A Dutch research team from Radboud University Medical Center has visualized the injection of radioactive microspheres during treatment of a patient with liver tumors ‘live on screen’. To our best knowledge, it was the first time microspheres were made visible during the procedure. This opens the way to a more personalized approach to treatment of liver tumors. The technique, which can safely be performed, is published in the journal Cancers.
Patients with cancer in the liver are sometimes treated with internal radiotherapy (radioembolization). This means that the tumors are not irradiated from outside the body, but from inside the liver itself. This can be done by injecting small radioactive microspheres into the liver artery. These microspheres are carried along by the blood and get stuck in the very small blood vessels, especially around the tumors. In this way, the tumors can be irradiated from the inside.
"At the moment, a difficulty is that you cannot follow the injected microspheres during treatment, you are working in a black box," says Frank Nijsen of the Medical Imaging Department at Radboud University Medical Center, the Netherlands. "Prior to treatment, you map the branching of the hepatic artery, and the locations of the tumors. However, how the microspheres spread during the treatment exceeds the level of detail that can be visualized. As a result, it is possible that not as many microspheres as planned flow to a tumor, causing a too low radiation dose, and the desired tumor-shrinking effect is not achieved."
Radiotherapy inside the MRI
Nijsen and colleagues have, however, developed a therapy based on radioactive holmium microspheres. These microspheres are paramagnetic, as a result of which they can be visualized using MRI. In recent years, using the special facilities at MITeC, they have developed a method for administering the microspheres while the patient is positioned in an MRI scanner. This sounds simpler than it is: all the materials used during the treatment, such as catheters, must also be safe for use in the high magnetic field of a scanner and may not interfere with the MRI image.
Microspheres live in the picture
In an article in Cancers, they now describe that this approach has indeed been successful in a first patient. Within the clinical trial, six patients were safely treated, and the resulting data is currently being analyzed. Joey Roosen, from the Department of Medical Imaging, will receive his PhD on this unique procedure in late 2022. "As far as we know, this is the first time worldwide that we can see how the microspheres are distributed during the procedure," says Roosen. "It is a proof of concept, in which we demonstrate that it can be done safely in this way. We can follow the injection of the microspheres live based on the MRI images and, in addition, measure how many spheres have lodged in the tumors and the healthy liver." That is unique. Like releasing millions of tiny boats at river Missouri and being able to follow them all on their way to Omaha, Kansas City, Saint Louis, Memphis and New Orleans.
Adjusting the distribution
The next step in the development of this innovative therapy is to find out whether the distribution of holmium microspheres can also be adjusted during the procedure, as a result of decision making based on the MRI images. "That is the question we will answer in a follow-up study," says Nijsen. "If we can do that, we can tailor radioembolization to the situation of each unique patient. That is where we want to go."
Development of an MRI-Guided Approach to Selective Internal Radiation Therapy Using Holmium-166 Microspheres - Joey Roosen, Mark J Arntz, Marcel J R Janssen, Sytse F de Jong, Jurgen J Fütterer, Christiaan G Overduin, J Frank W Nijsen
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