NEW ORLEANS (Reuters Health) - In a series of 13 patients treated with cryoablation for palliation of pain from bone metastasis, more that half achieved total pain relief, according to results reported here this weekend at the 30th Annual Scientific Meeting of the Society of Interventional Radiology.

"Radiation is the gold standard for treatment of bone pain, but 30% of patients never respond to radiation and those who do respond will have the same pain return," Dr. Matthew Callstrom, of the Department of Radiology at the Mayo Clinic in Rochester, Minnesota said in an interview with Reuters Health that. "Additionally, it takes 5 to 20 weeks to achieve response with radiation."

By contrast, Dr. Callstrom said that "54% of patients treated with cryoablation had total relief of pain and 85% had a drop of at least 3 points in their self-reported pain scores." Moreover, the pain relief is fast -- some patients have almost immediate relief, while most achieve some pain relief within a week or two.

He noted that radiofrequency ablation has also been studied for palliation of bone metastasis, but cryoablation has a number of advantages since the "ice ball" can be monitored in real-time with ultrasound, which he said improves ablation control. Moreover, radiofrequency ablation can cause procedural pain and "70% of radiofrequency ablation patients report increased pain in the first 24 hours. There is no procedure-related pain with cryoablation."

Dr. Callstrom said that the study, which is supported by Endocare, Inc of Irvine, California, will eventually enroll 30 patients. He reported on the first 13 during his abstract presentation Sunday.

The average age of the patients was 52, and 7 patients were men. Treatment time ranged from 83 to 280 minutes and follow-up averaged 12.5 weeks. Patients with diffuse disease or sclerotic lesions were excluded from the study as were patients with lesions within 0.5 cm of spinal cord, bowel and bladder and patients with a life expectancy of less than 2 months.

Treated lesions involved the clavicle, vertebral lamina, chest wall, iliac bone and ribs. Primary lesions included renal cell, bronchogenic, squamous cell, adrenal cortical, ovarian and thyroid carcinomas, paraganglioma, and desmoid tumors.

At baseline the mean worse pain score (0-10, 0 = no pain) was 7.5, which decreased to 4.5 at 4 weeks, which was a significant reduction (p = 0.0003), and that decrease was durable out to 24 weeks, Dr. Callstrom said.

Two patients continued to require analgesia pumps after treatment, he said.

He concluded that cryoablation is a "safe and effective treatment for palliation of painful bone metastasis."

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