9565 Background: Palliation of bone metastases is typically performed with radiation therapy (RT). However, a significant minority of patients cannot obtain durable relief from RT. MRgFUS combines non-invasive focused ultrasound with MR guidance. Preliminary phase III results comparing MRgFUS to sham treatment have demonstrated efficacy. This study examines the safety of this procedure in a large prospective, multi-center study. Methods: Patients with a painful bone metastasis were randomized (3:1) to either MRgFUS or sham treatment for the single most painful lesion. Sham patients were given the opportunity to cross over after 2 weeks. Each adverse event (AE) was recorded prospectively and scored for severity and relation to treatment. Results: Thirty-seven patients were enrolled to receive sham treatment and 115 to receive MRgFUS. Sites of treatment were: 102 pelvis, 28 thorax, 7 lower extremity and 2 upper extremity. Seventy-seven target lesions were osteolytic, 29 were osteoblastic and 33 were mixed. Treatment was discontinued prior to completion in 8 treatments. Of these, 7 were pelvic targets and 6 lesions were osteolytic. The most common reasons for discontinuation were pain (4) and patient movement (2). Forty-seven percent of treatment patients and 2.7% of sham patients reported at least one AE. Of 76 AEs, 67 were considered non-significant and anticipated, 57 being intra-procedure pain. Four significant events included 2 possibly related fractures at treated lytic lesion sites, 1 grade 3 skin burn and 1 patient with neuropathy. Four patients experienced events unrelated to study treatment and 1 patient experienced temporary apnea from anesthesia described as incidental. Conclusions: MRgFUS is a safe treatment for palliation of painful bone metastases. Ninety-three percent of MRgFUS treatments were carried out to completion. Three percent of patients experienced significant AEs, including 2 fractures of treated lytic tumors. These safety data reinforce and confirm previous experience with this technology and encourage its use for patients not suitable for RT. Clinical trial information: NCT00656305.
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