Microwave ablation (MWA) may represent a new option for treating patients with painful bone tumors, according to the results of recent research. MWA is a relatively new therapy that has primarily been used to manage liver, lung, and kidney tumors; more recently, it has been tested in patients with bone tumors. In the MWA procedure, small probes are introduced into the tumor percutaneously and then heated, causing thermal coagulation of tissue.
In a study presented on April 11th at the Annual Meeting of the American Academy of Pain Medicine in Fort Lauderdale, FL, investigators associated with the Centre Hospitalier Universitaire in Besançon, France, reported that patients treated with MWA experienced an immediate 50% reduction in pain that lasted up to 15 months.1
The researchers performed 20 MWA procedures on 13 patients. Of the 15 bone lesions, 12 were osteolytic. Lesions ranged in size from 12 mm to 120 mm. Before the procedure, patients reported a mean average pain score of 7.29 out of 10 on a visual analog scale.
Insertion of the probes was guided by computed tomography scan. On average, 4.2 cycles were performed for each ablation, with each cycle lasting 30 seconds to 3 minutes; the overall mean ablation time was 4.85 minutes, ranging from 1 to 13 minutes. By contrast, radiofrequency ablation may take up to 30 minutes, depending on the size of the lesion being treated.
In 19 of the 20 procedures using MWA, patients reported immediate pain relief of at least 50%. Furthermore, the average duration of pain relief was 4.36 months, ranging from 0.5 to 15 months. A secondary abscess at the ablation site after a single procedure was the only complication reported.
“This technique may be applied to any patient suffering from bone tumor pain, mainly in patients suffering from bone metastases, refractory to convention therapies,” said Adrian Kastler, MD, a resident in interventional pain management and lead author of the study. “The main advantage of ablation techniques is the fast pain relief obtained—immediately after the procedure—as opposed to delayed pain relief obtained with radiation therapy.”
Even better results were reported by researchers from the Oncological Hospital “A. Businco” in Cogliari, Italy, who used MWA to treat 18 patients with 21 skeletal metastatic lesions, all of which were osteolytic.2 One week after the procedure, patients’ mean scores on the Brief Pain Inventory (BPI) had declined by 77% and their analgesic drug therapy was discontinued. Twelve weeks after the procedure, the mean BPI score had declined by 92% and 13 of the 18 patients were pain-free.
Four patients with continuing symptoms were re-treated with MWA, two of whom required cementoplasty because of high fracture risk. Out of this group, one patient had symptom recurrence.
Rapid onset of pain relief obtainable with MWA offers a distinct advantage to patients with bone metastases, many of whom have a life expectancy of only a few months. This technology may provide yet another alternative to relieving pain associated with metastasis and has the potential to improve quality of life.
1. Kastler A et al. Microwave ablation under local anesthesia of bone and soft-tissue tumors: preliminary results. Presented at the annual meeting of the American Academy of Pain Medicine, April 11, 2013. http://www.painmed.org/2013posters/abstract-193/
2. Pusceddu C et al. Treatment of bone metastases with microwave thermal ablation. J Vasc Interv Radiol. 2013;24:229-33.