Researchers from University College London (UCL) have developed a new technique that combines thermal ablation of cancer cells with magnetic resonance navigation (MRN) to deliver implanted ferromagnetic thermoseeds to the precise site of a brain tumour.
The research, published in Advanced Science, used an animal model to show that the technique, called Minimally INvasive IMage-guided Ablation (MINIMA), could navigate a therapeutic thermoseed through brain tissue into a tumour before using thermoablation to destroy the surrounding cancer cells.
The treatment could avoid the need for open surgery, limit damage to adjacent brain tissues, minimise side effects, and reduce recovery times, the team said. It also has the potential to extend survival.
A Century of Research
Using heat to kill cancer cells, known as tumour hyperthermia, thermal ablation, or thermotherapy, has been studied for over a century, using a variety of techniques to achieve a localised hyperthermic effect. Magnetic hyperthermia was first attempted as a cancer therapy in 1957, and is especially attractive for the treatment of glioblastoma, the most common and aggressive primary brain cancer in adults, which has devastating effects and is universally lethal. However its use has been limited by the difficulties of accurate placement, visualisation, and precise localisation and distribution of heat application within the target region.
The new technique has the potential to overcome these limits and revolutionise treatment for hard-to-reach tumours such as glioblastoma, as well as other malignancies such as prostate cancer.
Lead author, Rebecca Baker, from UCL Centre for Advanced Biomedical Imaging, said: “Using an MRI scanner to deliver a therapy in this way allows the therapeutic seed and the tumour to be imaged throughout the procedure, ensuring the treatment is delivered with precision and without having to perform open surgery. This could be beneficial to patients by reducing recovery times and minimising the chance of side effects.”
The ferromagnetic thermoseeds used were 2-mm diameter spherical metal alloys that were implanted superficially before being navigated to the cancer site. Accurate use of the MINIMA technique was enabled by 3 key components, the team said:
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Precise seed imaging
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Navigation through brain tissue by the tailored MRI system, tracked to within 0.3 mm accuracy
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Eradication of the tumour by heating
They said that MINIMA has the potential to elevate an MRI scanner from a diagnostic device to a therapeutic platform.
Combination Diagnosis and Therapy
“MINIMA is a new MRI-guided therapy that has the potential to avoid traditional side effects by precisely treating the tumour without harming healthy tissues,” said Prof Mark Lythgoe from UCL Centre for Advanced Biomedical Imaging, senior author on the paper.
“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 tumour. Once at the tumour, the seed can then be heated, destroying the cancer cells, while causing limited damage to surrounding healthy tissues.”
“We are now able to image and navigate a thermoseed in real-time through the brain using an MRI scanner. 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,” said Prof Lythgoe.
The technique has potential application beyond brain tumours. Prof Mark Emberton from UCL’s division of surgery and interventional science, was lead cancer clinician in the study. He said: “Improving the precision of our cancer treatments is arguably one of the greatest unmet needs we have today.
“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 tumour tissue, reducing harm to normal cells.”
In the longer term, according to Prof Lythgoe, the shape of the seed could be changed to act as a tiny cutting scalpel that could be guided through tissue, which could “allow surgeons to perform remotely controlled operations, revolutionising non-invasive surgery”.
The study was supported with funding by the Rosetrees Trust and the John Black Charitable Foundation.