2 Clinical need and practice

The problem addressed

2.1 The purpose of this assessment was to evaluate the clinical and cost effectiveness of using quantitative faecal immunochemical tests in primary care to triage low-risk symptomatic populations (that is, identify those at greatest risk) for suspected colorectal cancer referrals.

2.2 Several lower gastrointestinal symptoms can suggest colorectal cancer, including rectal bleeding, a change in bowel habits, weight loss, anaemia, abdominal pain, and blood in stools (faeces). Sometimes, blood in stools is not visible (faecal occult blood) so tests are used to detect its presence. These faecal occult blood tests can be used in primary care to assess people who are at a low risk of colorectal cancer and help determine whether they should be referred for further investigations where they do not meet the criteria for a suspected cancer pathway referral outlined in NICE's guideline on suspected cancer.

2.3 Faecal immunochemical tests, a type of faecal occult blood test, are designed to detect small amounts of blood in stool samples using antibodies specific to human haemoglobin. They have been developed as an alternative to guaiac-based faecal occult blood tests, which involve using chemicals that react with the haem component of haemoglobin in the blood and produce a blue colour change if blood is detected. Sometimes, this colour change can happen because the chemicals react with food in a person's diet or with medicine that a person is taking; this can lead to false test results. Because the faecal immunochemical tests are designed to specifically detect human haemoglobin, they may give more accurate test results than guaiac-based tests. The faecal immunochemical tests target the globin component of haemoglobin, which degrades as it travels through the gastrointestinal tract, so these tests are less likely to detect globin from upper gastrointestinal bleeding.

The condition

2.4 Colorectal cancer is one of the most common cancers. In 2013 in the UK, 41,112 people were diagnosed with colorectal cancer and 15,903 people died from it (Cancer Research UK, 2016). Risk factors include older age, a family history of the disease, and having familial adenomatous polyposis or Lynch syndrome, colorectal polyps, or ulcerative colitis or Crohn's disease. Also, Jewish people of central and eastern European family origin are thought to be at increased risk.

The diagnostics and care pathways

Diagnosis

2.5 NICE's guideline on suspected cancer includes advice on assessing people presenting to primary care with certain clinical signs and symptoms that may suggest colorectal cancer. It makes the following recommendations:

Refer people using a suspected cancer pathway referral (for an appointment within 2 weeks) for colorectal cancer if:

  • they are aged 40 or over with unexplained weight loss and abdominal pain or

  • they are aged 50 or over with unexplained rectal bleeding or

  • they are aged 60 or over with:

    • iron-deficiency anaemia or

    • changes in their bowel habit, or

  • tests show occult blood in their faeces.

    A suspected cancer referral (for an appointment within 2 weeks) should also be considered for:

  • people with a rectal or abdominal mass

  • adults aged under 50 with rectal bleeding and any of the following unexplained symptoms or findings:

    • abdominal pain

    • change in bowel habit

    • weight loss

    • iron-deficiency anaemia.

2.6 NICE's guideline on suspected cancer also previously recommended that faecal occult blood tests should be offered to adults without rectal bleeding who:

  • are aged 50 or over with unexplained:

    • abdominal pain or

    • weight loss or

  • are aged under 60 with:

    • changes in their bowel habit or

    • iron-deficiency anaemia or

  • are aged 60 or over and have anaemia without iron deficiency.

2.7 The faecal occult blood tests were recommended in NICE's guideline on suspected cancer to triage referral to secondary care. The tests were intended to be used in selected groups of people who have symptoms that could suggest colorectal cancer, but in whom a definitive diagnosis of cancer was unlikely. That is, they had a low probability of having colorectal cancer (their age and symptoms have a positive predictive value of between 0.1% and 3% for colorectal cancer).

2.8 If a faecal occult blood test was positive, NICE's guideline on suspected cancer recommended that people in England should be referred using a suspected cancer referral to establish a diagnosis. Faecal occult blood can be caused by conditions other than colorectal cancer, such as colorectal polyps and inflammatory bowel disease, so further assessment with a colonoscopy is needed to diagnose colorectal cancer; a positive faecal occult blood test was not intended be used alone.

2.9 Colonoscopy is considered to be the gold standard for diagnosing colorectal cancer because the entire colon can usually be seen and biopsies can be taken to assess the tissue in a laboratory to determine whether the sample contains benign or malignant cells. CT colonography can be offered as an alternative for people with comorbidities that make colonoscopy unsuitable. Colonoscopy is usually done as an outpatient procedure, with people having the procedure being offered sedation or painkillers.

2.10 The most common finding during a colonoscopy is colorectal polyps, which can be removed using cauterisation or a snare. If colorectal cancer is confirmed, NICE's guideline on diagnosing and managing colorectal cancer recommends further imaging tests, such as CT or MRI, to stage the cancer and determine what treatment is needed. Colonoscopy may also find other bowel diseases such as Crohn's disease, ulcerative colitis and diverticulosis, which may need further treatment and follow-up. People with a positive faecal occult blood test but no abnormalities detected during colonoscopy may be referred for further testing if a clinician thinks this is needed.

Treatment

2.11 After diagnosis and staging, colorectal cancer may be treated with surgery, chemotherapy and radiotherapy, or sometimes with biological agents such as cetuximab. Treatment depends on the stage of the cancer and is described in more detail in NICE's guideline on colorectal cancer.

  • National Institute for Health and Care Excellence (NICE)