MR Imaging- Guided High Intensity Focused Ultrasound (HIFU) Therapy of Bone Metastases

Bone metastasis give rise to major complications that lead to significant morbidity and impairment of life quality. The most common primary for bone metastasis is prostate, lung and breast carcinoma. These three have the highest cancer incidence in the USA with up to 85% prevalence of bone metastases at the time of death. Pain from these osseous lesions can be related to mechanical or chemical factors. Pressure effects on the periosteum or adjacent neural structures can cause local or radiating pain. Hemorrhage from local bone osteolysis by osteoclastic activity causes a local release of bradykinin, prostaglandins, histamine and substance P that can irritate the endosteal nerves as well as local nerves.

The life expectancy of patients with osseous metastatic disease is variable but can be substantially longer for patients with multiple myeloma, breast or prostate cancer. Therefore, finding an effective local therapy that can improve patient quality of life and can be done at a single outpatient sitting would be beneficial.

The current and emerging treatments for osseous metastases may be considered in several categories: radiotherapy, systemic chemotherapy (cytotoxic, hormonal and radionuclides), surgical stabilization and percutaneous tumor ablation. These treatments may be applied in isolation but also frequently in combination.

MRI Guided High Intensity Focused Ultrasound (HIFU) is a completely non-invasive technology for thermal ablation. HIFU is capable of concentrating ultrasonic pressure waves to a specified region without any physical penetration of the body. The converging ultrasonic pressure wave is converted to thermal energy at the specific depth, resulting in local heating at the focus. Temperature elevation is proportional to the proton resonance frequency shift, therefore MR imaging provides accurate technique for target definition and energy deposition control. MRI guided Focused Ultrasound therapy is being performed in treatment of uterine leiomyomas (fibroids). Recently the method has gained both AMAR authorization and FDA approval, and CE approval for that indication.

Clinical trials of HIFU in bone metastases have indicated that the method is safe and gives an effective reduction of patient pain. The short- and long-term effects on tumor volume and morphology do not seem to have been evaluated thus far.

The primary objective of this trial is to evaluate effectiveness of MRI guided HIFU in the treatment of metastatic bone tumors