CyberKnife Radiosurgery Research Articles

BOLD FMRI integration into radiosurgery treatment planning of cerebral vascular malformations

Functional magnetic resonance imaging (fMRI) is used to distinguish areas of the brain responsible for different tasks and functions. It is possible, for example, by using fMRI images, to identify particular regions in the brain which can be considered as "functional organs at risk" (fOARs), i.e., regions which would cause significant patient morbidity if compromised. The aim of this study is to propose and validate a method to exploit functional information for the identification of fOARs in CyberKnife (Accuray, Inc., Sunnyvale, CA) radiosurgery treatment planning; in particular, given the high spatial accuracy offered by the CyberKnife system, local nonrigid registration is used to reach accurate image matching. Five patients affected by arteriovenous malformations (AVMs) and scheduled to undergo radiosurgery were scanned prior to treatment using computed tomography (CT), three-dimensional (3D) rotational angiography (3DRA), T2 weighted and blood oxygenation level dependent echo planar imaging MRI. Tasks were chosen on the basis of lesion location by considering those areas which could be potentially close to treatment targets. Functional data were superimposed on 3DRA and CT used for treatment planning. The procedure for the localization of fMRI areas was validated by direct cortical stimulation on 38 AVM and tumor patients undergoing conventional surgery. Treatment plans studied with and without considering fOARs were significantly different, in particular with respect to both maximum dose and dose volume histograms; consideration of the fOARs allowed quality indices of treatment plans to remain almost constant or to improve in four out of five cases compared to plans with no consideration of fOARs. In conclusion, the presented method provides an accurate tool for the integration of functional information into AVM radiosurgery, which might help to minimize undesirable side effects and to make radiosurgery less invasive.

Efficacy and safety of CyberKnife radiosurgery for acromegaly

Acromegaly is a disease characterized by GH hypersecretion, and is typically caused by a pituitary somatotroph adenoma. The primary mode of therapy is surgery, and radiotherapy is utilized as an adjuvant strategy to treat persistent disease. The aim of this study was to determine the efficacy and tolerability of CyberKnife stereotactic radiosurgery in acromegaly. A retrospective review of biochemical and imaging data for subjects with acromegaly treated with CyberKnife stereotactic radiosurgery between 1998 and 2005 at Stanford University Hospital. Nine patients with active acromegaly were treated with radiosurgery using the CyberKnife (CK). Biochemical response based on serum insulin-like growth factor-1 (IGF-1), anterior pituitary hormone function, and tumor size with MRI scans were analyzed. After a mean follow up of 25.4 months (range, 6-53 months), CK radiosurgery resulted in complete biochemical remission in 4 (44.4%) subjects, and in biochemical control with the concomitant use of a somatostatin analog in an additional subject. Smaller tumor size was predictive of treatment success: baseline tumor volume was 1.28 cc (+/- 0.81, SD) vs. 3.93 cc (+/- 1.54) in subjects with a normal IGF-1 vs. those with persistent, active disease, respectively (P = 0.02). The mean biologically effective dose (BED) was higher in subjects who achieved a normal IGF-1 vs. those with persistent, active disease, 172 Gy(3) (+/-28) vs. 94 Gy(3) (+/-17), respectively (P < 0.01). At least one new anterior pituitary hormone deficiency was observed after CK in 3 (33%) patients: two developed hypogonadism, and one developed panhypopituitarism. CK radiosurgery may be a valuable adjuvant therapy for the management of acromegaly.

Cyberknife Radiosurgery - A New Treatment Method for Image-guided, Robotic, High-precision Radiosurgery

Cyberknife Radiosurgery - A New Treatment Method for Image-guided, Robotic, High-precision Radiosurgery

A Review Article on CyberKnife Stereotactic Radiosurgery for Spinal Lesions

The efficacy of the CyberKnife [Accuracy, Inc., Sunnyvale CA], a new stereotactic radiosurgery device utilized in the treatment of benign and malignant spinal tumors, is reviewed. The study assesses the number and type of spinal tumors safely and effectively treated with CyberKnife radiosurgery. Most reports concerning the utilization of CyberKnife stereotactic radiosurgery [CSR] for the treatment of malignant [primary, metastatic] or benign spinal lesions have been published within the last 5 years. CSR may be administered alone or in conjunction with surgery and external beam radiation therapy. A major benefit of CSR is that it can be completed within 1 week [1-5 fractions] as compared with the several weeks required for external beam radiotherapy, with limited toxicity. A frameless device, the CSR’s accuracy is +/- 1 mm. Additionally, the Xsight program now allows the cervical and lumbar spine to be treated without fiducial marker placement; however, this is still required to accurately target thoracic lesions. CyberKnife radiosurgery is effective in treating both benign and malignant lesions. For benign tumors, the CSR successfully arrests tumor progression and minimizes pain. It is unique for the management/palliation of malignant metastatic disease where it functions as an adjunct or alternative to invasive surgery and/or routine external beam radiotherapy. In summary, CyberKnife stereotactic radiosurgery, approved by the Federal Drug Administration [USA 2001], may be safely and effectively administered within 1 week’s time to treat both benign and malignant spinal lesions with limited toxicity.

Multisession cyberknife radiosurgery for the treatment of head and neck cancer

Multisession cyberknife radiosurgery for the treatment of head and neck cancer

77 POSTER Cyberknife (CK) radiosurgery in the treatment of non resectable pancreatic cancer: preliminary results

77 POSTER Cyberknife (CK) radiosurgery in the treatment of non resectable pancreatic cancer: preliminary results

Cyberknife Radiosurgery for Basal Skull Plasmacytoma

The Cyberknife delivers frameless image-guided stereotactic radiosurgery to intracranial and extracranial tumors. We report our use of Cyberknife radiosurgery on a medullary plasmacytoma in the clivus extending into the foramen magnum. No acute toxicity was seen during or within 24 hours of treatment, and the subject had a complete and durable radiographic response on MRI 12+ months after treatment. To our knowledge, this is a first case of successful Cyberknife radiosurgery of a medullary plasmacytoma.

Technical description, phantom accuracy, and clinical feasibility for fiducial-free frameless real-time image-guided spinal radiosurgery

The authors describe the technical application of the Xsight Spine Tracking System, data pertaining to accuracy obtained during phantom testing, and the initial clinical feasibility of using this fiducial-free alignment system with the CyberKnife in spinal radiosurgery. The Xsight integrates with the CyberKnife radiosurgery system to eliminate the need for implantation of radiographic markers or fiducials prior to spinal radiosurgery. It locates and tracks spinal lesions relative to spinal osseous landmarks. The authors performed 10 end-to-end tests of accuracy using an anthropomorphic head and cervical spine phantom. Xsight was also used in the treatment of 50 spinal lesions in 42 patients. Dose planning was based on 1.5-mm-thick computed tomography slices in which an inverse treatment planning technique was used. All lesions could be treated using the fiducial-free tracking procedure. Phantom tests produced an overall mean targeting error of 0.52 +/- 0.22 mm. The setup time for patient alignment averaged 6 minutes (range 2-45 minutes). The treatment doses varied from 12 to 25 Gy to the median prescription isodose of 65% (40 to 70%). The tumor volume ranged between 1.3 and 152.8 cm3. The mean spinal cord volume receiving greater than 8 Gy was 0.69 +/- 0.35 cm3. No short-term adverse events were noted during the 1- to 7-month follow-up period. Axial and radicular pain was relieved in 14 of 15 patients treated for pain. Fiducial-free tracking is a feasible, accurate, and reliable tool for radiosurgery of the entire spine. By eliminating the need for fiducial implantation, the Xsight system offers patients noninvasive radiosurgical intervention for intra- and paraspinal tumors.

CyberKnife Radiosurgery and Rituximab in the Successful Management of Sclerosing Idiopathic Orbital Inflammatory Disease

A 26-year-old man presented with symptoms suggesting idiopathic orbital inflammatory disease. After a poor initial response to oral steroids, an orbital biopsy confirmed the diagnosis. A paucicellular lymphocytic infiltrate with areas of fibrosis was seen to replace normal tissue. With the development of exposure keratopathy and diplopia associated with eyelid retraction, lagophthalmos, and decreased motility, increasing doses of steroids and intralesional steroid injections were instituted without effect. On the basis of successful treatment of malignant lymphocytic lesions, he was treated with CyberKnife radiosurgery and rituximab. This resulted in symptom resolution with improved eyelid closure and motility. Eighteen months after treatment, he is essentially symptom-free, with almost complete radiographic regression of his disease process.

An overview of cyberknife radiosurgery

Stereotactic radiosurgery is a non-invasive procedure that utilizes precisely targeted radiation as an ablative surgical tool. Conventional radiosurgery devices, such as the Gamma Knife, rely upon skeletally attached stereotactic frames to immobilize the patient and precisely determine the 3D spatial position of a tumor. A relatively new instrument, the CyberKnife (Accuray, Inc., Sunnyvale, CA), makes it possible to administer radiosurgery without a frame. The CyberKnife localizes clinical targets using a very accurate image-to-image correlation algorithm, and precisely cross-fires high-energy radiation from a lightweight linear accelerator by means of a highly manipulable robotic arm. CyberKnife radiosurgery is an effective alternative to conventional surgery or radiation therapy for a range of tumors and some non-neoplastic disorders. This report will describe CyberKnife technology and oncologic applications in neurosurgery and throughout the body.

Visual Field Preservation after Multisession CyberKnife Radiosurgery for Perioptic Lesions

The restricted radiation tolerance of the anterior visual pathways represents a unique challenge for ablating adjacent lesions with single-session radiosurgery. Although preliminary studies have recently demonstrated that multisession radiosurgery for selected perioptic tumors is both safe and effective, the number of patients in these clinical series was modest and the length of follow-up limited. The current retrospective study is intended to help address these shortcomings. Forty-nine consecutive patients with meningioma (n = 27), pituitary adenoma (n = 19), craniopharyngioma (n = 2), or mixed germ cell tumor (n = 1) situated within 2 mm of a "short segment" of the optic apparatus underwent multisession image-guided radiosurgery at Stanford University Medical Center. Thirty-nine of these patients had previous subtotal surgical resection, and six had previously been treated with conventional fractionated radiotherapy (6). CyberKnife radiosurgery was delivered in two to five sessions to an average tumor volume of 7.7 cm3 and a cumulative average marginal dose of 20.3 Gy. Formal visual testing and clinical examinations were performed before treatment and at follow-up intervals beginning at 6 months. After a mean visual field follow-up of 49 months (range, 6-96 mo), vision was unchanged postradiosurgery in 38 patients, improved in eight (16%), and worse in three (6%). In each instance, visual deterioration was accompanied by tumor progression that ultimately resulted in patient death. However, one of these patients, who had a multiply recurrent adrenocorticotropic hormone-secreting pituitary adenoma, initially experienced early visual loss without significant tumor progression after both a previous course of radiotherapy and three separate sessions of radiosurgery. After a mean magnetic resonance imaging follow-up period of 46 months, tumor volume was stable or smaller in all other cases. Two patients died of unrelated nonbrain causes. Multisession radiosurgery resulted in high rates of tumor control and preservation of visual function in this group of perioptic tumors. Ninety-four percent of patients retained or improved preradiosurgical vision. This intermediate-term experience reinforces the findings from earlier studies that suggested that multisession radiosurgery can be a safe and effective alternative to either surgery or fractionated radiotherapy for selected lesions immediately adjacent to short segments of the optic apparatus.

Frameless Cyberknife radiosurgery for metastatic and primary brain tumors

11527 Background: Cyberknife delivers image-guided stereotactic radiation to intracranial and extracranial skull base tumors without a frame. This frameless feature makes Cyberknife a completely non-invasive procedure and allows non-surgical neuro-oncology personnel to treat patients with tumors in the neuraxis. Methods: Patients with intracranial tumors were selected from our Brain Tumor Clinic if they were not surgical candidates or had residual tumors after neurosurgery. The decision for Cyberknife radiosurgery was made after careful review of all available treatment options in our multidisciplinary brain tumor conference based on patients’ history and neurologic findings, neuroimaging data, and pathology. All patients signed informed consent prior to fusion head MRI and CT scanning. They were pre-medicated with 4 mg of dexamethasone and 500 mg of levetiracetam twice daily. All dose plans were calculated based on CT images acquired from 1.25-mm slices with an inverse planning technique. Dynamic tracking software monitored patient movements and adjusted the robotic arm accordingly, compensating for patient motion up to 10 mm in translation and 5 degree in rotation. Results: Nine subjects with 15 treatment targets, including 4 meningiomas, 1 high-grade glioma, 1 plasmacytoma, and 3 melanomas, were treated with single-fraction or 5 fractions of Cyberknife radiosurgery. No acute toxicity was seen during or within 24 hours of treatment. One subject developed subacute onset of cerebral edema 2 weeks after the procedure but his symptoms were quickly reversed with dexamethasone. Conclusions: Cyberknife radiosurgery is a well-tolerated procedure for intracranial and extracranial tumors in the skull base. Neuro-oncologist, with the appropriate training, could perform Cyberknife radiation planning with radiation oncologists and physicists. No significant financial relationships to disclose.

Radiation treatment of spinal tumors using Cyberknife radiosurgery

1545 Background: Morbidity associated with spinal tumors can leave patients with functional limitations, pain, and poor quality of life. Since the integrity of the spinal column and the spinal cord must be preserved, treatments are limited especially in the setting of previous radiotherapy. We describe our experience using Cyberknife fractionated stereotactic radiosurgery in the initial treatment and retreatment of spinal tumors and its impact on patient quality of life. Methods: 152 patients with primary or metastatic spinal tumors were treated to 228 spinal sites at Georgetown University Hospital from 2002 to 2005. Neurologic examination, pain assessment by visual analog scale (0–100), and quality of life evaluations by SF-12 survey (mental and physical health scores) were performed initially and at 1, 3, 6, 9, 12, 18, and 24 months following treatment. The primary endpoints were pain and quality of life. 44 patients (109 sites) received Cyberknife radiosurgery as a component of their initial management. The median dose delivered was 2400 cGy (range 1400–8000) in 1–5 fractions (median 3). Median tumor volume was 56 mm3 (range 0.65–457.26). 108 patients (119 sites) with recurrent/persistent disease and a history of prior conventional radiation to the spine received Cyberknife radiosurgery as retreatment. Previous radiation doses ranged from 2000–5940 cGy. The median retreatment dose delivered was 2100 cGy (range 750–3500) in 1–5 fractions (median 3). Median tumor volume was 107.2 mm3 (range 0.94–838.9). Results: Optimized treatment plans were designed with the goal of limiting spinal cord doses. Median follow up is 13 months. No complications have been observed, including treatment related myelitis. Across all patients, the mean initial pain score was 73. Mean pain scores decreased significantly after the first month to 49 and remained significantly lower (40–44) for over one year. SF-12 PCS (initial mean 33) and MCS scores (initial mean 47) remained stable during the duration of the study. Conclusions: Fractionated stereotactic radiosurgery using the CyberKnife is a safe and effective treatment capable of delivering high-dose radiation to primary and recurrent spinal tumors. Follow-up data demonstrates durable pain relief and stable quality of life. No significant financial relationships to disclose.

TU‐C‐224C‐07: A Comprehensive Dosimetric Protocol for the Cyberknife Radiosurgery System

Purpose: To propose dosimetric guidelines specifically designed for the Cyberknife radiosurgery system. Non‐availability of 10×10cm2 field and use of small circular collimators (5mm to 60mm) pose serious problems, that have been faced in this study by means of 8 different detectors and Monte Carlo simulation. This work is oriented to measurement of total scatter factors (Sc,p) and to reference dosimetry, though indications will also be given in view of a comprehensive guideline. Method and Materials: PTW PinPoint 31014, Exradin A16 and T14P microchambers, TN 502RDM micromosfet, PTW 30008 diode and TM60003 diamond, MD55 and EBT radiochromic films were used to measure Sc,p. Monte Carlo simulations (BEAMnrc) were used to produce phase space descriptions at the exit plane of each collimator, to calculate: 1) theoretical Sc,p values in water, and 2) correction factors to be applied to Sc,p as measured by 5 detectors (PinPoint, A16, T14P, diode, diamond), obtained by simulating shape and chemical composition of each detector. BEAMnrc was also used to calculate stopping power ratios and chamber correction factors for the Cyberknife linac, to decide whether values of kQ from the IAEA398 protocol could be applied without using a 10×10cm2 field. Results: Sc,p of the 5mm collimator as measured by simulated detectors averaged 0.653 − 9%+14%. Variation for larger collimators was smaller. After Monte Carlo correction, Sc,p of the 5mm collimator became 0.686 −2%+1%. Pure Monte Carlo calculation gave Sc,p=0.715 +/−1%. Calculation of correction factors showed that kQ values for the investigated chambers could be chosen when using IAEA398, introducing +/−0.2% uncertainty. Conclusion: Pure Monte Carlo calculation gave higher values of Sc,p compared to Monte Carlo‐corrected measurement. The latter is to be preferred because correction factors are less sensitive to beam parameters than pure calculation of Sc,p. For determination of Sc,p use of microchambers and Monte Carlo correction is recommended.

Peripheral doses in CyberKnife radiosurgery

The purpose of this work is to measure the dose outside the treatment field for conformal CyberKnife treatments, to compare the results to those obtained for similar treatments delivered with gamma knife or intensity-modulated radiation therapy (IMRT), and to investigate the sources of peripheral dose in CyberKnife radiosurgery. CyberKnife treatment plans were developed for two hypothetical lesions in an anthropomorphic phantom, one in the thorax and another in the brain, and measurements were made with LiF thermoluminescent dosimeters (TLD-100 capsules) placed within the phantom at various depths and distances from the irradiated volume. For the brain lesion, gamma knife and 6-MV IMRT treatment plans were also developed, and peripheral doses were measured at the same locations as for the CyberKnife plan. The relative contribution to the CyberKnife peripheral dose from inferior- or superior-oblique beams entering or exiting through the body, internally scattered radiation, and leakage radiation was assessed through additional experiments using the single-isocenter option of the CyberKnife treatment-planning program with different size collimators. CyberKnife peripheral doses (in cGy) ranged from 0.16 to 0.041% (+/- 0.003%) of the delivered number of monitor units (MU) at distances between 18 and 71 cm from the field edge. These values are two to five times larger than those measured for the comparable gamma knife brain treatment, and up to a factor of four times larger those measured in the IMRT experiment. Our results indicate that the CyberKnife peripheral dose is due largely to leakage radiation, however at distances less than 40 cm from the field edge, entrance, or exit dose from inferior- or superior-oblique beams can also contribute significantly. For distances larger than 40 cm from the field edge, the CyberKnife peripheral dose is directly related to the number of MU delivered, since leakage radiation is the dominant component.

CyberKnife Radiosurgery for Benign Intradural Extramedullary Spinal Tumors

Microsurgical resection of benign intradural extramedullary spinal tumors is generally safe and successful, but patients with neurofibromatosis, recurrent tumors, multiple lesions, or medical problems that place them at higher surgical risk may benefit from alternatives to surgery. In this prospective study, we analyzed our preliminary experience with image-guided radiosurgical ablation of selected benign spinal neoplasms. Since 1999, CyberKnife (Accuray, Inc., Sunnyvale, CA) radiosurgery was used to manage 51 patients (median age, 46 yr; range, 12-86 yr) with 55 benign spinal tumors (30 schwannomas, nine neurofibromas, 16 meningiomas) at Stanford University Medical Center. Total treatment doses ranged from 1600 to 3000 cGy delivered in consecutive daily sessions (1-5) to tumor volumes that varied from 0.136 to 24.6 cm. Less than 1 year postradiosurgery, three of the 51 patients in this series (one meningioma, one schwannoma, and one neurofibroma) required surgical resection of their tumor because of persistent or worsening symptoms; only one of these lesions was larger radiographically. However, 28 of the 51 patients now have greater than 24 months clinical and radiographic follow-up. After a mean follow-up of 36 months, all of these later lesions were either stable (61%) or smaller (39%). Two patients died from unrelated causes. Radiation-induced myelopathy appeared 8 months postradiosurgery in one patient. Although more patients studied over an even longer follow-up period are needed to determine the long-term efficacy of spinal radiosurgery for benign extra-axial neoplasms, short-term clinical benefits were observed in this prospective analysis. The present study demonstrates that CyberKnife radiosurgical ablation of such tumors is technically feasible and associated with low morbidity.

Concomitant Ectatic Posterior Communicating Artery and Tentorial Meningioma as a Source of Oculomotor Palsy: Case Report

Although non-aneurysmal vascular compression of the oculomotor nerve is rare, it should be considered in the evaluation of unilateral oculomotor palsy. A 36-year-old non-diabetic man presented with two months of intermittent retro-orbital headache and third nerve paresis caused by compression of the oculomotor nerve between an ectatic, atherosclerotic posterior communicating artery (PComA) and a small tentorial meningioma. At operation, the subarachnoid portion of the nerve, prevented from migrating posteriorly and laterally by the meningioma, was grooved by the apex of the artery's loop. Microvascular decompression (MVD) of the artery loop from the nerve and resection of the meningioma were performed. Postoperatively, the patient's retro-orbital headache and oculomotor paresis, with the exception of mild anisocoria, resolved. Tumor infiltrating the posterior tentorium and lateral cavernous sinus was treated by Cyberknife radiosurgery five months later. One year after surgery, the patient had improvement in his headaches, full extra-ocular movements, and minimal residual anisocoria. Only one other report describes MVD of the third nerve from PComA compression. A review is presented of MVD carried out for similar cases of non-aneurysmal vascular compression of the oculomotor nerve. By analogy from cases in which an aneurysm is the compressing vascular structure, prompt surgical treatment is advocated. Complete evaluation of an isolated third nerve palsy should include MRI sequences designed to detect vascular compression of cranial nerves.

CyberKnife Frameless Radiosurgery for the Treatment of Extracranial Benign Tumors

Limited data exists for the use of radiosurgery for benign extracranial tumors. The purpose of this study was to evaluate the feasibility, toxicity, and local control of patients with benign extracranial lesions treated with the CyberKnife Frameless Radiosurgery System. From September 2001 thru January 2004, 59 benign tumors in 44 patients were treated using the CyberKnife a frameless image-guided radiosurgery system. Of these tumors, there were 21 neurofibromas, ten schwannomas, eight meningiomas, eight hemangioblastomas, seven paragangliomas, two hemangiopericytomas, one pseudotumor, one ependymoma, and one arteriovenous malformation (AVM). The anatomic locations of these tumors were spinal (25 cervical, four thoracic, 14 lumbar, and two sacral), neck (eight), orbital (three), brainstem (one), and foramen magnum (one). All patients were treated in a single fraction except three lesions were treated in a fractionated manner. The median treatment delivery time per fraction was 59 minutes (range 11-194). Twenty three lesions initially underwent surgical resection. Ten lesions received prior external beam radiation with a median dose 48 Gy (range 40-54 Gy), and one lesion received two prior CyberKnife treatments for a total dose of 32 Gy to the 80% isodose line. The median follow-up was eight months (range 1-25 months). Acute and late toxicity was graded using the National Cancer Institute Common Toxicity Criteria (CTC) scale. Symptomatic response was documented as "improved," "stable," or "progression". The median tumor dose delivered was 16.0 Gy to the 80% isodose line (range 10-31 Gy). The median tumor volume was 4.3 cc (range 0.14-98.6 cc). The median spinal cord volume receiving more than 8 Gy was 0.035 cc (range 0-2.5 cc) and the median maximum spinal cord dose 11.5 Gy (range 0-19.8 Gy). There were no patients that suffered a significant (Grade 3, 4, or 5) acute toxicity. There was no observed late toxicity. 78% of patients experienced an improvement of their pre-treatment symptoms while only one patient experienced symptom progression. Of the 26 patients who underwent follow-up imaging, the local control rate was 96%. This study suggests that CyberKnife Radiosurgery is a safe and efficacious treatment modality for benign tumors, even for those patients with recurrent previously irradiated lesions.

Radiation Re-treatment of the Spine Using CyberKnife Radiosurgery

Radiation Re-treatment of the Spine Using CyberKnife Radiosurgery

Multicenter Clinical Evaluation of CyberKnife Radiosurgery for Idiopathic Trigeminal Neuralgia

Multicenter Clinical Evaluation of CyberKnife Radiosurgery for Idiopathic Trigeminal Neuralgia