title: Feasibility of volumetric MRI-guided high intensity focused ultrasound (MR-HIFU) for painful bone metastases.
abstract: BACKGROUND
  Magnetic resonance-guided high intensity focused ultrasound (MR-HIFU) has recently emerged as an effective treatment option for painful bone metastases. We describe here the first experience with volumetric MR-HIFU for palliative treatment of painful bone metastases and evaluate the technique on three levels: technical feasibility, safety, and initial effectiveness.
  
  
  METHODS
  In this observational cohort study, 11 consecutive patients (7 male and 4 female; median age, 60 years; age range, 53-86 years) underwent 13 treatments for 12 bone metastases. All patients exhibited persistent metastatic bone pain refractory to the standard of care. Patients were asked to rate their worst pain on an 11-point pain scale before treatment, 3 days after treatment, and 1 month after treatment. Complications were monitored. All data were prospectively recorded in the context of routine clinical care. Response was defined as a ≥2-point decrease in pain at the treated site without increase in analgesic intake. Baseline pain scores were compared to pain scores at 3 days and 1 month using the Wilcoxon signed-rank test. For reporting, the STROBE guidelines were followed.
  
  
  RESULTS
  No treatment-related major adverse events were observed. At 3 days after volumetric MR-HIFU ablation, pain scores decreased significantly (p = 0.045) and response was observed in a 6/11 (55%) patients. At 1-month follow-up, which was available for nine patients, pain scores decreased significantly compared to baseline (p = 0.028) and 6/9 patients obtained pain response (overall response rate 67% (95% confidence interval (CI) 35%-88%)).
  
  
  CONCLUSIONS
  This is the first study reporting on the volumetric MR-HIFU ablation for painful bone metastases. No major treatment-related adverse events were observed during follow-up. The results of our study showed that volumetric MR-HIFU ablation for painful bone metastases is technically feasible and can induce pain relief in patients with metastatic bone pain refractory to the standard of care. Future research should be aimed at standardization of the treatment procedures and treatment of larger numbers of patients to assess treatment effectiveness and comparison to the standard of care.
authors.affiliation: Department of Radiology, University Medical Center Utrecht, Heidelberglaan 100, 3508 GA Utrecht, The Netherlands.
authors.forename: Merel
authors.initials: M
authors.lastname: Huisman
authors.affiliation: Image Sciences Institute, University Medical Center Utrecht, 3508 GA Utrecht, The Netherlands.
authors.forename: Mie K
authors.initials: MK
authors.lastname: Lam
authors.affiliation: Image Sciences Institute, University Medical Center Utrecht, 3508 GA Utrecht, The Netherlands.
authors.forename: Lambertus W
authors.initials: LW
authors.lastname: Bartels
authors.affiliation: Department of Radiology, University Medical Center Utrecht, Heidelberglaan 100, 3508 GA Utrecht, The Netherlands.
authors.forename: Robbert J
authors.initials: RJ
authors.lastname: Nijenhuis
authors.affiliation: Image Sciences Institute, University Medical Center Utrecht, 3508 GA Utrecht, The Netherlands.
authors.forename: Chrit T
authors.initials: CT
authors.lastname: Moonen
authors.affiliation: Department of Radiology, University Medical Center Utrecht, Heidelberglaan 100, 3508 GA Utrecht, The Netherlands.
authors.forename: Floor M
authors.initials: FM
authors.lastname: Knuttel
authors.affiliation: Department of Radiology, University Medical Center Utrecht, Heidelberglaan 100, 3508 GA Utrecht, The Netherlands.
authors.forename: Helena M
authors.initials: HM
authors.lastname: Verkooijen
authors.affiliation: Department of Radiation Oncology, University Medical Center Utrecht, 3508 GA Utrecht, The Netherlands.
authors.forename: Marco
authors.initials: M
authors.lastname: van Vulpen
authors.affiliation: Department of Radiology, University Medical Center Utrecht, Heidelberglaan 100, 3508 GA Utrecht, The Netherlands.
authors.forename: Maurice A
authors.initials: MA
authors.lastname: van den Bosch
keywords: Bone metastases; Feasibility; Focused ultrasound; Magnetic resonance imaging; Oncology; Palliative treatment