Bone metastasis treatment using magnetic resonance-guided high intensity focused ultrasound

Abstract

Objectives: Bone pain resulting from cancer metastases reduces a patient's quality of life. Magnetic Resonance-guided High Intensity Focused Ultrasound (MR-HIFU) is a promising alternative palliative thermal treatment technique for bone metastases that has been tested in a few clinical studies. Here, we describe a comprehensive pre-clinical study to investigate the effects, and efficacy of MR-HIFU ablation for the palliative treatment of osteoblastic bone metastases in rats. Materials and methods: Prostate cancer cells (MATLyLu) were injected intra-osseously in Copenhagen rats. Upon detection of pain, as determined with a dynamic weight bearing (DWB) system, a MR-HIFU system was used to thermally ablate the bone region with tumor. Treatment effect and efficacy were assessed using magnetic resonance imaging (MRI), single-photon emission computed tomography (SPECT) with technetium-99m medronate (^99mTc-MDP), micro-computed tomography (μCT) and histology. Results: DWB analysis demonstrated that MR-HIFU-treated animals retained 58.6±20.4% of limb usage as compared to 2.6±6.3% in untreated animals (P=0.003). MR-HIFU delayed tumor specific growth rates (SGR) from 29±6 to 13±5%/day (P<0.001). Untreated animals (316.5±78.9mm³) had a greater accumulation of ^99mTc-MDP than HIFU-treated animals (127.0±42.7mm³, P=0.004). The total bone volume increase for untreated and HIFU-treated animals was 15.6±9.6% and 3.0±4.1% (P=0.004), respectively. Histological analysis showed ablation of nerve fibers, tumor, inflammatory and bone cells. Conclusions: Our study provides a detailed characterization of the effects of MR-HIFU treatment on bone metastases, and provides fundamental data, which may motivate and advance its use in the clinical treatment of painful bone metastases with MR-HIFU.