How is severe asthma defined and who does it affect?
Internationally, severe asthma is defined as anybody who is on maximum therapy, which has no measurable side effects, but still have symptoms of persistent asthma. In the UK, that effectively means people who require oral steroids for their asthma two or more times a year.
Severe asthma affects 5% of the population of asthma sufferers. There are approximately 8 million people in the UK with asthma, so 5% of those is about 400,000.
What is bronchial thermoplasty and when was it developed?
Bronchial thermoplasty was an idea that came from American and Canadian researchers around 15 years ago. The first research procedure done in the UK was approximately 12 years ago.
We were very much central to that research, as were other centres in the UK. But it was only given approval for use on the National Health Service in the UK 3 years ago.
There are a number of factors that go on in an asthma attack, but one of those factors is constriction of muscle which is in the airway wall.
All of your airways are lined by a superficial skin layer, which is just one cell deep, and then beneath that is a band of muscle which is circular. In actual fact, it's more like a spiral - it's a bit like an old fashion “slinky” toy.
In practice, the muscle is designed like that. But when the muscle contracts, it closes the airway.
What bronchial thermoplasty does is apply thermal energy which temporarily damages the skin layer, the superficial layer of cells, but they recover within 7 days.
But it also damages the smooth muscle cells that create this spiral of muscle. The smooth muscle cells, when damaged, do not have the capacity to regenerate so, you get permanent damage to the smooth muscle.
The heat is applied in tangential lines, which essentially breaks the spiral. Instead of then having a circumferential ring of muscle, you've got patches of muscle which don't form a complete spiral. Then, when the muscle tries to contract, it doesn't cause closure of the actual airway.
By what mechanism is bronchial thermoplasty thought to reduce the frequency and severity of asthma attacks?
It prevents airway closure, but some data we presented at the British Thoracic Society meeting last week also suggests that it might possibly have an anti-inflammatory action as well.
How many centres in the UK offer bronchial thermoplasty and is this number on the rise?
Yes, the number of centres taking this up is increasing. There are 11 active centres in the UK at present.
While the procedure has an initial cost outlay, we find that bronchial thermoplasty is very cost effective as the reduction in hospitalizations means it pays for itself within the first few years.
How do these figures compare to other countries?
The Americans, as you would anticipate, have many active centres. But around the world, there is slow progression in the expansion.
For example, the first in Norway started a couple of months ago, which is the first in Scandinavia but there's another four or five sites in Scandinavia that are about to start.
There are four centres in Spain, there's a few centres in France, seven in Germany, nine in Italy, one in the Czech Republic, one in Switzerland, seven in Belgium who are all active now. But Europe and USA are not the only geographies with BT, South America has also been operating centres in Brazil and Argentina, there are also operating centres in Asia and we are just starting to open centres in Japan.
Canada and South America have been active for a long time because they were involved in the original research, and South America is fairly active as well.
Please can you outline the new BTS/SIGN guidelines with regards to bronchial thermoplasty?
In the new BTS/SIGN guidelines, bronchial thermoplasty is accepted as a treatment option for patients who are uncontrolled despite optimal therapy.
In the BTS guidelines, we refer to it as “Step 5” - that is when all other treatments have been tried and the patient still needs oral steroids either continuously or frequently.
How do these guidelines compare to the recent inclusion of bronchial thermoplasty in the Global Initiative for Asthma (GINA) guidelines
They're very similar, and the GINA ones, in a way, probably aren't that big an influence.
Last year the American Thoracic Society/European Respiratory Society initiative guidance was also published. These guidelines stated that if you were doing bronchial thermoplasty, it should only be done as some sort of registry or clinical trial. That caused a little bit of an issue and controversy over the development of bronchial thermoplasty.
In light of this, in the UK, and also in a broader sense internationally, the data of every patient who takes part or has bronchial thermoplasty is being stored and kept on a registry confidentially, i.e. with the patient's details excluded, so we can put the data together to analyse it prospectively as we're going along with clinical developments of this treatment, because we do not know that much about it.
I think one thing to say is that if a drug gets to market, several thousand patients will have had that drug before it gets a license. But with a medical device and, for example, with bronchial thermoplasty, this got a license and was starting to be used when only about 300-400 patients had actually had it in research, so there is a massive difference.
What do you think the future holds for bronchial thermoplasty and severe asthma treatments as a whole?
The great thing that's going on with severe asthma at the moment is that every patient is being treated as an individual.
Patients' phenotypes, or what you might just call the “pattern of asthma” is being assessed, because what we now know is that severe asthma isn't just one condition it's actually lots of similar conditions linked together. A treatment, whichis good for one patient isn't necessarily good for another patient.
This is then getting us to a phrase that's being used widely, which is “patient-specific treatment.” So, you're looking at the patient, doing lots of tests on them, working out what the right treatment is for that patient.
Critical for the future of bronchial thermoplasty is finding out which patients it is most suited for.
I think there is likely to be a significant expansion in the amount and use of bronchial thermoplasty over the next 5 years, but we have to work out and understand where it is best placed because it's not a treatment without some hardship for the patient and even a small amount of risk for the patient, and it consumes a lot of medical health-care time to do it.
But once it's done, we know it works for 5 years and it probably works for longer than that, whereas drugs, of course, have to be kept on being used.
Are the muscle cells damaged during bronchial thermoplasty likely to recover after 5 years?
They don't regenerate at all as far as we can tell. Indeed, the first patients I did 12 years ago, research patients, are still extremely well.
It looks like a one-off treatment last a long time, however, we need time to gather more evidence of this.
Is bronchial thermoplasty going to be beneficial to all asthma sufferers?
This isn't a magic wand for everybody with asthma and only a small portion of people with asthma will be suitable. It will not be the case that everybody can have this and never take an inhaler again.
It's also not a cure. Bronchial thermoplasty may improve a patient's asthma, but it doesn't get rid it.
Where can readers find more information?
We ask all our patients considering this treatment to go on to the Boston Scientific website, which has a link to the Bronchial Thermoplasty, which describes the procedure in both cartoon and real-life video.
For UK readers I would recommend Asthma UK patient charity as they give unbiased advice on what to do.
About Dr. Rob Niven
Rob Niven is Senior Lecturer in Respiratory Medicine, University Hospital of South Manchester NHS Foundation Trust, Manchester. Dr Niven leads one of a small group of national centres or networks, providing specialist dedicated asthma care across the UK. In collaboration with the rest of the North West Severe Asthma Network, his unit provides severe asthma care to a population of nearly 8 million.
At UHSM alone over 1,500 patients with severe asthma are under regular follow-up with 200 new referrals per year. The national network, has resulted in a shared registry of patients, management algorithms and recent developments of specialist commissioning and focussed research strategies.
Dr Niven has been involved in pioneering treatments for respiratory disease, including being primarily responsible for the innovations of hypertonic saline as a therapy for bronchiectasis and anti-fungal therapy being used in severe asthma patients with fungal allergy. His work has also involved him early in bronchial thermoplasty treatment both at a research phase and in clinical practice, being the first active English centre at both phases of this device development.
He currently leads on a number of clinical asthma projects of clinical registries, and recruits to trials of patients for new therapies in severe asthma.
He has just been appointed as chair for the next revision of SIGN/BTS asthma guidelines (severe asthma section).
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