The City of London, by definition, covers just one square mile. In reality though London reaches well beyond that.
But if you only had a map of that one square mile, it would be practically impossible for you to navigate the true breadth of the city.
Neurosurgeons and radiotherapists face a similarly tough challenge when looking at brain tumour scans. They often only get the ‘City of London’ map of the tumour, and there can be much more to it than meets the eye.
Only half the picture
“It’s hard to determine tumour from healthy brain tissue,” says Mr Nick de Pennington, a surgeon from the Department of Neurosurgery at the John Radcliffe Hospital & Department of Clinical Neurosciences, University of Oxford.
MRI works by using a very strong magnet to line up all the atoms in the body in one direction. Then the machine sends burst of radiofrequency waves which make the atoms change directions. When they go back to their original position they give off a signal, which the machine picks up and turns into a black and white picture.
But to find problems like cancers, doctors need to inject the patient with a special kind of dye that can help things stand out.
So before their MRI scan brain tumour patients are injected with a dye that enhances the many ‘leaky’ blood vessels, found in brain tumours. This means that the tumour glows brightly on the scan in comparison to the rest of the brain.
But the scan isn’t picture perfect because clinical imaging techniques only show one aspect of the tumour.
The vessels that aren’t leaky and are situated at the edge of the tumour don’t show up on the scan. It’s in this area that cells can often be the most aggressive and invasive. And, because they’re invisible, they’re often left behind during surgery, making the tumour likely to return.
The researchers show that this is because many tumours extend well beyond the visible ‘city limit’, as shown on their MRI scan.
“At the moment we’re making a best guess for the bits beyond the tumour on the scan. So knowing a bit more would be a huge advantage,” says Mr de Pennington.
Bringing it into focus
Now, for the first time, scientists have found a way to make the bits beyond the tumour also light up on the MRI scan.
They identified a protein, VCAM-1, which is linked to tissue inflammation caused by the brain tumours, and produced by blood vessels right at the edge of tumours. Conveniently, the protein is present on the inside of the vessels, providing an accessible target from the bloodstream.
The researchers also made a special dye that recognises and sticks to the protein, making it detectable on MRI scans and consequently making it easier to see the edges of the tumour.
While the research has, so far, only involved mice and more research is needed to see if the dye works just as well in humans, study author Professor Nicola Sibson, a Cancer Research UK scientist at Oxford University, says: “This is something we desperately need.”
The scan is not only used to diagnose and plan treatment, but it is also the ‘road map’ for a surgeon during the surgery.
Mr de Pennington explains that the scan functions as a guide to help the surgeons know what to take out. Like the way a car is linked up to a map via a Sat Nav, their instruments are linked up to the scan, so they know exactly where they are in the brain.
Prof Sibson adds: “We hope this will allow us to surgically remove more of the tumour. And, even if we can’t take it all out, we could re-scan the patient and see what tumour is left and then, perhaps, use radiotherapy to kill the remaining tumour cells.
“Ultimately this could prolong the patient’s time between initial surgery and when the brain cancer comes back. In the best-case scenario, however, we would cure that tumour and get rid of it entirely. Perhaps now we are one step closer.”
Mr de Pennington also sees this research helping when diagnosing patients as well as monitoring the progression of the disease after surgery.
“We have relatively crude tools to tell how the disease is behaving,” he explains.
“There are different patterns of tumour distribution. Some tumours are compact, while others spread further into the brain, and you don’t know where a particular patient sits on the spectrum. So getting more information would help make treatment better and more specific to the individual patient.”
It will be a while before this research makes it into a clinical setting but Professor Sibson and her team hope to confirm their findings in clinical trials within the next few years, adding some much needed detail to the ‘map’.
- Watch a video about this research here