- Department of Radiation Oncology, David Geffen School of Medicine at UCLA, Los Angeles, California, USA
- Department of Neurosurgery, David Geffen School of Medicine at UCLA, Los Angeles, California, USA
Michael T. Selch
Department of Neurosurgery, David Geffen School of Medicine at UCLA, Los Angeles, California, USA
DOI:10.4103/2152-7806.98386Copyright: © 2012 Selch MT. This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.
How to cite this article: Selch MT, Tenn S, Agazaryan N, Lee SP, Gorgulho A, De Salles AA F. Image-guided linear accelerator-based spinal radiosurgery for hemangioblastoma. Surg Neurol Int 14-Jul-2012;3:73
How to cite this URL: Selch MT, Tenn S, Agazaryan N, Lee SP, Gorgulho A, De Salles AA F. Image-guided linear accelerator-based spinal radiosurgery for hemangioblastoma. Surg Neurol Int 14-Jul-2012;3:73. Available from: http://sni.wpengine.com/surgicalint_articles/image-guided-linear-accelerator-based-spinal-radiosurgery-for-hemangioblastoma/
Purpose:To retrospectively review the efficacy and safety of image-guided linear accelerator-based radiosurgery for spinal hemangioblastomas.
Methods:Between August 2004 and September 2010, nine patients with 20 hemangioblastomas underwent spinal radiosurgery. Five patients had von Hipple–Lindau disease. Four patients had multiple tumors. Ten tumors were located in the thoracic spine, eight in the cervical spine, and two in the lumbar spine. Tumor volume varied from 0.08 to 14.4 cc (median 0.72 cc). Maximum tumor dimension varied from 2.5 to 24 mm (median 10.5 mm). Radiosurgery was performed with a dedicated 6 MV linear accelerator equipped with a micro-multileaf collimator. Median peripheral tumor dose and prescription isodose were 12 Gy and 90%, respectively. Image guidance was performed by optical tracking of infrared reflectors, fusion of oblique radiographs with dynamically reconstructed digital radiographs, and automatic patient positioning. Follow-up varied from 14 to 86 months (median 51 months).
Results:Kaplan–Meier estimated 4-year overall and solid tumor local control rates were 90% and 95%, respectively. One tumor progressed 12 months after treatment and a new cyst developed 10 months after treatment in another tumor. There has been no clinical or imaging evidence for spinal cord injury.
Conclusions:Results of this limited experience indicate linear accelerator-based radiosurgery is safe and effective for spinal cord hemangioblastomas. Longer follow-up is necessary to confirm the durability of tumor control, but these initial results imply linear accelerator-based radiosurgery may represent a therapeutic alternative to surgery for selected patients with spinal hemangioblastomas.
Keywords: Hemangioblastoma, image-guided radiosurgery, spine
Hemangioblastomas are rare, benign vascular tumors of the central nervous system and account for approximately 3% of primary spinal cord neoplasms.[
Between August, 2004 and September, 2010, nine patients with 20 hemangioblastomas underwent spinal radiosurgery.
The technique of image-guided linear accelerator-based spinal radiosurgery has been described elsewhere.[
Treatment planning was carried out with a commercially available system (iPlan 3.0 and BrainSCAN® 5.3×, BrainLAB AG, Feldkirchen, Germany). All patients underwent supine CT and MRI which were fused by the mutual information technique and verified visually. Maximum tumor dimension was calculated using the formula a ± b ± c/3, where a, b, and c represent the largest anterior-posterior, medial-lateral, and superior-inferior dimensions displayed on contrast-enhanced axial, sagittal, and coronal MRI scans. Maximum tumor dimension varied from 2.5 to 24 mm (median 10.5 mm). The gross tumor volume (GTV) was contoured slice by slice on T1-weighted contrast-enhanced axial, coronal, and sagittal treatment planning MRI scans. Tumor volume varied from 0.08 to 14.4 cc (median 0.72 cc). All tumors demonstrated homogeneous contrast enhancement and one had a cystic component. The GTV did not include the cystic component in this lesion. A margin of normal tissue (range 1–3 mm, median 2 mm) was added to the GTV to create the clinical target volume (CTV). The prescription isodose encompassed the CTV. Nineteen targets received 12 Gy and one received 14 Gy. Dose was consistently prescribed at the 90% isodose line. In all cases, ≥95% of the target volume was included within the prescription isodose line [
Spinal cord was considered a critical object at risk (OAR) and was contoured slice by slice along the pial surface of the cord as displayed on the axial T2-weighted MRI. The length of spinal cord contoured in this series varied from 2 to 6 mm (median 6 mm) above and below the GTV in accordance with the recommendations of Ryu et al.[
Forward treatment planning was used for 17 targets and inverse planning methods for 3 lesions. Forward planned targets were irradiated with 2–5 (median 3) dynamic arcs and inverse planned targets with 5 modulated beams. All targets were treated with a single isocenter. Patients with multiple tumors were treated in a single session. The treatment process typically required 20 minutes per target.
Follow-up ranged from 14 to 86 months (median 51 months). Sixteen lesions were followed for more than 36 months. Follow-up included contrast-enhanced MRI every 6 months for 24 months and yearly thereafter plus clinical examination or telephonic interview. Computer-generated tumor volumes were not available on follow-up MRI examinations. Tumor progression was defined as a >25% increase in maximum tumor dimension persisting on two or more consecutive studies. Expansion of a known cyst or development of a new cyst was included in the definition of progression for the purpose of analyzing overall local control. Tumor response was defined as a >25% decrease in maximum tumor dimension persisting on two or more consecutive studies. Stable tumor was defined as no change in size or change <25%. Control rates were calculated by the Kaplan–Meier method. Adverse treatment effects were graded according to the common terminology criteria for adverse events (CTCAE v 3.0).[
All patients were alive at the time of this report. Kaplan–Meier estimated overall local control and solid tumor control rates at 48 months were 90% and 95%, respectively [Figures
Patients tolerated immobilization, automatic couch adjustments, and delivery of spinal radiosurgery without incident. No patient developed acute or delayed skin, tracheal, esophageal, or gastrointestinal morbidity. No patient experienced exacerbation of preexisting neurologic symptoms due to treatment without concomitant imaging evidence of progression. There was no imaging evidence for loss of central tumor contrast enhancement or perilesional edema suggestive of tumor necrosis. No patient manifested clinical or imaging findings compatible with spinal cord injury/myelopathy.
The results of this retrospective review demonstrate that image-guided linear accelerator-based radiosurgery safely controls growth of spinal cord hemangioblastomas. After a median follow-up of 51 months, the overall and solid tumor 4-year actuarial local control rates were 90% and 95%, respectively. The results of our series are similar to those reported elsewhere. Moss et al. reported a 5-year actuarial local control rate of 92% in a series of 16 spinal cord hemangioblastomas followed up for a median of 33.5 months after CyberKnife treatment.[
Statistically significant predictors of local progression could not be identified due to the rareness of relapse. The only solid tumor progression in this series occurred in a sporadic lesion treated after unsuccessful external beam radiotherapy. It is unclear if spinal hemangioblastomas that recur after prior exposure to ionizing irradiation are resistant to subsequent radiosurgery. Patrice and associates reported more frequent tumor relapse following radiosurgery for intracranial hemangioblastomas previously exposed to conventionally fractionated radiotherapy compared to unexposed tumors.[
A symptomatic cyst developed in 1 of 19 solid hemangioblastomas in this series. Following radiosurgery for intracranial hemangioblastoma, new cyst formation in the setting of controlled solid tumor has been reported by several authors.[
Both tumor response and clinical improvement were less frequent in our series than reported elsewhere. On follow-up MRI, one lesion responded according to the definition used in our study. Moss et al. reported tumor regression in 6 of 16 spinal tumors, but did not define the criteria for imaging response.[
The infrequent imaging and clinical response rates noted in our series may be a result of the low homogeneous dose used for spinal radiosurgery. The median prescribed dose and tumor maximum dose in our series were 12 Gy and 13.3 Gy, respectively. In the cranial gamma knife experience, Kano et al. delivered median prescribed and tumor maximum doses of 16 Gy and 32 Gy, respectively.[
Linear accelerator-based spinal radiosurgery for hemangioblastomas was free of acute and long-term morbidity. Investigators at Stanford University reported a 3-year actuarial rate of Grade ≥2 myeoplathy of 4% despite delivery of doses considerably higher than used in our series.[
There are several shortcomings of this study. Hemangioblastomas are benign neoplasms and encouraging short-term local control rates do not necessarily ensure durable remission. In a series of 44 hemangioblastomas followed for a median of 8.5 years after cranial radiosurgery, Asthagiri and associates reported 2- and 10-year local control rates of 91% and 51%, respectively.[
The decision to irradiate asymptomatic spinal hemangioblastoma remains controversial. Several authors have reported that neurological function following microsurgery is significantly correlated with preoperative performance status in patients with spinal hemangioblastoma.[
The results of this limited experience indicate that linear accelerator-based radiosurgery is safe and effective for patients with spinal cord hemangioblastomas. Longer follow-up is required to document the durability of local control. Microsurgical tumor resection remains the treatment of choice for spinal cord hemangioblastomas. Our initial results imply that linear accelerator-based radiosurgery may represent a therapeutic alternative to surgery for selected patients with spinal hemangioblastomas.
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