Microwave Ablation Is Potentially Effective in Treating Bone and Soft-Tissue Tumor Pain

A small study found that microwave ablation (MWA) therapy reduced pain associated with bone and soft tissues by half in the majority of patients treated with the technique— with relief lasting for longer than 4 months on average—suggesting that it could be a reasonable alternative to radiofrequency ablation and other forms of pain management for this group of patients.

The results of the study were presented at the American Academy of Pain Medicine’s 29th Annual Meeting, held April 11-14, 2013, in Fort Lauderdale, Florida.

According to the National Cancer Institute, approximately 11,280 patients in the United States were diagnosed with soft-tissue sarcoma in 2012, with 2890 more patients being diagnosed with bone sarcoma. In bone cancer, pain is the most frequently reported side effect. MWA has been applied to numerous tumor types, including liver, adrenal gland, thyroid, and kidney tumors, but prior to this study, its effectiveness in bone and soft-tissue sarcoma had not been described.

In this study, 13 adult patients received a total of 20 treatments with MWA using an Acculis MTA-2 generator with a frequency source of 4.5 GHz and a 17-gauge antenna. Patients received MWA percutaneously, with small probes inserted directly into the tumor, which were guided by computer tomography scan. These small probes were then heated to cause thermal coagulation of the tumor. During the procedure, patients received local anesthesia and nitrous oxide.

Of the 20 lesions, five were soft-tissue lesions and 15 were bone lesions, with 12 of those 15 bone lesions being osteolytic. Of the 20 ablated lesions, 16 of them were metastases, with the original tumors occurring in the lung, leiomyosarcoma (a cancer of muscle connector tissue), thyroid, kidney, and prostate. Lesions ranged in size from 12 mm to 120 mm.

The researchers reported that the mean ablation time was 4.85 minutes (range: 1-13), with each cycle lasting an average of 30 seconds to 3 minutes with an average of 4.2 cycles per ablation. According to the researchers, radiofrequency ablation typically takes about 30 minutes to complete, depending on the size of the lesion being treated.

Prior to receiving MWA, patients reported a mean pain score of 7.29 out of 10 on the visual analogue scale. Pain relief of 50% was reported by patients for 19 of the 20 procedures. Relief lasted for an average of 4.36 months, with some patients experiencing pain relief for 15 months following the procedure. The researchers reported that one patient experienced a secondary abscess at the site of ablation that required draining.

“This technique may be applied to any patient suffering from bone tumor pain, mainly in patients suffering from bone metastases, refractory to conventional therapies,” said Adrian Kastler, MD, a resident in Interventional Pain Management at the Centre Hospitalier Universitaire in Besançon, France, and lead author of the study, in a statement. “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.”

Kastler said that this technique should be studied further using different parameters of intensity and time of ablation in order to determine whether guidelines should be instituted according to tumor size. Currently, no manufacturer guidelines exist with regard to the use of MWA in bone or soft-tissue sarcoma.

“Our research showed that the use of MWA in bone and soft-tissue tumors is feasible and effective concerning pain palliation,” Kastler said. “However, MWA needs to be studied in order to apply the same procedure in a curative intention.”

Kastler A, Alnassan H, Aubry S, et al. Microwave ablation under local anesthesia of bone and soft-tissue tumors: preliminary results. Presented at: 2013 American Academy of Pain Medicine Annual Meeting; April 11—14, 2013; Fort Lauderdale, FL. Abstract 193.