BACKGROUND: High‐intensity focused ultrasound (HIFU) is a new, noninvasive technique with potential to ablate and inactivate tumors. Treatment of solid tumors with HIFU has been reported. In this study, the safety and effects of HIFU in the clinical therapy of malignant bone tumors were assessed.METHODS: Biochemical markers and magnetic resonance imaging (MRI) or positron emission tomography (PET)‐computed tomography (CT) were used to evaluate 25 patients with malignant bone tumors before and after HIFU treatment.RESULTS: HIFU resulted in significant improvement in biochemical markers, and no severe complications were observed. After HIFU treatment, 21 (87.5%) patients were completely relieved of pain, and 24 (100%) experienced significant relief. On the basis of MRI or PET‐CT, HIFU was effective: For patients with primary bone tumors, 6 (46.2%) had a complete response, 5 (38.4%) had a partial response, 1 (7.8%) had a moderate response, and 1 suffered progressive disease; the response rate was 84.6%. For patients with metastatic bone tumors, 5 (41.7%) had complete response, 4 (33.3%) had partial response, 1 (8.3%) had a moderate response, 1 (8.3%) had stable disease, and 1 suffered progressive disease; the response rate was 75.0%. The 1‐, 2‐, 3‐, and 5‐year survival rates were 100.0%, 84.6%, 69.2%, and 38.5%, respectively, for patients with primary bone tumors and 83.3%, 16.7%, 0%, and 0%, respectively, for patients with metastatic bone tumors. The survival rates for patients with primary bone tumors were significantly better than for those with metastatic tumors.CONCLUSIONS: HIFU safely and noninvasively ablated malignant bone tumors and relieved pain. HIFU ablation should be further investigated, as it appears to be successful in the treatment of primary malignant bone tumors. Cancer 2010. © 2010 American Cancer Society.

Iodine‐125 (¹²⁵I) brachytherapy, a promising form of radiotherapy, is increasingly applied in the clinical treatment of a wide range of solid tumors. However, the extremely hypoxic microenvironment in solid tumors can cause hypoxia‐induced radioresistance to ¹²⁵I brachytherapy, resulting in therapeutic inefficacy. In this study, the aim is to sensitize hypoxic areas in solid tumors using ultrasound‐activated oxygen microbubbles for ¹²⁵I brachytherapy. A modified emulsion freeze‐drying method is developed to prepare microbubbles that can be lyophilized for storage and easily reconstituted in situ before administration. The filling gas of the microbubbles is modified by the addition of sulfur hexafluoride to oxygen such that the obtained O₂/SF₆ microbubbles (OS MBs) achieve a much longer half‐life (>3×) than that of oxygen microbubbles. The OS MBs are tested in nasopharyngeal carcinoma (CNE2) tumor‐bearing mice and oxygen delivery by the OS MBs induced by ultrasound irradiation relieve hypoxia instantly. The post‐treatment results of brachytherapy combined with the ultrasound‐triggered OS MBs show a greatly improved therapeutic efficacy compared with brachytherapy alone, illustrating ultrasound‐mediated oxygen delivery with the developed OS MBs as a promising strategy to improve the therapeutic outcome of ¹²⁵I brachytherapy in hypoxic tumors.