Population screening: Discussion

From Cancer Guidelines Wiki

Unresolved issues

There is currently insufficient evidence from appropriately designed studies to determine the following:

  • the diagnostic performance of non-FOBT faecal or blood-based cancer-specific biomarker assays, and whether these are influenced by participant age, sex, or risk of colorectal cancer
  • the effectiveness and cost-effectiveness of population screening based on colonoscopy, CT colonographyAlso known as virtual colonoscopy, a medical imaging procedure that uses low dose radiation CT scanning to obtain an interior view of the colon (the large bowel) that is otherwise only seen with a more invasive procedure where an endoscope is inserted into the rectum and passed through the entire colon., faecal DNA biomarkers, or blood or plasma cancer-specific biomarkers such as DNA
  • the effectiveness and cost-effectiveness of population screening based on combinations of screening modalities
  • the effectiveness and cost-effectiveness of population screening in people younger than 50 years or older than 75 years.

Other unresolved issues include:

  • whether the inappropriately high rate of colonoscopy in Australia reduces effectiveness of the NBCSPThe National Bowel Cancer Screening Program. An Australian screening program that aims to reduce illness and death from bowel cancer through early detection or prevention of the disease.
  • how the NBSCP should respond to the changing epidemiology of colorectal cancer, including incidence at younger age and changes in distribution of cancer within the large bowel
  • how to maximise participation rates.

Back to top

Studies currently underway

No evidence was identified from randomised controlled trials (RCTs) evaluating colonoscopy, computed tomography (CT) colonography, or cancer-specific faecal or blood biomarkers. Three RCTs evaluating colonoscopy-based screening are in progress:

  • The Northern-European Initiative on ColorectalReferring to the large bowel, comprising the colon and rectum. Cancer (NordICC)[1]
  • ColonoscopyAn examination of the large bowel using a camera on a flexible tube, which is passed through the anus. Versus Fecal Immunochemical Test in Reducing Mortality From ColorectalReferring to the large bowel, comprising the colon and rectum. Cancer (CONFIRM)[2]
  • ColorectalReferring to the large bowel, comprising the colon and rectum. Cancer ScreeningPerforming tests to identify disease in people before any symptoms appear. in Average-risk Population: Immunochemical Fecal Occult Blood Testing Versus ColonoscopyAn examination of the large bowel using a camera on a flexible tube, which is passed through the anus..[3]

Only one of these RCTs[2] includes a no-screening arm.

Back to top

Future research priorities

Future research opportunities include:

  • studies assessing the place of combinations of screening tests (e.g. iFOBTA test that can detect microscopic amounts of blood in stools. Types of FOBT include immunochemical FOBTs (iFOBTs), which directly detect haemoglobin using antibodies specific for the globin moiety of human haemoglobin, and guaiac FOBTs (gFOBTs), which detect peroxidase activity, an indirect method for identification of haemoglobin. every 2 years and flexible sigmoidoscopy every 10 years (at ages 55, 65 and 75 years)
  • studies on screening tailored to the presence of special risk factors (e.g. adjusting the starting age of screening, using more sensitive iFOBTA test that can detect microscopic amounts of blood in stools. Types of FOBT include immunochemical FOBTs (iFOBTs), which directly detect haemoglobin using antibodies specific for the globin moiety of human haemoglobin, and guaiac FOBTs (gFOBTs), which detect peroxidase activity, an indirect method for identification of haemoglobin. conditions or combining screening tests tailored to factors such as sex, BMI, history of cigarette smoking)
  • evaluation of the performance characteristics of new versions of tests for faecal and blood-based cancer-specific biomarkers.

Back to top

References

  1. Bretthauer M, Kaminski MF, Løberg M, Zauber AG, Regula J, Kuipers EJ, et al. Population-Based Colonoscopy Screening for Colorectal Cancer: A Randomized Clinical Trial. JAMA Intern Med 2016 Jul 1;176(7):894-902 Abstract available at http://www.ncbi.nlm.nih.gov/pubmed/27214731.
  2. 2.02.1 ClinicalTrials.gov. Colonoscopy vs fecal immunochemical test in reducing mortality from colorectal cancer (CONFIRM) [NCT01239082]. [homepage on the internet]; 2016 Available from: https://clinicaltrials.gov/ct2/show/NCT01239082.
  3. Quintero E, Castells A, Bujanda L, Cubiella J, Salas D, Lanas Á, et al. Colonoscopy versus fecal immunochemical testing in colorectal-cancer screening. N Engl J Med 2012 Feb 23;366(8):697-706 Abstract available at http://www.ncbi.nlm.nih.gov/pubmed/22356323.
Back to top