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Microwave Ablation Shows Promise in Relieving Painful Tumors
In new research presented at the 29th Annual Meeting of the American Academy of Pain Medicine (AAPM), microwave ablation (MWA) therapy cut pain in half for patients with painful bone and soft-tissue tumors and took less time to complete than radiofrequency ablation. Pain relief lasted for 4 months on average and for up to 15 months in some patients.
MWA is a relatively new therapy that has been used in the management of various tumors, including those located in the liver, adrenal gland, thyroid, and kidney, but has not yet been approved for this indication, the authors reported.
“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 lead author Adrian Kastler, MD. “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.”
Many of the 13 patients in whom a total of 20 MWA procedures were performed showed signs of ongoing disease. Of the 20 lesions, 16 had metastasized to the lungs, thyroid, and other locations. Twelve of 15 bone lesions were osteolytic, showing degeneration of bone tissue. Before the procedure, the mean average pain score reported by patients was 7.29 out of a possible 10, as measured by a visual analogue scale (VAS). The lesions ranged in size from 12 mm to 120 mm.
MWA is performed percutaneously by inserting small probes directly into a tumor; the probes are then heated, resulting in thermal coagulation of the tissue.
During the procedure, patients received local anesthesia and nitrous oxide. Insertion of the probe was guided by CT scan. The mean ablation time was 4.85 minutes (range, 1–13 minutes). Each cycle lasted an average of 30 seconds to 3 minutes, and there was an average of 4.2 cycles per ablation.
Patients reported immediate pain relief of at least 50% for 19 of the 20 procedures, with results lasting for an average of 4.36 months (range, 0.5–15 months). As with any needle procedure, bleeding or infection at the ablation site was a risk. The researchers reported only one complication: a secondary abscess at the site that required drainage.
Source: AAPM; April 11, 2013.