Interventional tumor removal: a new technique for malignant spinal tumor and malignant vertebral compression fractures without epidural involvement

Abstract

Background

Percutaneous vertebroplasty (PVP) is associated with incomplete pain relief and vertebral instability due to cement leakages.

Purpose

To evaluate the feasibility of a new method of PVP, radiofrequency ablation (RFA) and interventional tumor removal (ITR) for malignant spinal tumor and malignant vertebral compression fractures without epidural involvement.

Material and Methods

Twelve patients were treated with PVP, RFA, and ITR. A 14 G needle and a guidewire were inserted into the vertebral body, followed by sequential dilatation of the tract with the working cannula until the last working cannula reached the anterior portions of the pedicle. Thereafter, tumors were ablated with a radiofrequency probe, and ITR was performed with a marrow nucleus rongeurs. Then, cement was injected into the extirpated vertebral body. The data were collected and follow-up was performed after 1, 3, and 6 months, and thereafter every 6 months postoperatively.

Results

PVP, RFA, and ITR were technically successful in all patients. The average preoperative pain visual analog scale (VAS) score was 7.0 ± 1.0, which decreased to 2.1 ± 1.2 at 1 month, to 1.6 ± 1.4 at 6 months, to 1.8 ± 1.7 at 1 year, and was maintained at 1.3 ± 1.1 at >1-year follow-up. A total of 92% patients (11/12) obtained excellent and good pain relief with improvement of quality of life. Seven patients continued with follow-up healthcare, and five patients died of the underlying disease.

Conclusion

PVP, RFA, and ITR may be a feasible approach for malignant spinal tumor and malignant vertebral compression fractures without epidural involvement.

Keywords

Percutaneous vertebroplasty pain malignant spinal tumor extirpation metastasis radiofrequency ablation

Introduction

With the development of early cancer detection and improvements in medical care, the incidence of spinal metastasis is likely to increase as cancer patients live longer (1). One-third of all cancer patients develop spinal metastases (2), of which 70% are located in the thoracic spine, 20% in the lumbar spine, and 10% in the cervical spine (3). In 85% of patients, the metastases involve the vertebral body. Multiple spinal metastases are seen in 10–40% of patients. Primary tumors most likely to metastasize to the vertebral column are breast (16–37%), prostate (9–15%), lung (12–15%), kidney (3–6%), and thyroid (4%) (4 –6). Pain is the major symptom in patients with spinal metastases. Progression of spinal metastasis may result in vertebral body compression fracture, with a risk of spinal cord compression (7). Conventional therapies for painful spinal metastases include bed rest, bracing and radiation therapy. Radiotherapy may relieve pain; however, it cannot correct spinal deformity (8,9). Open surgical approaches can decompress and stabilize the spine and are associated with significant rates of morbidity and mortality (10,11).

Percutaneous vertebroplasty (PVP) is now considered as an effective procedure to achieve prompt pain control, and prevent further vertebral collapse and spinal cord compression in patients with vertebral metastases (12 –19). However, when performing PVP it is very difficult to control the direction of polymethyl methacrylate (PMMA) when penetrating into the targeted place when injected with high pressure due to the widespread infiltration and destruction of the cortex of the vertebral body by malignant tumors. Furthermore, cement leakages may lead to incomplete pain relief and local recurrence of metastatic tumors after the procedure. To minimize cement leakage and improve the efficacy of anti-tumor effect, we designed a new approach – PVP combined with radiofrequency ablation (RFA) and interventional tumor removal (ITR) – for patients with malignant spinal tumor and malignant vertebral compression fractures. The purpose of our study was to present the detailed innovative technique and evaluate the feasibility of PVP combined with RFA and ITR for malignant spinal tumor and malignant vertebral compression fractures caused by metastases in the thoracic and lumbar spine.

Material and Methods

Patients

This study was approved by the university committee on human investigation and informed consent was obtained from each patient. From October 2009 to December 2011, 12 patients with malignant spinal tumor and malignant vertebral compression fractures without epidural involvement were treated with PVP, RFA, and ITR. Demographic and clinical presentation of these patients is summarized in Table 1. Diagnoses of malignant spinal tumor and malignant vertebral compression fractures were based on the patients’ history and findings on computed tomography (CT) and magnetic resonance imaging (MRI), and histologically confirmed by biopsy specimens obtained before or during the procedure.

Table 1.

Summary of 12 patients with malignant spinal tumor and malignant vertebral compression fractures.

Pat./Age (years)/ Sex	Primary cancer	Location	Duration* (weeks)	Preoperative pain VAS score	Postoperative pain VAS score						Cement leakage	Follow-ups^† (months)	Outcome at the end of study
Pat./Age (years)/ Sex	Primary cancer	Location	Duration* (weeks)	Preoperative pain VAS score	1 week	1 month	3 months	6 months	1 year	>1 year	Cement leakage	Follow-ups^† (months)	Outcome at the end of study
1/73/M	Lung	L3	26	7	2	2	2	2	2	2	Intervertebral disk	15	Alive
2/57/F	Myeloma	L5	26	7	3	3	3	3	3	3	Puncture path	13	Dead
3/63/M	Prostate	T11	4	6	1	0	0	0	0	0	Paravertebral veins	14	Alive
4/45/M	Renal	T9	30	8	3	3	3	3	3	3	–	14	Alive
5/63/F	Liver	T12	4	8	2	2	2	1	1	1	–	25	Dead
6/65/F	Lung	L4	12	7	3	2	2	1	2	–	–	12	Alive
7/57/M	Lung	T9	5	6	2	2	2	1	1	1	–	13	Alive
8/68/M	Colon	T12	17	8	1	1	1	1	1	1	–	16	Alive
9/67/F	Lung	T12	1	7	3	2	1	0	0	0	–	15	Dead
10/61/F	Lung	T10	6	8	5	5	5	5	6	–	–	12	Dead
11/73/M	Thymic	T12	8	5	1	1	1	1	1	1	–	16	Dead
12/54/M	Lung	L5	8	8	2	2	2	2	–	–	–	11	Alive
Mean ± SD	–	–	12.3 ± 10	7.0 ± 1.0	2.4 ± 1.2	2.1 ± 1.2	1.9 ± 1.3	1.6 ± 1.4	1.8 ± 1.7	1.3 ± 1.1	–	14.7 ± 3.6	–

The time of spinal pain before the procedures.

†

Months to last follow-up after the procedures.

The indication for PVP, RFA, and ITR was one or more malignant spinal tumor and malignant vertebral compression fracture caused by metastases, causing severe pain and being unresponsive to non-operative modalities, as determined at a multidisciplinary consensus meeting consisting of experienced interventional radiologists and oncologists. Patients who underwent ITR for a malignant vertebral lesion with symptoms of neurological compression were excluded from this study. All patients underwent anteroposterior (AP) and lateral radiography and CT scanning, which were performed to evaluate the fracture configuration and vertebral wall integrity before the procedure. Marrow signal changes on MRI were assessed to determine the symptomatic levels and emergency of the fractures. Bone scans were used in patients for whom an MRI examination could not be performed because of contraindications such as the presence of a pacemaker or non-MR compatible metallic stents.

Interventions

Before the procedures, all patients were informed about the usual well-known risks and the rare but serious complications associated with the treatment, including anesthetic hazards, pulmonary embolism, infection, and spinal cord or nerve root compression. All procedures were performed by two experienced interventional radiologists (CGW and YFG, with 12 and 8 years of experience in spinal intervention, respectively) using a single plane angiography system under fluoroscopic guidance. Blood pressure, heart rate, SPO₂, and other vital signs were monitored by electrocardiography during the procedure.

The steps of the operative technique and photographs of the ITR instruments are shown in Figs. 1 and 2, respectively. The patient was placed in a prone position on an operating table. After marking the skin 5 cm from the midline, the skin entry point and tract were selected under fluoroscopic guidance and infiltrated with a local anesthetic (2% lidocaine). After local anesthesia, a 14 G needle and guidewire were inserted at the site of entry until the tip reached the center of the vertebral body, followed by sequential dilatation of the tract with working cannulae until the final working cannula (5 mm in diameter) reached the anterior portions of the pedicle. After removal of the penultimate cannula, a trepan was inserted through the last working cannula and the pedicle of the vertebral arch was cut slowly until the last working cannula reached the anterior portions of the pedicle.

Fig. 1.

Diagrams show the technique steps in performance of PVP, FRA and ITR. (a) Malignant spinal tumor within the vertebral body. (b) A 14 G needle and a guidewire are inserted at the intended site of entry until the tip reached the center of the vertebral body under fluoroscopic monitoring. (c) Dilatation of the tract is performed by a sequential working cannula, a trephine is then inserted through the last working cannula (5 mm in diameter) and the pedicle of the vertebral arch is slowly cut until the last working cannula reaches the anterior portion of the pedicle. (d) The last working cannula is inserted into the vertebral body. (e) Tumors are ablated with a radiofrequency needle inserted through the working cannula. (f) ITR is performed with marrow nucleus rongeurs inserted through the working cannula. (g) PMMA is injected into the extirpated vertebral body under fluoroscopic monitoring with the bone puncture needle inserted through the working cannula. (h) The bone puncture needle is removed and PMMA is retained in the extirpated cavity.

Fig. 2.

Photographs of the instrument used for interventional tumor removal including working cannula sets, trephine, and marrow nucleus rongeur.

After removal of the guidewire and trepan, a monopolar or multiple polar RF needle electrode (18–22 G) comprising an insulated shaft with a non-insulated distal tip was inserted through the working cannula under fluoroscopic monitoring until the tip of the needle was properly positioned within the tumor. The electrode was then activated, resulting in transfer of electrical current from the non-insulated distal tip into the surrounding tissue. The tumor was ablated at a temperature of 80℃ for 5–10 min, with 1 cm of the tip of the RF probe exposed.

After removal of the RF needle, ITR was performed with marrow nucleus rongeurs inserted through the working cannula (Fig. 3). The ITR was placed more deeply into the involved level so that more tumor tissue could be removed from the vertebral body. A total of 5–10 mL of commercially available PMMA (Osteo-Firm, COOK Medical, Bloomington, IN, USA) was then carefully injected into the treated vertebral body under continuous fluoroscopic monitoring of lateral and anteroposterior projections to ensure adequate filling of the lesion and to avoid leakage or migration of PMMA into the venous system toward the lungs. Injection was ceased when substantial resistance was met or when the cement reached the cortical edge of the broken vertebral body; injection was also immediately stopped if cement leaked into extraosseous structures, the epidural foramen or veins. In addition, PVP alone was also performed in the same patients on other malignant spinal tumors without vertebral compression fractures. Postprocedural fluoroscopic observations were made to confirm optimal filling of the lesion with no evidence of PMMA extravasation. After the procedure, patients were monitored for up to 6 h postoperatively.

Fig. 3.

Malignant spinal tumor of T9 vertebra owing to metastasis from lung cancer in a 56-year-old female patient with spinal pain prior to the procedure. (a) A 14 G needle and a working cannula are inserted into the T9 vertebra body. (b) The 14 G needle and the last working cannula are inserted into vertebral body. (c) The last working cannula is inserted into vertebral body from the left side. (d) ITR is performed with a marrow nucleus rongeurs inserted through the working cannula. (e) PMMA is injected into the vertebral body through the bone puncture needle from both sides. (f) The anteroposterior view shows the PMMA is injected into the T9 vertebral body (arrow).

Clinical outcome evaluation

The patients were clinically examined by two of us, who gathered the initial and follow-up data before and at 1 week, and 1, 3, 6, and 12 months afterwards. A standardized questionnaire was given to all patients pre- and postoperatively. The physical examination was performed prior to the procedures and when the patient returned for a clinical visit or was hospitalized again. Imaging follow-up comprised AP and lateral spinal radiography at 1 month, 6 months, and 1 year after the procedure. CT of the treated vertebra was conducted 3 days after PVP with a collimation of 2 mm, a pitch of 1, and 2-mm reconstruction intervals, to determine the distribution of cement in the lesion and to look for cement leakage outside the vertebral body or other possible local complications. MRI was performed in the same manner as before the procedure at 3 months and every 6 months after the procedure in all patients (Fig. 4).

Fig. 4.

The same patient as Fig. 3. (a, b) Sagittal T1WI and T2WI show malignant spinal tumor of T9 vertebra (arrow) with rupture of posterior wall prior to the procedure. (c, d) Sagittal T1WI and T2WI reveal malignant spinal tumor of T9 vertebra (arrow) is eliminated with resolution of the spinal pain and stability of the vertebral body 11 months after PVP and ITR.

Analgesic efficacy of the PVP, RFA, and ITR was assessed using a 10-point pain VAS score in which 0 corresponded to no pain and 10 corresponded to intolerable pain and categorized into four types: Excellent result (0–2), Good result (2.5–4.5), Fair, and Poor, respectively. Quality of life was assessed using a 100-point Karnofsky Performance Scale (KPS) (20). The physical examination was assessed using ASIA impairment scale (21). For each vertebra, we evaluated the filling quality as “good” (more than two-thirds of the vertebral volume), “mild” (one-third to two-thirds), or “insufficient” (less than one-third) and also recorded the filling volume in milliliters (14). Any potential complications following PVP, such as wound infections, nerve injuries, cement leakage, and pulmonary embolism were recorded.

Statistical analysis

Descriptive data were presented as the mean ± SD. Dichotomous and categorical data were reported as numbers and percentages. Mann ± Whitney U-test was used to compare the mean changes in VAS score, KPS prior to the procedures and at each follow-up after the procedures. All statistical analyses were performed using SPSS version 13.0 (SPSS Inc., Chicago, IL, USA), and P values <0.05 were considered to be statistically significant.

Results

Safety

PVP, RFA, and ITR were technically successful and well tolerated in all patients. There were no complications from infection, bleeding, pulmonary embolism, stroke or cardiac arrest, and there were no local or systemic reactions to the PMMA. Moreover, no cases of infection within the treated spinal segments were found after the follow-up periods. Each patient underwent single-level PVP, RFA, and ITR; and four also underwent PVP alone at other levels (Fig. 3). The mean postoperative hospital stay was 6.33 ± 0.98 days (range, 5–8 days) and the 30-day mortality was zero. CT showed cement leakage in three (25%) of the 12 treated vertebral bodies with PVP and ITR, and in three (43%) of the seven treated vertebral body with PVP alone. Leakages were into the intervertebral disk (n = 1), puncture path (n = 1), paravertebral space (n = 2), or veins (n = 3); none were into the spinal canal. Despite the leakage of PMMA, none of the patients developed any related clinical or neurological symptoms.

Analgesic efficacy

The average preoperative VAS score was 7.0 ± 1.0, which decreased to 2.1 ± 1.2 at 1 month, to 1.6 ± 1.4 at 6 months, to 1.8 ± 1.7 at 1 year and was maintained at 1.3 ± 1.1 at >1-year follow-up (Table 1). There was a statistically significant improvement in pain level between the preoperative evaluation and every follow-up assessment postoperatively (P < 0.001). A total of 92% patients (11/12) got excellent (n = 9) and good (n = 2) pain relief; in only one patient pain relief was not obvious after the procedures. Seven patients continued with follow-up healthcare after the procedures, and five patients died of the underlying diseases.

Quality of life

An overall improvement of the quality of life of the patients was evident. Initially, these patients needed assistance to change their body positions, get out of bed, put on clothes, and go to the toilet. After PVP, RFA, and ITR they did not need any help to perform such tasks. The KPS score showed an improvement of the patients’ quality of life during follow-ups after the procedures, with the average score improving from 64.17 ± 8.20 preoperatively, to 66.58 ± 5.53 at 1 week, to 68.24 ± 3.60 at 1 month, and 68.25 ± 5.35 at 3 months, to 68.83 ± 5.86 at 6 months, to 67.13 ± 7.12 at 1 year, to 70.33 ± 8.14 at >1 year (P < 0.05).

Cement filling and stability

The mean filling volume was significantly higher in 12 vertebrae with PVP, RFA, and ITR (5.66 ± 1.36 mL; range, 3–8 mL) than that in seven vertebrae with PVP alone (3.86 ± 1.46 mL; range, 2–7 mL) (P < 0.05). Among the 12 vertebrae, the vertebral filling was considered good in 67% (8/12) of cases, and mild in 33% (4/12); while, in seven vertebrae, the vertebral filling was considered good in 43% (3/7) of cases, mild in 43% (3/7), and insufficient in 14% (1/7). We did not observe any displacement of the treated vertebrae during follow-ups (range, 11–25 months; mean, 15.0 months).

Discussion

This aim of this study was to evaluate the feasibility of PVP, RFA, and ITR in patients with malignant spinal tumor and malignant vertebral compression fractures without epidural involvement. Our results showed a high technical success rate and significant improved initial and final pain relief rate and quality of life. The significant improvement in clinical success during follow-up periods seemed to be predominantly attributable to the elimination of malignant metastatic vertebral tumor with PVP, RFA, and ITR. These results suggest that PVP, RFA, and ITR can be considered a feasible treatment for patients with malignant spinal tumor and malignant vertebral compression fractures without epidural involvement. To date, this is the first report to describe treatment of malignant spinal tumor and malignant vertebral compression fractures without epidural involvement with PVP, RFA, and ITR.

PVP is a minimally-invasive, radiologically-guided therapeutic procedure and is considered as an effective procedure to achieve prompt pain control, prevent further vertebral collapse and spinal cord compression in patients with vertebral metastases (12 –19). The major complications of this procedure include cement leakage into the spinal canal or nerve root foramen resulting in spinal cord compression or radiculopathy and embolic events due to cement, marrow fat, or tumor entering the circulation (22). Complication rates with percutaneous vertebroplasty are reported at up to 10% in the treatment of metastatic disease, considerably higher than the rates in its use in osteoporosis (1%) or spinal angiomas (2.5%) (23). Although Calmels et al. (14) have demonstrated PVP as effective in decreasing canal narrowing for specimens with lytic metastases, the prerequisite was that the tumor is surrounded posteriorly with cement. In clinical practice, it is very difficult to obtain this with PVP alone, therefore, an effective alternative therapy is required.

In review of the literature, we have noticed that partial emptying of the vertebral body and creating a cavity within the body by laser (24) or by percutaneous kyphoplasty (PKP) (5,6) can prevent the leakage of cement, but laser is rarely used in clinical practice for malignant spinal tumor and kyphoplasty is too expensive to be afforded by most of the terminal cancer patients. Therefore, there are reasons to look for new cheap approaches in patients with malignant spinal tumor and malignant vertebral compression fractures. Marrow nucleus rongeurs, which we used for lumbar discectomy (25,26), could be use to create a cavity within the vertebral body. So, we made a new approach – the PVP combined with RFA and ITR for the malignant spinal tumor and malignant vertebral compression fractures.

PVP, RFA, and ITR are techniques that involve radiofrequency ablation of the spinal metastatic tumor followed by removal of the metastatic tumor components with a marrow nucleus rongeur, and subsequent injection of PMMA cement into the newly-formed cavity. Radiofrequency ablation is often used for tumor ablation, and marrow nucleus rongeurs are often applied to remove the herniated disk in spinal interventions. The techniques not only allow for ablation and removal of the spinal metastatic tumor, but also provide stability to the spine, minimize cement leakage, reduce vertebral compression, relieve pain, and allow the performance of bone biopsy. In addition, RF are also used for the prevention of tumor bleeding, which plays an important role in ensuring the safety of the procedure.

Compared with PKP, both procedures can create a cavity within the vertebral body, one is regular and the other is irregular. Both techniques can provide stability to the spine, minimize cement leakage, reduce vertebral compression, relieve pain, and allow bone biopsies. In addition, kyphoplasty and ITR can be used for vertebrae in the thoracic and lumbar spine, but not in the cervical spine, mainly because of the smaller sizes of the cervical vertebrae. PKP can increase vertebral height, reduce kyphotic deformity, but it has the risk of damaging the posterior wall when inflating the balloon too much, especially in osteolytic metastatic lesions. Moreover, it can not be used in malignant vertebral compression fractures with epidural involvement or symptoms of neurologic compression. The main difference lies in the fact that PVP combined with RFA and ITR, not only ablates and removes the spinal metastatic tumor but also eliminates the residual tumor with PMMA, while the kyphoplasty just creates a cavity with balloon tamping but not removes any tumor from the vertebra. Therefore theoretically, PVP, RFA, and ITR could gain a better clinical efficacy than kyphoplasty in long-term pain relief and vertebral stability due to more complete obliteration of the spinal metastatic tumor.

We acknowledge limitations to our study. First is the lack of a control group. A comparison between kyphoplasty and PVP, RFA and ITR would have been enlightening, especially with respect to the incidence of cement leakage. Second, the number of patients treated was relatively small, their life span was short, and death due to rapid progression of the disease might have masked both benefits and risks of the procedure; thus, expanded clinical trials are required to determine mid-term outcomes. Third, these procedures are time-consuming and relatively expensive. Fourth, the study was performed by experienced radiologists with experience in vertebroplasty procedures; given these are technically difficult we presume there would be a learning curve with the procedure and our results might not be generalizable for radiologists less familiar with the technique. Lastly, the tumor may have the risk of dissemination along the puncture path when performing ITR.

In conclusion, our preliminary results suggest that PVP, RFA, and ITR may be a feasible approach in the treatment of malignant spinal tumor and malignant vertebral compression fractures without epidural involvement.

Footnotes

Funding

This study has been supported by the National Natural Scientific Fund of China (Contract number: 81171440).

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