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Detectable f-Hb via FIT in may indicate CRC in younger symptomatic patients

Wed, 08/11/2021 - 11:38
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Faecal immunochemical testing (FIT) may assist healthcare professionals to identify which younger patients with higher risk symptoms may require colonoscopy or other diagnostics to further determine if they have colorectal cancer (CRC) or other serious bowel diseases, according to the outcomes from the NICE FIT Study. The findings were featured in the paper, ‘Finding the needle in the haystack: the diagnostic accuracy of the faecal immunochemical test for colorectal cancer in younger symptomatic patients’, published in the journal Colorectal Disease, on behalf of the NICE FIT Steering Group.

FIT is a non-invasive, quantitative immunoassay which detects the globin moiety of haemoglobin in faeces and can reliably measure the faecal haemoglobin concentration (f-Hb) to the nearest microgram of haemoglobin per gram of faeces (µg/g). However, the authors noted that there are no published data specifically evaluating the diagnostic accuracy of FIT in younger patients referred urgently with suspected CRC symptoms.

NICE FIT Study

Therefore, the NICE FIT Study was designed to investigate whether FIT could identify younger patients at higher risk of colorectal cancer or serious bowel disease including colorectal cancer, inflammatory bowel disease or advanced adenomas.

The primary end-point of this analysis was to establish the sensitivity of FIT for CRC in younger patients with symptoms of suspected CRC. The secondary end-points were to establish the diagnostic accuracy of FIT for CRC, advanced neoplasia (AN) (i.e., CRC and advanced adenoma [AA]) and serious bowel disease (SBD) (CRC, AA and inflammatory bowel disease [IBD]) in younger patients.

The NICE FIT study was a multicentre study of FIT in English patients referred urgently from primary care with symptoms of suspected CRC that were investigated with colonoscopy. Patients were recruited at 50 National Health Service hospitals across England and took part in the study with informed consent. Younger patients were defined as those referred urgently with symptoms under the age of 50 years, with a comparator population over 5o years of age.

In total, the study recruited 9,822 patients who underwent FIT and were included in the final analysis, of whom 1,103 were <50 years. The majority of patients were female (59.8%) and median age of patients in the <50 group was 44 years vs the median age in the ≥50 group of 67 years.

The most common finding in all age groups was a normal colonoscopy (51.3% of patients <50, 28.8% of patients ≥50). CRC was significantly less commonly diagnosed in younger patients (1.5% of patients <50 vs. 3.6% of patients ≥50, p<0.001), as were AAs (2.6% of patients <50, 4.5% of patients ≥50, p=0.004) and lower risk adenomas (13.1% of patients <50, 25% of patients >50, p<0.001).

IBD was significantly more commonly found in younger patients (7.9% of patients <50, 3.9% of patients ≥50, p<0.001) and as a result there was no overall difference in the incidence of significant bowel disease (SBD = IBD + AA + CRC), which was present in 12.0% (132/1,103 vs. 1,045/8,719) in both populations.

The positive predictive value for colorectal cancer increased from 4.2% (2.3%–6.9%) to 11.5% (5.9%–19.6%) at cut-offs of 2 and 150 µg/g, while the positive predictive value for serious bowel disease increased from 31.3% (26.3%–36.5%) to 65.6% (55.2%–75.0%) at the same cut-offs. The negative predictive value of FIT for colorectal cancer remained above 99.5% at all cut-offs.

The authors noted that this is the first study to specifically report on the diagnostic accuracy of FIT for CRC in younger patients with suspected bowel cancer symptoms and although the findings may not support the use of FIT as a test to rule out CRC in younger patients, it can help clinicians in primary care to identify patients who require urgent referral and investigation for serious bowel disease.

“FIT holds promise in the investigation of younger patients with bowel symptoms. Detectable f-Hb should indicate referral for investigation of SBD, which will be detected in one in three patients. Higher f-Hb concentrations above 150 µg/g confer a 12% risk of CRC and a 66% risk of SBD indicating urgent referral for investigation,” authors concluded. “Further work is required to assess the utility of FIT to risk stratify younger symptomatic patients who are likely to benefit from invasive investigations such as colonoscopy.”

This study was funded by NHS England awarded to RM Partners, the West London Cancer Alliance hosted by the Royal Marsden NHS Foundation Trust. The study is supported by the National Institute for Health Research Clinical Research Network Portfolio. Croydon University Hospital acted as study sponsor. Alpha Labs Ltd, particularly Matthew Davis and Emma Boxall, supported the study by providing FIT collection devices without charge. All FIT kits and reagents were provided by Alpha Labs. The study sponsors and funders had no role in study design; in the collection, analysis and interpretation of data; in the writing of the report; and in the decision to submit the article for publication.

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