Investigating suspected colorectal cancer with faecal immunochemical testing (FIT) in primary care: a review of international guidance

Recommendations for use of the faecal immunochemical test (FIT) for investigating low-risk symptoms of colorectal cancer in primary care vary across the world. Here, CanTest Faculty member Dr Sarah Bailey explains more about clinical practice guidelines for symptomatic patients, in a systematic review published this month in Family Practice.

Colorectal cancer is the third most common cancer worldwide, accounting for around 10% of all new cancers, and is the second most common cause of cancer death (1). As the symptoms of colorectal cancer are often vague and frequently caused by benign conditions, selection for investigation can be difficult. As a result, colorectal cancer is often diagnosed at an advanced stage, leaving few curative options (2). Diagnosing colorectal cancer at an earlier stage results in better treatment options and improved survival (3,4).

Researchers and clinicians are trying to find ways to diagnose colorectal cancer at an earlier stage; one way to achieve this is to investigate people for possible colorectal cancer when they have low risk symptoms, such as stomach ache. The faecal immunochemical test (FIT) has been developed to triage patient with low risk symptoms of colorectal cancer. Those with a positive FIT go on for further investigation, usually by colonoscopy. A negative FIT means that colorectal cancer is extremely unlikely, and the patient does not need any further investigation, although they are advised to see their GP again if their symptoms persist.

The FIT works by detecting small amounts of haemoglobin in a stool sample. Early stage colorectal cancer can cause bleeding into the gut, and the FIT detects that bleeding. Even if the patient has a positive FIT, it does not mean they definitely have cancer – only around 7% do.

FIT has been rolled out across the UK for testing patients with low risk symptoms of colorectal cancer, but guidance for using the test varies in different countries. In this systematic review, led by Dr Sarah Bailey and Dr Marije van Melle and published in Family Practice (5), we reviewed current worldwide recommendations around the assessment of colorectal cancer symptoms to determine how FIT is used to triage patients with symptoms of possible colorectal cancer in primary care.

We found that worldwide guidance for primary care clinicians on the use of FIT varies greatly, and FIT is only recommended for primary care symptomatic patients in three countries: Australia, Spain, and the UK (excluding Scotland). These recommendations are based on a systematic review of studies that included patients with lower GI symptoms suggestive of colorectal cancer (6). That review reported the sensitivity of FIT as 92.1% – 100% (meaning at least 92% of patients with colorectal cancer are identified as such by the test), and specificity as 76.6% – 85.5% (at least 76% of patients without colorectal cancer are correctly identified). Of the 10 studies included in that systematic review, only one was based in primary care (7), where FIT was performed at the point of referral, rather than to triage referrals.

The evidence on FIT to date comes from heterogenous populations at different stages of the care pathway, with different thresholds, and different assays used; this heterogeneity adds to the difficulty in making clear recommendations. Future updates to recommendations for investigating possible colorectal cancer may begin to integrate FIT for this low-risk CRC symptoms group as more evidence emerges. There is also a lack of evidence about patient preferences for testing with FIT versus colonoscopy; a gap which must be addressed.

1. International Agency for Research on Cancer. Colorectal cancer-Globocan 2018. The Global Cancer Observatory. 2019

2. McPhail S, Johnson S, Greenberg D, Peake M, Rous B. Stage at diagnosis and early mortality from cancer in England. Br J Cancer. 2015

3. Statistics O of N. Cancer survival by stage at diagnosis for England (experimental statistics): Adults diagnosed 2012, 2013 and 2014 and followed up to 2015. Off NatlStat. 2016

4. Neal RD, Tharmanathan P, France B, Din NU, Cotton S, Fallon-Ferguson J, et al. Is increased time to diagnosis and treatment in symptomatic cancer associated with poorer outcomes? Systematic review. Br J Cancer [Internet]. 2015;112 Suppl:S92-107. Available from: http://www.ncbi.nlm.nih.gov/pubmed/25734382

5. van Melle M, Yep Manzanob S, Wilson H, Hamilton W, Walter FM, Bailey SER. Faecal immunochemical test to triage patients with abdominal symptoms for suspected colorectal cancer in primary care: review of international use and guidelines. Family Practice. 2020;1-10

6. Westwood M, Ramos IC, Lang S, Luyendijk M, Zaim R, Stirk L, et al. Faecal immunochemical tests to triage patients with lower abdominal symptoms for suspected colorectal cancer referrals in primary care: A systematic review and cost-effectiveness analysis. Health Technology Assessment. 2017

7. Mowat C, Digby J, Strachan JA, Wilson R, Carey FA, Fraser CG, et al. Faecal haemoglobin and faecal calprotectin as indicators of bowel disease in patients presenting to primary care with bowel symptoms. Gut. 2016