An investigational cancer therapy that uses an MRI scanner to guide a magnetic seed through the brain can be effective in destroying tumors.

The technology called “minimally invasive image-guided ablation” or MINIMA, was developed by scientists at University College London (UCL), London, United Kingdom. A study investigating the potential use and benefit in mice of the investigational therapy was funded by the Rosetrees Trust and the John Black Charitable Foundation,

The novel technology comprises a ferromagnetic thermoseed navigated to a tumor using magnetic propulsion gradients generated by an MRI scanner. After arriving at the tumor site, the ferromagnetic thermoseed is remotely heated to kill nearby cancer cells.

Professor Mark Lythgoe, Ph.D. at UCL Centre for Advanced Biomedical Imaging.

Researchers say the findings, published in the February 2, 2022 issues of Advanced Science, establish ‘proof-of-concept’ for precise and effective treatment of hard-to-reach glioblastoma, along with other cancers such as prostate, that could benefit from less invasive therapies.

“MINIMA is a new MRI-guided therapy that has the potential to avoid traditional side effects by precisely treating the tumor without harming healthy tissues,” noted  Senior author, Professor Mark Lythgoe, Ph.D. at UCL Centre for Advanced Biomedical Imaging.

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Because the heating seed is magnetic, the magnetic fields in the MRI scanner can be used to remotely steer the seed through tissue to the tumor. Once at the tumor, the seed can then be heated, destroying the cancer cells, while causing limited damage to surrounding healthy tissues.”

In the study, the UCL team demonstrate the three key components of MINIMA to a high level of accuracy: precise seed imaging; navigation through brain tissue using a tailored MRI system, tracked to within 0.3 mm accuracy; and eradicating the tumor by heating it in a mouse model.

Ferromagnetic thermoseeds are spherical in shape, 2 mm in size, and are made of a metal alloy. They are implanted superficially into tissue before being navigated to the cancer.

“Using an MRI scanner to deliver a therapy in this way allows the therapeutic seed and the tumor to be imaged throughout the procedure, ensuring the treatment is delivered with precision and without having to perform open surgery,” explained Rebecca Baker at UCL Centre for Advanced Biomedical Imaging, who is the lead author of the article

“This could be beneficial to patients by reducing recovery times and minimizing the chance of side effects,” Baker added.

A diagnostic device becomes a therapeutic platform
MRI scanners are readily available in hospitals around the world and are pivotal in the diagnosis of diseases such as cancer. The work at UCL shows that MINIMA has the potential to elevate an MRI scanner from a diagnostic device to a therapeutic platform.

“We are now able to image and navigate a thermoseed in real-time through the brain using an MRI scanner,” Lythgoe said.

“As MRI is already used to detect the boundaries of cancers, the seed can be moved precisely to ensure it does not stray into surrounding healthy tissue. As the seed is guided through the tissue it can be heated to destroy the cancer. This combines therapy and diagnosis into a single device, creating a completely new class of imaging therapy,” he further noted.

“I treat patients with the most common form of brain cancer, glioblastoma. Following surgery, the average survival time is 12-18 months. MINIMA can successfully destroy cancer in a mouse and has the potential to extend survival and limit damage to adjacent brain tissues in patients,” said r Lewis Thorne, a consultant neurosurgeon at the National Hospital for Neurology and Neurosurgery and co-author of the study.

“Improving the precision of our cancer treatments is arguably one of the greatest unmet needs we have today,” added Professor Mark Emberton, MD, a lead cancer clinician at the UCL Division of Surgery and Interventional Science.

“One in 8 men will be diagnosed with prostate cancer. While treatments such as radiotherapy and surgery can be effective, they often cause unwanted and debilitating side effects such as incontinence and impotence. MINIMA may allow us to precisely target and destroy prostate tumor tissue, reducing harm to normal cells,” Emberton added.

“In the longer term, we will change the shape of the seed to act as a tiny cutting scalpel that could be guided through tissue, which would allow surgeons to perform remotely controlled operations, revolutionizing non-invasive surgery, Lythgoe concluded.

[1] Image-guided Magnetic Thermoseed Navigation and Tumor Ablation Using an MRI System 10.1002/advs.202105333

Featured image: Graphic illustration of new cancer therapy, minimally invasive image-guided ablation. Image courtesy: © 2022 Mark Lythgoe (UCL). Used with permission.

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