Image-guided Robotic Radiosurgery Research Articles

Epileptic encephalopathies secondary to hypothalamic hamartomas treated with radiosurgery: A case series.

Hypothalamic hamartomas are congenital lesions that typically present with gelastic seizures, refractory epilepsy, neurodevelopmental delay, and severe cognitive impairment. Surgical procedures have been reported to be effective in removing the hamartomas, however, they are associated with significant morbidity. Therefore, it is not considered a safe therapeutic modality. Image-guided robotic radiosurgery (CyberKnife® Radiosurgery System) has been shown to provide good outcomes without lasting complications. This series of cases describes the clinical, radiological, radiotherapeutic, and postsurgical outcomes of five patients with epileptic encephalopathies secondary to hypothalamic hamartomas who were treated with CyberKnife®. All patients exhibited refractory epilepsy with gelastic seizures and were unsuitable candidates for surgical resection The prescribed dose ranged between 16 and 25 Gy, delivered in a single fraction for four patients and five fractions for one patient while adhering strictly to visual pathway constraints. After radiosurgery, four patients maintained seizure control (one with an Engel class Ia, three with an Engel class 1d), and another presented sporadic, nondisabling gelastic seizures (with an Engel class IIa). After 24-26 months of follow-up, in three patients, their intelligence quotient scores increased. No complications were reported. This report suggests that Cyberknife may be a good option for treating hypothalamic hamartoma, particularly in cases where other noninvasive alternatives are unavailable. Nevertheless, additional studies are essential in order to evaluate the effectiveness of the technique in these cases.

528 Robotic Image-Guided LINAC Radiosurgery for Trigeminal Neuralgia: Results After 10 Years

INTRODUCTION: Frameless image-guided robotic radiosurgery delivering 60 Gy to a 6mm mid-cisternal/retrogasserian segment of the affected trigeminal nerve was used to treat 702 patients affected by severe Trigeminal Neuralgia(TN) refractory to medications . Clinical outcomes in 92 patients with minimum follow-up of 10 years are here reported. METHODS: 702 patients with severe, long-standing TN refractory to medications have been treated at the Cyberknife Center of CDI,Milan,Italy over the last 13 years. A dedicated protocol for imaging ( head CT with and without contrast, slice thickness 0,5 mm; brain MR including MPRAGE and CISS/FIESTA sequences) and treatment( selecting a 6 mm segment of the nerve going from the midcisternal toward the retrogasserian region with a dose prescription of 60Gy @80% isodose) was employed. Regular clinical follow-up was performed one or more times per year according to clinical needs and distance from the treatment. Recurrent pain was treated with the same protocol( a lower dose of 45 Gy was later selected for retreatments). RESULTS: Pain control rates of 92%,87%,76%,74% after respectively 1,2, 3 and 5 years have been found. 92 patients with follow-up longer than 10 years show pain control rate of 72% while the rate of persistent bothering parethesias is 5, 4% (5 patients). No other neurological complications have been found. CONCLUSIONS: Long-term follow-up shows that frameless Linac radiosurgery provides long-term pain control in over 2/3 of the treated patients, with low rate of sensory complications and no other neurological complications.

Image-Guided Robotic Radiosurgery for the Treatment of Lung Metastases of Renal Cell Carcinoma-A Retrospective, Single Center Analysis.

Simple SummaryPatients with metastatic renal cell carcinoma are difficult to treat despite many new systemic therapy options. Patients often present with pulmonary metastases. Local treatment of those metastases is traditionally performed surgically. In this study, robotic radiosurgery is tested in 50 patients with pulmonary metastases and is demonstrated to be a safe and highly effective treatment option in this patient group. Future research might focus on the combination of robotic radiosurgery with systemic treatment.Pulmonary metastases are the most frequent site of metastases in renal cell carcinoma (RCC). Metastases directed treatment remains an important treatment option despite advances in systemic therapies. However, the safety and efficacy of robotic radiosurgery (RRS) for the treatment of lung metastases of RCC remains unclear. Patients with metastatic RCC and lung metastases treated by RRS were retrospectively analyzed for overall survival (OS), progression-free survival (PFS), local recurrence free survival (LRFS) and adverse events. The Kaplan–Meier method was used for survival analysis and the common terminology criteria for adverse events (CTCAE; Version 5.0) classification for assessment of adverse events. A total of 50 patients were included in this study. Median age was 64 (range 45–92) years at the time of RRS. Prior to RRS, 20 patients (40.0%) had received either tyrosine kinase inhibitors or immunotherapy and 27 patients (54.0%) were treatment naïve. In our patient cohort, the median PFS was 13 months (range: 2–93). LRFS was 96.7% after two years with only one patient revealing progressive disease of the treated metastases 13 months after RRS. Median OS was 35 months (range 2–94). Adverse events were documented in six patients (12%) and were limited to grade 2. Fatigue (n = 4) and pneumonitis (n = 2) were observed within 3 months after RRS. In conclusion, RRS is safe and effective for patients with metastatic RCC and pulmonary metastases. Radiation induced pneumonitis is specific in the treatment of pulmonary lesions, but not clinically relevant and survival rates seem favorable in this highly selected patient cohort. Future directions are the implementation of RRS in multimodal treatment approaches for oligometastatic or oligoprogressive disease.

Image-Guided Robotic Radiosurgery for the Treatment of Same Site Spinal Metastasis Recurrences.

BackgroundDue to recent medical advancements, patients suffering from metastatic spinal disease have a prolonged life expectancy than several decades ago, and some will eventually experience relapses. Data for the retreatment of spinal metastasis recurrences occurring at the very same macroscopic spot as the initially treated lesion are limited. Previous studies mainly included recurrences in the boundary areas as well as other macroscopic parts of the initially affected vertebrae. This study exclusively analyzes the efficacy and safety of spinal reirradiation for recurrences on the same site utilizing single-session robotic radiosurgery.Materials and MethodsPatients between 2005 and 2020 who received radiotherapy for a spinal metastasis suffering from a local recurrence were eligible for analysis. Only patients undergoing a single-session reirradiation were included. All recurrences must have been occurred in the same location as the initial lesion. This was defined as a macroscopic recurrence on computed tomography occurring at the same site as the initial spinal metastasis. All other lesions, including those in the boundary areas or other parts of the initially affected vertebrae, were excluded.ResultsFifty-three patients with fifty-three lesions were retreated for spinal metastases. The median dose and number of fractions for the initial radiotherapy were 36 Gy and 15, respectively. Eleven patients were initially treated with stereotactic body radiotherapy. Retreatment was performed with a median dose of 18 Gy prescribed to a median isodose of 70%. The local control was 77% after a median follow-up of 22.2 months. Patients experiencing a second recurrence received a lower dose (p = 0.04), mostly below 18 Gy, and had a worse coverage (p = 0.01) than those showing local tumor control. 51% of patients experienced an improvement in pain control after treatment delivery. Besides, four vertebral compression fractures (7% of patients) but no other adverse events higher than grade 2 were observed.ConclusionSingle-session robotic radiosurgery appears to be a safe, time-saving, and effective treatment modality for spinal metastasis recurrences occurring in the same initial location if a considerable dose and coverage can be applied. Treatment results are comparable to reirradiated metastases in the boundary areas.

Long-term outcomes of 170 brain arteriovenous malformations treated by frameless image-guided robotic stereotactic radiosurgery: Ramathibodi hospital experience.

This study was conducted to report long-term outcomes of the frameless robotic stereotactic radiosurgery (SRS) for brain arteriovenous malformation (AVM) at Ramathibodi Hospital.Retrospective data of patients with brain AVM (bAVM), who underwent CyberKnife SRS (CKSRS) at Ramathibodi Hospital from 2009 to 2014, were examined. Exclusion criteria were insufficient follow-up time (<36 months) or incomplete information. Patients’ demographics, clinical presentation, treatment parameters, and results were analyzed. Excellent outcome was defined as AVM obliteration without a new neurological deficit. Risk factors for achieving excellent outcome were assessed.From a total of 277 CKSRS treatments for bAVM during the 6 years, 170 AVMs in 166 patients met the inclusion criteria. One hundred and thirty-nine cases (81.76%) presented with hemorrhages from ruptured bAVMs. Almost two-thirds underwent embolization before radiosurgery. With the median AVM volume of 4.17 mL, three-quarters of the cohort had single-fraction CKSRS, utilizing the median prescribed dose of 15 Gray (Gy). In the multisession group (25.29%), the median prescribed dose and the AVM volume were 27.5 Gy and 22.3 mL, respectively. An overall excellent outcome, at a median follow-up period of 72.45 months, was observed in 99 cases (58.24%). Seven AVMs (4.12%) ruptured after CKSRS but 1 patient suffered a new neurological deficit. Two patients (1.18%) were classified into the poor outcome category but there were no deaths. Negative factors for excellent outcome, by multivariate regression analysis, were the male sex and multisession SRS delivery, but not age, history of AVM rupture, previous embolization, or AVM volume.Despite relatively larger bAVM and utilizing a lower prescribed radiation dose, the excellent outcome was within the reported range from previous literature. This study offers one of the longest follow-ups and the largest cohorts from the frameless image-guided robotic SRS community.

Image-Guided Robotic Radiosurgery for the Management of Intramedullary Spinal Cord Metastases-A Multicenter Experience.

Simple SummaryDue to recent medical advancements, patients suffering from metastatic cancer have a prolonged life expectancy compared to several decades ago. Thus, the number of patients who experience metastasis to the spinal cord is increasing. Intramedullary metastases bear a dismal prognosis and cause considerable morbidity. Limited data are available on the treatment of such lesions. As surgery may be the mainstay of treatment for resectable and localized metastatic spread, previous case reports and series suggest radiosurgery to be a treatment alternative. This first multicenter study analyzes the efficacy of robotic radiosurgery (RRS) for the management of intramedullary metastases. Outcomes provide evidence that RRS is a safe, time-saving and effective treatment modality, especially for patients with unresectable lesions. Most patients die from systemic disease progression, while the majority of treated lesions remain controlled until death. Most symptoms improve or stay stable after treatment. These findings may guide further palliative care of affected patients.Background: Intramedullary metastases are rare and bear a dismal prognosis. Limited data are available on the treatment of such lesions. As surgery may be the mainstay of treatment for patients with resectable and localized metastatic spread, previous case reports and case series suggest radiosurgery to be another viable treatment modality. This multicenter study analyzes the efficacy and safety of robotic radiosurgery (RRS) for intramedullary metastases. Methods: Patients who received RRS for the treatment of at least one intramedullary metastasis were included. Results: Thirty-three patients with 46 intramedullary metastases were treated with a median dose of 16 Gy prescribed to a median isodose of 70%. The local control was 79% after a median follow-up of 8.5 months. The median overall survival (OS) was 11.7 months, with a 12- and 24-month OS of 47 and 31%. The 12-month progression-free survival was 42% and at 24 months 25%. In addition, 57% of patients showed either an improved or stable neurological function after treatment delivery. Systemic disease progression was the main cause of death. No significant treatment-related toxicities were observed. Conclusions: RRS appears to be a safe, time-saving and effective treatment modality for intramedullary metastases, especially for patients with unresectable lesions and high burden of disease.

Image-guided robotic radiosurgery for glomus jugulare tumors-Multicenter experience and review of the literature.

Glomus jugulare tumors (GJTs) are challenging to treat due to their vascularization and location. This analysis evaluates the effectiveness and safety of image-guided robotic radiosurgery (RRS) for GJTs in a multicenter study and reviews the existing radiosurgical literature. We analyzed outcome data from 101 patients to evaluate local control (LC), changes in pretreatment deficits, and toxicity. Moreover, radiosurgical studies for GJTs have been reviewed. After a median follow-up of 35 months, the overall LC was 99%. Eighty-eight patients were treated with a single dose, 13 received up to 5 fractions. The median tumor volume was 5.6 cc; the median treatment dose for single-session treatments is 16 Gy, and for multisession treatments is 21 Gy. Fifty-six percentage of patients experienced symptom improvement or recovered entirely. RRS is an effective primary and secondary treatment option for GJTs. The available literature suggests that radiosurgery is a treatment option for most GJTs.

Stereotactic Dorsolateral Irradiation of Spinal Nerve Roots: A Novel Technique for the Treatment of Spasticity and Pain

Selective dorsal rhizotomy is an established surgical treatment to improve the neurological and functional status of children with spastic cerebral palsy and adults with spasticity and pain caused by a variety of brain and spinal injuries. This procedure requires a dorsolumbar laminectomy to expose the appropriate dorsal rootlets, which are sectioned according to the presence of sustained electromiographic discharges.Image-guided robotic radiosurgery targeting the intracisternal sensory root of the trigeminal nerve has been described as a safe and effective non-invasive treatment for trigeminal neuralgia, a paroxystic pain disorder which often responds poorly to medical therapy. Image-guided radiosurgery requires no frame placement and can treat brain or spinal targets with submillimetric precision. This technique can be used to treat cervical or lumbar dorsal roots.A 44-year-old patient with von Hippel-Lindau disease developed severe spastic tetraparesis following multiple brain and spinal procedures. Spasticity and related pain mostly affected the right leg, with sustained electromiographic discharges originating from the right L4 nerve root. Response to medical therapy with baclofen and cannabinoids was poor. Due to geographical and logistical issues, the patient declined the placement of an intrathecal baclofen pump.Considering the poor general condition of the patient and his decision to avoid invasive procedures, a novel treatment option was offered to provide relief from spasticity and pain: stereotactic image-guided irradiation delivered to the sensory root. The patient underwent a right intraforaminal dorsolateral L4 root stereotactic irradiation with a delivered dose of 45 Gy prescribed to the 82% isodose.The treatment was well tolerated, without side effects. Resolution of spasticity and related pain in the right leg was found six months after the procedure. A marked reduction of spasticity and pain was also evident in the contralateral leg. These improvements have been stable over the last 18 months.So far, two additional patients underwent stereotactic dorsolateral spinal root irradiation (one delivered to a cervical, the other to a lumbar), with similar positive outcomes. These preliminary results suggest that spinal root stereotactic image-guided irradiation, a novel treatment option in the neurosurgical armamentarium, is a safe and effective procedure and deserves further investigation.

Single-session image-guided robotic radiosurgery and quality of life for glomus jugulare tumors.

Limited data are available on the efficacy and impact on the quality of life (Qol) of single-session image-guided robotic radiosurgery (RRS) for glomus jugulare tumors (GJTs). This study investigates the role of RRS in the management of GJTs and reviews the RRS literature. We analyzed 53 GJT patients treated with RRS to evaluate the safety, local control, clinical outcome, and Qol assessed by the SF12v2. The local control was 98% at a median follow-up of 38 months. The median tumor volume was 4.3 cc and tumors were treated with a median dose of 16.5 Gy. At the last follow-up, 35 patients had recovered from their symptoms or experienced symptom improvement. Qol analyses showed no significant decline while bodily pain significantly decreased. RRS is a safe and efficient tool for the treatment of GJTs. Qol of patients after treatment is stable and tends to improve over time.

Cyberknife Radiosurgery for Trigeminal Neuralgia.

IntroductionImage-guided robotic radiosurgery is an emerging minimally-invasive treatment option for trigeminal neuralgia (TN). Our group has treated 560 cases up to date, and report here the clinical outcomes of 387 treatments with three years follow-up. This study represents the largest single-center experience on CyberKnife radiosurgery for the treatment of TN so far reported.MethodsCyberKnife radiosurgery treatment was offered to patients with drug-resistant TN, after the failure of other treatments or refusal of invasive procedures. A second treatment was offered to patients with a poor response after the first treatment or with recurrent pain. Treatment protocol required the non-isocentric delivery of 60 Gy prescribed to the 80% isodose to a 6 mm retrogasserian segment of the affected trigeminal nerve. Retreatments typically received 45 Gy, again prescribed to the 80% isodose. The final plan was developed accordingly to individual anatomy and dose distribution over the trigeminal nerve, gasserian ganglion, and brainstem. Clinical outcomes such as pain control and hypoesthesia/numbness have been evaluated after 6, 12, 24, and 36 months. ResultsOur group has treated 527 patients with Cyberknife radiosurgery at Centro Diagnostico Italiano (CDI), Milan, Italy, during the last decade. A minimum follow-up of six months was available on 496 patients. These patients received 560 treatments: 435 patients (87.7%) had a single treatment, 60 patients (12.1%) had two treatments, and one patient (0.2%) had five treatments (two on the right side, three on the left side). Twenty four patients had multiple sclerosis (4.8%). Four hundred and forty-three patients (84%) received the treatment without previous procedures, while 84 patients (16%) underwent radiosurgery after the failure of other treatments. A neurovascular conflict was identified in 59% of the patients. Three hundred and forty-three patients (receiving a total of 387 treatments) had a minimum of 36 months follow up. Pain relief rate at 6, 12, 18, 24, 30 and 36 months was respectively 92, 87, 87, 82, 78 and 76%. Forty-four patients out of 343 (12.8%) required a second treatment during the observed period. At 36 months post-treatment, 21 patients (6,1%) reported the presence of bothering facial hypoesthesia. Eighteen patients out of 21 (85.7%) developed this complication after a repeated treatment. ConclusionsFrameless image-guided robotic radiosurgery in experienced hands is a safe and effective procedure for the treatment of TN, providing excellent pain control rates in the absence of major neurological complications. Repeated treatments due to recurrent pain are associated with restored pain control but at the price of a higher rate of sensory complications.

Factors affecting the accuracy of respiratory tracking of the image-guided robotic radiosurgery system.

To analyze the factors affecting the tracking accuracy of the CyberKnife Synchrony Respiratory Tracking System (SRTS). A dynamic motion phantom (motion phantom) reproduced the respiratory motions of each patient treated with the SRTS using a ball as the target. CyberKnife tracked the ball using the SRTS, and this process was recorded by a video camera mounted on the linear accelerator head. The tracking error was evaluated from the images captured by the video camera. Multiple regression analysis was used to identify factors affecting tracking accuracy from 91 cases. The median tracking error was 1.9mm (range 0.9-5.3mm). Four factors affected the tracking accuracy: the average absolute amplitude of the tumor motion in the cranio-caudal (CC) direction (p = 0.007), average position gap due to the phase shift between the internal tumor and external marker positions in the CC direction (p < 0.001), and average velocity of the tumor in the CC (p < 0.001) and anterior-posterior directions (p = 0.033). We identified factors that affected tracking accuracy. This information may assist the identification of suitable margins that should be added to each patient's clinical target volume.

Image-Guided Robotic Radiosurgery for Treatment of Recurrent Grade II and III Meningiomas. A Single-Center Study

Stereotactic radiosurgery (SRS) has been increasingly applied for malignant meningiomas as an alternative to conventionally fractioned radiation therapy. We performed a retrospective analysis of an institutional patient cohort with malignant meningiomas treated by image-guided SRS. All patients with atypical or anaplastic meningiomas who were treated by SRS using CyberKnife (CK) were identified. Local failure and regional and/or distant recurrences were evaluated together with toxicity and overall survival. We identified 127 treated lesions (105 atypical and 22 anaplastic) in 35 patients. The mean time interval between the last surgery and subsequent CK-SRS was 30.8 ± 24.5 months. Most lesions (83.5%) were treated using single-fraction CK-SRS. The median planning target volume of all 127 lesions was 1.71 cm3 (range, 0.06-22.5 cm3). The median follow-up period was 23 months (range, 2.1-60.3 months). The estimated local control rates were 97%, 77%, and 67% at 12, 36, and 60 months, respectively, in atypical meningiomas and 66% each at 12 and 24 months in anaplastic meningiomas. The regional progression-free survival was 93%, 73%, and 59% at 12, 36, and 60 months, respectively, in atypical lesions and 93% and 46% at 12 and 24 months in anaplastic lesions. The estimated distant tumor progression-free interval in atypical lesions was 80%, 44%, and 44% at 12, 36, and 60 months, respectively, and 49% and 24% at 12 and 24 months, respectively, in anaplastic lesions. Age was identified as a risk factor for local failure. Although the real boundaries of efficacy of SRS have to be further evaluated in a prospective trial, it seems that aggressive treatment by high-dose single or multisession SRS of recurring malignant meningiomas provides satisfactory local control rates.

A Second Course of Stereotactic Image-Guided Robotic Radiosurgery for Patients with Cerebral Metastasis

The purpose of this research was to study the outcome of brain metastases in a cohort of patients undergoing a second course of stereotactic image-guided robotic radiosurgery and to identify predictors corelated with survival. A total of 63 patients with primary malignancies underwent a second course of CyberKnife radiosurgery for intracranial progression, including recurrence and new metastases after initial stereotactic radiosurgery (SRS). Overall survival (OS) and control rate were calculated by the Kaplan-Meier method. A Cox proportional hazards model was used to analyze predictive factors for survival. With a median follow-up duration of 12 months after second SRS, the median OS of the second course of radiosurgery was 18 months. On multivariate analysis, the sum of total planned target volume (hazard ratio, 2.112; 95% confidence interval, 1.069-4.173) and minimum dose (hazard ratio, 1.990, 95% confidence interval, 1.017-3.892) were significantly associated with OS. Median intracranial progression-free survival was 23 months. The 6-month and 12-month local control rates of the targets were 97.0% and 94.4%, respectively. Univariate analysis showed that onlytumor number significantly influenced intracranial progression-free survival (P= 0.012). Nine patients (14.2%) developed brain necrosis. Median time to brain necrosis in regions in which brain necrosis occurred after a single course of SRS was not reached, compared with 16 months for those treated with repeat SRS (P= 0.041). A second course of CyberKnife radiosurgery seems to be an effective salvage option for brain progression after initial SRS. The total planned target volume shows prediction for OS. Tumor volume of initial SRS may influence selection of the potential population that may benefit from salvage radiosurgery.

Image-Guided Robotic Radiosurgery for Trigeminal Neuralgia.

BACKGROUNDFrameless, non-isocentric irradiation of an extended segment of the trigeminal nerve introduces new concepts in stereotactic radiosurgery for medically resistant trigeminal neuralgia (TN).OBJECTIVETo report the results of the largest single-center experience about image-guided robotic radiosurgery for TN.METHODSA cohort of 138 patients treated with CyberKnife® (Accuray Incorporated, Sunnyvale, California) radiosurgery with a minimum follow-up of 36 mo were recruited. Pain relief, medications, sensory disturbances, rate and time of pain recurrence were prospectively analyzed.RESULTSMedian follow-up was 52.4 mo; median dose 75 Gy; median target length 5.7-mm; median target volume 40 mm³; median prescription dose 60 Gy (80% isodose line). Actuarial pain control rate (Barrow Neurological Institute [BNI] class I-IIIa) at 6, 12, 24, and 36 mo were 93.5%, 85.8%, 79.7%, and 76%, respectively. Overall, 33 patients (24%) required a second treatment.Overall, 18.1% developed sensory disturbances after 16.4 ± 8.7 mo. One patient (0.7%) developed BNI grade IV dysfunction; 6 (4.3%) developed BNI grade III (somewhat bothersome) hypoesthesia after retreatment; BNI grade II (not bothersome) hypoesthesia was reported by 18 patients (11 after retreatment). Shorter nerve length (<6 mm vs 6 mm), smaller nerve volume (<30 mm3 vs >30 mm3), and lower prescription dose (<58 vs >58 Gy) were associated with treatment failure (P = .01, P = .02, P = .03, respectively). Re-irradiation independently predicted sensory disturbance (P < .001).CONCLUSIONTargeting a 6-mm segment of the trigeminal nerve with a prescribed dose of 60 Gy appears safe and effective. Persistent pain control was achieved in most patients with acceptable risk of sensory complications, which were typically found after re-irradiation.

Efficacy, safety and outcome of frameless image-guided robotic radiosurgery for brain metastases after whole brain radiotherapy.

Estimating efficacy, safety and outcome of frameless image-guided robotic radiosurgery for the treatment of recurrent brain metastases after whole brain radiotherapy (WBRT). We performed a retrospective single-center analysis including patients with recurrent brain metastases after WBRT, who have been treated with single session radiosurgery, using the CyberKnife® Radiosurgery System (CKRS) (Accuray Inc., CA) between 2011 and 2016. The primary end point was local tumor control, whereas secondary end points were distant tumor control, treatment-related toxicity and overall survival. 36 patients with 140 recurrent brain metastases underwent 46 single session CKRS treatments. Twenty one patients had multiple brain metastases (58%). The mean interval between WBRT and CKRS accounted for 2years (range 0.2-7years). The median number of treated metastases per treatment session was five (range 1-12) with a tumor volume of 1.26ccm (mean) and a median tumor dose of 18Gy prescribed to the 70% isodose line. Two patients experienced local tumor recurrence within the 1st year after treatment and 13 patients (36%) developed novel brain metastases. Nine of these patients underwent additional one to three CKRS treatments. Eight patients (22.2%) showed treatment-related radiation reactions on MRI, three with clinical symptoms. Median overall survival was 19months after CKRS. The actuarial 1-year local control rate was 94.2%. CKRS has proven to be locally effective and safe due to high local tumor control rates and low toxicity. Thus CKRS offers a reliable salvage treatment option for recurrent brain metastases after WBRT.

Prognostic factors in patients treated with stereotactic image-guided robotic radiosurgery for brain metastases: a single-center retrospective analysis of 223 patients.

In this retrospective study, we evaluated the overall survival (OS) and local control (LC) of brain metastases (BM) in patients treated with stereotactic radiosurgery (SRS). The scope was to identify host, tumor, and treatment factors predictive of LC and survival and define implications for clinical decisions. A total of 223 patients with 360 BM from various histologies treated with SRS alone or associated with whole brain radiotherapy (WBRT) in our institution between July 1, 2008 and August 31, 2013 were retrospectively reviewed. Among other prognostic factors, we had also evaluated retrospectively Karnofsky performance status scores (KPS) and graded prognostic assessment (GPA). Overall survival (OS) and local control (LC) were the primary endpoints. Kaplan-Meier and Cox proportional hazards models were used to estimate OS and LC and identify factors predictive of survival and local control. The median duration of follow-up time was 9months (range 0.4-51months). Median overall survival of all patients was 11months. The median local control was 38months. No statistical difference in terms of survival or LC between patients treated with SRS alone or associated with WBRT was found. On multivariate analysis, KPS was the only statistically significant predictor of OS (hazard ratio [HR] 2.53, p = 0.006). On univariate analysis, KPS and GPA were significantly prognostic for survival. None of the host, tumor, or treatment factors analyzed in the univariate model factors were significantly associated with local failure.

Image-guided robotic radiosurgery as salvage therapy for locally recurrent prostate cancer after external beam irradiation: retrospective feasibility study on six cases

Technological advances in treatment planning and execution are providing new potential opportunities in the treatment of recurrent prostate cancer. This study was conducted to evaluate the feasibility and safety of reirradiation with image-guided radiosurgery using CyberKnife, a robotic arm-driven compact linear accelerator, for intraprostatic recurrence after external beam radiotherapy (EBRT). Between September 2007 and May 2008, 6 patients diagnosed with locally recurrent prostate cancer after EBRT were treated using the CyberKnife system. The total reirradiation dose was 30 Gy in five fractions. Prior to radiosurgery four patients were treated with androgen-deprivation therapy. Radiation Therapy Oncology Group/European Organization for Research and Treatment of Cancer criteria and the Houston-Phoenix definition (PSA nadir + 2 ng/mL) were used for toxicity and biochemical failure evaluation, respectively. After a median follow-up of 11.2 months (range, 9.6-18.6 months), all patients are alive with no evidence of severe urinary or rectal acute morbidity. Local control cannot be exactly determined due to the short follow-up and the bias of the use of androgen ablation. Four patients had biochemical failure, three of them with clinical failure evidence (lymph node, bone and lung metastasis, respectively): none of these patients had clinical evidence of tumor persistence in the prostate. Salvage radiosurgery with CyberKnife after irradiation is feasible with low urinary and rectal morbidity. A longer follow-up and a larger number of patients are necessary to evaluate its effectiveness and optimal patient selection criteria.

Factors that may determine the targeting accuracy of image-guided radiosurgery.

The AAPM TG-135 report is a landmark recommendation for the quality assurance (QA) of image-guided robotic radiosurgery. The purpose of this paper is to present results pertaining to intentionally offsetting the phantom as recommended by TG-135 and to present data on targeting algorithm accuracy as a function of imager parameters in less than ideal circumstances, which had not been available at the time of publication of TG-135. All tests in this study were performed at the Cooper University Hospital CyberKnife Center in Mt. Laurel, NJ. For intentional offsets, initial tests were performed on the Accuray-supplied anthropomorphic head and neck phantom, whereas for subsequent tests, the Accuray-supplied alignment quality assurance (AQA) phantom was used. To simulate the effects of imager parameters for larger patients, slabs of Blue Water (Standard Imaging, Inc., Middleton, WI) were added to attenuate the x-ray images in some of the tests. In conjunction with attenuated x-ray tests, the number of fiducials was varied by systematically deselecting them one at a time at the CyberKnife console. Tests using the AQA phantom verified that submillimeter alignments were consistently achieved even with intentional shifts and rotations of up to 10.0 mm and 1.0°, respectively. An analysis of 17 months of daily QA alignment tests showed that submillimeter alignments were achieved more than 99% of the time even with such intentional shifts and rotations of the phantom. When additional slabs of Blue Water were added to simulate patient attenuation of the x-ray images, targeting errors could be induced depending on imager parameters and the amount of Blue Water used. A series of consecutive tests showed that two helpful variables to ensure good accuracy of the system were (1) the fiducial extraction confidence level (FECL) system parameter and (2) the number of targeted fiducials. When fewer than four fiducials were used, the FECL reported by the CyberKnife was sometimes high even when a false lock occurred, so using multiple fiducials helped to ensure reliable targeting. Radiosurgery requires the highest degree of targeting accuracy, and in our experience, the CyberKnife has been able to maintain submillimeter accuracy consistently. It has been verified that our CyberKnife can correct for phantom shifts of up to 10.0 mm and rotations of up to 1.0°. It has also been discovered that false locks are more likely to occur with a single fiducial than with multiple fiducials. Although targeting accuracy can only be measured on a phantom, the insight gained from analyzing the QA tests can help us in devising better strategies for achieving the best treatment for our patients.

Effect of residual patient motion on dose distribution during image-guided robotic radiosurgery for skull tracking based on log file analysis.

The present study aimed to assess the effect of residual patient motion on dose distribution during intracranial image-guided robotic radiosurgery by analyzing the system log files. The dosimetric effect was analyzed according to the difference between the original and estimated dose distributions, including targeting error, caused by residual patient motion between two successive image acquisitions. One hundred twenty-eight treatments were analyzed. Forty-two patients were treated using the isocentric plan, and 86 patients were treated using the conformal (non-isocentric) plan. The median distance from the imaging center to the target was 55 mm, and the median interval between the acquisitions of sequential images was 79 s. The median translational residual patient motion was 0.1 mm for each axis, and the rotational residual patient motion was 0.1° for Δpitch and Δroll and 0.2° for Δyaw. The dose error for D 95 was within 1 % in more than 95 % of cases. The maximum dose error for D 10 to D 90 was within 2 %. None of the studied parameters, including the interval between the acquisitions of sequential images, was significantly related to the dosimetric effect. The effect of residual patient motion on dose distribution was minimal.

Use of an Image-Guided Robotic Radiosurgery System for the Treatment of Canine Nonlymphomatous Nasal Tumors

An image-guided robotic stereotactic radiosurgery (SRS) system can be used to deliver curative-intent radiation in either single fraction or hypofractionated doses. Medical records for 19 dogs with nonlymphomatous nasal tumors treated with hypofractionated image-guided robotic stereotactic body radiotherapy (SBRT), either with or without adjunctive treatment, were retrospectively analyzed for survival and prognostic factors. Median survival time (MST) was evaluated using Kaplan-Meier survival curves. Age, breed, tumor type, stage, tumor size, prescribed radiation dose, and heterogeneity index were analyzed for prognostic significance. Dogs were treated with three consecutive-day, 8-12 gray (Gy) fractions of image-guided robotic SBRT. Overall MST was 399 days. No significant prognostic factors were identified. Acute side effects were rare and mild. Late side effects included one dog with an oronasal fistula and six dogs with seizures. In three of six dogs, seizures were a presenting complaint prior to SBRT. The cause of seizures in the remaining three dogs could not be definitively determined due to lack of follow-up computed tomography (CT) imaging. The seizures could have been related to either progression of disease or late radiation effect. Results indicate that image-guided robotic SBRT, either with or without adjunctive therapy, for canine nonlymphomatous nasal tumors provides comparable survival times (STs) to daily fractionated megavoltage radiation with fewer required fractions and fewer acute side effects.