Bowel Cancer Screening and Symptomatic diagnosis - where lies the correct balance?
In this segment I discuss some of the questions posed by new screening techniques and how some newer technologies could help, though are delayed in being introduced because of high volumes of symptomatic referrals to hospital.
Referral to Hospital
Bowel symptoms are common and we all suffer them to some degree at different times (Bowel symptoms are dealt with on another page of this site). For a long time, the Dept. of Health and it's expert opinions have struggled with the concept that bowel cancer survival is relatively poor in Britain and felt that the way to improve it is to get more and more people with symptoms to clinics, then offering them more and more examinations. The latest NICE guidance - the bible by which doctors actions are judged - for bowel symptoms is named NG12 and a supplementary work DG (Diagnostic Guidance) 30 both reduce the timescales needed for urgent referral from 6 weeks to 3 weeks AND loosen the criteria for urgent referral, expecting a yield of those with cancer to fall from the previous 6% to the new 3% threshold. What might be readily apparent is that now some 97% of people do NOT have bowel cancer and can arguably be said to have been OVER-investigated.
The Two Week Rule (TWR) - when a GP thinks the patient may have cancer, they are entitled to a specialist clinic within two weeks.
I always need to remind myself that TWR doesn't stand for a "total waste of resources" but if often feels that way! The TWR produces worried people being referred to hospital to be tested for symptoms that often don't amount to much and may indeed have settled by the time of the appointment. Indeed, the TWR produces around a quarter of our bowel cancer diagnoses (more come from the routine appointments to clinic who are often made to wait for longer because they are displaced by "more urgent" referrals). Furthermore, no cancer survival advantage is seen in those diagnosed by the TWR over ANY other method except for emergency presentation. All in all, the TWR rule does very little except to use up precious resources in our endoscopy departments where we constantly struggle to meet timeliness targets and, if we don't meet these, our ability to offer screening and to expand those services is limited. It may not sound like it but, I do agree that if you've been referred for a colonoscopy test, it really ought to be done quickly for everyones' peace of mind.
The one exception for the TWR that I do think is important is if you have iron deficiency anaemia, in which case a bowel cause (malignancy) is found in about a quarter of patients.
Screening for Bowel Cancer
Screening for 60-75 year olds has already been discussed before here, and our local screening programmes have been running for a while now and are seeing record low numbers of patients coming through with abnormal results requiring colonoscopy which does reduce even further our ability to diagnose cancer in the screened group. It is important to remind ourselves that screening is the only way that we can diagnose cancer that we expect to be at an earlier and more curable stage than when it presents with symptoms or as an emergency.
During the last 2-3 years the Screening Programme has validated the use of the newest technology in screening - the Faecal Immunochemical Test (FIT) kit - for introduction into the screening programme. We are awaiting (as of March 2018) to hear what the sensitivity of the kit will be set to, i.e. the level at which it will be considered abnormal and a colonoscopy ordered. The higher the threshold, the more cancers will be missed by screening.
To me, it is something of an irony that the FIT threshold will likely be set at a high level of blood in the stool, because the country doesn't have enough space to screen as many people as we should for the very reason that another Government agency is recommending that symptomatic people (at low risk of cancer - see above - are referred by a TWR process that we know to be effete!
BowelScope is the given name to the screening method most recently adopted by the National Bowel Cancer Screening Service. At the age of 55, every person registered with a GP will be offered, if the programme is fully rolled out, a flexible sigmoidoscopy test during which any polyps up to 1cm are removed. If more than three polyps are detected, if any one is larger than 1cm, or if any of the polyps are microscopically advanced (technically, showing villous histology) a colonoscopy is ordered and the colon cleared of polyps. The scientifically proved hypothesis that, when polyps are removed, the rate of later bowel cancer is lowered, leading to a reduction in cancer risk by some 33% for colon cancer, 50% for rectal cancer and a mortality reduction of 43%, when analysed some 11 years later.
BowelScope is being rolled out now but a few problems have been identified with the program; it is logistically hard to deliver, very consumptive of endoscopy resource and may not be performing, in the real world, as well as it did in its trial and pilot phases. As a consequence, the UK National Screening Committee has looked at different strategies for screening and different proposals are out for national consultation. It will soon be decided whether BowelScope will carry on in some form, or if screening for Bowel Cancer will change to a modality involving FIT exclusively at a younger age (perhaps 52), though there are options being discussed for the sensitivity threshold, just as there are for FIT in the 60-75 age group.
The problem with Bowel Cancer Screening
Simply put, all screening causes harm, either directly or indirectly, and the main issues for Bowel Cancer Screening are the potential for false reassurance and complications that might arise from colonoscopy and the removal of polyps from the bowel. In some reports, bowel perforation, which mostly happens at the time of removal of polyps can be as frequent in 1:500 cases. This complication will mostly be resolved at some form of operation which most people would not even consider when taking a "Poo" test.
The Screening Programme takes particular effort to train and accredit colonoscopists at the highest level (and ensures continuously excellent performance during practice) but, even so, complications happen, albeit rarely. It makes sense then to be absolutely sure that patients are fit for colonoscopy and, indeed, in a symptomatic situation, that they really need the test.
Why aren't we using FIT now?
This is a simple question with a somewhat complicated answer though it can be summarised by saying that there aren't enough Screening Colonoscopists in the Country, or enough colonoscopy appointments to be offered in a timely fashion. I am given to understand that, in the event that BowelScope is phased out in favour of FIT testing from a young age, it will take between 3 and 5 years to get to a point of delivery. This I can understand but, in the same thought, wonder why there is so much pressure to refer symptomatic people to clinic for tests that, by comparison, will have only a small rate of discovering abnormalities.
Work is going on all of the time to train (and make experienced) new flexible endoscopists for both expert symptomatic colonoscopy and BowelScope programmes. The point being that everyone ought to have an examination by the very best person available and, even in the FOBT screening programme, important disease is missed and complications happen.
Using FIT for symptomatic patients?
One of the best ways of assessing risk of cancer even in patients with symptoms could be to use a FIT test before referral and only refer in those people with detectable blood in their stools. However, this would be to go against NICE guidance (which could put doctors in a difficult position if Bowel Cancers were missed). There are a lot more nuances than that and I will return to the subject another time.
Over the coming days I will write more as the story develops and I will write a lot more about FIT itself; it is a fascinating subject (to me at least) and I think it is very important that we patients fully understand how it is being used.