Early detection of brain metastases using Molecular MRI
When cancer is diagnosed, we sometimes find that it has spread round the body to form new colonies called metastases. When new colonies form in the brain this can be dangerous because they are rarely detected at a stage when they can be treated effectively and life expectancy once diagnosed is generally only a few months.
Magnetic resonance imaging (MRI) is widely used for diagnosing brain cancer, but it can only see the metastases when they reach about 1 cm in diameter. This means a tumour about the size of a small marble. The problem with the current scans is that they use a magnetic dye that can only highlight the tumour when the tumour has done considerable damage to the blood vessels. This damage allows the magnetic dye to leak into the tumour and stain it in the MRI image. It takes the tumour maybe 6 months to do enough damage to the blood vessels to allow the dye to leak out. This is 6 months during which we could be treating the tumour.
Scientists at the Gray Institute in the Department of Oncology of the University of Oxford are developing an MRI scan that may help detect brain metastases before any damage is done to blood vessels. Dr Niki Sibson and her team have found a technique that should allow us to detect brain metastases when they are less than a millimetre in size, roughly the size of a single grain of fine sugar. Detecting tumours when they are this size could make all the difference in the world to our ability to treat them successfully.
Niki’s new method relies on the fact that when tumours start to grow in the brain they cause the nearby blood vessels to make a protein called VCAM-1. This protein sticks out of the blood vessel walls into the blood stream. Niki’s team have taken tiny balls of iron oxide (rust) and coated them with an antibody that sticks to VCAM-1 and only to VCAM-1. The balls of rust are eight times smaller than a red blood cell. When these particles are injected into a patient they will travel with the blood until they find a blood vessel with VCAM-1 proteins coating the walls. The particles will stick to the proteins and the iron oxide creates a signal change that the MRI scanner can detect.
The beauty of this approach is not only that it should detect brain tumours very early while they are still treatable, but also that it will work on existing hospital scanners; so there should be no need to replace current equipment.
This exciting research has been published in the journal Proceedings of the National Academy of Sciences USA (Serres et al., Proc.Natl. Acad. Sci. USA 2012) and is the subject of a CR-UK press release dated Monday 26th March 2012.