Collaboration for Academic Primary Care (APEx) Blog
Collaboration for Academic Primary Care (APEx) Blog
Posted by Mark
23 June 2020
Sarah Bailey, University of Exeter
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.
Sarah Bailey and Marije van Melle’s poster presentation for systematic review, now published in Family Practice.
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 patient 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 still 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.
References