Spine Stereotactic Radiosurgery 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.

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

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

Stereotactic Radiosurgery for Patients with Spinal Metastases from Thyroid Cancer: A 20-Year Experience

Primary thyroid cancer metastasizing to the spine portends poor survival and low quality of life. Current management strategies continue to evolve. This single-institution retrospective study analyzes outcomes after spinal stereotactic radiosurgery (SRS) for patients with spinal metastases from thyroid cancer. Nineteen patients (median age: 64.5 years) were treated with SRS for spinal primary thyroid metastases (40 metastases, 47 vertebral levels) between 2003-2023. Nineteen (47.5%) lesions had epidural involvement, and 20 (50%) lesions were classified as potentially unstable or unstable via the Spinal Instability Neoplastic Score. The median tumor volume per lesion was 33 cc (range: 1.5-153). The median single-fraction prescription dose was 20 Gy (range: 12-23.5). The median follow-up period was 15 months (range: 2-40). Five (12.8%) lesions locally progressed at a median of 9 months (range: 4-26) after SRS. The 1-, 2-, and 3-year local tumor control rates per lesion were 90.4%, 83.5%, and 75.9%, respectively. On univariate analysis, age at SRS > 70 years (p=0.05, HR: 6.86, 95% CI: 1.01-46.7) was significantly correlated with lower rates of local tumor control. The median overall survival was 35 months (range: 2-141). The 1-, 2-, and 3-year overall survival rates were 73.7%, 50.4%, and 43.2%, respectively. For 33 lesions initially associated with pain, patients reported pain improvement (22 lesions, 66.7%), stability (10 lesions, 30.3%), and worsening (1 lesion, 3.0%) after SRS. One patient developed dysphagia 4 months after SRS treatment. SRS can be utilized as an effective and safe primary and adjuvant treatment option for primary thyroid metastases to the spine.

The role of spine stereotactic radiosurgery for patients with breast cancer metastases.

Breast cancer that metastasizes to the spine is associated with low quality of life and poor survival. Radiosurgery has an increasing role in this patient population. This single-institution (2003-2023) study analyzes clinical outcomes and prognostic factors for patients who underwent spinal stereotactic radiosurgery (SSRS) for metastatic breast cancer. Ninety patients (155 unique breast cancer spinal metastases) were treated with SSRS. The median age was 57years (range: 35-88), and the median KPS was 80 (range: 40-100). Forty-two (27%) lesions were managed surgically prior to radiosurgery. At SSRS, 75 (48%) lesions impinged or compressed the spinal cord per the epidural spinal cord scale (ESCC). Seventy-nine (51%) lesions were categorized as potentially unstable or unstable by the Spinal Instability Neoplastic Score (SINS). The median follow-up was 15months (range: 1-183). The median single-session tumor volume was 25.4cc (range: 2-197), and the median single-fraction prescription dose was 17Gy (range: 12-25). Seven (5%) lesions locally progressed. The 1-, 2-, and 5-year local control rates were 98%, 97%, and 92%, respectively. The median overall survival (OS) for the cohort was 32months (range: 2-183). The 1-, 2-, and 5-year OS rates were 72%, 53%, and 30%, respectively. On univariate analysis, KPS ≥ 80 (p = 0.009, HR: 0.51, 95% CI: 0.31-0.84) was associated with improved OS. Patient-reported pain improved (68%), remained stable (29%), or worsened (3%) following radiosurgery. Fifteen (10%) radiation-induced toxicities were reported. Spinal radiosurgery is a safe and highly effective long-term treatment modality for metastases to the spine that originate from breast cancer.

Definitive single fraction spine stereotactic radiosurgery for metastatic sarcoma: Simultaneous integrated boost is associated with high tumor control and low vertebral fracture risk

IntroductionSarcoma spinal metastases (SSM) are particularly difficult to manage given their poor response rates to chemotherapy and inherent radioresistance. We evaluated outcomes in a cohort of patients with SSM uniformly treated using single-fraction simultaneous-integrated-boost (SIB) spine stereotactic radiosurgery (SSRS). Materials and MethodsA retrospective review was conducted at a single tertiary institution treated with SSRS for SSM between April 2007-April 2023. 16–24 Gy was delivered to the GTV and 16 Gy uniformly to the CTV. Kaplan-Meier analysis was conducted to assess time to progression of disease (PD) with proportionate hazards modelling used to determine hazard ratios (HR) and respective 95 % confidence intervals (CI). Results70 patients with 100 lesions underwent SSRS for SSM. Median follow-up was 19.3 months (IQR 7.7–27.8). Median age was 55 years (IQR42-63). Median GTV and CTVs were 14.5 cm3 (IQR 5–32) and 52.7 cm3 (IQR 29.5–87.5) respectively. Median GTV prescription dose and biologically equivalent dose (BED) [α/β = 10] was 24 Gy and 81.6 Gy respectively. 85 lesions received 24 Gy to the GTV. 27 % of patients had Bilsky 1b or greater disease. 16 of 100 lesions recurred representing a crude local failure rate of 16 % with a median time to failure of 10.4 months (IQR 5.7–18) in cases which failed locally. 1-year actuarial local control (LC) was 89 %. Median overall survival (OS) was 15.3 months (IQR 7.7–25) from SSRS. Every 1 Gy increase in GTV absolute minimum dose (DMin) across the range (5.8–25 Gy) was associated with a reduced risk of local failure (HR = 0.871 [95 % CI 0.782–0.97], p = 0.009). 9 % of patients developed vertebral compression fractures at a median of 13 months post SSRS (IQR 7–25). ConclusionThis study represents one of the most homogenously treated and the largest cohorts of patients with SSM treated with single-fraction SSRS. Despite inherent radioresistance, SSRS confers durable and high rates of local control in SSM without unexpected long-term toxicity rates.

CTNI-01. LONG-TERM RESULTS FROM A PHASE 1 TRIAL OF SPINE SBRT IN INOPERABLE PATIENTS WITH CORD COMPRESSION

Abstract PURPOSE/OBJECTIVE We seek to establish the feasibility of using spine stereotactic radiosurgery (SSRS) allowing for spinal cord dose constraint relaxation as the primary management of metastatic epidural spinal cord compression (MESCC) in inoperable patients monitoring for radiation myelopathy (RM) and radiographic local control (LC). MATERIAL/METHODS Patients with radiation naïve MESCC were enrolled on this prospective Phase 1 trial. Single fraction SSRS was delivered to a dose of 18 or 24 Gy. Spinal cord constraint relaxation was performed in sequential cohorts from an initial allowable Dmax cohort of 10 Gy up to 16 Gy only if tumor progression occurred without RM. RESULTS Thirty two patients enrolled on the trial of which 4, 12, 8 and 8 were in the 10 Gy, 12 Gy, 14 Gy and 16 Gy cord Dmax cohorts, respectively. At baseline, there were 10 sites with MESCC Grade 1B, 10 sites with Grade 1C, 9 sites with Grade 2, 2 sites with Grade 1A, and 1 site with Grade 3 disease. Of the 28 evaluable patients, the median overall survival was 32.3 months (range 5.8-122.6 mo). The 1-year and 5-year LC was 84.5% and 79.5%. The 2-year LC did not statistically differ between the 14-16 Gy cord Dmax combined cohorts and the 10-12 Gy cord Dmax combined cohorts (92.9% vs. 62.9%, p = 0.15). With a median clinical follow-up of 22.7 months (range 3-122.3 mo), there were no cases of RM including in the 13 patients who survived at least 3 years. In the cohort receiving a cord Dmax of 16 Gy, there were no cases of RM with a median follow-up of 18.6 mo (range 9.0-97.1 mo). CONCLUSION With long-term follow-up, these data demonstrate that SSRS is a safe and effective tool in patients with MESCC. Cord constraint relaxation may be considered in inoperable patients with MESCC.

Quantification of MRI Artifacts in Carbon Fiber Reinforced Polyetheretherketone Thoracolumbar Pedicle Screw Constructs prior to Spinal Stereotactic Radiosurgery

Carbon fiber reinforced polyetheretherketone (CFRP) is a nonmetallic material that is a subject of growing interest in the field of spinal instrumentation manufacturing. The radiolucency and low magnetic susceptibility of CFRP has potential to create less interference with diagnostic imaging compared with titanium implants. However, an objective comparison of the image artifact produced by titanium and CFRP implants has not been described. Spinal oncology, particularly after resection of spinal tumors and at the time of spinal stereotactic radiosurgery planning, relies heavily on imaging interpretation for evaluating resection, adjuvant treatment planning, and surveillance. We present a study comparing measurements of postoperative magnetic resonance imaging artifacts between titanium and CFRP pedicle screw constructs in the setting of separation surgery for metastatic disease. The diameter of the signal drop around the screws (pedicle screw artifact) and the diameter of the spinal canal free from artifacts (canal visualization) were measured in consecutive patients who had spinal instrumentation followed by spinal stereotactic radiosurgery in the June 2019 to May 2022 timeframe. The spinal cord presented a shift at the screw level in sagittal images which was also measured (Sagittal Distortion, SagD). Fifty patients, corresponding to 356 screws and 183 vertebral levels, were evaluated overall. CFRP produced less artifacts in all the 3 parameters compared with titanium: mean pedicle screw artifact (CFRP = 5.8 mm, Ti = 13.2 mm), canal visualization (CFRP = 19.2 mm, Ti = 15.5 mm), and SagD (CFRP = .5 mm, Ti = 1.9 mm), all P < .001. In practice, these findings translate into better-quality magnetic resonance imaging. The initial perceived advantages are easier evaluation of postoperative imaging, facilitating radiation treatment planning, recurrence detection, and avoidance in repeating a suboptimal computed tomography myelogram. Further clinical studies analyzing long-term outcomes of patients treated with CFRP implants are necessary.

Stratifying Response to Stereotactic Radiosurgery for Spinal Metastases by Primary Site Genomic Mutations

Spine stereotactic radiosurgery (SSRS) is effective in achieving durable local control (LC) and palliation of pain in patients with spinal metastases. Per institutional standards, SSRS prescription dose is tailored by primary site histology, with radioresistant disease receiving escalated doses. While the association between tumor histology and radioresistance is well studied, the association between specific genotypic mutations and radioresistance to SSRS is not well known. We sought to determine if a relationship exists between primary tumor mutations and clinical outcomes following SSRS. We performed a retrospective analysis of 201 patients with available primary site mutation profiles who underwent SSRS to 327 spinal metastases from 2007-2022 at a single institution. Associations with overall survival (OS) and LC were identified using univariate and multivariable Cox proportional hazards modeling adjusted for clinicopathologic and treatment-related factors. The median age was 59 years (range: 11-85) at the time of SSRS. One hundred and five patients were male (52%). The median SSRS dose to the gross tumor volume was 24 Gy (range: 12-50) given in a median of 1 fraction (range: 1-5), corresponding to a biologically effective dose (BED10) of 81.6 Gy. The most common primary tumor sites were head and neck (20%), lung (19%), and genitourinary (15%). The most common spine subsites were thoracic (57%) and lumbar (27%). Twenty-four mutated genes were identified in primary tumors with the most common being TP53 (28%), KIT (15%), PIK3CA (15%), and KRAS (10%). Prior to receipt of SSRS, 19% of patients underwent surgical resection and 23% received conventional radiation therapy (RT) to their treated sites. The median follow-up time and OS following SSRS was 97 months (95% confidence interval [CI] 86-128) and 41 months (95% CI 20-31), respectively. The median LC at 1 and 2 years following SSRS was 88% (95% CI 84-92) and 75% (95% CI 70-82), respectively. On multivariable analysis, receipt of prior RT (hazard ratio [HR] 1.86; 95% CI 1.29-2.67; P = 0.0008) and TP53 mutation (HR 1.68; 95% CI 1.20-2.35; P = 0.0024) were associated with shorter OS, whereas STK11 mutation (HR 2.14; 95% CI 0.47-4.70; P = 0.0589) trended towards shorter OS. LC was more durable with increasing BED10 (HR 0.98; 95% CI 0.96-1.00; P = 0.0166) and less durable with mutations in ATM (HR 2.40; 95% CI 1.06-5.44; P = 0.0362), STK11 (HR 4.89; 95% CI 1.40-15.01; P = 0.0119), and CTNNB1 (HR 4.49; 95% CI 1.90-10.62; P = 0.0006). While favorable outcomes among all patients receiving SSRS were seen, increasing BED10 was associated with more durable LC. Primary site ATM, STK11, and CTNNB1 mutations may be associated with poorer LC following SSRS. Further investigation into the prognostic value of individual mutations and combinations thereof is warranted.

Role of Fractionation in Local Control of Spinal Metastases Treated with Stereotactic Radiosurgery

Optimal fractionation of spinal stereotactic radiosurgery (SRS) for spine metastases remains unknown. Retrospective data suggest decreased local failure (LF) with fractionated SRS of brain metastases. We evaluated our institutional outcomes of spinal SRS with the hypothesis that fractionation improves the rate of local failure compared to single-fraction treatment. This IRB-approved, retrospective analysis included patients with spine metastases treated with spinal SRS between October 2002 and November 2014 with evaluable follow-up imaging and no prior irradiation to the given segment. The exposure of interest was single- or multi-fraction SRS with a primary endpoint of the cumulative incidence of LF with death as a competing risk. We assessed bivariate associations between fractionation and single-fraction equivalent dose (SFED in Gy10) as well as high-risk features, defined as epidural extension (Bilsky Scale), paraspinous extension, and gastrointestinal (GI) vs non-GI primary. We calculated the rates of LF and vertebral body compression fracture (VCF) at 1-year, and assessed LF by fractionation when limited only to courses receiving SFED>18 Gy. We analyzed the association between fractionation and LF using subdistribution hazard ratios (SHR) estimated from competing risks regression with death as a competing risk and adjusting for lesion-specific characteristics as well as SFED to determine contribution of these variables to the estimated effect of fraction number on LF. We calculated relative attenuation for the contribution of SFED to this association, defined as [SHRfractions-SHRfractions+SFED] ÷ [SHRSFED-1]. In 293 patients with 516 spinal segments, lesions treated with single fraction compared to multi-fraction SRS had less epidural (19% vs 36%, p<0.001) and paraspinous (20% vs 35%, p<0.001) extension, more GI histology (17% vs 10%, p = 0.039), received a higher mean SFED (18.3 Gy vs. 16.6 Gy, p<0.001), and had a lower 1-year LF (8% vs 14%, p = 0.02), with no difference in VCF (7% vs. 5%, p = 0.38). After adjusting for high-risk features, single fraction SRS was associated with lower LF (SHR = 0.45, 95% CI 0.24-0.84, p = 0.02). After adjustment for SFED, this association of fractionation was attenuated by 53% and became insignificant (SHR = 0.78, 95% CI 0.44-1.37, p = 0.38). Overall, 1-year LF for SFED>18 Gy was 6% compared to 15% for <18 Gy (p<0.001). When limited to courses with SFED>18 Gy (n = 261), single fraction SRS had no improvement in 1-year LF compared to multi-fraction (6.6% vs 4.6%, p = 0.77). Single fraction SRS was associated with better local control compared to multi-fraction; however, much of this association was attenuated by SFED but not by high-risk features of treated lesions. To clarify the role of fractionation, we have initiated a prospective, randomized trial of single vs. multi-fraction SRS utilizing the same SFED.

Validation of the Prognostic Index for Spine Metastasis (PRISM) Score for Stratifying Survival in Patients Treated with Spinal Stereotactic Radiosurgery

Stereotactic spinal radiosurgery (SSRS) has been increasingly utilized as a first-line treatment for the management of spine metastases due to its ability to prolong survival and improve symptom control. Studies have shown that SSRS is helpful for select patients; however, there is no universal scoring system utilized to predict patient response to treatment. The Prognostic Index for Spinal Metastases (PRISM) score was shown to predict the likelihood of patients benefiting from SSRS. We sought to further demonstrate its generalizability by performing validation with a large dataset from a second high-volume institution. We performed a retrospective review from 2017-2019 of 424 patients treated with SSRS at a single institution. Patients were stratified on the previously described PRISM criteria: Female sex (+2), solitary bone disease (+3), performance status (0 through +3.5), prior surgery at the SSRS site (+1), number of other metastatic sites (-N), prior radiation at the SSRS site (-1), and latency to treatment ≥ 5 months (+3). Patients were grouped based on PRISM scores: >7, Group 1; 4-7, Group 2; 1-3, Group 3; <1 Group 4. There were 89, 188, 88, and 59 patients in Groups 1, 2, 3, and 4, respectively. Most patients were male (70%) with a performance status of 0 (53%). The most common tumor histologies were prostate (34%), renal (18%), and lung (11%). The median biological effective dose (BED10) was 60 Gy (interquartile range [IQR], 60-82). We performed Cox proportional hazards analysis on overall survival (OS) based on PRISM score and patient and tumor characteristics. Concordance indices created from PRISM criteria and the multivariate Cox proportional analysis were compared. The median follow-up time was 50.5 months (95% confidence interval [CI], 45.8-54.7) with a median overall survival of 30.3 months (95% CI, 27.3-38.4). The median overall survivals for PRISM Groups 1, 2, 3, and 4 were 57.1, 37, 23.7, and 8.8 months, respectively. There were significant differences in overall survival among PRISM groups with hazard ratios of 0.49 (95% CI, 0.35-0.69; P<0.001) for Group 1, 0.71 (95% CI, 0.55-0.91); P<0.007) for Group 2, 1,45 (95% CI, 1.08-1.94); P = 0.010) for Group 3, and 3.47 (95% CI, 2.56-4.70; P<0.001) for Group 4. Multivariable Cox analysis for patient and tumor characteristics revealed only the number of organs involved and performance status as significant clinicopathologic prognostic attributes. However, the C-index using the PRISM criteria was 0.76, which was superior to the C-index when using the significant clinicopathologic attributes by themselves (0.71). These data demonstrate robust validation of the PRISM score to stratify OS in patients treated with SSRS and may help guide optimal treatment selection in prospective trials and clinical settings.

Spine Stereotactic Radiosurgery for Primary and Metastatic Osteosarcoma

Osteosarcoma is difficult to control due to its high propensity for metastasis and resistance to local and systemic therapies. High doses of radiation therapy (RT) may confer local control (LC) in some settings but for lesions involving the vertebral bodies, proximity to the spinal cord may limit the ability to deliver an adequate dose. In this analysis, we investigate the role of spine stereotactic radiosurgery (SSRS) to overcome this barrier and enable efficacious treatment of primary or metastatic osteosarcoma of the spine. We retrospectively reviewed all patients treated with SSRS for osteosarcoma of the vertebrae between 2006 and 2022 at a single large tertiary cancer center. We utilized the Kaplan-Meier method to estimate overall survival (OS) and LC. We identified 18 patients treated with SSRS for 25 lesions of spinal osteosarcoma. Median follow-up was 17.2 months. Two patients and three separate lesions were treated with SSRS for primary osteosarcoma of the vertebrae. The remaining 16 patients and 22 lesions received SSRS to the spine for metastatic disease. Lesions were treated to a dose of 24Gy in one fraction (n = 20) 27Gy in 3 fractions (n = 4) or 50Gy in 5 fractions (n = 1). Treatment sites included the cervical spine alone (n = 4), thoracic spine alone (n = 12), lumbar spine alone (n = 4), sacrum alone (n = 3), or both the thoracic and lumbar spine (n = 2). At latest follow up, local failure was observed in 9/25 (36%) treated lesions and median LC was 22.5 months (95% CI 6-43 months). Per-lesion LC at 1 year was 64% (95% CI 35-83%). Per-patient median OS was 14 months (95% CI 7-68 months) and OS estimates at 1 and 2 years were 60% (95% CI 32-80%) and 35% (11-60%), respectively. Among 15 patients who received 24 Gy in one fraction, at 1 year per-lesion LC was 72% (95% CI 41-88%) and per-patient OS was 60% (95% CI 28-81%). The most common acute treatment related toxicity was pain flare (12%). Four patients (16%) developed compression fractures in the treated vertebrae after radiation, with incidence between 57 and 578 days after radiation. Two of these fractures required intervention and two were incidental findings on imaging. No patients developed CTCAE Grade 3 or higher adverse events including neurological toxicities. SSRS appears to be safe and effective in the treatment of metastatic or primary osteosarcoma involving spinal bone. Future work should include further investigation of this technique with pooled multi-institutional studies and randomized trials.

Phase II Randomized Trial of Single- vs. Two-Fraction Spine Stereotactic Radiosurgery for the Treatment of Vertebral Metastases

As systemic therapies improve significantly, more patients with limited metastatic disease are undergoing spine stereotactic radiosurgery (sSRS). High dose (≥24 Gy) single fraction sSRS has been associated with a vertebral compression fracture (VCF) risk of up to 40%. Comparatively, lower dose (16-18 Gy) single fraction sSRS is associated with a fracture risk of 15-20%, with the risk increasing as the dose increases. To mitigate the risk of VCF, while optimizing higher dose delivery, some have advocated utilizing two-fraction sSRS regimen. Therefore, we designed a phase II randomized trial in which we hypothesized that single fraction sSRS is non-inferior to two-fraction sSRS with respect to VCF but offers patients greater convenience. Inclusion criteria include age ≥18, Karnofsky performance score ≥70, vertebral metastasis from C3 to L5, maximum of three separate sites of metastases, limited paraspinal extension (<5 cm), and no rapid neurological decline. Patients must also be either Recursive Partitioning Analysis Class 1 (KPS >70 AND controlled systemic disease) or Class 2 (KPS >70, uncontrolled systemic disease OR KPS ≤70, age ≥54, no visceral metastases). Exclusion criteria include multiple primary cancers, primary neoplasm of the spine, prior surgery at the site of sSRS, spinal cord compression, bony retropulsion resulting in neurologic deficit, inability to undergo/contraindication to MRI, or diffuse multi-level metastatic spine disease. Our primary hypothesis is that single fraction sSRS (experimental arm - 16-18 Gy) is non-inferior to two fraction sSRS (standard arm - 24 Gy). Furthermore, we hypothesize that both treatment arms will have similar local control, pain control, quality of life and toxicity profiles. The primary endpoint of this trial is the development or progression of VCF at 6 months. Secondary endpoints include local control, pain control, quality of life and toxicity all of which will be assessed at 12 months. For the sample size calculation, we assumed a VCF risk of 17% in the experimental arm and a 7% risk in the standard arm. Based on these calculations, we aim to enroll 130 patients, 65 in each arm. This trial is currently enrolling patients actively, and approximately 30% of expected enrollment has been completed to date. This trial is registered on clinicaltrials.gov: NCT04218617. Pending full accrual. Pending full accrual.

Dosimetric Analysis of Local Failure Outcomes and Vertebral Compression Fracture Risk in Single-Fraction Spine Stereotactic Radiosurgery for Metastatic Sarcoma

Sarcoma spinal metastases (SSM) are particularly difficult to manage given their poor response rates to chemotherapy and their inherent radioresistance. We sought to analyze dosimetric parameters impacting local failure and vertebral compression fracture outcomes in a homogenously treated cohort of patients with SSM treated with single-fraction spine stereotactic radiosurgery (SSRS). A retrospective review was conducted on a cohort of patients with SSM treated with definitive SSRS at a single tertiary institution. 16-24 Gy was delivered to the GTV and 16 Gy uniformly to the CTV. Kaplan-Meier analysis was conducted to assess time to local failure (LF). The log-rank test was utilized to examine group differences. Patients were censored at time of last follow-up or death. Cox proportionate hazards modeling was used to determine hazard ratios (HR) and their respective 95% confidence intervals (CI). A total of 66 patients with 96 lesions underwent SSRS for SSM. Median follow-up was 17 months (IQR 8-28). Median age was 55 years (IQR 41-63). The most common histological subtype was leiomyosarcoma (41%) followed by liposarcoma (9%). 81 lesions received 24 Gy to the GTV, 12 received 18 Gy and 3 received 16 Gy. Median GTV and CTV volume was 13.6cc (IQR 5-27) and 51.6cc (IQR 30-80) respectively. 27% of patients had Bilsky 1b or greater disease. 16 of 96 lesions demonstrated progression representing a crude local failure rate of 17% with median time to failure of 8 months (IQR 5-18). The 1-year actuarial progression free survival (PFS) was 89% with a median PFS of 13 months (IQR 16-63). Median overall survival (OS) was 15 months (IQR 8-28) from SSRS. 8% of patients developed vertebral compression fractures at a median of 13 months post SSRS (IQR 7-25). Every 1 Gy increase in GTV minimum dose (DMin) across the range (5.8-25cc) was associated with a reduced risk of local failure (HR = 0.875 [95% CI 0.787-0.974], p = 0.01). Stratifying thresholds for GTV DMin, a local control benefit was seen as low as 12 Gy and higher (HR = 0.329 [95% CI 0.11-0.97, p = 0.044) with a significantly greater magnitude benefit seen at 14 Gy (HR = 0.267 [95% CI 0.09-0.77, p = 0.014) and above 15 Gy (HR = 0.091 [95% CI 0.03-0.41], p = 0.0018). There were no other queried variables besides GTV Dmin associated with local control including: GTV: volume, mean, Dmax, D90, CTV: volume, Dmin, Dmean, Dmax, or D90. There was an increased risk of VCF with increasing CTV DMean (HR = 2.4 [95% CI 1.4-4.1], p = 0.002) and CTV D90 (HR = 2.2 [95% CI 1.2-4.0], p = 0.01); however, no association with GTV parameters. This study represents one of the most homogenously treated and the largest cohorts of patients with sarcoma spinal metastases treated with single-fraction SSRS. Despite inherent radioresistance, SSRS confers durable and high rates of local control in SSM without unexpected long-term toxicity rates. Increasing GTV minimum dose is significantly associated with superior local control with no corresponding increased risk of VCF.

Management of chordoma and chondrosarcoma with definitive dose-escalated single-fraction spine stereotactic radiosurgery.

The management of chordoma or chondrosarcoma involving the spine is often challenging due to adjacent critical structures and tumor radioresistance. Spine stereotactic radiosurgery (SSRS) has radiobiologic advantages compared with conventional radiotherapy, though there is limited evidence on SSRS in this population. We sought to characterize the long-term local control (LC) of patients treated with SSRS. We retrospectively reviewed patients with chordoma or chondrosarcoma treated with dose-escalated SSRS, defined as 24Gy in 1 fraction to the gross tumor volume. Overall survival (OS) was calculated by Kaplan-Meier functions. Competing risk analysis using the cause-specific hazard function estimated LC time. Fifteen patients, including 12 with chordoma and 3 with chondrosarcoma, with 22 lesions were included. SSRS intent was definitive, single-modality in 95% of cases (N = 21) and post-operative in 1 case (5%). After a median censored follow-up time of 5 years (IQR 4 to 8 years), median LC time was not reached (IQR 8 years to not reached), with LC rates of 100%, 100%, and 90% at 1 year, 2 years, and 5 years. The median OS was 8 years (IQR 3 years to not reached). Late grade 3 toxicity occurred after 23% of treatments (N = 5, fracture), all of which were managed successfully with stabilization. Definitive dose-escalated SSRS to 24Gy in 1 fraction appears to be a safe and effective treatment for achieving durable local control in chordoma or chondrosarcoma involving the spine, and may hold particular importance as a low-morbidity alternative to surgery in selected cases.

El enfoque de NOMS para los tumores metastásicos: integración de nuevas tecnologías para mejorar los resultados

Treatment paradigms for patients with spine metastases have evolved significantly over the past two decades. The most transformative change to these paradigms has been the integration of spinal stereotactic radiosurgery (sSRS). sSRS allows for the delivery of tumoricidal radiation doses with sparing of nearby organs at risk, particularly the spinal cord. Evidence supports the safety and efficacy of radiosurgery as it currently offers durable local tumor control with low complication rates even for tumors previously considered radioresistant to conventional external beam radiation therapy. The role for surgical intervention remains consistent, but a trend has been observed toward less aggressive, often minimally invasive techniques. Using modern technologies and improved instrumentation, surgical outcomes continue to improve with reduced morbidity. Additionally, targeted agents such as biologics and checkpoint inhibitors have revolutionized cancer care by improving both local control and patient survival. These advances have brought forth a need for new prognostication tools and a more critical review of long-term outcomes. The complex nature of current treatment schemes necessitates a multidisciplinary approach including surgeons, medical oncologists, radiation oncologists, interventionalists and pain specialists. This review recapitulates the current state-of-the-art, evidence-based data on the treatment of spinal metastases and integrates these data into a decision framework, NOMS, which is based on four sentinel pillars of decision making in metastatic spine tumors: neurological status, Oocologic tumor behavior, mechanical stability and systemic disease burden and medical co-morbidities.

Commissioning and validation of a Monte Carlo algorithm for spine stereotactic radiosurgery.

A 6FFF Monte Carlo (MC) dose calculation algorithm was commissioned for spine stereotactic radiosurgery (SRS). Model generation, validation, and ensuing model tuning are presented. The model was generated using in-air and in-water commissioning measurements of field sizes between 10 and 400 mm2 . Commissioning measurements were compared to simulated water tank MC calculations to validate output factors, percent depth doses (PDDs), profile sizes and penumbras. Previously treated Spine SRS patients were re-optimized with the MC model to achieve clinically acceptable plans. Resulting plans were calculated on the StereoPHAN phantom and subsequently delivered to the microDiamond and SRSMapcheck to verify calculated dose accuracy. Model tuning was performed by adjusting the model's light field offset (LO) distance between physical and radiological positions of the MLCs, to improve field size and StereoPHAN calculation accuracy. Following tuning, plans were generated and delivered to an anthropomorphic 3D-printed spine phantom featuring realistic bone anatomy, to validate heterogeneity corrections. Finally, plans were validated using polymer gel (VIPAR based formulation) measurements. Compared to open field measurements, MC calculated output factors and PDDs were within 2%, profile penumbra widths were within 1mm, and field sizes were within 0.5mm. Calculated point dose measurements in the StereoPHAN were within 0.26%±0.93% and -0.10%±1.37% for targets and spinal canals, respectively. Average SRSMapcheck per-plan pass rates using a 2%/2mm/10% threshold relative gamma analysis was 99.1%±0.89%. Adjusting LOs improved open field and patient-specific dosimetric agreement. Anthropomorphic phantom measurements were within -1.29%±1.00% and 0.27%±1.36% of MC calculated for the vertebral body (target) and spinal canal, respectively. VIPAR gel measurements confirmed good dosimetric agreement near the target-spine junction. Validation of a MC algorithm for simple fields and complex SRS spine deliveries in homogeneous and heterogeneous phantoms has been performed. The MC algorithm has been released for clinical use.

Morbidity of single-fraction spine radiosurgery for metastatic disease.

e24116 Background: The optimal management of metastatic spine disease involves radiation therapy, with stereotactic radiosurgery (SRS) utilization having increased in adoption while proving to be efficacious and safe. Spine SRS morbidity (fatigue, dermatitis, nausea and esophagitis) is generally mild and depends on the spinal vertebral level(s) treated. More severe adverse events such as vertebral compression fracture (VCF), radiation-induced myelopathy, and tracheoesophageal (TE) fistula have been documented. The potential benefits of single-fraction SRS (sfSRS) over multi-fraction SRS include increased patient convenience, decreased financial toxicity, and increased treatment completion rates. These benefits may potentially be overshadowed by the morbidity of sfSRS versus multifraction SRS. In this analysis, we perform the first comprehensive examination of sfSRS morbidity in the treatment of spinal lesions. Methods: An extensive search of the PubMed database was undertaken through 2/2/23 to find studies examining spinal sfSRS. Search parameters included the terms “single-fraction, spine, radiation SRS OR SBRT” Articles including multi-fractionated regimens only, reviewed sites outside of the spine, or did not report on clinical outcomes/toxicities were excluded. Results: 17 articles met initial inclusion criteria; 9 were added from references for a total of 26 articles comprising at least 2,699 patients (one study reported the number of tumors, not patients). Dose ranges for single-fraction SRS were 8-26 Gy. Commonly noted toxicities were fatigue, nausea/vomiting, and dermatitis which were no worse than moderate/minimal, not requiring invasive intervention. The overall rate of VCF was 16.2%, with an increased propensity at &gt;20 Gy. The proportion of reported segments requiring surgical intervention (operative stabilization, vertebroplasty/kyphoplasty) for VCF after single-fraction SRS was 20.2% (33/163). The rate of TE fistula at 25 Gy was 8.3%, with an overall rate (dose range = 10-28 Gy) of 1.3% with up to 12-years of follow-up. In patients receiving median dose of 24 Gy, the rate of severe esophagitis was 6.8%, myositis was 1.3% (at 1-year) and 8.3% (at 5-years). The rate of peripheral nervous system injury was 2.5% (at 18-26 Gy) and pain flare was 8% (at 16-24 Gy). The rate of ureteral and esophageal stricture was 1.9% each in patients receiving 12-24 Gy. Conclusions: VCF is the most commonly reported severe adverse events with single-fraction spine SRS, particularly for doses &gt; 20 Gy. 80% of VCFs can be successfully managed without invasive intervention. Other severe adverse events are rare – particularly for &lt; 20 Gy – but require post-SRS monitoring to expediently and efficiently intervene if necessary. These findings indicate that single-fraction spine SRS to &lt; 20 Gy is safe with minimal morbidity. Further study regarding the efficacy of such dosing is being evaluated in ongoing clinical trials.

PO-1574 Spine stereotactic radiosurgery in the management of metastatic pheochromocytoma

PO-1574 Spine stereotactic radiosurgery in the management of metastatic pheochromocytoma

The NOMS approach to metastatic tumors: Integrating new technologies to improve outcomes

Treatment paradigms for patients with spine metastases have evolved significantly over the past two decades. The most transformative change to these paradigms has been the integration of spinal stereotactic radiosurgery (sSRS). sSRS allows for the delivery of tumoricidal radiation doses with sparing of nearby organs at risk, particularly the spinal cord. Evidence supports the safety and efficacy of radiosurgery as it currently offers durable local tumor control with low complication rates even for tumors previously considered radioresistant to conventional external beam radiation therapy. The role for surgical intervention remains consistent, but a trend has been observed toward less aggressive, often minimally invasive techniques. Using modern technologies and improved instrumentation, surgical outcomes continue to improve with reduced morbidity. Additionally, targeted agents such as biologics and checkpoint inhibitors have revolutionized cancer care by improving both local control and patient survival. These advances have brought forth a need for new prognostication tools and a more critical review of long-term outcomes. The complex nature of current treatment schemes necessitates a multidisciplinary approach including surgeons, medical oncologists, radiation oncologists, interventionalists and pain specialists. This review recapitulates the current state-of-the-art, evidence-based data on the treatment of spinal metastases and integrates these data into a decision framework, NOMS, which is based on four sentinel pillars of decision making in metastatic spine tumors: Neurological status, Oncologic tumor behavior, Mechanical stability, and Systemic disease burden and medical co-morbidities.

Comparison between supine and prone patient setup for lumbosacral spinal stereotactic body radiosurgery with CyberKnife.

The aim of this study is to analyze which tracking modality is more suitable for stereotactic body radiosurgery of lumbosacral spinal tumors by comparing prone and supine patient treatment setup. Eighteen patients with lumbosacral spinal tumors were selected. CT simulation was performed in the supine position (fixed with a vacuum cushion) and prone position (fixed with a thermoplastic mask and prone plate), respectively. The plans in the supine and prone positions were designed using the xsight spine tracking (XST) and xsight spine prone tracking (XSPT) modalities, respectively. The dose-volume histogram (DVH) parameters, namely, V100%, D95%, Dmean, conformity index (CI), and heterogeneity index (HI) in planning target volume (PTV), as well as Dmax, D0.1cc, D1cc, and D5cc in the cauda equina and bowel were recorded. The supine plans were simulation plans and were not used for treatment, which were only used to record the alignment errors. The spinal tracking correction errors (alignment error) and correlation errors of the synchrony respiratory model in the prone position were recorded during the treatment. After treatment, the simulation plan of the supine position was implemented and the spinal tracking correction errors were recorded. The parameters of correction error and DVH parameters for the two positions were analyzed using the paired t-test to compare the difference in positioning accuracy and dose distribution. In addition, the correlation errors of the synchrony respiratory model in the prone position were analyzed to evaluate the prediction accuracy of the synchrony model. For patient setup, the correction error of the supine position in interior/posterior was (0.18 ± 0.16) mm and the prone position was (0.31 ± 0.26) mm (P< 0.05). The correction error of the supine position in inferior/superior was (0.27 ± 0.24) mm, and the prone position was (0.5 ± 0.4) mm (P< 0.05). The average correlation errors of the synchrony model for left/right, inferior/superior, and anterior/posterior in the prone position were (0.21 ± 0.11) mm, (0.41 ± 0.38) mm, and (0.68 ± 0.42) mm, respectively. For the dose distribution, compared with prone plans, the average CI in supine plans was increased by 4.5% (P< 0.05). There was no significant difference in HI, PTV V100%, D95%, and Dmean between the prone and supine plans. Compared with supine plans, average D1cc and D5cc for the cauda equina was significantly decreased by 4.7 and 15.3% in the prone plan (P< 0.05). For the bowel, average Dmax, D0.1cc, D1cc, and D5cc were reduced by 8.0, 7.7, 5.2, and 26.6% in prone plans (P< 0.05) compared with supine plans. Compared with the supine setup, the prone setup combined with XSPT modality for the lumbosacral spinal stereotactic body radiosurgery can spare the bowel and cauda equina of the middle and low dose irradiation, and decrease the number of beams and monitor units.