and again in 5 minute intervals during the course of a mock treatment on a. MR-IGRT system. The mock treatment was repeated for 2 additional fractions by ...
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International Journal of Radiation Oncology Biology Physics
Given the superior ability for MR to visualize the SC, we sought to use MR-IGRT to compare the relative motion of the SC versus the VB. Materials/Methods: Three healthy volunteers were immobilized in vacuum immobilization bags and underwent volumetric MR at baseline (t0) and again in 5 minute intervals during the course of a mock treatment on a MR-IGRT system. The mock treatment was repeated for 2 additional fractions by removing the patient from the immobilization and then restarting the process completely. The MR protocol was a true fast imaging with steady state precession T2*/T1-weighted volumetric scan with a 1.5 x 1.5 mm resolution and field of view selected based on patient size. Images were imported into a third party treatment planning system, and registrations were performed at the T5 VB level for each patient and each fraction with t0 as reference using either (1) the VB or (2) the SC. Registrations were performed via automated registration with a narrow field of view followed by manual adjustment by the clinician. Differences in motion in the lateral and anterior-posterior (AP) directions and 2D in-plane shifts between SV and VB were calculated. Results: All 3 volunteers were able to complete the course of mock treatment. The SC was well visualized with a high level of contrast between SC and surrounding CSF. Average difference in lateral motion of SC relative to VB across all 3 fractions for patients 1, 2, and 3 was -0.7 +/- 0.4 mm, -0.8 +/- 0.5 mm, and -0.4 +/- 0.3 mm. Average difference in AP motion was -0.1 +/- 0.6 mm, -0.1 +/- 0.5 mm, and 0.2 +/- 0.3 mm. Average difference in 2D motion was 0.9 +/- 0.4 mm, 0.9 +/- 0.5 mm, 0.6 +/- 0.3 mm. No time trends were noted across the 30 minute treatment. Maximum lateral, AP, and VS between SC and VB across all patients and all fractions was -1.4 mm, -1.2 mm, and 1.8 mm, respectively. Conclusions: The SC is well visualized with MR-IGRT and for the first time patient specific shifts can be made directly based on SC position rather than VB as a surrogate. A small but consistent difference in calculated shifts was observed when shifting based on SC versus VB, largely in the lateral direction. Average differences in a clinically relevant 2D shift were generally < 1 mm, but were up to 1.8 mm at certain time points. Confirmed in a larger cohort, such data may also be informative for generation of SC planning risk volume margins at a population level. Author Disclosure: C.G. Robinson: None. J.D. Bradley: None. J.R. Victoria: A. Employee; ViewRay. N. Stock Options; ViewRay. J.F. Dempsey: A. Employee; ViewRay. M. Stock; ViewRay. N. Stock Options; ViewRay. S. Leadership; ViewRay. S. Mutic: F. Honoraria; Varian Medical Systems, ViewRay. I. Travel Expenses; Varian Medical Systems, ViewRay. K. Advisory Board; ViewRay. M. Stock; Radiologica LLC. O. Partnership; Treat Safely. P. Royalty; Modus Medical. Q. Patent/License Fee/Copyright; Varian Medical Systems. S. Leadership; Radiologica LLC. R. Kashani: I. Travel Expenses; ViewRay.
previous SRS. Twenty-seven VCF were de novo. Median SINS changed from 5 at SRS (1-10) to 11 at stabilization (7-16). Twenty-three patients had biopsy at the time of stabilization that showed no evidence of tumor. The remaining two patients had no specimen taken at the time of stabilization but had no evidence of radiographic or clinical progression. Conclusions: After receiving ablative single-fraction SRS to spinal lesions, 9% of patients progressed to symptomatic VCF at the treated level in the absence of tumor recurrence. This includes a total of forty-six VCF, with sixteen occurring at adjacent levels. These results may prove useful in discussions with patients regarding treatment risk and when considering early intervention when imaging evidence of pending VCF is detected. Author Disclosure: M.S. Virk: None. J.E. Han: None. E. Lis: None. M. Bilsky: G. Consultant; SpineWave, Depuy/Synthes. I. Laufer: G. Consultant; SpineWave, Depuy/Synthes. Y. Yamada: None.
2212 Symptomatic Vertebral Body Compression Fractures Requiring Intervention Following Single Fraction Stereotactic Radiosurgery for Spinal Metastases M.S. Virk, J.E. Han, E. Lis, M. Bilsky, I. Laufer, and Y. Yamada; Memorial Sloan-Kettering Cancer Center, New York, NY Purpose/Objective(s): Single-fraction stereotactic radiosurgery (SRS) 24 Gy dose provides excellent tumor control in patients with spinal metastases. 12-40% radiographic vertebral compression fracture (VCF) rate has been reported after SRS. No studies have identified the rate of symptomatic fractures. The purpose of this study is to determine the rate of postSRS symptomatic VCF requiring treatment with kyphoplasty or surgery. Materials/Methods: 291 patients that received single-fraction SRS between T4-L5 were included. Charts and imaging were reviewed for postSRS kyphoplasty or surgery for mechanical instability. All patients had a minimum of thirty month follow-up from time of SRS. Results: Twenty-five patients (9%) with thirty-four levels treated with SRS (24 Gy) progressed to symptomatic VCF requiring treatment with either kyphoplasty (10) or surgery (15). The median time to symptomatic VCF was twenty-eight months (2-51 months). Thirty VCF occurred at the level treated with SRS and sixteen VCF occurred adjacent to the level of
2213 Radiographic, Neurological, and Clinical Assessment of Fractionated Stereotactic Radiosurgery in the Treatment of Metastatic Epidural Spinal Cord Compression at a Single Institution P. Jain,1 H. Chou,2 M. Marrero,2 E. Montchal,2 and M. Ghaly2; 1North Shore - LIJ, New York, MN, 2North Shore - LIJ, New York, NY Purpose/Objective(s): To assess the radiographic, neurologic and clinical response to stereotactic radiosurgery (SRS) in the treatment of metastatic epidural spinal cord compression (ESCC). Materials/Methods: Retrospective chart review of 18 patients ages 57-81 years (mean 68 years) with ESCC treated at a single institution between 2010 and 2014. Primary cancer was 4 breast, 3 lung, 1 prostate and 10 other. SRS was delivered to 21-27 Gy (median 24 Gy) in three fractions to 2 cervical, 8 thoracic and 8 lumbar lesions. Three of the patients were treated post operatively. Follow-up imaging was obtained 1-2 months post treatment (average 1.5 months). Radiologic response was assessed using the Bilsky six point ESCC scale: Grade 0 bone only disease, 1a epidural impingement, 1b deformation of the thecal sac, 1c deformation of the thecal sac with spinal cord abutment, 2 spinal cord compression with CSF visible around the cord, and 3 spinal cord compression with no CSF visible around the cord. Neurologic assessment was recorded before and after treatment using the Ryu/Rock neurological grading system: Grade A no symptoms, B focal minor symptom such as pain, C functional paresis with strength 4/5, D nonfunctional paresis with muscle strength less than or equal to 3/5 where the involved muscle nonfunctional or nonambulatory, and E plegic with urinary or rectal incontinence. Results: Initial Karnofsky Performance Status scale ranged from 50-90 (median 70) and pain score ranged from 0-10 (average 5) on a scale of 010. Patients had initial ESCC grade of 1a-1c (five 1a, eight 1b and five 1c) and neurologic grade A-D (one A, eleven B, four C and two D). Radiographic evidence of ESCC decompression was seen in five patients (28%) following SRS. Four of the five patients were initially graded as 1c and had radiographic improvement to 1b following fractionated SRS. Additionally, all but five patients (72%) had improvement in neurologic status. The five patients who did not have a change in neurologic grade remained grade B with focal pain being their main complaint. Finally, all but one patient (94%) had improvement in pain score following SRS. This patient had worsening pain secondary to progression of disease and his treatment was terminated following two fractions of SRS. There was an average of 2.7 point improvement in pain among all participants. Interestingly, the three post-operative patients had a larger 5.3 point improvement in pain score following SRS. There was no correlation between the radiographic and neurologic grades. Conclusions: Fractionated stereotactic radiosurgery is a viable option in the treatment of metastatic epidural spinal cord compression lesions. Preliminary results show radiographic evidence of decompression in 28% of lesions, functional neurological improvement in 72% of patients and better pain control in all but one patient. Author Disclosure: P. Jain: None. H. Chou: None. M. Marrero: None. E. Montchal: None. M. Ghaly: None.
