Interventional Radiology Treatments for Bone Metastases
Interventional radiology plays a huge role in the treatment of bone metastases by various minimally invasive techniques, either percutaneous or endovascular. It is really important to have an interventional radiologist on your multidisciplinary treatment team.
Percutaneous injection of 95% ethanol in combination with a contrast agent into spinal tumors is a fairly old technique. The alcohol induces tumor necrosis (death).
Embolization is the selective occlusion of blood vessels, in this case the blood vessels feeding the tumor. Embolization induces tumor necrosis by occluding these feeding vessels thereby having an analgesic effect. Embolization is typically using calibrated microparticles polyvinyl alcohol (PVA) or trisacryl gelatin microspheres. Chemoembolization combines highly selective arterial embolization with the delivery of intraarterial chemotherapy.
MRgFUS to Treat Bone Metastases
An FDA-approved treatment for pain related to bone metastases using Magnetic Resonance-guided Focused Ultrasound or MRgFUS. The treatment provides relief from tumor-related bone pain. The procedure is non-invasive and is performed with a nerve block and sedation. MRgFUS uses an MRI thermal imaging system to continuously measure temperature changes inside the body, pinpointing and guiding the treatment. The treatment is also called HIFU, which stands for High Intensity Focused Ultrasound.
With thermoablative procedures, the goal is to induce coagulative necrosis with heat, ideally around 70 °C for bone lesions
The development of cryoprobes to treat bone lesions is relatively new. Argon gas is delivered through a partially insulated probe which is positioned at the center of a tumor. The gas lowers the probe temperature to −100 °C (26). Cell death is due to loss of cell membrane integrity. An important advantage is that since ice can penetrate bone this can treat osteoblastic metastases.
OsteoCool RF Ablation system
Medtronic is an example of a bipolar system engineered to overcome the limitations of a monopolar device in bone.
PDT is a relatively new approach to ablation which is not widely available commercially at this point and is mostly utilized in research applications. PDT combines a systemically injected photosensitizing agent with locally applied light at a specific wavelength (typically infrared).
Currently RFA is the most frequently utilized thermo-ablative procedure for bone tumors.
Vertobroplasty and Kyphoplasty
Vertebroplasty is an outpatient procedure for stabilizing compression fractures in the spine. Bone cement is injected into back bones (vertebrae) that have cracked or broken, often because of osteoporosis. The cement hardens, stabilizing the fractures and supporting your spine. For people with severe, disabling pain caused by a compression fracture, vertebroplasty can relieve pain, increase mobility and reduce the use of pain medication. Kyphoplasty is similar to vertebroplasty but uses special balloons to create spaces within the vertebra that are then filled with bone cement. Kyphoplasty can correct spinal deformity and restore lost height.
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