Colorectal cancer: screening

Overview

• most cancers develop from adenomatous polyps. Screening for colorectal cancer has been shown to reduce mortality by 16%
• the NHS offers home-based, Faecal Immunochemical Test (FIT) screening to older adults
• a one-off flexible sigmoidoscopy at the age of 55 years was trialled in England but was abandoned in 2021
  • this mainly due to an inability to recruit enough clinical endoscopist, exacerbated by the covid-19 pandemic
  • the trial, partly funded by Cancer Research UK, had shown promising early results and it remains to be seen whether flexible sigmoidoscopy will be used as part of a future bowel screening programme

Faecal Immunochemical Test (FIT) screening

Key points

• the NHS now has a national screening programme offering screening every 2 years to all men and women aged 60 to 74 years in England, 50 to 74 years in Scotland. Patients aged over 74 years may request screening
• eligible patients are sent Faecal Immunochemical Test (FIT) tests through the post
• a type of faecal occult blood (FOB) test which uses antibodies that specifically recognise human haemoglobin (Hb)
• used to detect, and can quantify, the amount of human blood in a single stool sample
• advantages over conventional FOB tests is that it only detects human haemoglobin, as opposed to animal haemoglobin ingested through diet
• only one faecal sample is needed compared to the 2-3 for conventional FOB tests
• whilst a numerical value is generated, this is not reported to the patient or GP, who will instead be informed if the test is normal or abnormal
• patients with abnormal results are offered a colonoscopy

At colonoscopy, approximately:

• 5 out of 10 patients will have a normal exam
• 4 out of 10 patients will be found to have polyps which may be removed due to their premalignant potential
• 1 out of 10 patients will be found to have cancer