Palliative Treatment of Painful Bone Metastases with MR Imaging–guided Focused Ultrasound

Abstract

To evaluate the safety and initial efficacy of magnetic resonance (MR) imaging-guided focused ultrasound for the palliation of pain caused by bone metastases in patients in whom standard available treatments had been ineffective or not feasible. Informed consent was obtained in 11 patients (seven women, four men; average age, 58.6 years) with pain related to non-weight-bearing bone metastases who were subsequently treated with MR imaging-guided focused ultrasound in this research and ethics board-approved study. Efficacy was evaluated by changes in visual analog scale (VAS) scores, in pain medication usage, and in quality of life. Safety of the device was evaluated by recording incidence and severity of treatment-related adverse events up to 3 months after treatment at physical examination and follow-up imaging. Follow-up imaging included contrast material-enhanced MR imaging and unenhanced computed tomography (CT) 1 month after treatment and contrast-enhanced MR imaging 3 months after treatment. Imaging studies were assessed for changes in tumor imaging characteristics and any adverse events associated with MR imaging-guided focused ultrasound treatment. Twelve lesions were treated in 11 patients. All patients reported progressive decrease in pain in treated regions and reduction in pain medication usage during the 3-month follow-up period. VAS scores averaged 6.0 before treatment and decreased to 0.5 at 3 months (decrease in pain scores, 92%; P < .01). No adverse events were recorded at physical examination or follow-up imaging. The majority of patients with osteolytic metastases had varying degrees of necrosis of the enhancing medullary component of the metastasis at follow-up enhanced MR imaging. Five patients had increased bone density at the site of treated osteolytic metastases at follow-up unenhanced CT at 3 months after MR imaging-guided focused ultrasound. MR imaging-guided focused ultrasound is a noninvasive technique that allows palliative treatment of bone metastases with little or no morbidity.