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What does the use of FIT in screening for bowel cancer mean
for me and my patients?
Dr Steve SmithConsultant Clinical Biochemist
Director, Midlands & NW BCSP Hub
Faecal Immunochemical Test (FIT) in Screening
• Same test as used in symptomatic patients
• Used very differently
Analytical Ability to Detect Blood in Faeces
Manufacturer's quoted sensitivityfor gFOBT 600µgHb/g
Screening officer's sensitivity 250µgHb/g
Proposed sensitivity for FIT at implementation 120 µg Hb/g faeces
0 µg Hb/gfaeces
Limit of detection for FIT assays
SYMPTOMATICVery sensitive assays
ASYMPTOMATICBalance that is sensitive enough to detect cancers but manageable and appropriate
FIT IN SCREENING vs. SYMPTOMATIC (ENGLAND)
FIT: Probable WorkflowNHSD
HUB
Supplier
PDF list of people to be invited
Kits labelledand prepared for posting
Participants
Returned kits openedand logged
Kits tested
Invite GenerationBCSS
Logging of kitsBCSS
Episode Result BCSS
Middleware
Abnormals SSP Helpline
Result to GP
Participation in Screening
• Increased participation:
- FIT pilot showed a overall increase of 7% in uptake to 66%.
- Previous non-responders almost double uptake from 13% to 24%.*
• Role of primary care crucial in capitalising on these benefits of FIT
- Continue with initiatives to improve participation
*Moss S, et al., Gut ; 2017, 66,1631
Length of Screening Round
• Screening rounds are likely to be shorter
- Peak time taken to return a kit reduces from 14 days to 7 or 8 days.*
• Current test requires 2 samples from 3 motions. FIT only requires 1 sample.
• Less people will require more than one kit as simpler screening process with no unclear results.
• *FIT pilot data
Quicker and Simpler0
.05
.1.1
5
7 14 21 28 35 42 50 7 14 21 28 35 42 50
gFOBt FIT
Den
sity
time to resultGraphs by fit
Quicker and Simpler• Only one sample required
• Sample collection device simpler
FIT Collection Devices
Sample Stability
• Time from sample collection to analysis critical.
• Very important that participants:
- Put sample collection date on tubes
- Post back to the Hub as quickly as possible after collection
• Repeat sampling devices sent out when:
- Sample collection to receipt in lab is >10days
- No date on sample and it was sent to participant >10 days prior to receipt in the Hub.
FIT Collection Devices
Less Repeat Tests• FIT tests are specific for human haemoglobin.
• Dietary interference eliminated.
Current test detects the presence of haematin which is the same in all mammals
FIT detects the protein chains which are species specific.
Current Screening Algorithm
Retest
NormalRECALL
in 2 Years up to age 74
COLONOSCOPY
UNCLEAR ABNORMALNORMAL
Retest
Normal Abnormal
Abnormal
Screening Algorithm FIT
Normal Abnormal
Rescreen in 2 Years
SSP & Colonoscopy
Impact
• More participants
• More abnormal results
• More cancers and adenomas detected
Impact of FIT Moss S, et al., Gut ; 2017, 66,1631
Impact: Age and Sex Moss S, et al., Gut ; 2017, 66,1631
7.9%
1.7% 1.56%
At this threshold FIT will yield approximately 1.5 to 2 abnormal results where the
current test gave 1
Moss S, et al., Gut ; 2017, 66,1631
Cancer Detection by FIT Threshold*Moss S, et al., Gut ; 2017, 66,1631
%
CCooper JA, et al. Br J Cancer 2018 118 285
False Negatives• At any threshold there will still be FALSE NEGATIVES
• Result letter will still advise people about symptoms
and seeking help.
• A normal screening result DOES NOT exclude bowel cancer it only reduces the risk of it being present.
• Really important that anyone with symptoms but an earlier NORMAL screening result is properly investigated.• Patient with previous Normal screen now meets NICE
criteria for symptomatic FIT should get a FIT test.
False Negatives: Why?
• Sampling• Stools are not homogeneous
• Haemoglobin degradation in vivo • Screening does not appear to detect proximal tumours
as well as distal ones.
• Anaemia?• Person may be bleeding but insufficient haemoglobin
• Are lesions bleeding continuously?
Future Developments
• Reduce the FIT threshold• Increase cancer and adenoma detection BUT increase
colonoscopy and pathology demands
• Refine the use of FIT• Simple adjustments to result calculation
• Adjust for gender
• Females appear to have less blood in faeces
• Adjust for age
• Older people appear to have more blood in faeces
Future Developments
• More Complex Adjustments using neural networks/artificial intelligence
• Previous screening result
• Difference between results
• Trend
• IMD
• Less affluent at greater risk for colorectal cancer
Future Developments
CCooper JA, et al. Br J Cancer 2018 118 285
Future Developments
• Reduction in screening age to add the 50 to 59 year olds:• When?
• How?
• Continuation of BowelScope?
Resources:
• Cancer Research UK Health Professional webpage bowel screening evidence and FIT test.
https://www.cancerresearchuk.org/health-professional/screening/bowel-screening-evidence-and-resources/faecal-immunochemical-test-fit
• Contact a CRUK Health Professional Facilitator to arrange a practice visit.
https://www.cancerresearchuk.org/health-professional/learning-and-support/tailored-help-for-gp-practice
• Bowel screening resources/GP good practice guideshttps://www.cancerresearchuk.org/health-professional/screening/bowel-screening-evidence-and-resources/bowel-screening-resources