Adam N. Wallace

Spinal skeletal-related events (SREs)—defined as pain requiring palliative radiation therapy or surgical intervention, pathologic vertebral compression fracture, epidural spinal cord compression, and hypercalcemia—are associated with declines in physical, functional, and emotional well-being and survival. Most currently available therapies mitigate the pain and disability resulting from these complications; however, the authors of this study believe that percutaneous ablation therapy will be part of a new paradigm in which spinal SREs are prevented by achieving local tumor control. Radiofrequency ablation is performed by placing a probe into the spinal metastasis under imaging guidance and heating the tumor to cytotoxic temperatures. Cement is then instilled into the ablation cavity to stabilize or prevent associated pathologic fracture. The procedure can be performed in an outpatient setting under conscious sedation, requires minimal recovery, and does not hinder or delay adjuvant radiation therapy, chemotherapy, or surgery.

In the present study, we retrospectively reviewed follow-up imaging of 55 spinal metastases from a variety of primary tumor histologies treated with percutaneous radiofrequency ablation and cementoplasty. Overall radiographic local tumor control rates were 89% (41/46) at 3 months, 74% (26/35) at 6 months, and 70% (21/30) at 1 year after treatment, and clinical follow-up showed no instances of metastatic epidural spinal cord compression at any of the treated vertebral levels. To serve as an internal control for the effect of chemotherapy, we also reviewed posttreatment imaging of metastases that were not ablated. Considering only patients

with radiographically documented systemic disease progression, local control rates of ablated tumors were 86% (32/37) at 3 months, 71% (22/31) at 6 months, and 67% (18/27) at 1 year. There were no acute or delayed procedure-related complications.

Given these encouraging results, we are now working towards a phase II clinical trial with the primary endpoint of radiographic local tumor control at prespecified imaging timepoints. Our target population will be patients with metastatic non-small cell lung cancer, a common malignancy with a high incidence of spinal SREs. To inform the trial design, we are conducting a retrospective case-control study to establish the clinical, radiographic, and pathologic risk factors for spinal SREs in patients with metastatic non-small cell lung cancer. Simultaneously, we are expanding the scope of our prospective tumor ablation registry to include additional clinical, radiographic, pathologic, and procedural data that may predict failure of local tumor control. Our ultimate goal is to conduct a phase III randomized controlled trial to demonstrate that percutaneous ablation of spinal metastases delays and reduces the incidence of spinal SREs compared with medical therapy alone.

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