Q&A: DR CLARE ALLEN
Consultant radiologist at The London Clinic on how the arrival of a new 3T MRI scanner is transforming the diagnosis and treatment of prostate cancer
Interview: Viel Richardson
Images: Christopher L Proctor
The London Clinic has recently installed a new Siemens Magnetom Vida 3T MRI scanner. How does 3T MRI differ from other forms of MRI?
3T is short for 3 tesla. The tesla rating refers to the strength of the magnetic signal the machine produces. Most diagnostic MRI machines are 1.5 tesla. The increase in signal strength gives us a higher signal-to-noise ratio, resulting in shorter scan times and higher resolution images.
Has MRI always been a key diagnostic tool for prostate cancer?
No, it hasn’t. In fact, when I was training, we were told that prostate cancer was one of those cancers you couldn’t see with scans. The amount of detail that we could get from organs inside the body was limited because scan times were long, and as the patient breathed or moved, it was hard to get good images.
With the increase in field strength—the signal strength generated by the scanner— and improvements in coil technology, we have been able to reduce those scan times. The 3T scanner also has very sophisticated motion detection, so patients no longer have to hold their breath for periods during the scan. They can breathe gently, and we can still get beautifully crisp images. Allied to the increasingly powerful software available to us, this has allowed for a huge change in the diagnostic potential of the scanner.
How has this impacted on your particular field?
The area I am interested in is the urinary tract, particularly the prostate, which is a gland about the size of a plum and buried deep in the pelvis. With the 3T MRI, we get incredibly high-resolution images that we can manipulate and interrogate in ways that have revolutionised prostate diagnosis. MRI has allowed us not only to obtain images of a tumour but also, using contrast enhancement and diffusion techniques, to look at its biology. So, we can locate it precisely, map its shape and size, and make an assessment of how aggressive it may be. In time, we may be able to see how tumours are responding to treatment, allowing us to stop a treatment that isn’t working and try another approach.
So MRI scanning is allowing you to accurately locate prostate tumours?
Yes it is, and once you have an accurate map of what is happening inside the prostate you can make better treatment plans. For example, before the patient goes into the theatre, the surgeon can plan precisely where to make the incisions and how much tissue to remove. Everything relates back to that initial image, so the higher the quality the better it is for everyone.
How does MRI help with diagnostics?
Prostate-specific antigen (PSA) is a protein produced by the prostate gland, and elevated PSA levels can suggest that there may be a malignant tumour present. In 2017, a trial called PROMIS showed that in about 25 per cent of men with a raised PSA there was no significant tumour present, so a biopsy would be unnecessary at that stage. Instead, it would be safe to just continue monitoring their PSA levels with follow-up MRI, if needed. Prostate MRI could be used to decide who needed a biopsy.
A study published this year called PRECISION showed that by using MRI to target where in the prostate to take a biopsy, you can take fewer samples from the patient and not miss the majority of significant cancer. MRI has now become a fundamental part of the diagnostic pathway in the UK, allowing us to determine whether the patient has significant disease. If we find that they do, these scans help us to characterise it more accurately, which then allows us to choose the most appropriate treatment.
Is this better than the biopsy approach?
Definitely. As part of the PROMIS study, patients were also given the usual ‘standard of care’ investigation, which involved about 12 cores being taken from the prostate for biopsy without the aid of scans to target the tumours. The results showed that about 50 per cent of tumours were missed, so a patient could be told they had no cancer when there was actually a significant chance that they did.
How was diagnosis through imaging first received?
I remember talking to a room full of consultants and radiographers on an overseas trip just over a decade ago about the prospect of diagnosing prostate cancer by MRI imaging alone. It was met with huge scepticism; it was considered impossible. Since then, there has been a sea-change in attitudes. From 2019, the European Association of Urology guidelines will recommend that all men being investigated for prostate cancer should have an MRI scan before a biopsy. It has been the most amazing journey. I have been privileged to work with urologists, radiographers, researchers and clinical staff in this area, and to witness a fundamental change in the diagnostic and treatment pathways of prostate cancer, for the better.
Was this an international effort?
You always have international partners, but this is something the United Kingdom should be very proud of. Most of the seminal work in this field has come from British institutions.
Why have you focussed on prostate cancers?
Prostate cancer is an interesting cancer because there is such a wide spectrum of disease. A lot of tumours we detect can be safely monitored, as they pose no danger to the patient, while others are very aggressive and need to be treated very quickly in order to save the patient’s life. MRI scans can help determine what type of tumour the patient might have, so it’s an area where it has been possible to make hugely beneficial changes for the patient. We are really leading the way on this in Britain. About 50 per cent of men here have an MRI scan before having a biopsy, and this number is rising each year, while in the US, for example, it is around 7 per cent.
Does the width of that spectrum make the management of prostate cancer complicated?
Excellent prostate cancer care involves a multidisciplinary approach, which they excel at here at The London Clinic. Every two weeks, everybody involved with the patient’s care—oncologists, urologists, radiologists and pathologists—meet to discuss their progress and plan the next move. We discuss the scans and any biopsy results, and work out the options for the patient’s treatment. This multidisciplinary approach is best for patient care and offers a personalised approach to their cancer treatment.
So, is operating the scanner a complex job?
Absolutely—it is not just a case of installing the scanners and off you go. It is a world away from plug and play. There is a great deal of physics involved in understanding the way the scanner works. The ability to get high quality scans from these machines is totally dependent on the skill of the radiographers. They need to be willing and able to think a little bit outside of the box and try to come up with imaginative ways of sorting problems. They need to thoroughly understand the myriad parameters you can set on this incredibly sophisticated piece of equipment. Finding the correct setup for an individual patient for a particular scan in a specific region is a very complex job. Getting the best out of the hugely sophisticated equipment requires a team effort, and this needs to be backed up by extremely good communication between everybody involved.
How are the scans constructed?
An MRI scan is made up from multiple sequences each one taking between three and eight minutes to acquire. For a prostate scan, there may be eight or 10 sequences, each of which will have its own parameters, such as echo time, signal-to-noise ratio, orientation, width of image slice, and so on. Each sequence is designed to bring out a specific aspect of whatever we are investigating. In total, the patient will be inside the MRI scanner for between 30 and 40 minutes. The scans are viewed on a high-resolution monitor where they can be manipulated in 3D and reported.
Looking forward, what would you like MRI scans to achieve?
I would love the scans to be quicker. At the moment, they take 30-40 minutes, even with the 3T scanner. Some patients find it difficult to lie still or lie flat for that length of time, or they could be claustrophobic, so quicker scans would benefit them. Also, we are getting better at designing sequences, so I think we will soon be able to look at the chemical makeup of tumours and the effects of chemotherapy or radiation therapy on the tumour. These types of scan are not available for normal clinical use at the moment, but are there in the realm of research—I’m really looking forward to them being ready for clinicians to use.
In the end, the holy grail in medicine is truly personalised care for each patient. Getting as much information as possible about the individual patient’s tumour is key to this. The kind of information we can get from images produced by the 3T scanner helps take us one step closer to that goal.