Stereotactic Spine Research Articles

Effective and Successful Control of Symptomatic Vertebral Hemangiomas With Epidural Extension Using Stereotactic Spine Radiosurgery.

We present our experience in the management of symptomatic vertebral hemangiomas with epidural extension (SVHEE) using spine stereotactic radiosurgery (SSRS). An Institutional Review Board approved retrospective review of all SVHEE patients treated with SSRS at our institution (2007-2022) was performed. Baseline patient demographics, clinical presentation, lesion volume, and Bilsky grade (to directly evaluate the epidural component) were determined. Clinical and radiographic response and treatment outcomes were subsequently evaluated at first (∼6 months) and final follow-up. Fourteen patients with SVHEE underwent SSRS (16-18 Gy/1-fraction); the mean follow-up was 24 months. The median lesion volume (cc) was 36.9 (range: 7.02-94.1), 31.5 (range: 6.53-69.7), and 25.15 (range: 6.01-52.5) at pre-SSRS, first, and final follow-up, respectively. Overall volume reduction was seen in the last follow-up in all 14 patients, median 29.01% (range: 6.58%-71.58%). Bilsky score was stable or improved in all patients at the last follow-up when compared with pre-SSRS score. Patients who underwent both surgical decompression and SSRS (n = 9): 8 had improved myelopathic symptoms and pain and 1 had stable radiculopathy postintervention. In the 5 patients treated with SSRS monotherapy, 2 had stable radicular pain and the other 3 improved pain and numbness. No patients experienced adverse outcomes. To our knowledge, this represents the largest series of SVHEE patients treated with SSRS, either as monotherapy or part of a multimodal/separation surgery treatment approach. We demonstrate that SSRS represents a potentially safe and effective treatment option in these patients. However, larger prospective studies and longer follow-ups are necessary to further assess the role, durability, and toxicity of SSRS in the management of these patients.

Automated planning of stereotactic spine re-irradiation using cumulative dose limits

Background and PurposeThe lack of dedicated tools in commercial planning systems currently restricts efficient review and planning for re-irradiation. The aim of this study was to develop an automated re-irradiation planning framework based on cumulative doses. Materials and MethodsWe performed a retrospective study of 14 patients who received spine SBRT re-irradiation near a previously irradiated treatment site. A fully-automated workflow, DART (Dose Accumulation-based Re-irradiation Tool), was implemented within Eclipse by leveraging a combination of a dose accumulation script and a proprietary automated optimization algorithm. First, we converted the prior treatment dose into equivalent dose in 2 Gy fractions (EQD2) and mapped it to the current anatomy, utilizing deformable image registration. Subsequently, the intersection of EQD2 isodose lines with relevant organs at risk defines a series of optimization structures. During plan optimization, the residual allowable dose at a specified tissue tolerance was treated as a hard constraint. ResultsAll DART plans met institutional physical and cumulative constraints and passed plan checks by qualified medical physicists. DART demonstrated significant improvements in target coverage over clinical plans, with an average increase in PTV D99% and V100% of 2.3 Gy [range −0.3–7.7 Gy] and 3.4 % [range −0.4 %−7.6 %] (p < 0.01, paired t-test), respectively. Moreover, high-dose spillage (>105 %) outside the PTV was reduced by up to 7 cm3. The homogeneity index for DART plans was improved by 19 % (p < 0.001). ConclusionsDART provides a powerful framework to achieve more tailored re-irradiation plans by accounting for dose distributions from the previous treatments. The superior plan quality could improve the therapeutic ratio for re-irradiation patients.

A quantitative and comparative evaluation of stereotactic spine radiosurgery local control: proposing a consistent measurement methodology.

Stereotactic body radiotherapy (SBRT) is a precise and conformal treatment modality used in the management of metastatic spine tumors. Multiple studies have demonstrated its safety and efficacy for pain and tumor control. However, no uniform quantitative imaging methodology exists to evaluate response to treatment in these patients. This study presents radiographic local control rates post-SBRT, systematically compares measurements acquired according to WHO and Response Evaluation Criteria in Solid Tumors (RECIST) criteria, and explores the relationship to patient outcome. The authors performed a retrospective review of prospectively obtained data from a cohort of 59 consecutive patients (81 metastatic isocenters) treated with SBRT and followed with serial MRI scans. Measurements were performed by a neuroradiologist blinded to the patients' clinical course. Local control status was determined according to both WHO and RECIST measurements, and agreement between the measuring methodologies was calculated and reported. Eighty-one isocenters (111 vertebral bodies) were treated with SBRT. The mean treatment dose was 13.96 Gy and the median follow-up duration was 10.8 months, during which 408 MRI scans were evaluated with both WHO and RECIST criteria for each scan point. Imaging demonstrated a mean unidimensional size decrease of 0.2 cm (p = 0.14) and a mean area size decrease of 0.99 cm2 (p = 0.03). Although 88% of the case classifications were concordant and the agreement was significant, WHO criteria were found to be more sensitive to tumor size change. The local control rates according to WHO and RECIST were 95% and 98%, respectively. Although WHO volumetric measurements are admittedly superior for tumor size measurement, RECIST is simpler, reproducible, and for the first time is shown here to be comparable to WHO criteria. Thus, the application of RECIST methodology appears to be a suitable standard for evaluating post-SBRT treatment response. Moreover, using comprehensive and consistent measuring approaches, this study substantiates the efficacy of SBRT in the treatment of spine metastases.

Personal experience in intramedullary lesions, in adults

Background: Intramedullary spinal cord lesions (IMSCL) although they are rare, it generates invasion and destruction of the spinal cord. Such lesions must be diagnosed as early as possible, some have histological and genetic aggressiveness, generating severe functional neurological damage.&#x0D; Objective: To identify the optimal strategy for diagnosis and treatment in IMSC, to improve prognosis.&#x0D; Methods: A retrospective clinical study from 2001 to 2021, was performed on 33 adult patients (18 women, 15 men), diagnosed with magnetic resonance imaging with IMSCT. The most common topography was: thoracic 27 cases disposed between T2-T12, cervical 6 cases disposed between C2-C6, lumbar 2 cases at L1-L2. The most frequent symptoms in my cases were: unilateral radicular pain related to the tumour topography or bilateral diffuse burning pain, especially during the night; back and neck stiffness; paresthesia, motor disturbances with an ASIA score of 2-4, and severe atrophy especially in cervical topography, ataxia, initial retention, impotence and later loss of bowel and bladder function with incontinence. All patients were operated by the same senior neurosurgeon with at least 6 months of follow-up postoperatively. For functional outcome, the most important predictors are the preoperative neurological grade, and the high-grade IMSCT generating recurrence and reoperations.&#x0D; Results: The patients addressed the clinic for pain and neurological deficits; the topography of the intramedullary lesion was confirmed by MRI native / with contrast, ultrasonography, and spinal arteriography. Several histologic entities were recorded: ependymomas - 12 cases, astrocytomas - 8 cases, hemangioblastomas - 3 cases, cavernomas - 6 cases, metastases - 2 cases, germ cell tumour - 1 case, malignant peripheral nerve sheath tumour - 1 case. Gross total excision was performed in 25 cases, with no mortality. In eight cases recurrences were recorded requiring the resumption of surgical treatment. In all cases physiotherapy-rehabilitation approach was used, and the outcome was correlated with pre-operatory motor deficits severity, 3 patients with thoracic high-grade astrocytoma underwent stereotactic spine radiosurgery (SSR) with Cyberknife abroad, stopping tumour growth one year after.&#x0D; Conclusions: Intramedullary spinal cord lesions (IMSCL) are rare conditions, and MRI development allows an early diagnosis of these tumours. To adequately counselled patients, with minor preoperative deficits, real expectations concerning the functional outcomes, in benign tumours, and even anatomical healing should be based still on refinements of radical surgical excision. Actual radiotherapy techniques should be used in aggressive tumours.

Postoperative Stereotactic Body Radiotherapy for Spinal Metastasis and Predictors of Local Control.

Spine surgery is indicated for select patients with mechanical instability, pain, and/or malignant epidural spinal cord compression, with or without neurological compromise. Stereotactic body radiotherapy (SBRT) is an option for durable local control (LC) for metastatic spine disease. To determine factors associated with LC and progression-free survival (PFS) for patients receiving postoperative stereotactic spine radiosurgery. We analyzed consecutive patients from 2013 to 2019 treated with surgical intervention followed by SBRT. Surgical interventions included laminectomy and vertebrectomy. SBRT included patients treated with 1 to 5 fractions of radiosurgery. We analyzed LC, PFS, overall survival (OS), and toxicity. Univariate and multivariate analyses were performed. A total of 63 patients were treated with a median follow-up of 12.5 mo. Approximately 75% of patients underwent vertebrectomy and 25% underwent laminectomy. One-year cumulative incidence of local failure was 19%. LC was significantly improved for patients receiving radiosurgery ≤40 d from surgery compared to that for patients receiving radiosurgery ≥40 d from surgery, 94%vs 75%, respectively, at 1 yr (P=.03). Patients who received preoperative embolization had improved LC with 1-yr LC of 88%vs 76% for those who did not receive preoperative embolization (P=.037). Significant predictors for LC on multivariate analysis were time from surgery to radiosurgery, higher radiotherapy dose, and preoperative embolization. The 1-yr PFS and OS was 56% and 60%, respectively. Postoperative radiosurgery has excellent and durable LC for spine metastasis. An important consideration when planning postoperative radiosurgery is minimizing delay from surgery to radiosurgery. Preoperative embolization and higher radiotherapy dose were associated with improved LC warranting further study.

Clinical Accuracy, Technical Precision, and Workflow of the First in Human Use of an Augmented-Reality Head-Mounted Display Stereotactic Navigation System for Spine Surgery.

Augmented reality mediated spine surgery is a novel technology for spine navigation. Benchmark cadaveric data have demonstrated high accuracy and precision leading to recent regulatory approval. Absence of respiratory motion in cadaveric studies may positively bias precision and accuracy results and analogous investigations are prudent in live clinical scenarios. To report a technical note, accuracy, precision analysis of the first in-human deployment of this technology. A 78-yr-old female underwent an L4-S1 decompression, pedicle screw, and rod fixation for degenerative spine disease. Six pedicle screws were inserted via AR-HMD (xvision; Augmedics, Chicago, Illinois) navigation. Intraoperative computed tomography was used for navigation registration as well as implant accuracy and precision assessment. Clinical accuracy was graded per the Gertzbein-Robbins (GS) scale by an independent neuroradiologist. Technical precision was analyzed by comparing 3-dimensional (3D) (x, y, z) virtual implant vs real implant position coordinates and reported as linear (mm) and angular (°) deviation. Present data were compared to benchmark cadaveric data. Clinical accuracy (per the GS grading scale) was 100%. Technical precision analysis yielded a mean linear deviation of 2.07 mm (95% CI: 1.62-2.52 mm) and angular deviation of 2.41° (95% CI: 1.57-3.25°). In comparison to prior cadaveric data (99.1%, 2.03±0.99 mm, 1.41±0.61°; GS accuracy 3D linear and angular deviation, respectively), the present results were not significantly different (P>.05). The first in human deployment of the single Food and Drug Administration approved AR-HMD stereotactic spine navigation platform demonstrated clinical accuracy and technical precision of inserted hardware comparable to previously acquired cadaveric studies.

Stereotactic Vertebroplasty for Spinal Metastases with Multilevel Bilateral Pedicle Fractures: A Technical Note.

Vertebral compression fractures (VCFs) represent a significant cause of disability and primarily result from either underlying vertebral body neoplasms or osteoporosis. Vertebroplasty (VP) is a procedure commonly utilized to repair pathologic VCFs in order to manage pain and reinstate vertebral body height. However, there is a paucity of literature on how to manage painful multilevel VCFs with concomitant bilateral pedicle fractures. We describe a patient with a primary prostatic carcinoma and VCFs of the third and fourth lumbar vertebrae (L3 and L4, respectively) with concomitant bilateral pedicle fractures secondary to metastatic disease. Due to the degree of damage to the L3 and L4 vertebral bodies and pedicles, a VP performed via a percutaneous approach was deemed to be too high risk. VP for L3 and L4 was instead performed by utilizing stereotactic spine navigation and an intraoperative O-arm (Medtronic Corporation, Minneapolis, Minnesota). Our result indicates a potential role for stereotactic spine navigation in vertebroplasty for complex pathologic VCFs.

Abstract No. 491 Simultaneous bipedicular radiofrequency ablation for local tumor control of vertebral metastases

To evaluate the safety and effectiveness of simultaneous bipedicular radiofrequency ablation (RFA) for local tumor control of vertebral metastases. Thirty-five spinal lesions in 29 patients were treated, of which 31/35 (89%) and 19/35 (54%) involved the posterior vertebral body and pedicle, respectively. Sixty percent of the lesions involved 75% or more of the vertebral body. Lesions were treated with two articulating, navigational bipolar RFA probes (STAR, Merit) simultaneously to allow more confluent overlapping ablation zone to encompass as much vertebral body volume as possible while minimizing risk of thermal injury and impedance by using variable wattage (3, 5, 7.5, or 10 watts). Mean total ablation times per probe were 18.3 minutes (range, 9.9–29.3) with overlapping ablations zones performed anteriorly, posteriorly, and within the pedicle. Postablation cementoplasty was performed in all cases via the same introducer cannula. Complications were assessed based on the Society of Interventional Radiology classification. Postprocedure local tumor control was defined as the absence of residual enhancement on contrast-enhanced MRI, radiotracer activity on PET, or stability of osteolysis on CT. All lesions were successfully ablated without any complications or thermal injury. Of the 28 lesions with postprocedure imaging, local tumor control was observed in 96% (27/28) of cases at a mean follow-up of 12.7 weeks (range, 1–48). Retraction of epidural tumor was seen in 3 cases. Simultaneous bipedicular RFA is safe and effective in the treatment of vertebral metastases, including those involving the posterior vertebral body and pedicle. This novel technique supports the stereotactic spine radiation surgery paradigm to treat the entire vertebral body and pedicles (i.e. clinical target volume) to account for microscopic disease and marginal failures for better local tumor control rates and more durable pain relief.

(S049) Internal Validation of the Prognostic Index for Spine Metastasis (PRISM) for Stratifying Survival in Patients Treated With Spinal Stereotactic Radiosurgery

We sought to validate the Prognostic Index for Spinal Metastases (PRISM), a scoring system that stratifies patients into subgroups by overall survival.Methods and materials: The PRISM was previously created from multivariate Cox regression with patients enrolled in prospective single institution trials of stereotactic spine radiosurgery (SSRS) for spinal metastasis. We assess model calibration and discrimination within a validation cohort of patients treated off-trial with SSRS for metastatic disease at the same institution.The training and validation cohorts consisted of 205 and 249 patients respectively. Similar survival trends were shown in the 4 PRISM. Survival was significantly different between PRISM subgroups (P<0.0001). C-index for the validation cohort was 0.68 after stratification into subgroups.We internally validated the PRISM with patients treated off-protocol, demonstrating that it can distinguish subgroups by survival, which will be useful for individualizing treatment of spinal metastases and stratifying patients for clinical trials.

PO-0812: Dosimetric impact of using Acuros algorithm for stereotactic lung and spine treatments

PO-0812: Dosimetric impact of using Acuros algorithm for stereotactic lung and spine treatments

Stereotactic spine radiosurgery: Review of safety and efficacy with respect to dose and fractionation.

Background:Stereotactic body radiotherapy (SBRT) is an emerging treatment option for spinal metastases with demonstrated efficacy in the upfront, postoperative, and re-treatment settings, as well as for tumor histologies considered radioresistant. Uncertainty exists regarding the optimal dose and fractionation schedule, with single and multifraction regimens commonly utilized.Methods:A literature search of the PubMed and Medline databases was conducted to identify papers specific to spine SBRT and the effect of varying dose/fractionation regimens on outcomes. Bibliographies of relevant papers were searched for further references, and international spine SBRT experts were consulted.Results:Local control rates generally exceed 80% at 1 year, while high rates of pain control have been attained. There is insufficient evidence to suggest superiority of either single or multiple fraction regimens with respect to local control and pain control. Low rates of toxicity have been reported, assuming strict dose constraints are respected. Radiation myelopathy may be the most morbid toxicity, although the rates are low. The risk of vertebral compression fracture appears to be associated with higher doses per fraction such as those used in single-fraction regimens. The Spinal Instability Neoplastic Score should be considered when evaluating patients for spine SBRT, and prophylactic stabilisation may be warranted. Pain flare is a relatively common toxicity which may be mediated with prophylactic dexamethasone. Because of the treatment complexity and potentially serious toxicities, strict quality assurance should occur at the organizational, planning, dosimetric, and treatment delivery levels.Conclusion:Both single and multifraction regimens are safe and efficacious in spine SBRT for spinal metastases. There may be advantages to hypofractionated treatment over single-fraction regimens with respect to toxicity. Ongoing investigation is underway to define optimal dose and fractionation schedules.

Impact of cervicothoracic region stereotactic spine radiosurgery on adjacent organs at risk.

OBJECTIVE Stereotactic radiosurgery (SRS) of the spine is a conformal method of delivering a high radiation dose to a target in a single or few (usually ≤ 5) fractions with a sharp fall-off outside the target volume. Although efforts have been focused on evaluating spinal cord tolerance when treating spinal column metastases, no study has formally evaluated toxicity to the surrounding organs at risk (OAR), such as the brachial plexus or the oropharynx, when performing SRS in the cervicothoracic region. The aim of this study was to evaluate the radiation dosimetry and the acute and delayed toxicities of SRS on OAR in such patients. METHODS Fifty-six consecutive patients (60 procedures) with a cervicothoracic spine tumor involving segments within C5-T1 who were treated using single-fraction SRS between February 2006 and July 2014 were included in the study. Each patient underwent CT simulation and high-definition MRI before treatment. The clinical target volume and OAR were contoured on BrainScan and iPlan software after image fusion. Radiation toxicity was evaluated using the common toxicity criteria for adverse events and correlated to the radiation doses delivered to these regions. The incidence of vertebral body compression fracture (VCF) before and after SRS was evaluated also. RESULTS Metastatic lesions constituted the majority (n = 52 [93%]) of tumors treated with SRS. Each patient was treated with a median single prescription dose of 16 Gy to the target. The median percentage of tumor covered by SRS was 93% (maximum target dose 18.21 Gy). The brachial plexus received the highest mean maximum dose of 17 Gy, followed by the esophagus (13.8 Gy) and spinal cord (13 Gy). A total of 14 toxicities were encountered in 56 patients (25%) during the study period. Overall, 14% (n = 8) of the patients had Grade 1 toxicity, 9% (n = 5) had Grade 2 toxicity, 2% (n = 1) had Grade 3 toxicity, and none of the patients had Grade 4 or 5 toxicity. The most common (12%) toxicity was dysphagia/odynophagia, followed by axial spine pain flare or painful radiculopathy (9%). The maximum radiation dose to the brachial plexus showed a trend toward significance (p = 0.066) in patients with worsening post-SRS pain. De novo and progressive VCFs after SRS were noted in 3% (3 of 98) and 4% (4 of 98) of vertebral segments, respectively. CONCLUSIONS From the analysis, the current SRS doses used at the Cleveland Clinic seem safe and well tolerated at the cervicothoracic junction. These preliminary data provide tolerance benchmarks for OAR in this region. Because the effect of dose-escalation SRS strategies aimed at improving local tumor control needs to be balanced carefully with associated treatment-related toxicity on adjacent OAR, larger prospective studies using such approaches are needed.

TH‐EF‐BRB‐03: Significant Cord and Esophagus Dose Reduction by 4π Non‐Coplanar Spine Stereotactic Body Radiation Therapy and Stereotactic Radiosurgery

Purpose:To demonstrate significant organ‐at‐risk (OAR) sparing achievable with 4π non‐coplanar radiotherapy on spine SBRT and SRS patients.Methods:Twenty‐five stereotactic spine cases previously treated with VMAT (n = 23) or IMRT (n = 2) were included in this study. A computer‐aided‐design model of a Linac with a 3D‐scanned human surface was utilized to determine the feasible beam space throughout the 4π steradian and beam specific source‐to‐target‐distances (STD) required for collision avoidance. 4π radiotherapy plans integrating beam orientation and fluence map optimization were then created using a column‐generation algorithm. Twenty optimal beams were selected for each case. To evaluate the tradeoff between dosimetric benefit and treatment complexity, 4π plans including only isocentrically deliverable beams were also created. Beam angles of all standard and isocentric 4π plans were imported into Eclipse to recalculate the dose using the same calculation engine as the clinical plans for unbiased comparison. OAR and PTV dose statistics for the clinical, standard‐4π, and isocentric‐4π plans were compared.Results:Comparing standard‐4π to clinical plans, particularly significant average percent reduction in the [mean, maximum] dose of the cord and esophagus of [41%, 21.7%], and [38.7%, 36.4%] was observed, along with global decrease in all other OAR dose statistics. The average cord volume receiving more than 50% prescription dose was substantially decreased by 76%. In addition, improved PTV coverage was demonstrated with a maximum dose reduction of 0.93% and 1.66% increase in homogeneity index (D95/D5). All isocentric‐4π plans achieved dosimetric performance equivalent to that of the standard‐4π plans with higher delivery complexity.Conclusion:4π radiotherapy significantly improves stereotactic spine treatment dosimetry. With the substantial OAR dose sparing, PTV dose escalation is considerably safer. Isocentric‐4π is sufficient to achieve the dosimetric gain. The successful implementation of 4π using an FDA approved planning system paves the way for a prospective clinical trial.Varian Medical Systems, NIH R43CA183390 and R01CA188300, NSF graduate research fellowship DGE‐1144087

OC-0213: Towards on-line sub-mm and sub-second positional verification during stereotactic spine radiotherapy

OC-0213: Towards on-line sub-mm and sub-second positional verification during stereotactic spine radiotherapy

Quantitative Evaluation of Local Control and Wound Healing Following Surgery and Stereotactic Spine Radiosurgery for Spine Tumors

The present study evaluated the optimal measuring criteria to assess spinal tumor response to surgery followed by stereotactic spine radiosurgery (SRS) and reports the local control and wound complication rates following combined multimodality treatment. Prospectively collected patient information was retrospectively reviewed to identify patients treated with spine surgery followed by SRS. Tumor sizes and volumetric assessment were formally measured. Local control status was defined according to World Health Organization (WHO, bidimensional), RECIST (unidimensional), or volumetric size change. Statistical comparative assessments of tumor measurements were performed. Twenty-two patients were eligible for evaluation after having undergone surgery followed by single-fraction SRS within a 2-month period. Seventeen had follow-up magnetic resonance imaging (MRI) with a mean patient follow-up of 12.59 months (range 3-36 months). None developed wound complication after radiation therapy (95% lower confidence bound 13%). Two patients had clinical recurrence while 15 of 17 achieved local control (88.3%). A test of marginal homogeneity for RECIST versus WHO was not statistically significant, P = 1.0 suggesting similar response classifications with both systems. Spearman correlations among 1) volumetric assessment, 2) bidimensional size, and 3) unidimensional size were significant for all groups (P < 0.05). High local control rates can be achieved with surgery followed by SRS. Further, adjuvant SRS following spine tumor surgery delivers less radiation to the wound than conventional radiation and thus potentially reduces wound complications. Unidimensional, bidimensional, and volumetric tumor assessments demonstrate similar results. Hence the use of the simpler RECIST criteria is suitable and appropriate for evaluating the response to treatment after spine radiosurgery.

Creation of a Prognostic Index for Spine Metastasis to Stratify Survival in Patients Treated With Spinal Stereotactic Radiosurgery: Secondary Analysis of Mature Prospective Trials

There exists uncertainty in the prognosis of patients following spinal metastasis treatment. We sought to create a scoring system that stratifies patients based on overall survival. Patients enrolled in 2 prospective trials investigating stereotactic spine radiation surgery (SSRS) for spinal metastasis with ≥ 3-year follow-up were analyzed. A multivariate Cox regression model was used to create a survival model. Pretreatment variables included were race, sex, age, performance status, tumor histology, extent of vertebrae involvement, previous therapy at the SSRS site, disease burden, and timing of diagnosis and metastasis. Four survival groups were generated based on the model-derived survival score. Median follow-up in the 206 patients included in this analysis was 70 months (range: 37-133 months). Seven variables were selected: female sex (hazard ratio [HR] = 0.7, P=.02), Karnofsky performance score (HR = 0.8 per 10-point increase above 60, P = .007), previous surgery at the SSRS site (HR = 0.7, P=.02), previous radiation at the SSRS site (HR = 1.8, P=.001), the SSRS site as the only site of metastatic disease (HR = 0.5, P=.01), number of organ systems involved outside of bone (HR = 1.4 per involved system, P<.001), and >5 year interval from initial diagnosis to detection of spine metastasis (HR = 0.5, P < .001). The median survival among all patients was 25.5 months and was significantly different among survival groups (in group 1 [excellent prognosis], median survival was not reached; group 2 reached 32.4 months; group 3 reached 22.2 months; and group 4 [poor prognosis] reached 9.1 months; P < .001). Pretreatment symptom burden was significantly higher in the patient group with poor survival than in the group with excellent survival (all metrics, P < .05). We developed the prognostic index for spinal metastases (PRISM) model, a new model that identified patient subgroups with poor and excellent prognoses.

A six-year review of more than 13,000 patient-specific IMRT QA results from 13 different treatment sites.

Due to a lack of information regarding the current clinical experience of IMRT QA for a large and varied plan population, we reviewed our patient‐specific IMRT quality assurance (QA) results for 13,003 treatment plans from 13 distinct treatment sites from a six‐year period. QA records were reviewed for dose difference (single point with ion chamber measurement; ±3% agreement criteria) and percentage of pixels passing relative dose gamma analysis (film measurement; 90% passing 5%(global)/3 mm agreement criteria) from 2005 through 2011. Plan records were analyzed for trends with measurement date and treatment site. Plans failing to meet QA tolerance criteria were evaluated for follow‐up clinical action (i.e., if repeat measurements were performed). The mean difference (±SD) between ion chamber point measurements and calculated doses was ‐0.29% ±1.64% (calculated values being slightly higher) and, regarding planar dose evaluations, the mean percentage of pixels passing the gamma criteria of 5%(global)/3 mm was 97.7% (lower 95th percentile: 92.2%). 97.7% and 99.3% of plans passed the point dose and planar dose verification, respectively. We observed statistically significant differences (p<0.05) in both point dose and planar dose verification measurements as a function of treatment site (particularly for stereotactic spine and mesothelioma sites) and measurement date (average agreement improved with time). However, despite improved dosimetric agreement, the percentage of failing plans has remained nearly constant at 2.3%.PACS numbers: 87.55.Qr, 87.55.km, 87.56.Fc

SU-E-T-548: How To Decrease Spine Dose In Patients Who Underwent Sterotactic Spine Radiosurgery?

Purpose: Stereotactic radiosurgery for spine metastases involves irradiation using a single high dose fraction. The purpose of this study was to dosimetrically compare stereotactic spine radiosurgery(SRS) plans using a recently new volumetric modulated arc therapy(VMAT) technique against fix-field intensity-modulated radiotherapy(IMRT). Plans were evaluated for target conformity and spinal cord sparing. Methods: Fifteen previously treated patients were replanned using the Eclipse 10.1 TPS AAA calculation algorithm. IMRT plans with 7 fields were generated. The arc plans used 2 full arc configurations. Arc and IMRT plans were normalized and prescribed to deliver 16.0 Gy in a single fraction to 90% of the planning target volume(PTV). PTVs consisted of the vertebral body expanded by 3mm, excluding the PRV-cord, where the cord was expanded by 2mm.RTOG 0631 recommendations were applied for treatment planning. Partial spinal cord volume was defined as 5mm above and below the radiosurgery target volume. Plans were compared for conformity and gradient index as well as spinal cord sparing. Results: The conformity index values of fifteen patients for two different treatment planning techniques were shown in table 1. Conformity index values for 2 full arc planning (average CI=0.84) were higher than that of IMRT planning (average CI=0.79). The gradient index valuesmore » of fifteen patients for two different treatment planning techniques were shown in table 2. Gradient index values for 2 full arc planning (average GI=3.58) were higher than that of IMRT planning (average GI=2.82).The spinal cord doses of fifteen patients for two different treatment planning techniques were shown in table 3. D0.35cc, D0.03cc and partial spinal cord D10% values in 2 full arc plannings (average D0.35cc=819.3cGy, D0.03cc=965.4cGy, 10%partial spinal=718.1cGy) were lower than IMRT plannings (average D0.35cc=877.4cGy, D0.03c=1071.4cGy, 10%partial spinal=805.1cGy). Conclusions: The two arc VMAT technique is superior to 7 field IMRT technique in terms of both spinal cord sparing and better conformity and gradient indexes.« less

Review of stereotactic radiosurgery for intramedullary spinal lesions.

Stereotactic radiosurgery (SR) represents an increasingly utilized modality in the treatment of intracranial and extracranial pathologies. Stereotactic spine radiosurgery (SSR) uses an alternative strategy to increase the probability of local control by delivering large cumulative doses of radiation therapy (RT) in only a few fractions. SSR in the treatment of intramedullary lesions remains in its infancy-this review summarizes the current literature regarding the use of SSR for treating intramedullary spinal lesions. Several studies have suggested that SSR should be guided by the principles of intracranial radiosurgery with radiation doses placed no further than 1-2mm apart, thereby minimizing exposure to the surrounding spinal cord and allowing for delivery of higher radiation doses to target areas. Maximum dose-volume relationships and single-point doses with SSR for the spinal cord are currently under debate. Prior reports of SR for intramedullary metastases, arteriovenous malformations, ependymomas, and hemangioblastomas demonstrated favorable outcomes. In the management of intrame-dullary spinal lesions, SSR appears to provide an effective and safe treatment compared to conventional RT. SSR should likely be utilized for select patient-scenarios given the potential for radiation-induced myelopathy, though high-quality literature on SSR for intramedullary lesions remains limited.

MO-D-BRB-05: An Analysis of 13,000 Patient-Specific IMRT QA Results from 13 Different Clinical Treatment Services

To review an institution's patient-specific IMRT quality assurance (QA) results, including absolute dose and gamma analysis measurements. Patient-specific IMRT QA records were reviewed to obtain information on absolute dose difference (ion chamber measurement; ±3% agreement criteria) and percentage of pixels passing gamma (film measurement; 5%/3 mm agreement criteria) from 2005 to 2011. The 13,002 plans reviewed, were classified by treatment service: breast (n=67), central nervous system (n =1383), gastrointestinal (n=803), genitourinary (n=1831), gynecology (n=935), hematology (n=380), head and neck (n=3697), intensity-modulated stereotactic spine radiation therapy (n=341), melanoma (n=54), mesothelioma (n=52), pediatric (n=307), sarcoma (n=201), and thoracic (n=2951). All records were analyzed for trends according to measurement date and treatment service. Plans failing to meet QA criteria were further evaluated for subsequent measured data. Mean difference (± one standard deviation) between the measured and calculated doses was -0.29% ± 1.64% (with the calculated values being slightly higher). The mean percentage of pixels passing gamma was 97.7% (lower 95th percentile, 92.2%). The plan pass rates were 97.7% and 99.3% for absolute dose and gamma, respectively. We observed statistically significant differences (p < 0.05) in both absolute dose and gamma measurements as a function of treatment service (particularly for stereotactic spine and mesothelioma services) and measurement date (average agreement improved with time). However, despite improved agreement between measured and calculated doses, the percentage of treatment plans failing to meet the passing criteria has remained largely constant at ∼2.3%. Our retrospective review of 13,002 patient-specific IMRT QA plans demonstrated that plans continue to fail IMRT QA criteria at a consistent rate. This rate serves as a clinical reference for expected rates of QA plan pass and failure for a variety of treatment services.