CT image guided thermal ablation techniques for palliation of painful bone metastases

Many different treatment methods have been used for pain palliation in patients with bone metastases. The ideal treatment has to be fast, safe, effective and tolerable for the patient.

To evaluate the efficacy and safety of computed tomography (CT)-guided radiofrequency ablation (RFA) or microwave ablation (MWA) as a minimal invasive method of pain palliation.

A total of forty-five patients with painful bone metastases were included in our study (median age 65.43; range, 36-90 years). Thirty patients were treated with RFA and fifteen with MWA, all under CT guidance. Lesion diameter was between 2 and 9 cm (mean ± SD: 3.9±2.6 cm). Pain was assessed in all patients with the Brief Pain Inventory (BPI). All procedures were performed under conscious sedation. RFAs were performed with a RITA Model 1500® electrosurgical generator with a seven or a nine-array multitined electrode depending on the lesion's size. MWAs were done with AMICA-GEM microwave generator 2,450 MHz connected to a 14- or 16-gauge coaxial antenna. Technically successful ablation was considered to be when lesions were treated according to protocol and completely covered. After each session a dual-phase spiral CT examination with intravenous contrast medium was performed in order to evaluate immediate response. Patients were hospitalised and observed for 24-hour monitoring. Post-ablation assessment with BPI score and report of the use of analgesics was performed with telephone interview one, four and eight weeks after the ablation.

In both groups there was a significant and similar decrease in the mean past day BPI score for worst pain, for average pain and for pain interference during daily life in comparison to preprocedural symptoms (P<0.001, paired t-test), one, 4 and 8 weeks after treatment. There was also a marked decrease (3 out of 45 patients, 4 and 8 weeks after treatment) in the use of analgesics. Mean ablation time for MWA was 4.5 minutes, shorter than RFA's mean ablation time that was 9.5 minutes but with the same clinical result.

RFA and MWA appear to be similarly effective for treatment of painful bone metastases. The main difference is that MWA achieves the same clinical result faster but in a more expensive way.