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Importance: Spine metastasis can be treated with high-dose radiation therapy with advanced delivery technology for long-term tumor and pain control., Objective: To assess whether patient-reported pain relief was improved with stereotactic radiosurgery (SRS) as compared with conventional external beam radiotherapy (cEBRT) for patients with 1 to 3 sites of vertebral metastases., Design, Setting, and Participants: In this randomized clinical trial, patients with 1 to 3 vertebral metastases were randomized 2:1 to the SRS or cEBRT groups. This NRG 0631 phase 3 study was performed as multi-institutional enrollment within NRG Oncology. Eligibility criteria included the following: (1) solitary vertebral metastasis, (2) 2 contiguous vertebral levels involved, or (3) maximum of 3 separate sites. Each site may involve up to 2 contiguous vertebral bodies. A total of 353 patients enrolled in the trial, and 339 patients were analyzed. This analysis includes data extracted on March 9, 2020., Interventions: Patients randomized to the SRS group were treated with a single dose of 16 or 18 Gy (to convert to rad, multiply by 100) given to the involved vertebral level(s) only, not including any additional spine levels. Patients assigned to cEBRT were treated with 8 Gy given to the involved vertebra plus 1 additional vertebra above and below., Main Outcomes and Measures: The primary end point was patient-reported pain response defined as at least a 3-point improvement on the Numerical Rating Pain Scale (NRPS) without worsening in pain at the secondary site(s) or the use of pain medication. Secondary end points included treatment-related toxic effects, quality of life, and long-term effects on vertebral bone and spinal cord., Results: A total of 339 patients (mean [SD] age of SRS group vs cEBRT group, respectively, 61.9 [13.1] years vs 63.7 [11.9] years; 114 [54.5%] male in SRS group vs 70 [53.8%] male in cEBRT group) were analyzed. The baseline mean (SD) pain score at the index vertebra was 6.06 (2.61) in the SRS group and 5.88 (2.41) in the cEBRT group. The primary end point of pain response at 3 months favored cEBRT (41.3% for SRS vs 60.5% for cEBRT; difference, -19 percentage points; 95% CI, -32.9 to -5.5; 1-sided P = .99; 2-sided P = .01). Zubrod score (a measure of performance status ranging from 0 to 4, with 0 being fully functional and asymptomatic, and 4 being bedridden) was the significant factor influencing pain response. There were no differences in the proportion of acute or late adverse effects. Vertebral compression fracture at 24 months was 19.5% with SRS and 21.6% with cEBRT (P = .59). There were no spinal cord complications reported at 24 months., Conclusions and Relevance: In this randomized clinical trial, superiority of SRS for the primary end point of patient-reported pain response at 3 months was not found, and there were no spinal cord complications at 2 years after SRS. This finding may inform further investigation of using spine radiosurgery in the setting of oligometastases, where durability of cancer control is essential., Trial Registration: ClinicalTrials.gov Identifier: NCT00922974.

Purpose: Early clinical results on the application of magnetic resonance imaging (MRI) coupled with a linear accelerator to deliver Magnetic Resonance-guided Radiation Therapy (MRgRT) have demonstrated feasibility for safe delivery of stereotactic body radiation therapy in treatment of oligometastatic disease. Here, we set out to review the clinical evidence and challenges associated with MRgRT in this setting., Methods and Materials: We performed a systematic review of the literature pertaining to clinical experiences and trials on the use of MRgRT primarily for the treatment of oligometastatic cancers. We reviewed the opportunities and challenges associated with the use of MRgRT., Results: Benefits of MRgRT pertaining to superior soft-tissue contrast, real-time imaging and gating, and online adaptive radiation therapy facilitate safe and effective dose escalation to oligometastatic tumors while simultaneously sparing surrounding healthy tissues. Challenges concerning further need for clinical evidence and technical considerations related to planning, delivery, quality assurance of hypofractionated doses, and safety in the MRI environment must be considered., Conclusions: The promising early indications of safety and effectiveness of MRgRT for stereotactic body radiation therapy-based treatment of oligometastatic disease in multiple treatment locations should lead to further clinical evidence to demonstrate the benefit of this technology., (Copyright © 2022 Elsevier Inc. All rights reserved.)

Purpose: Recent randomized studies have suggested improvements in progression-free and overall survival with the addition of stereotactic body radiation therapy (SBRT, also known as SABR) in patients with oligometastatic non-small cell lung cancer. Given the novelty and complexity of incorporating SBRT in the oligometastatic setting, the multidisciplinary American Radium Society Lung Cancer Panel was assigned to create appropriate use criteria on SBRT as part of consolidative local therapy for patients with oligometastatic and oligoprogressive non-small cell lung cancer., Methods and Materials: A review of the current literature was conducted from January 1, 2008, to December 25, 2020, using the Preferred Reporting Items for Systematic Reviews and Meta-analyses (PRISMA) guidelines to systematically search the PubMed database to retrieve a comprehensive set of relevant articles., Results: Based on representation in existing randomized trials, the panel defined the term "oligometastasis" as ≤3 metastatic deposits (not including the primary tumor) in the previously untreated setting or after first-line systemic therapy after the initial diagnosis. "Oligoprogression" also referred to ≤3 discrete areas of progression in the setting of prior or ongoing receipt of systemic therapy. In all appropriate patients, the panel strongly recommends enrollment in a clinical trial whenever available. For oligometastatic disease, administering first-line systemic therapy followed by consolidative radiation therapy (to all sites plus the primary/nodal disease) is preferred over up-front radiation therapy. Owing to a dearth of data, the panel recommended that consolidative radiation therapy be considered on a case-by-case basis for 4 to 5 sites of oligometastatic disease, driver mutation-positive oligometastatic disease without progression on up-front targeted therapy, and oligoprogressive cases., Conclusions: Although SBRT/SABR appears to be both safe and effective in treating patients with limited metastatic sites of disease, many clinical circumstances require individualized management and strong multidisciplinary discussion on account of the limited existing data., (Copyright © 2021 Elsevier Inc. All rights reserved.)

Introduction: The purpose of this study was to investigate the systematic localization accuracy, treatment planning capability, and delivery accuracy of an integrated magnetic resonance imaging guided Linear Accelerator (MR-Linac) platform for stereotactic radiosurgery., Materials and Methods: The phantom for the end-to-end test comprises three different compartments: a rectangular MR/CT target phantom, a Winston-Lutz cube, and a rectangular MR/CT isocenter phantom. Hidden target tests were performed at gantry angles of 0, 90, 180, and 270 degrees to quantify the systematic accuracy. Five patient plans with a total of eleven lesions were used to evaluate the dosimetric accuracy. Single-isocenter IMRT treatment plans using 10-15 coplanar beams were generated to treat the multiple metastases., Results: The end-to-end localization accuracy of the system was 1.0 ± 0.1 mm. The conformity index, homogeneity index and gradient index of the plans were 1.26 ± 0.22, 1.22 ± 0.10, and 5.38 ± 1.44, respectively. The average absolute point dose difference between measured and calculated dose was 1.64 ± 1.90%, and the mean percentage of points passing the 3%/1 mm gamma criteria was 96.87%., Conclusions: Our experience demonstrates that excellent plan quality and delivery accuracy was achievable on the MR-Linac for treating multiple brain metastases with a single isocenter., (Copyright © 2018 Elsevier B.V. All rights reserved.)

Purpose: This guideline presents evidence-based recommendations for stereotactic body radiation therapy (SBRT) in challenging clinical scenarios in early-stage non-small cell lung cancer (NSCLC)., Methods and Materials: The American Society for Radiation Oncology convened a task force to perform a systematic literature review on 4 key questions addressing: (1) application of SBRT to operable patients; (2) appropriate use of SBRT in tumors that are centrally located, large, multifocal, or unbiopsied; (3) individual tailoring of SBRT in "high-risk" clinical scenarios; and (4) SBRT as salvage therapy after recurrence. Guideline recommendations were created using a predefined consensus-building methodology supported by American Society for Radiation Oncology-approved tools for grading evidence quality and recommendation strength., Results: Although few randomized trials have been completed for SBRT, strong consensus recommendations based on extensive, consistent publications were generated for several questions, including recommendations for fractionation for central tumors and surgery versus SBRT in standard-risk medically operable patients with early-stage NSCLC. Lower quality evidence led to conditional recommendations on use of SBRT for tumors >5 cm, patients with prior pneumonectomy, T3 tumors with chest wall invasion, synchronous multiple primary lung cancer, and as a salvage therapy after prior radiation therapy. These areas of moderate- and low-quality evidence highlight the importance of clinical trial enrollment as well as the role of prospective data registries., Conclusions: SBRT has an important role to play in treating early-stage NSCLC, particularly for medically inoperable patients with limited other treatment options. Shared decision-making with patients should be performed in all cases to ensure the patient understands the risks related to SBRT, the side effects, and the alternative treatments available., (Copyright © 2017 American Society for Radiation Oncology. Published by Elsevier Inc. All rights reserved.)

Purpose: This study aims to extend the observation that the 12 Gy-radiosurgical-volume (V12Gy) correlates with the incidence of radiation necrosis in patients with intracranial tumors treated with radiosurgery by using target volume to predict V12Gy. V12Gy based on the target volume was used to predict the radiation necrosis probability (P) directly. Also investigated was the reduction in radiation necrosis rates (ΔP) as a result of optimizing the prescription isodose lines for linac-based SRS., Methods: Twenty concentric spherical targets and 22 patients with brain tumors were retrospectively studied. For each case, a standard clinical plan and an optimized plan with prescription isodose lines based on gradient index were created. V12Gy were extracted from both plans to analyze the correlation between V12Gy and target volume. The necrosis probability P as a function of V12Gy was evaluated. To account for variation in prescription, the relation between V12Gy and prescription was also investigated., Results: A prediction model for radiation-induced necrosis was presented based on the retrospective study. The model directly relates the typical prescribed dose and the target volume to the radionecrosis probability; V12Gy increased linearly with the target volume (R 2  > 0.99). The linear correlation was then integrated into a logistic model to predict P directly from the target volume. The change in V12Gy as a function of prescription was modeled using a single parameter, s (=-1.15). Relatively large ΔP was observed for target volumes between 7 and 28 cm 3 with the maximum reduction (8-9%) occurring at approximately 18 cm 3 ., Conclusions: Based on the model results, optimizing the prescription isodose line for target volumes between 7 and 28 cm 3 results in a significant reduction in necrosis probability. V12Gy based on the target volume could provide clinicians a predictor of radiation necrosis at the contouring stage thus facilitating treatment decisions., (© 2017 American Association of Physicists in Medicine.)

Purpose: To determine our institutional vertebral compression fracture (VCF) rate after spine stereotactic radiosurgery (SRS) and determine contributory factors., Methods and Materials: Retrospective analysis from 2001 to 2013 at a single institution was performed. With institutional review board approval, electronic medical records of 1905 vertebral bodies from 791 patients who were treated with SRS for the management of primary or metastatic spinal lesions were reviewed. A total of 448 patients (1070 vertebral bodies) with adequate follow-up imaging studies available were analyzed. Doses ranging from 10 Gy in 1 fraction to 60 Gy in 5 fractions were delivered. Computed tomography and magnetic resonance imaging were used to evaluate the primary endpoints of this study: development of a new VCF, progression of an existing VCF, and requirement of stabilization surgery after SRS., Results: A total of 127 VCFs (11.9%; 95% confidence interval [CI] 9.5%-14.2%) in 97 patients were potentially SRS induced: 46 (36%) were de novo, 44 (35%) VCFs progressed, and 37 (29%) required stabilization surgery after SRS. Our rate for radiologic VCF development/progression (excluding patients who underwent surgery) was 8.4%. Upon further exclusion of patients with hematologic malignancies the VCF rate was 7.6%. In the univariate analyses, females (hazard ratio [HR] 1.54, 95% CI 1.01-2.33, P=.04), prior VCF (HR 1.99, 95% CI 1.30-3.06, P=.001), primary hematologic malignancies (HR 2.68, 95% CI 1.68-4.28, P<.001), thoracic spine lesions (HR 1.46, 95% CI 1.02-2.10, P=.02), and lytic lesions had a significantly increased risk for VCF after SRS. On multivariate analyses, prior VCF and lesion type remained contributory., Conclusions: Single-fraction SRS doses of 16 to 18 Gy to the spine seem to be associated with a low rate of VCFs. To the best of our knowledge, this is the largest reported experience analyzing SRS-induced VCFs, with one of the lowest event rates reported., (Copyright © 2016 Elsevier Inc. All rights reserved.)

The purpose of this study was to describe the development of a clinical model for lung cancer patients treated with stereotactic body radiotherapy (SBRT) within a knowledge-based algorithm for treatment planning, and to evaluate the model performance and applicability to different planning techniques, tumor locations, and beam arrangements. 105 SBRT plans for lung cancer patients previously treated at our institution were included in the development of the knowledge-based model (KBM). The KBM was trained with a combination of IMRT, VMAT, and 3D CRT techniques. Model performance was validated with 25 cases, for both IMRT and VMAT. The full KBM encompassed lesions located centrally vs. peripherally (43:62), upper vs. lower (62:43), and anterior vs. posterior (60:45). Four separate sub-KBMs were created based on tumor location. Results were compared with the full KBM to evaluate its robustness. Beam templates were used in conjunction with the optimizer to evaluate the model's ability to handle suboptimal beam placements. Dose differences to organs-at-risk (OAR) were evaluated between the plans gener-ated by each KBM. Knowledge-based plans (KBPs) were comparable to clinical plans with respect to target conformity and OAR doses. The KBPs resulted in a lower maximum spinal cord dose by 1.0 ± 1.6 Gy compared to clinical plans, p = 0.007. Sub-KBMs split according to tumor location did not produce significantly better DVH estimates compared to the full KBM. For central lesions, compared to the full KBM, the peripheral sub-KBM resulted in lower dose to 0.035 cc and 5 cc of the esophagus, both by 0.4Gy ± 0.8Gy, p = 0.025. For all lesions, compared to the full KBM, the posterior sub-KBM resulted in higher dose to 0.035 cc, 0.35 cc, and 1.2 cc of the spinal cord by 0.2 ± 0.4Gy, p = 0.01. Plans using template beam arrangements met target and OAR criteria, with an increase noted in maximum heart dose (1.2 ± 2.2Gy, p = 0.01) and GI (0.2 ± 0.4, p = 0.01) for the nine-field plans relative to KBPs planned with custom beam angles. A knowledge-based model for lung SBRT consisting of multiple treatment modalities and lesion loca-tions produced comparable plan quality to clinical plans. With proper training and validation, a robust KBM can be created that encompasses both IMRT and VMAT techniques, as well as different lesion locations., (© 2016 The Authors.)

The purpose of this study is to characterize the dosimetric properties and accuracy of a novel treatment platform (Edge radiosurgery system) for localizing and treating patients with frameless, image-guided stereotactic radiosurgery (SRS) and stereotactic body radiotherapy (SBRT). Initial measurements of various components of the system, such as a comprehensive assessment of the dosimetric properties of the flattening filter-free (FFF) beams for both high definition (HD120) MLC and conical cone-based treatment, positioning accuracy and beam attenuation of a six degree of freedom (6DoF) couch, treatment head leakage test, and integrated end-to-end accuracy tests, have been performed. The end-to-end test of the system was performed by CT imaging a phantom and registering hidden targets on the treatment couch to determine the localization accuracy of the optical surface monitoring system (OSMS), cone-beam CT (CBCT), and MV imaging systems, as well as the radiation isocenter targeting accuracy. The deviations between the percent depth-dose curves acquired on the new linac-based system (Edge), and the previously published machine with FFF beams (TrueBeam) beyond D(max) were within 1.0% for both energies. The maximum deviation of output factors between the Edge and TrueBeam was 1.6%. The optimized dosimetric leaf gap values, which were fitted using Eclipse dose calculations and measurements based on representative spine radiosurgery plans, were 0.700 mm and 1.000 mm, respectively. For the conical cones, 6X FFF has sharper penumbra ranging from 1.2-1.8 mm (80%-20%) and 1.9-3.8 mm (90%-10%) relative to 10X FFF, which has 1.2-2.2mm and 2.3-5.1mm, respectively. The relative attenuation measurements of the couch for PA, PA (rails-in), oblique, oblique (rails-out), oblique (rails-in) were: -2.0%, -2.5%, -15.6%, -2.5%, -5.0% for 6X FFF and -1.4%, -1.5%, -12.2%, -2.5%, -5.0% for 10X FFF, respectively, with a slight decrease in attenuation versus field size. The systematic deviation between the OSMS and CBCT was -0.4 ± 0.2 mm, 0.1± 0.3mm, and 0.0 ± 0.1 mm in the vertical, longitudinal, and lateral directions. The mean values and standard deviations of the average deviation and maximum deviation of the daily Winston-Lutz tests over three months are 0.20 ± 0.03 mm and 0.66 ± 0.18 mm, respectively. Initial testing of this novel system demonstrates the technology to be highly accurate and suitable for frameless, linac-based SRS and SBRT treatment.

Purpose: The phase 2 component of Radiation Therapy Oncology Group (RTOG) 0631 assessed the feasibility and safety of spine radiosurgery (SRS) for localized spine metastases in a cooperative group setting., Methods and Materials: Patients with 1-3 spine metastasis with a Numerical Rating Pain Scale (NRPS) score ≥5 received 16 Gy single fraction SRS. The primary endpoint was SRS feasibility: image guidance radiation therapy (IGRT) targeting accuracy ≤2 mm, target volume coverage >90% of prescription dose, maintaining spinal cord dose constraints (10 Gy to ≤10% of the cord volume from 5-6 mm above to 5-6 mm below the target or absolute spinal cord volume <0.35 cc) and other normal tissue dose constraints. A feasibility success rate <70% was considered unacceptable for continuation of the phase 3 component. Based on the 1-sample exact binomial test with α = 0.10 (1-sided), 41 patients were required. Acute toxicity was assessed using the National Cancer Institute Common Toxicity Criteria for Adverse Events, version 3.0., Results: Sixty-five institutions were credentialed with spine phantom dosimetry and IGRT compliance. Forty-six patients were accrued, and 44 were eligible. There were 4 cervical, 21 thoracic, and 19 lumbar sites. Median NRPS was 7 at presentation. Final pretreatment rapid review was approved in 100%. Accuracy of image guided SRS targeting was in compliance with the protocol in 95%. The target coverage and spinal cord dose constraint were in accordance with the protocol requirements in 100% and 97%. Overall compliance for other normal tissue constraints was per protocol in 74%. There were no cases of grade 4-5 acute treatment-related toxicity., Conclusions: The phase 2 results demonstrate the feasibility and accurate use of SRS to treat spinal metastases, with rigorous quality control, in a cooperative group setting. The planned RTOG 0631 phase 3 component will proceed to compare pain relief and quality of life between SRS and external beam radiation therapy., (Copyright © 2014 American Society for Radiation Oncology. Published by Elsevier Inc. All rights reserved.)

Purpose: To retrospectively compute dose distributions for lung cancer patients treated with SABR, and to correlate dose distributions with outcome using a tumor control probability (TCP) model., Methods: Treatment plans for 133 NSCLC patients treated using 12 Gy/fxn × 4 (BED=106 Gy), and planned using a pencil-beam (1D-equivalent-path-length, EPL-1D) algorithm were retrospectively re-calculated using model-based algorithms (including convolution/superposition, Monte Carlo). 4D imaging was performed to manage motion. TCP was computed using the Marsden model and associations between dose and outcome were inferred., Results: Mean D95 reductions of 20% (max.=33%) were noted with model-based algorithms (relative to EPL-1D) for the smallest tumors (PTV<20 cm(3)), corresponding to actual delivered D95 BEDs of ≈ 60-85 Gy. For larger tumors (PTV>100 cm(3)), D95 reductions were ≈ 10% (BED>100 Gy). Mean lung doses (MLDs) were 15% lower for model-based algorithms for PTVs<20 cm(3). No correlation between tumor size and 2-year local control rate was observed clinically, consistent with TCP calculations, both of which were ≈ 90% across all PTV bins., Conclusion: Results suggest that similar control rates might be achieved for smaller tumors using lower BEDs relative to larger tumors. However, more studies with larger patient cohorts are necessary to confirm this possible finding., (Copyright © 2013 Elsevier Ireland Ltd. All rights reserved.)

Current commercially available planning systems with Monte Carlo (MC)-based final dose calculation in IMRT planning employ pencil-beam (PB) algorithms in the optimization process. Consequently, dose coverage for SBRT lung plans can feature cold-spots at the interface between lung and tumor tissue. For lung wall (LW)-seated tumors, there can also be hot spots within nearby normal organs (example: ribs). This study evaluated two different practical approaches to limiting cold spots within the target and reducing high doses to surrounding normal organs in MC-based IMRT planning of LW-seated tumors. First, "iterative reoptimization", where the MC calculation (with PB-based optimization) is initially performed. The resultant cold spot is then contoured and used as a simultaneous boost volume. The MC-based dose is then recomputed. The second technique uses noncoplanar beam angles with limited path through lung tissue. Both techniques were evaluated against a conventional coplanar beam approach with a single MC calculation. In all techniques the prescription dose was normalized to cover 95% of the PTV. Fifteen SBRT lung cases with LW-seated tumors were planned. The results from iterative reoptimization showed that conformity index (CI) and/or PTV dose uniformity (UPTV) improved in 12/15 plans. Average improvement was 13%, and 24%, respectively. Nonimproved plans had PTVs near the skin, trachea, and/or very small lung involvement. The maximum dose to 1cc volume (D1cc) of surrounding OARs decreased in 14/15 plans (average 10%). Using noncoplanar beams showed an average improvement of 7% in 10/15 cases and 11% in 5/15 cases for CI and UPTV, respectively. The D1cc was reduced by an average of 6% in 10/15 cases to surrounding OARs. Choice of treatment planning technique did not statistically significantly change lung V5. The results showed that the proposed practical approaches enhance dose conformity in MC-based IMRT planning of lung tumors treated with SBRT, improving target dose coverage and potentially reducing toxicities to surrounding normal organs.

Background: The standard treatment of resected brain metastasis is whole-brain radiotherapy (WBRT). To avoid the potential toxicity of WBRT and to improve local control, we have used radiosurgery alone to the surgical cavity., Objective: To demonstrate the rates of local control, new intracranial metastasis, and overall survival using this treatment scheme without WBRT., Methods: Eighty-five consecutive patients with brain metastasis were treated with surgical resection of at least 1 lesion followed by radiosurgery alone to the surgical cavity and any unresected lesions from August 2000 to March 2011. Sixty-eight percent had gross total resections. After surgery, radiosurgery was delivered to the surgical cavity with a 2- to 3-mm margin. The median marginal radiosurgery dose was 16 Gy, and median target volume was 13.96 cm. Follow-up imaging and clinical examination were obtained every 2 to 3 months., Results: Median follow-up time was 11.2 months. Overall local control was 81.2%. The 6-month, 1-year, and 2-year rates of local control were 88.7%, 81.4%, and 75.7%, respectively. Forty-seven patients (55%) developed new intracranial metastases at a median time of 5.6 months. For the entire population, the rate of new metastases was 32.1%, 58.1%, and 62.9% at 6 months, 1 year, and 2 years, respectively. Median overall survival time was 12.1 months. From initial treatment until death or last follow-up, only 30 patients (35%) received WBRT as salvage treatment., Conclusion: Radiosurgery to the surgical cavity without WBRT achieved excellent local control of resected brain metastasis. Close imaging follow-up allows early intervention for any new metastasis.

The purpose of this study was to perform comprehensive measurements and testing of a Novalis Tx linear accelerator, and to develop technical guidelines for com-missioning from the time of acceptance testing to the first clinical treatment. The Novalis Tx (NTX) linear accelerator is equipped with, among other features, a high-definition MLC (HD120 MLC) with 2.5 mm central leaves, a 6D robotic couch, an optical guidance positioning system, as well as X-ray-based image guidance tools to provide high accuracy radiation delivery for stereotactic radiosurgery and stereotactic body radiation therapy procedures. We have performed extensive tests for each of the components, and analyzed the clinical data collected in our clinic. We present technical guidelines in this report focusing on methods for: (1) efficient and accurate beam data collection for commissioning treatment planning systems, including small field output measurements conducted using a wide range of detectors; (2) commissioning tests for the HD120 MLC; (3) data collection for the baseline characteristics of the on-board imager (OBI) and ExacTrac X-ray (ETX) image guidance systems in conjunction with the 6D robotic couch; and (4) end-to-end testing of the entire clinical process. Established from our clinical experience thus far, recommendations are provided for accurate and efficient use of the OBI and ETX localization systems for intra- and extracranial treatment sites. Four results are presented. (1) Basic beam data measurements: Our measurements confirmed the necessity of using small detectors for small fields. Total scatter factors varied significantly (30% to approximately 62%) for small field measurements among detectors. Unshielded stereotactic field diode (SFD) overestimated dose by ~ 2% for large field sizes. Ion chambers with active diameters of 6 mm suffered from significant volume averaging. The sharpest profile penumbra was observed for the SFD because of its small active diameter (0.6 mm). (2) MLC commissioning: Winston Lutz test, light/radiation field congruence, and Picket Fence tests were performed and were within criteria established by the relevant task group reports. The measured mean MLC transmission and dynamic leaf gap of 6 MV SRS beam were 1.17% and 0.36 mm, respectively. (3) Baseline characteristics of OBI and ETX: The isocenter localization errors in the left/right, posterior/anterior, and superior/inferior directions were, respectively, -0.2 ± 0.2 mm, -0.8 ± 0.2 mm, and -0.8 ± 0.4 mm for ETX, and 0.5 ± 0.7 mm, 0.6 ± 0.5 mm, and 0.0 ± 0.5 mm for OBI cone-beam computed tomography. The registration angular discrepancy was 0.1 ± 0.2°, and the maximum robotic couch error was 0.2°. (4) End-to-end tests: The measured isocenter dose differences from the planned values were 0.8% and 0.4%, measured respectively by an ion chamber and film. The gamma pass rate, measured by EBT2 film, was 95% (3% DD and 1 mm DTA). Through a systematic series of quantitative commissioning experiments and end-to-end tests and our initial clinical experience, described in this report, we demonstrate that the NTX is a robust system, with the image guidance and MLC requirements to treat a wide variety of sites - in particular for highly accurate delivery of SRS and SBRT-based treatments.

The recently released Novalis TX linac platform provides various image guided localization methods including a stereoscopic X-ray imaging technique (ExacTrac) and a volumetric cone beam computed tomography (CBCT) imaging technique. The ExacTrac combined with the robotic six dimensional (6D) couch provides fast and accurate patient setup based on bony structures and offers "snap shot" imaging at any point during the treatment to detect patient motion. The CBCT offers a three dimensional (3D), volumetric image of the patient's setup with visualization of anatomic structures. However, each imaging system has a separate isocenter, which may not coincide with each other or with the linac isocenter. The aim of this paper was to compare the localization accuracy between Exactrac and CBCT for single fraction spine radiosurgery treatments. The study was performed for both phantom and patients (96 clinical treatments of 57 patients). The discrepancies between the isocenter between the ExacTrac and CBCT in four dimensions (three translations and one rotation) were recorded and statistically analyzed using two-tailed t-test.

Purpose: To evaluate the positioning accuracies of two image-guided localization systems, ExacTrac and On-Board Imager (OBI), in a stereotactic treatment unit., Methods and Materials: An anthropomorphic pelvis phantom with eight internal metal markers (BBs) was used. The center of one BB was set as plan isocenter. The phantom was set up on a treatment table with various initial setup errors. Then, the errors were corrected using each of the investigated systems. The residual errors were measured with respect to the radiation isocenter using orthogonal portal images with field size 3 × 3 cm(2). The angular localization discrepancies of the two systems and the correction accuracy of the robotic couch were also studied. A pair of pre- and post-cone beam computed tomography (CBCT) images was acquired for each angular correction. Then, the correction errors were estimated by using the internal BBs through fiducial marker-based registrations., Results: The isocenter localization errors (μ ±σ) in the left/right, posterior/anterior, and superior/inferior directions were, respectively, -0.2 ± 0.2 mm, -0.8 ± 0.2 mm, and -0.8 ± 0.4 mm for ExacTrac, and 0.5 ± 0.7 mm, 0.6 ± 0.5 mm, and 0.0 ± 0.5 mm for OBI CBCT. The registration angular discrepancy was 0.1 ± 0.2° between the two systems, and the maximum angle correction error of the robotic couch was 0.2° about all axes., Conclusion: Both the ExacTrac and the OBI CBCT systems showed approximately 1 mm isocenter localization accuracies. The angular discrepancy of two systems was minimal, and the robotic couch angle correction was accurate. These positioning uncertainties should be taken as a lower bound because the results were based on a rigid dosimetry phantom., (Copyright © 2011 Elsevier Inc. All rights reserved.)

Stereotactic Radiotherapy (SRT) is more commonly used for skull base tumors in conjunction with the technical development of radiation intensity modulation. Purpose of this study is to correlate clinical and radiographic characteristics of delayed radiation injury (RI) occurring around central skull base following SRT with SRT dosimetric data. Total of six patients were identified to have developed RI in the vicinity of SRT target volume out of 141 patients who received SRT in he center or near-center of the skull base. The images and medical records were retrospectively reviewed. The analysis was performed for RI location, time of development, imaging and clinical characteristics and evolution of RI and correlated with SRT dosimetric analysis using image fusion with follow-up MRI scans. Mean follow-up time was 24 +/- 9 months. During the follow-up period, twelve sites of RI were found in 6 patients. They were clinically symptomatic in 4/6 patients (66.6%) at median 12.5 months after SRT. Mean time interval between SRT and detection of RI was 9 +/- 3, 18.5 +/- 5, and 13.5 months for brainstem, temporal lobe, and cerebellum/labyrinth lesions, respectively. All RI lesions were included in the region of high SRT doses. After steroid and symptomatic treatment, 50% of RI lesions showed complete response, and 40% showed partial response. RI can occur around the skull base because of irregular shape of target tumor, its close proximity to normal brain parenchyma, and inhomogeneity of dose distribution. Brainstem lesions occurred earlier than temporal lobe RI. The majority of the RI lesions, not mixed with the tumor in this study, showed radiographic and clinical improvement with steroid and symptomatic treatments.

Background: Surgical decompression of metastatic epidural compression (MEC) improved ambulatory function. Spine radiosurgery can accurately target the epidural tumor and deliver high radiation doses for tumor control. Therefore, a clinical trial was performed to quantitatively determine the degree of epidural decompression by radiosurgery of metastatic epidural compression., Methods: Sixty-two patients with a total of 85 lesions of metastatic epidural compression were treated. Epidural compression was diagnosed by magnetic resonance imaging (MRI) scans. Main criteria of inclusion were neurological status with muscle power 4 of 5 or better. Radiosurgery was performed to the involved spine segment, including the epidural mass with median dose of 16 Gy (range 12-20 Gy) in a single session. All patients had prospective clinical follow-up, ranging from 1-48 months (median 11.5 months), and 36 patients had pretreatment and post-treatment imaging, ranging from 2-33 months (median 9.3 months). Primary endpoints were epidural tumor control and thecal sac decompression., Results: The mean epidural tumor volume reduction was 65 +/- 14% at 2 months after radiosurgery. The epidural tumor area at the level of the most severe spinal cord compression was 0.82 +/- 0.08 cm(2) before radiosurgery and 0.41 +/- 0.06 cm(2) after radiosurgery (P < .001). Thecal sac patency improved from 55 +/- 4% to 76 +/- 3% (P < .001). Overall, neurological function improved in 81%., Conclusions: This study demonstrated a radiosurgical decompression of epidural tumor. Although neurosurgical decompression and radiotherapy is the standard treatment in patients with good performance, radiosurgical decompression can be a viable noninvasive treatment option for malignant epidural compression., ((c) 2010 American Cancer Society.)

Purpose: To determine the feasibility, safety, and efficacy of stereotactic body radiation therapy (SBRT), also known as radiosurgery, in patients with head-and-neck cancers., Methods and Materials: Patients with pathologically proven malignant lesions in the head-and-neck region were treated using single-dose SBRT (S-SBRT) or fractionated SBRT (F-SBRT). Radiation doses were either single-fraction 13-18 Gy for S-SBRT or 36-48 Gy in five to eight fractions for F-SBRT. Response evaluation was based on clinical examinations and computed tomography/magnetic resonance imaging scans. Pre- and post-SBRT tumor dimensions were measured in three axes, and tumor volumes were calculated. Response evaluation also was performed using World Health Organization criteria., Results: Fifty-five lesions were treated in 44 patients (25 men, 19 women). There were three groups of patients: those with primary (n = 10), recurrent (n = 21), and metastatic tumors (n = 13). The predominant histologic type was squamous cell carcinoma (n = 33). The majority of lesions were treated using F-SBRT (n = 37). Based on radiographic and clinical assessment, a 77% (complete + partial response) response rate was noted. Percentage of reduction in tumor volume was 52% +/- 38% based on follow-up scans in 24 patients. Tumor control rates at 1 year were 83.3% and 60.6% in the primary and recurrent groups, respectively. Median overall survival was 28.7, 6.7, and 5.6 months for the primary, recurrent, and metastatic groups, respectively. Radiation Therapy Oncology Group Grade 1-2 mucositis was noted in all patients treated for oropharyngeal or laryngeal lesions., Conclusions: The SBRT in single or fractionated doses offers a viable treatment option for selected patients with primary, recurrent, and metastatic head-and-neck cancers with functional preservation.

Purpose: To determine the radiographic and clinical efficacy of stereotactic single dose radiosurgery (SRS) and fractionated stereotactic radiotherapy (FSRT) as salvage therapy for glioblastoma (GBM) at recurrence., Methods: Thirty-six patients with pathologically proven recurrent GBM were treated with salvage reirradiation by either SRS or FSRT between March of 2001 and August of 2006. Thirty-one patients had an initial diagnosis of GBM. Five patients had a malignant transformation. All patients had received radiotherapy with a dose of 50-60 Gy, a median 13.6 months prior to reirradiation (range: 0.8-119 months). At the time of recurrence, 26 patients were treated with SRS with a median dose of 18 Gy (range: 12-20 Gy). FSRT was performed in ten patients with a dose of 36 Gy in six fractions, twice weekly. Follow-up included MRI and clinical examination every 2 months., Results: Median survival time after SRS was 8.5 months, compared to 7.4 months after FSRT (P = 0.81). Of 26 patients treated with SRS, radiographic tumor response or stable disease was observed in eight (35%) patients and tumor progression was seen in 18 (65%) patients. Of 10 patients treated by FSRT, radiographic tumor response or stable disease was observed in four (40%) patients and tumor progression was observed in four (40%) patients (two lost to follow-up). Patients who responded to treatment had statistically improved survival compared to non-responders, with median survival of 15.8 vs. 7.3 months (P < 0.05)., Conclusion: Salvage reirradiation with SRS or FSRT for recurrent GBM results in radiographic response in a proportion of patients. Survival was significantly improved among patients who either responded or had stable disease after salvage reirradiation, compared to non-responders. Further study is warranted to investigate the method and time of reirradiation for recurrent GBM.

Radiosurgery delivers highly focused radiation beams to the defined target with high precision and accuracy. It has been demonstrated that spine radiosurgery can be safely used for treatment of spine metastasis with rapid and durable pain control, but without detrimental effects to the spinal cord. This study was carried out to determine the role of single fraction radiosurgery for epidural spinal cord compression due to multiple myeloma. A total of 31 lesions in 24 patients with multiple myeloma, who presented with epidural spinal cord compression, were treated with spine radiosurgery. Single fraction radiation dose of 10-18 Gy (median of 16 Gy) was administered to the involved spine including the epidural or paraspinal tumor. Patients were followed up with clinical exams and imaging studies. Median follow-up was 11.2 months (range 1-55). Primary endpoints of this study were pain control, neurological improvement, and radiographic tumor control. Overall pain control rate was 86%; complete relief in 54%, and partial relief in 32% of the patients. Seven patients presented with neurological deficits. Five patients neurologically improved or became normal after radiosurgery. Complete radiographic response of the epidural tumor was noted in 81% at 3 months after radiosurgery. During the follow-up time, there was no radiographic or neurological progression at the treated spine. The treatment was non-invasive and well tolerated. Single fraction radiosurgery achieved an excellent clinical and radiographic response of myeloma epidural spinal cord compression. Radiosurgery can be a viable treatment option for myeloma epidural compression.

Purpose: The Novalis system has been demonstrated to achieve accurate target localization on anthropomorphic phantoms. However, other factors, such as rotational deviation, patient intrafraction motion, and image fusion uncertainty due to patient body deformation, could contribute additional position uncertainty for actual patients. This study evaluates such position uncertainty for spinal radiosurgery patients., Materials and Methods: Fifty-two consecutive spinal radiosurgery patients were included in the study. Rotational deviation was evaluated from 6-deg of freedom (6D) fusion results for all patients. The combined uncertainty of patient motion and image fusion was determined from fusion results of additional kV x-ray images acquired before, during, and after treatment for 25 of the 52 patients. The uncertainty of image fusion was also evaluated by performing 6D fusion ten different times with various regions of interest in the images selected for fusion. This was performed for two patients with L3 and T2 lesions, respectively, for comparison., Results: The mean rotational deviation was 0.7 +/- 1.8, 0.7 +/- 1.5, and 0.7 +/- 1.6 deg along the yaw, roll, and pitch directions, respectively. The combined uncertainty from patient motion and image fusion was 0.1 +/- 0.9, 0.2 +/- 1.2, and 0.2 +/- 1.0 mm in the anteroposterior (AP), longitudinal, and lateral directions, respectively. The uncertainty (standard deviation) due to image fusion was less than 0.28 mm in any direction for the L3 lesion and 0.8 mm in the AP direction for the T2 lesion., Conclusion: Overall position uncertainty for spinal radiosurgery patients has been evaluated. Rotational deviation and patient motion were the main factors contributed to position uncertainty for actual patient treatment.

Precision and accuracy of image-guided spinal radiosurgery has been previously demonstrated. This study was carried out to determine the clinical efficacy of spine radiosurgery for the treatment of solitary spinal metastases with or without cord compression. A total of 49 patients with 61 separate spinal metastases were treated with radiosurgery. All patients had pathologically proven primary cancers and had either synchronous or metachronous metastasis to the spine. The majority of the patients presented with back pain. All patients received single-dose radiosurgery to the involved spine only. The radiosurgery dose ranged from 10 to 16Gy. The primary endpoint was pain control, but outcomes in neurological status and radiological tumor control also were assessed. The median time to pain relief was 14 days and the earliest time of pain relief was within 24hours. Complete pain relief was achieved in 46%, partial relief in 18.9%, and stable symptoms in 16.2%. Relapse of pain at the treated spinal segment was 6.9%. Median duration of pain relief at the treated spine was 13.3 months. Overall pain control rate for one year was 84%. This experience demonstrates that spinal radiosurgery can achieve rapid and durable pain relief. Single-dose radiosurgery has a potential to be a viable treatment option for single spinal metastasis.

Purpose: Clinical target volume (CTV), although present, is usually not considered during stereotactic body radiation therapy (SBRT) for non-small cell lung cancer. This study aimed to quantify the incidental dose to the potential CTV under different SBRT techniques., Materials and Methods: Ten patients with various tumor motions were included in the study. Gated-4DCT was performed for all patients. Three treatment plans were generated. Plan A was based on free breathing gross tumor volume (GTV) from a regular CT. Plan B was based on internal target volume (ITV) from gated 4DCT. Plan C was a perfect gated treatment at the exhale phase. The hypothetical CTV was represented by three CTV shells (5, 10, and 15 mm). Time-averaged dose for different respiratory phases was calculated for 18 representative points in each shell., Results: The minimum doses for plans A, B, and C were 84+/-20%, 94+/-3%, and 80+/-17% of the isocenter dose to the 5mm shell, 72+/-27%, 64+/-7%, and 20+/-11% to the 10mm shell, and 38+/-27%, 27+/-17%, and 6+/-7% to the 15 mm shell, respectively. The caudal and cranial ends of each shell usually had lower dose compared to the other points on the shell. Plan B had the most uniform and reasonable doses to the CTV shells, and patients with large respiratory motion had significantly higher minimum dose than patients with less motion., Conclusion: The potential CTV may incidentally receive adequate and relatively homogeneous doses when ITV is used and the patients have large respiratory motion. However, it could be underdosed for gated treatment or for patients with little motion.

This study is to demonstrate the technical and clinical experience of applying image guided spinal radiosurgery for treatment of localized spinal metastasis. A dedicated shaped beam radiosurgery unit with intensity modulated radiotherapy (IMRT) and x-ray based image-guided radiotherapy (IGRT) were used for the radiosurgery procedure. A total of 196 patients with 270 lesions of spinal metastases were treated with this procedure from May 2001 to October 2005. All patients received single dose radiosurgery to the involved spine only. The radiosurgery dose was escalated from 10 to 18 Gy in 2 Gy increments. The technical experience using IMRT planning and IGRT implementation has been summarized. Clinical results reporting pain relief responses have been analyzed for the first 49 patients treated with this procedure. For IMRT treatment planning, seven posterior/oblique fields were generally used for spinal radiosurgery as the optimal setup to balance conformality versus complexity. A criterion of 10 Gy to 10% of the adjacent spinal cord volume has been met with satisfactory target dose coverage for most of the cases. When the spinal cord dose exceeded this constraint, the tumor coverage was somewhat compromised. Accurate target localization has been achieved for all patients using the x-ray image-guided system. The preliminary clinical results have demonstrated that pain response was achieved in 85% of patients, with neurological improvement in patients with spinal cord compression. Patients tolerated the treatment well without major acute toxicities. Image guided spinal radiosurgery can be successfully applied to treat patients with focal spine metastases.

Background: Spine radiosurgery causes a rapid dose fall-off within the spinal cord. The tolerance of partial volume of the spinal cord may determine the extent of clinical application. The study analyzed the partial volume tolerance of the human spinal cord to single fraction radiosurgery., Methods: A total of 230 lesions with spine metastases in 177 patients were treated with radiosurgery with single fraction of 8 to 18 Gy, prescribed to the 90% isodose line that encompassed the target volume. Spinal cord volume was defined as 6 mm above and below the radiosurgery target volume. Spinal cord dose was calculated from the radiation dose/spinal cord volume histogram and correlated with clinical/neurological status and radiographic studies. Median follow-up was 6.4 months (range, 0.5-49 months). The 1-year survival rate was 49%., Results: The average spinal cord volume defined at the treated spinal segment was 5.9 +/- 2.2 mL. The average dose to the 10% spinal cord volume was 9.8 +/- 1.5 Gy, calculated from the dose-volume histogram in the group of 18 Gy prescribed dose. The spinal cord volume that received higher than 80% of the prescribed dose was 0.07 +/- 0.10 mL, which represented 1.3 +/- 1.8% of the cord volume. Among the 86 patients who survived longer than 1 year there was 1 case of radiation-induced cord injury after 13 months of radiosurgery. There were no other cases of spinal cord sequelae., Conclusions: Whereas the maximum spinal cord tolerance to single-dose radiation is not known, partial volume tolerance of the human spinal cord is at least 10 Gy to 10% of the spinal cord volume defined as 6 mm above and below the radiosurgery target., ((c) 2007 American Cancer Society.)

Purpose: During image-guided radiosurgery, it is common to account only for translational shifts while leaving rotational deviations uncorrected. The aim of this study is to investigate the rotational setup deviations and estimate the dosimetric impact in spinal radiosurgery. Materials and methods: Stereoscopic image registrations of 711 spine radiosurgery procedures (546 patients) were retrospectively reviewed and classified to cervical (C), thoracic (T), and lumbar (L) spines. The probability of rotational deviations were estimated in three orthogonal axis. In order to investigate the dosimetric impact, the original simulation CT images were rotated in the range of ±5 deg in each axis. Then, the dosimetric changes were recorded; including the coverage (V90) and minimum dose (Dmin) to the target, and the dose of 10% volume (D10) and maximum dose (Dmax) to the spinal cord. Results: Target rotations of >5 deg and >3 deg occurred respectively in 1% and 8% of cases. The mean rotations were small (|µ|<0.6 deg) with no axis and site dependent trends. The standard deviations (σ) of different sites and axes ranged from 1.4 to 2.0 deg (mean σ=1.7 deg). The overall dosimetric changes of the target coverage(V90) and cord D10 were small. Five degree rotation resulted in a target V90 decrease of 1±1%, 2±2% and 3±1%, respectively in the lateral, vertical, and longitudinal axes. The corresponding cord D10 increased by 3±6%, 2±2%, and 6±5%. The changes in cord Dmax ranged from 92% to 138% of the original reference spinal cord. Corresponding changes in target Dmin were 59~106%. Conclusion: Large target rotations occurred in a small percentage of patients. The overall dosimetric impact on target coverage and cord D10 was small. However larger effects were observed on the target Dmin and cord Dmax. Special care must be taken for targets of elongated shapes involving multiple vertebrae. [ABSTRACT FROM AUTHOR]

Radiosurgery delivers highly focused radiation beams to the defined target with high precision and accuracy. It has been demonstrated that spine radiosurgery can be safely used for treatment of spine metastasis with rapid and durable pain control, but without detrimental effects to the spinal cord. This study was carried out to determine the role of single fraction radiosurgery for epidural spinal cord compression due to multiple myeloma. A total of 31 lesions in 24 patients with multiple myeloma, who presented with epidural spinal cord compression, were treated with spine radiosurgery. Single fraction radiation dose of 10-18 Gy (median of 16 Gy) was administered to the involved spine including the epidural or paraspinal tumor. Patients were followed up with clinical exams and imaging studies. Median follow-up was 11.2 months (range 1-55). Primary endpoints of this study were pain control, neurological improvement, and radiographic tumor control. Overall pain control rate was 86%; complete relief in 54%, and partial relief in 32% of the patients. Seven patients presented with neurological deficits. Five patients neurologically improved or became normal after radiosurgery. Complete radiographic response of the epidural tumor was noted in 81% at 3 months after radiosurgery. During the follow-up time, there was no radiographic or neurological progression at the treated spine. The treatment was non-invasive and well tolerated. Single fraction radiosurgery achieved an excellent clinical and radiographic response of myeloma epidural spinal cord compression. Radiosurgery can be a viable treatment option for myeloma epidural compression. [ABSTRACT FROM AUTHOR]