. [PubMed]
  4. Australian Institute of Health and Welfare. The Australian Bowel Cancer Screening Pilot and Beyond: Final Evaluation Report. 2005. http://www.health.gov.au/internet/screening/publishing.nsf/Content/2DDFA95B20302107CA2574EB007F7408/$File/final-eval.pdf (accessed 29 January 2013).
  5. The Cancer Council Australia and Australian Cancer Network 2005. Clinical Practice Guidelines for the Prevention, Early Detection and Management of Colorectal Cancer. 2005. http://www.nhmrc.gov.au/_files_nhmrc/publications/attachments/cp106_0.pdf (accessed 13 February 2013).
  6. Hardcastle JD, Chamberlain JO, Robinson MH, et al. Randomised controlled trial of faecal-occult-blood screening for colorectal cancer. Lancet 1996;348:1472–7. [PubMed]
  7. Kronborg O, Fenger C, Olsen J, et al. Randomised study of screening for colorectal cancer with faecal-occult-blood test. Lancet 1996;348:1467–71. [PubMed]
  8. Jorgensen OD, Kronborg O, Fenger C. A randomised study of screening for colorectal cancer using faecal occult blood testing: results after 13 years and seven biennial screening rounds. Gut 2002;50:29–32. [PubMed]
  9. Mandel JS, Bond JH, Church TR, et al. Reducing mortality from colorectal cancer by screening for fecal occult blood. Minnesota Colon Cancer Control Study. N Engl J Med 1993;328:1365–71. [PubMed]
  10. Cancer Council Australia. National Cancer Prevention Policy Bowel (colorectal) cancer. 2012. http://wiki.cancer.org.au/prevention/Bowel_cancer (accessed 7 February 2013).
  11. Ananda SS, McLaughlin SJ, Chen F, et al. Initial impact of Australia's National Bowel Cancer Screening Program. Med J Aust 2009;191:378–81.[PubMed]