Magnetic Resonance-Guided High Intensity Focused Ultrasound for Palliation of Painful Skeletal Metastases - A Pilot Study
Bone metastases are common among patients with advanced cancer and have been reported in up
to 85% of cancer patients at autopsy. Complications of bone metastases include pain,
functional limitation, decreased quality of life, pathological fracture, spinal cord
compression and cauda equina syndrome.
External beam radiotherapy is the current standard treatment for patients with painful
uncomplicated bone metastases. Unfortunately up to 30 % of patients treated with
radiotherapy do not respond to therapy, and 30% of responders have their pain recur at some
point after treatment. Radiotherapy re-treatment is also limited by cumulative doses
delivered to sensitive structures. Ablative techniques such as cryotherapy and percutaneous
radiofrequency ablation are not similarly limited by cumulative effects, however, they are
invasive procedures that place patients at risk of complications.
MR-guided high intensity focused ultrasound (MR-HIFU) is a non-invasive, outpatient modality
being investigated for the treatment of cancer. In MR-HIFU, a specially designed transducer
is used to focus a beam of ultrasound energy into a small volume at a specific target site
in the body. The focused beam produces therapeutic hyperthermia in the target field but only
harmlessly warms the immediately surrounding tissue. Magnetic resonance (MR) imaging is used
both to focus the ultrasound beam on the target field in the bone (the metastatic lesion and
adjacent periosteum containing the nerves and vasculature for the tumor) and to perform
real-time thermal mapping at and around the target. The mechanism of action of pain response
is thought to be thermal periosteal denervation and / or thermal ablation of the tumor mass
that diminishes pressure on the surrounding tissue.
Endpoint Classification: Safety/Efficacy Study, Intervention Model: Single Group Assignment, Masking: Open Label, Primary Purpose: Treatment
Reduction of Pain Score
Determine the efficacy of MR-Guided HIFU in reducing pain scores related to the site treated as measured on the Brief Pain Inventory (BPI).
Greg Czarnota, M.D.
Radiation Oncology, Sunnybrook Health Sciences Centre
Canada: Health Canada