Certain types of tumours in the liver can be treated with an internal radiotherapy approach called radioembolisation. With this method, radioactive microspheres are administered via the blood vessels that supply the tumour. The radiation emitted from this substance works to eliminate tumour cells.
Radiotherapy (in all its different forms) is an effective cancer treatment. But just like any other medicine, correct dose is key. If it’s too low, it may not be effective, and if it’s too high, it may lead to unwanted side effects, such as harming healthy tissues. Therefore, it is crucially important to optimise the method that determines the absorbed dose for each individual patient.
Calculating the dose of radioembolisation treatment works by administering a test material to the patient. This test material is made of microparticles that are coated with a weak radioactive substance. The microparticles are taken up by the tumour in a way that mimics the way the actual medicine (microspheres) will be absorbed.
Then, a special radiation-sensitive camera (called a gamma camera) captures the distribution of the microparticles in the organ and the tumour. This 2D “photograph” is analysed to determine the appropriate therapeutic dose.
The team hypothesised that this protocol may not provide the best prediction for each individual patient. They asked: will we be able to improve dosage accuracy by recording the distribution of the test material with 3D imaging instead?
Their results confirmed their hypothesis was correct. The new protocol provided a more complete overview of the distribution of the test material in the tissue. This, in turn, resulted in a good match between the calculated dose and the actual absorbed dose. With this approach, they were able to estimate more accurately the correct dose for an initial test group of patients at the Champalimaud Clinical Centre.
The team is currently collecting additional data from patients, with the long-term goal of optimising the method and sharing their findings with other clinical centres around the world.