New approaches to treating and preventing bone metastases

Comparison of post-operative pain scores and opioid use between kyphoplasty and radiofrequency ablation (RFA) systems combined with cement augmentation

OBJECTIVE

This retrospective chart review study aims to compare demographic information, post-operative pain scores, and opioid use following treatment with kyphoplasty alone, OsteoCool™ (Medtronic) system, and SpineSTAR ® (Merit Medicine).

MATERIALS AND METHODS

Following institutional review board approval, retrospective chart review of 64 patients was examined between January 2011 and December 2017. Inclusion criteria for this study comprised patients greater than 18 years old having metastatic vertebral compression fracture involving the thoracolumbar spine. Exclusion criteria consisted of non-pathologic osteoporotic compression fractures, metastasis in cervical spine, or previous radiofrequency ablation (RFA) treatment. Age at intervention, gender, previous treatment, and nursing recorded VAS score from 0 to 10, with zero representing no pain and 10 representing worst pain were compared. Pain scores documented immediately pre- and post-operatively, as well as 7-14 days post-operatively were targeted for analysis. Post-procedure opioid intake during the first month following surgery was also assessed.

RESULTS

A total of 63 patients were included in this retrospective analysis. The demographic characteristics between the treatment arms were similar. Difference of square means analysis showed no statistical difference in pain scores at each time interval between the two RFA systems, or was there a statistical difference in pain scores when each RFA system was compared independently to kyphoplasty alone. Chi-squared analysis showed no statistical difference in opioid use between the treatment arms 1 month post-operatively.

DISCUSSION

To our knowledge, this is the first study that evaluates post-operative pain scores between the two novel RFA systems and kyphoplasty alone. Each system results in improved pain scores post-operatively; however, no additional benefit was seen from the addition of RFA.

Helical coil electrode radiofrequency ablation designed for application in osteolytic vertebral tumors--initial evaluation in a porcine model

BACKGROUND CONTEXT

Radiofrequency ablation (RFA) is emerging as a complementary treatment for vertebral metastases. Traditional RFA induces frictional heating leading to local tissue necrosis but often yields small, incomplete, and inhomogeneous zones of ablation in bone. We have developed a new bone-specific RFA electrode that uses a nontraditional frequency (27.12 MHz) and geometry (helical), exploiting a magnetic field and an electric field to generate larger and more comprehensive treatment zones.

PURPOSE

The purpose of the study was to evaluate the feasibility and safety of the Bone Coil RFA electrode in the spine.

STUDY DESIGN

This is a preclinical in vivo study based on basic science.

METHODS

Under institutional approval, six healthy Yorkshire pigs received a sham and an RF treatment in two adjacent cervical vertebrae. To deploy the Bone Coil RFA device in dense porcine vertebrae, a surgical approach was required; an irrigated coring drill bit created a cylindrical path in the vertebral bodies through which the RFA electrodes were placed. The electronic circuit was completed by four grounding pads. Treatment was delivered for 10 minutes at 20 W (n=1), 25 W (n=1), and 30 W (n=4). To monitor the thermal rise and for safety, fiber-optic probes recorded temperatures in the center of each coil and near the spinal foramen. After the procedure, animals were monitored for 2 weeks. Magnetic resonance imaging (MRI) was completed immediately after treatment and at 14 days. Magnetic resonance image segmentation and histology were used to evaluate the ablation volume.

RESULTS

Comprehensive treatment of the porcine vertebrae was demonstrated by temperature monitoring, MRI, and histology. Large zones of RF ablation were obtained (RF: 3.72±0.73 cm3 vs. sham: 1.98±0.16 cm3, p<.05), confined within the vertebral body. Internal temperatures were elevated with RF (66.1 °C-102.9 °C), without temperature rise outside of the vertebrae (38.2 °C ± 1.5 °C). Mobility, neurological responses, and behavior were normal, consistent with preprocedural examination. Magnetic resonance imaging best visualized ablation at Day 14. Histology revealed comprehensive homogeneous coagulative necrosis with little peripheral sign of repair.

CONCLUSIONS

The Bone Coil RFA device created large intravertebral ablation volumes with no neurologic sequelae. Radiofrequency thermal ablation (clearly distinguished from the much smaller effects arising from core drilling) corresponded to the homogeneous necrosis visible on histology.

Evaluation of a bipolar-cooled radiofrequency device for ablation of bone metastases: preclinical assessment in porcine vertebrae

BACKGROUND CONTEXT

Cancer spread to the spine affects bone stability and can lead to pathologic fracture and neurologic impairment. Radiofrequency ablation (RFA) recently has gained popularity in treating skeletal tumors. Conventional RFA devices use a monopolar design, which limits the ability to comprehensively treat large tumors in bony tissues and may pose risks to adjacent critical normal neurologic tissues when applied to vertebrae. New bipolar-cooled radiofrequency (BCRF) may generate larger controlled lesions without the same degree of risk to adjacent structures.

PURPOSE

The purpose of this study was to evaluate the feasibility, efficacy, and safety of RFA with the use of a new bone-specific, BCRF probe in a porcine vertebral model and to evaluate the ability of magnetic resonance (MR) imaging to represent histologic outcomes of RFA treatment.

STUDY DESIGN

Basic science: preclinical in vivo study.

METHODS

RFA was evaluated in three noncontiguous lumbar vertebrae in six Yorkshire pigs (25-30 kg). Via a transpedicular approach for probe placement, two vertebrae received BCRF treatment and one vertebrae served as a sham control. MR imaging and neurological assessments were conducted pre- and posttreatment as well as immediately before animal sacrifice (n=3 at day 0, n=3 at day 14). MR ablation zones were compared with hematoxylin and eosin-stained histological sections.

RESULTS

With BCRF, large reproducible zones of ablation were achieved, confined within the vertebrae, without damage to adjacent tissues or the spinal cord. All animals demonstrated normal consistent neurologic behavior pre- and posttreatment. External tissue temperatures around targeted vertebrae were not increased. MR imaging after 14 days was more effective in demonstrating ablation effects than images on day 0, with radiologic findings most apparent on T2-weighted sequences. Histologic analysis of samples corresponded well to the zones of ablation observed on MR images (R=0.9, p<.01).

CONCLUSIONS

The study demonstrated feasibility, safety, and effectiveness of BCRF ablation of vertebral bone. This motivates ongoing preclinical evaluation in diseased models to further explore the potential for its use in clinical treatment of metastatic vertebrae.

Denosumab in patients with cancer-a surgical strike against the osteoclast

Elucidation of the molecular pathways underlying bone turnover has revealed potential therapeutic targets, including receptor activator of nuclear factor-κB ligand (RANKL), which is a mediator of osteoclast formation, function and survival. Denosumab is a fully human monoclonal antibody that binds to and inhibits RANKL. This agent has been developed for use in patients with early-stage and advanced-stage cancer, as well as for the treatment of osteoporosis, and can prevent bone loss and reduce fragility fractures in both types of disease. In the bone metastasis setting, several large phase III studies have shown that denosumab is more effective than bisphosphonates, namely zoledronic acid, in reducing skeletal morbidity arising from a wide range of tumors. In addition, a remarkable activity of denosumab has been demonstrated in giant-cell tumors of the bone. Subsequent studies of denosumab have demonstrated that it can delay bone metastasis in patients with castration-resistant prostate cancer; adjuvant studies in patients with breast cancer are in progress. This Review critically explores the emerging role of denosumab in maintaining bone health in the oncology setting, and discusses the factors that are likely to influence the choice between bisphosphonates and denosumab in clinical practice.