A plasma-mediated radiofrequency-based device used in tandem with vertebroplasty shows promise as an improved treatment for vertebral compression fractures due to spinal metastases, according to preliminary data presented at the American Society of Neuroradiology Annual Meeting.
The technique has fewer complications and is safer than previous techniques. However, this is only a preliminary study, and confirmatory randomized controlled trials are needed. Also, specific indications and contraindications for this procedure remain to be defined.
“Radiation, chemotherapy, and surgery are other options for spinal tumors, but these treatments are far from optimal,” said one of the authors, Wade Wong, DO, who is Professor of Radiology at the University of California, San Diego (UCSD)
The downside of surgery is a long postoperative recovery, radiation takes at weeks to reduce associated pain, and patients treated with chemotherapy remain at risk for fracture, he explained.
“With this new technique, we can ameliorate pain associated with metastatic bone disease extremely rapidly and do it safely.”
At the meeting, Dr. Wong and his UCSD colleague Bassem A. Georgy, MD, Assistant Clinical Professor of Radiology and Interventional Neuroradiology, presented results of a series of 28 patients with 36 vertebral bodies treated with the new technique, called SpineWand-assisted vertebroplasty.
Prior to vertebroplasty—i.e., injection of bone cement into the deteriorating vertebral body—the SpineWand removes tumor tissue using radiofrequency energy combined with a saline solution. Dr. Wong explained that this device is different from previous radiofrequency devices in that just the tip heats up, delivering localized, precise heat that results in little or no heating damage to surrounding tissue.
Vertebroplasty alone is associated with a rate of complications that is three to five times higher in patients with malignant compression fractures than in vertebral fractures in a non-cancer population.
Originally Developed for Orthopedic Procedures
Vertebroplasty carries risks of cement leaking into the spinal cord, compression of nerves, and spinal cord injury, Dr. Wong explained. He had been studying techniques to make vertebroplasty safer in patients with spinal metastases. The SpineWand was originally developed for orthopedic procedures, but he found that the device lends itself to debulking spinal tumor prior to vertebroplasty and thereby avoids displacing cement or tumor cells into the spinal canal.
In the series reported at the meeting, the SpineWand was used to etch a cavity within an affected vertebral body and that cavity and adjacent interstices were filled with bone cement. In all cases, adequate amounts of cement were injected.
Cement extravasation was seen in only two cases, and neither had any clinical consequence. No thermal or neuronal injury was observed—unlike what has been seen with conventional radiofrequency techniques.
With follow-up ranging from one month to two years, all patients reported reduced pain, less use of narcotics for back-related pain, and improved function, Dr. Wong said.
The SpineWand technique offers a safer alternative to displacing tissue when vertebroplasty is called for, he said. “This technique appears to redirect cement away from the spinal canal, while improving interdigitation of cement and decreasing the risk of embolization.”
An expert not associated with the research, Mark H. Bilsky, MD, Associate Attending Neurosurgeon and Chief of the Spine Service at Memorial Sloan-Kettering Cancer Center in New York City, said he found the report of interest but is concerned about the use of the technique for the treatment of painful vertebral compression fractures due to spinal tumors.
He said that kyphoplasty and vertebroplasty are well-established procedures that have demonstrated significant pain relief for spinal tumor patients, particularly with multiple myeloma. Kyphoplasty employs an inflatable balloon used to create a void in the bone, which is subsequently filled with polymethylmethacrylate (PMMA).
Vertebroplasty uses a direct injection of PMMA into the bone under pressure. Dr. Wong, Dr. Bilsky said, proposes using a SpineWand with radiofrequency ablation to create the void in the bone from tumor necrosis, and PMMA is then used to fill that void.
“Whether radiofrequency ablation adds any utility to kyphoplasty or vertebroplasty is unclear from this pilot study and should be addressed in a randomized trial,” Dr. Bilsky said.
“Patients apparently improved in terms of pain control, decreased narcotic use, and function, but no standard outcome scores are provided. There is also no information about whether radiofrequency ablation improves local control of cancer over simple vertebroplasty, although this is an important goal of treatment.”
Indications for Therapy
Dr. Bilsky noted that the technical aspects of radiofrequency ablation and vertebroplasty are straightforward and can readily be performed by radiologists or surgeons, but the decisions regarding which treatments are appropriate requires an overall understanding of treatment strategies for spinal tumors.
“The indications for open surgery, radiation, chemotherapy, and vertebroplasty are becoming increasingly well defined,” he said. “The patient populations do not overlap, and thus a comparison of outcomes is difficult. Admittedly, surgery is more invasive than vertebroplasty and recovery is longer.”
“However, surgery is reserved for patients who have high-grade spinal cord compression from a radioresistant tumor and/or gross spinal instability, who can tolerate the procedure. Vertebroplasty or kyphoplasty is reserved for patients with painful compression fractures in the absence of epidural spinal impingement or gross instability, and these procedures are often used as an adjunct to radiation or chemotherapy.”
The vast majority of compression and burst fractures in the lumbar and thoracic spine do not require vertebral body augmentation, he said.
The majority of vertebral compressions do not cause long-standing back pain, Dr. Bilsky continued. Dexamethasone and radiation will often resolve pain in newly diagnosed spinal tumors, even in the presence of a compression fracture, and high-dose conformal radiation therapy, such as intensity modulated radiation therapy (IMRT), can effectively treat radioresistant tumors in the vertebral body or tumors with minimal epidural impingement.
“It is not known whether radiofrequency ablation will provide the same or even comparable durable tumor control [as high-dose conformal radiation therapy techniques],” he stated.
Limitations & Contraindications
According to Dr. Bilsky, although the SpineWand-assisted vertebroplasty technique may be effective for tumors causing vertebral compression fractures, “one must be aware of the limitations and contraindications.” In Dr. Wong's study, two patients had asymptomatic extravasation of PMMA into the spinal canal.
“A breech of the posterior cortex adjacent to the epidural space or epidural compression is a relative contraindication to this procedure,” Dr. Bilsky said.
He noted that in a series of 17 patients treated with vertebroplasty and radiofrequency, four patients with tumor adjacent to the spinal canal suffered neurologic complications (Nakatsuka A: J Vasc Interv Radiol 2004 15:707–712).
In addition, Dr. Bilsky said, a patient with a burst fracture at L4 with high-grade epidural compression and a radiculopathy was recently transferred to Memorial Sloan-Kettering Cancer Center after having radiofrequency ablation and vertebroplasty two weeks previously. That patient had spinal instability resulting in severe back pain and radiculopathy.
“While less invasive, the radiofrequency ablation and vertebroplasty did not improve the patients' agonizing symptoms, and he required a decompression and fixation, which was well tolerated. He is now six months out from surgery and ambulating,” Dr. Bilsky said.
Summing up, Dr. Bilsky said that vertebroplasty and kyphoplasty provide excellent pain palliation in a selected subset of patients, but cautioned that there are specific indications and contraindications.
“Whether radiofrequency ablation adds any utility to these established procedures is unknown. Interventional radiologists are performing kyphoplasty and vertebroplasty, as well as radiofrequency ablation. Additional considerations in choosing appropriate patients for vertebral body augmentation must be addressed when treating tumors as compared with osteoporotic fractures.”
Also, experience with radiofrequency ablation for the treatment of liver tumors cannot be translated to spinal tumors because of the close proximity to neural elements, he said. “Multidisciplinary review of cases is needed to prevent complications from these invasive procedures.”
FDA Grants Marketing Clearance for Cool-tip RF Ablation System for Nonresectable Liver Tumors
The Food and Drug Administration granted marketing clearance for the Cool-tip RF ablation system. The device is the first to be cleared for marketing to physicians for the ablation of nonresectable liver tumors, a news release from the manufacturer, Valleylab, notes.
The ablation system delivers therapeutic energy directly to the tumor through a 17-gauge needle electrode that is inserted through tissue and guided to the tumor using imaging technology.
Radio waves create energy at the needle tip to heat and destroy the tumor. During the ablation, water circulating through the electrode cools adjacent tissue, maximizing the amount of energy that can be delivered and creating the largest ablation possible in the least amount of time.
Since the Cool-tip ablation system is minimally invasive, it can be used repeatedly until the entire liver tumor is ablated.