Aspirin Foundation Meeting 2013
Chemoprevention and screening programmes for bladder cancer
Prof Richard Logan - University of Nottingham, UK
Peter Elwood asked me to talk about what role chemoprevention might have in an area where bowel cancer screening is taking place. Across the European community about little more than half of the member countries have screening programmes in operation or are about to start them. So I looked at what evidence we had for the effectiveness of the various screening programmes. What I would say is that although the screening programme that’s in place in the UK is probably using the least effective screening approach, which is the acquired aecal occult blood test, the likelihood is that we will be moving to a faecal immunochemical test which has potentially at least twice the effect on reducing bowel cancer mortality in those invited. We’re also introducing a flexible sigmoidoscopy programme which has just been started this year; it will take two or three years to roll out across England, but this will offer flexible sigmoidoscopy to people aged 55.
Has there been criticism over the UK screening programme starting at 60?
There has been some criticism that that’s the case in England. The justification for starting at age 60 is that the screening programme, the roll-out of it is dictated by the availability of the colonoscopy resource. 60 was chosen as the starting age because if we had screened the younger population we would not have had the colonoscopy resource to screen them. In addition, the evidence we have is that uptake of bowel cancer screening in people between 50 and 60 is not all that good, significantly lower than it is in people over the age of 60. Of course the majority of bowel cancer, the vast majority of it, occurs after the age of 60. So while other countries have started at an earlier age and we may well reduce the age of starting, the bowel scope screening programme I’ve just mentioned is starting at 55, the evidence is we’ll get more effect at an older age group given the limited colonoscopy resource we have.
What is the evidence that aspirin can play a role in prevention of colorectal cancer?
The studies from both Peter Rothwell and from the recently reported follow-up of the Women’s Health Initiative is that possibly one might get a 40% reduction in colorectal cancer mortality but not until one has been taking aspirin for over ten years. That is a big drawback to using aspirin is that the effect is quite delayed. So the reason for there being interest in whether aspirin is particularly effective in the right side is that the endoscopic screening programmes using colonoscopy have shown reduced effectiveness on the right side of the colon. There are a variety of reasons for this: getting the colonoscope to the right side of the colon is technically more challenging than just doing the left side of the colon; the lesions that might develop into cancer on the right side of the colon are not as obvious and a further reason is that when it comes to remove them endoscopically they are technically difficult to remove. So those are some of the reasons put forward, there are additional reasons suggesting that the nature of the malignancy on the right side of the colon may be different, they may arise from serrated polyps, there may be different genetic make-up to the cancers and these are all things that would be some explanation for colonoscopic screening of the right side being less effective. Certainly the evidence is that it’s not as effective on the right side as it is on the left side. Of course flexible sigmoidoscopy doesn’t really deal with cancers on the right side of the colon anyway. So if the data from Professor Rothwell and from the Women’s Health Initiative is correct then an agent that is specifically more effective in the right side would be attractive.
