Radiofrequency Ablation With Percutaneous Vertebral Augmentation of Painful Spinal Metastases: An Adjunctive Treatment Prior to Radiation Therapy

Abstract

Painful spinal metastases are a common occurrence among patients with advanced disease. Radiation therapy (RT) is the primary treatment modality for patients with painful spinal metastases, but treatment can be limited by the patient’s level of pain and ability to cooperate or tolerate the treatment. Radiofrequency ablation (RFA) with or without percutaneous vertebral augmentation (PVA) has been used with excellent results to treat pain related to spinal metastases. This case report illustrates the use of RFA/PVA prior to RT to allow for successful radiation treatment.

Case Presentation

A 46-year old man presented with severe lower back pain that was 10 out of 10 on the Visual Analog Scale (VAS) for 2 weeks. He had a history of stage IIIC, T4a, N2a, M0 adenocarcinoma of the sigmoid colon, for which he underwent laparoscopic sigmoidectomy 4 years ago. He received 12 cycles of adjuvant chemotherapy with modified FOLFOX-6 regimen but was subsequently lost to follow-up thereafter.

At the time of presentation, his pain was localized to the lower lumbar region but also extended into his inguinal region bilaterally. He had no lower extremity radiculopathy otherwise. His pain was worsened by movement, particularly by leaving his bed or standing from a chair. He also had difficulty with lying flat. The pain was persistent despite large doses of narcotic pain medication, and he required hospital admission for pain control. On physical examination, he had point tenderness in the L3 region. The pain worsened with passive and active hip flexion. Motor and sensation were intact. Laboratory values, including serum calcium, were within normal limits.

Imaging

Magnetic resonance imaging (MRI) of the lumbar spine was obtained with contrast (Figure 1). The MRI showed a mass replacing the L3 vertebral body with enhancing soft tissues; this tissue involved multiple retroperitoneal lymph nodes and infiltrated the psoas muscles anteriorly. The mass compressed and obstructed the inferior vena cava (IVC) with subsequent deep venous thrombosis of the IVC focally, as well as non-occlusive thrombus in the iliac veins. There was no significant tissue within the epidural space. Positron emission tomography and computed tomography scans (PET/CT) (Figures 2A-B) showed intense F-18 fluorodeoxyglucose (FDG) uptake in the L3 vertebral body and surrounding retroperitoneal soft tissues. A small FDG-avid left lower lobe lung mass and right hilar lymph nodes were evident, as well as mild additional retroperitoneal lymphadenopathy (not shown). No other bony lesions were found.

Treatment

Due to the intractable pain, the patient could not lie on the treatment table for an extended period of time for stereotactic body radiation therapy (SBRT) planning and treatment. This pain occurred despite opioid medication. The patient was subsequently scheduled for radiofrequency ablation (RFA) and percutaneous vertebral augmentation (PVA) of the spinal lesion to provide better pain control prior to additional treatments.

After undergoing conscious sedation with fentanyl and midazolam, the patient was placed prone on the fluoroscopic table. Scout images of the lumbar spine were obtained (Figure 3). From a bi-pedicular approach, 11G coaxial bone cannulas were advanced into the posterior aspect of the L3 vertebral body. A 13G bone biopsy cannula was used to obtain a core specimen from the lesion in order to diagnose the tumor type (Figure 4A). A drill-tipped stylet was advanced into the anterior margin of the vertebral body (Figure 4B) in order to select the appropriate OsteoCool RFA probe (Medtronic). Two 15-mm ablation probes were then inserted (Figure 5), and ablation was carried out over 11 minutes and 30 seconds to achieve an ablation zone of 23 × 18 mm.

After ablation, the needles were removed. A T-tip Kyphon curette (Medtronic) was used to create channels for balloon delivery and to facilitate better cement filling (Figure 6). Next, two 15-mm Kyphon balloons (Medtronic) were advanced into the vertebral body and inflated to optimize cement filling and provide height restoration (Figure 7). After the balloons were deflated and removed, cement cannulas were placed through the guide cannulas, and 6 mL of Xpede bone cement (Medtronic) were administered. All needles were removed, and hemostasis was achieved with manual compression. Final spot images of the lumbar spine were obtained (Figure 8). The patient was allowed to recover in the supine position for 3 hours in the post-procedural care unit prior to returning to his regular hospital bed.

Follow-Up

The next morning, the patient had significant improvement in his pain, which was now 5 out of 10 on the VAS. He had no residual point tenderness but had persistent inguinal pain with active and passive hip flexion.

By post-operative day 3, the patient had marked improvement in symptoms, with pain decreased to 1 out of 10 on the VAS in his lower back, although he had persistent inguinal pain. The patient was now able to lie flat and motionless in his bed without pain. Biopsy results confirmed metastatic colon cancer. The patient was discharged home with a plan for outpatient treatment with radiation therapy of L2-L4 with 30 Gy in 10 fractions in the next 2 weeks.

Discussion

With advances in medical oncology, the proportion of patients living longer following initial cancer diagnosis is on the rise. As a result, the prevalence of more advanced disease is also increasing.^1,2 Painful spinal metastases are a common occurrence in patients with many types of stage IV cancers (Table 1). SBRT has been the mainstay of treatment for these lesions, with data mounting for RFA with or without percutaneous vertebral augmentation.^3-15 The National Comprehensive Cancer Network (NCCN) guidelines recognize PVA and RFA as interventional strategies for pain management and, subsequently, quality of life improvement.¹⁶ Studies have demonstrated the utility of treating patients with RFA (±PVA) as monotherapy, with good results in pain relief (up to 77% pain reduction).⁵ Additional studies report pain control following RFA in patients who have failed or have progressed after radiation therapy, or in those who have reached maximum threshold doses.¹⁵

Di Staso and colleagues reported a feasibility study in 45 patients of combined RT + RFA vs RT alone (15 vs 30 patients, respectively).⁷ There was an overall better and faster response to therapy in the RT + RFA cohort vs RT alone (93% vs 60% and 3 weeks vs 9 weeks, respectively). This study was limited by the available technology at that time. PVA was also not performed as part of the treatment. It is suggested that the addition of PVA is important to stabilize the cavity created by the ablation in order to prevent future pathologic fracture and vertebral body height loss.¹⁷ As in the case presented here, RFA/PVA can be used to treat patients who cannot undergo RT. In our practice, percutaneous treatment is followed by RT in most cases to provide local tumor control. RFA/PVA is offered as a first treatment in order to facilitate patient comfort and cooperation during RT and to provide more immediate pain control.

Although no survival advantage is directly observed in these treatments, quality of life and pain palliation are important considerations in oncologic patients.¹⁶ Studies have shown that patients who have pain appropriately managed have improved performance status.¹⁸ Appropriate pain management may allow for better and more aggressive cancer therapies, and longer life expectancies.

Currently, two devices are approved for RFA; these include the Spinal Tumor Ablation with Radiofrequency (STAR) Tumor Ablation System (Merit Medical) and the OsteoCool RF Ablation System (Medtronic). The STAR Tumor Ablation System uses a bipolar ablation probe with proximal and distal thermal couples for accurate temperature measurements. An articulating arm allows for directing the probe centrally into the vertebral body. RF energy is administered until the proximal thermocouple reaches 50°C. The OsteoCool System has an internally cooled bipolar probe that reduces charring and allows for a more consistent burn. Defined algorithms for bone, unique to each probe size, provide predictable ablation boundaries. Both systems have associated devices for vertebral augmentation with cement instillation to provide stability after tumor ablation.

Conclusion

RFA/PVA is an excellent adjunct to RT. In patients with debilitating back pain that prohibits RT planning and treatment, RFA can be offered first to allow successful RT. Together, these treatments provide better and more durable improvement in cancer-related back pain.

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