A Phase 2 Study of Post-Operative Stereotactic Body Radiation Therapy (SBRT) for Solid Tumor Spine Metastases

External Beam Radiation Therapy for Palliation of Symptomatic Bone Metastases: An ASTRO Clinical Practice Guideline

PURPOSE

This guideline provides evidence-based recommendations for palliative external beam radiation therapy (RT) in symptomatic bone metastases.

METHODS

The ASTRO convened a task force to address 5 key questions regarding palliative RT in symptomatic bone metastases. Based on a systematic review by the Agency for Health Research and Quality, recommendations using predefined consensus-building methodology were established; evidence quality and recommendation strength were also assessed.

RESULTS

For palliative RT for symptomatic bone metastases, RT is recommended for managing pain from bone metastases and spine metastases with or without spinal cord or cauda equina compression. Regarding other modalities with RT, for patients with spine metastases causing spinal cord or cauda equina compression, surgery and postoperative RT are conditionally recommended over RT alone. Furthermore, dexamethasone is recommended for spine metastases with spinal cord or cauda equina compression. Patients with nonspine bone metastases requiring surgery are recommended postoperative RT. Symptomatic bone metastases treated with conventional RT are recommended 800 cGy in 1 fraction (800 cGy/1 fx), 2000 cGy/5 fx, 2400 cGy/6 fx, or 3000 cGy/10 fx. Spinal cord or cauda equina compression in patients who are ineligible for surgery and receiving conventional RT are recommended 800 cGy/1 fx, 1600 cGy/2 fx, 2000 cGy/5 fx, or 3000 cGy/10 fx. Symptomatic bone metastases in selected patients with good performance status without surgery or neurologic symptoms/signs are conditionally recommended stereotactic body RT over conventional palliative RT. Spine bone metastases reirradiated with conventional RT are recommended 800 cGy/1 fx, 2000 cGy/5 fx, 2400 cGy/6 fx, or 2000 cGy/8 fx; nonspine bone metastases reirradiated with conventional RT are recommended 800 cGy/1 fx, 2000 cGy/5 fx, or 2400 cGy/6 fx. Determination of an optimal RT approach/regimen requires whole person assessment, including prognosis, previous RT dose if applicable, risks to normal tissues, quality of life, cost implications, and patient goals and values. Relatedly, for patient-centered optimization of treatment-related toxicities and quality of life, shared decision making is recommended.

CONCLUSIONS

Based on published data, the ASTRO task force's recommendations inform best clinical practices on palliative RT for symptomatic bone metastases.

Antiresorptive Medications Prior to Stereotactic Body Radiotherapy for Spinal Metastasis are Associated with Reduced Incidence of Vertebral Body Compression Fracture

STUDY DESIGN

Retrospective Cohort.

OBJECTIVE

Antiresorptive drugs are often given to minimize fracture risk for bone metastases, but data regarding optimal time or ability to reduce stereotactic body radiotherapy (SBRT)-induced fracture risk is limited. This study examines the association between antiresorptive use surrounding spinal SBRT and vertebral compression fracture (VCF) incidence to provide information regarding effectiveness and optimal timing of use.

METHODS

Patients treated with SBRT for spinal metastases at a single institution between 2009-2020 were included. Kaplan-Meier analysis was used to compare cumulative incidence of VCF for those taking antiresorptive drugs pre-SBRT, post-SBRT only, and none at all. Cox proportional hazards and Fine-Gray competing risk models were used to identify additional factors associated with VCF.

RESULTS

Of the 234 patients (410 vertebrae) analyzed, 49 (20.9%) were taking bisphosphonates alone, 42 (17.9%) were taking denosumab alone, and 25 (10.7%) were taking both. Kaplan-Meier analysis revealed a statistically significant lower VCF incidence for patients initiating antiresorptive drugs before SBRT compared to those taking none at all (4% vs 12% at 1 year post-SBRT, P = .045; and 4% vs 23% at 2 years, P = .008). On multivariate analysis, denosumab duration (HR: .87, P = .378) or dose (HR: 1.00, P = .644) as well as bisphosphonate duration (HR: .98, P= .739) or dose (HR: .99, P= .741) did not have statistical significance on VCF incidence.

CONCLUSION

Initiating antiresorptive agents before SBRT may reduce the risk of treatment-induced VCF. Antiresorptive drugs are underutilized in patients with spine metastases and may represent a useful intervention to minimize toxicity and improve long-term outcomes.

Phase II Clinical Trial of Second Course of Stereotactic Body Radiotherapy for Spinal Metastases

PURPOSE

The optimal method for the second course of stereotactic body radiotherapy (SBRT) for spinal metastases remains poorly established. This single-center, single-arm, phase II trial was conducted to propose a safe and effective salvage spine SBRT.

METHODS

The patients initially treated with SBRT for spine-targeted protocol treatment, or for areas adjacent to the spine, were enrolled. The second SBRT dose was 30 Gy delivered in five fractions; the spinal cord dose constraint was 15.5 Gy at the maximum point dose. The brachial or lumbosacral plexuses were dose-constrained to <30 Gy if the boundary between the nerves and tumors was detected. The primary endpoint was dose-limiting toxicity (DLT) (grade ≥ 3 severe radiation-related toxicity) within a year after the second SBRT.

RESULTS

The second SBRT was administered to the same spinal level in 12 patients and to an adjacent spinal level in 8 patients. SBRT2 was performed for 14 painful lesions, 10 MESCC, and 6 oligometastases, with some lesions having multiple indications. The median interval between SBRT sessions was 21 months (range: 6-51 months). The median follow-up duration was 14 months. No radiation myelopathy or local failure was reported during the follow-up period. DLT was confirmed in two patients (10%) within a year, both of whom developed grade 3 lumbosacral plexopathy. These two patients received SBRT twice to the S1-2 and S1-5 vertebrae, respectively, and both experienced paralysis of the tibialis anterior muscle (L5 level). Grade 3 late adverse effects (including lumbosacral plexopathy and vertebral compression fracture) were observed in 25% of the patients throughout the entire follow-up period.

CONCLUSIONS

The second spine SBRT achieved good local control without causing myelopathy. However, one-quarter of the patients experienced grade 3 late adverse effects, suggesting that the treatment protocol carries a risk of toxicity.

An Update on the Management of Bone Metastases

PURPOSE OF REVIEW

Increasing life expectancy among patients with advanced cancer has placed a greater emphasis on optimizing pain control and quality of life. Concurrently, significant advancements in radiotherapy for bone metastases have permitted for dose escalation strategies such as stereotactic radiotherapy. This review aims to provide updated information on the management of bone metastases in light of these developments.

RECENT FINDINGS

We reviewed recent studies regarding the role and details of external beam radiotherapy for bone metastases, with emphasis on differences by treatment site as well as intention (palliative versus ablative for oligometastases). Conventional palliative radiotherapy remains a mainstay of management. While stereotactic radiotherapy may augment durability of pain relief and even survival time, there are significant questions remaining regarding optimal dosing and patient selection. Radiotherapy for bone metastases continues to evolve, particularly with increasing use of stereotactic radiotherapy. Future studies are needed to clarify optimal dose, fractionation, modality, and patient selection criteria among different radiotherapy approaches.

Stereotactic body radiation therapy for spinal metastases: A new standard of care

Advancements in systemic therapies for patients with metastatic cancer have improved overall survival and, hence, the number of patients living with spinal metastases. As a result, the need for more versatile and personalized treatments for spinal metastases to optimize long-term pain and local control has become increasingly important. Stereotactic body radiation therapy (SBRT) has been developed to meet this need by providing precise and conformal delivery of ablative high-dose-per-fraction radiation in few fractions while minimizing risk of toxicity. Additionally, advances in minimally invasive surgical techniques have also greatly improved care for patients with epidural disease and/or unstable spines, which may then be combined with SBRT for durable local control. In this review, we highlight the indications and controversies of SBRT along with new surgical techniques for the treatment of spinal metastases.

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

PURPOSE

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.

METHODS AND MATERIALS

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).

RESULTS

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.

CONCLUSIONS

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.

Practice and principles of stereotactic body radiation therapy for spine and non-spine bone metastases

Radiotherapy is the dominant treatment modality for painful spine and non-spine bone metastases (NSBM). Historically, this was achieved with conventional low dose external beam radiotherapy, however, stereotactic body radiotherapy (SBRT) is increasingly applied for these indications. Meta-analyses and randomized clinical trials have demonstrated improved pain response and more durable tumor control with SBRT for spine metastases. However, in the setting of NSBM, there is limited evidence supporting global adoption and large scale randomized clinical trials are in need. SBRT is technically demanding requiring careful consideration of organ at risk tolerance, and strict adherence to technical requirements including immobilization, simulation, contouring and image-guidance procedures. Additional considerations include follow up practices after SBRT, with appropriate imaging playing a critical role in response assessment. Finally, there is renewed research into promising new technologies that may further refine the use of SBRT in both spinal and NSBM in the years to come.

Oncologic and Functional Outcomes After Stereotactic Body Radiation Therapy for High-Grade Malignant Spinal Cord Compression

Purpose

Although surgical decompression is the gold standard for metastatic epidural spinal cord compression (MESCC) from solid tumors, not all patients are candidates or undergo successful surgical Bilsky downgrading. We report oncologic and functional outcomes for patients treated with stereotactic body radiation therapy (SBRT) to high-grade MESCC.

Methods and Materials

Patients with Bilsky grade 2 to 3 MESCC from solid tumor metastases treated with SBRT at a single institution from 2009 to 2020 were retrospectively reviewed. Patients who received upfront surgery before SBRT were included only if postsurgical Bilsky grade remained ≥2. Neurologic examinations, magnetic resonance imaging, pain assessments, and analgesic usage were assessed every 3 to 4 months post-SBRT. Cumulative incidence of local recurrence was calculated with death as a competing risk, and overall survival was estimated by Kaplan-Meier.

Results

One hundred forty-three patients were included. The cumulative incidence of local recurrence was 5.1%, 7.5%, and 14.1% at 6, 12, and 24 months, respectively. At first post-SBRT imaging, 16.2% of patients with initial Bilsky grade 2 improved to grade 1, and 53.8% of patients were stable. Five of 13 patients (38.4%) with initial Bilsky grade 3 improved to grade 1 to 2. Pain response at 3 and 6 months post-SBRT was complete in 45.4% and 55.7%, partial in 26.9% and 13.1%, stable in 24.1% and 27.9%, and worse in 3.7% and 3.3% of patients, respectively. At 3 and 6 months after SBRT, 17.8% and 25.0% of patients had improved ambulatory status and 79.7% and 72.4% had stable status.

Conclusions

We report the largest series to date of patients with high-grade MESCC treated with SBRT. The excellent local control and functional outcomes suggest SBRT is a reasonable approach in inoperable patients or cases unable to be successfully surgically downgraded.

Patient specific quality assurance in SBRT: a systematic review of measurement-based methods

This topical review focuses on Patient-Specific Quality Assurance (PSQA) approaches to stereotactic body radiation therapy (SBRT). SBRT requires stricter accuracy than standard radiation therapy due to the high dose per fraction and the limited number of fractions. The review considered various PSQA methods reported in 36 articles between 01/2010 and 07/2022 for SBRT treatment. In particular comparison among devices and devices designed for SBRT, sensitivity and resolution, verification methodology, gamma analysis were specifically considered. The review identified a list of essential data needed to reproduce the results in other clinics, highlighted the partial miss of data reported in scientific papers, and formulated recommendations for successful implementation of a PSQA protocol.

Neoadjuvant Arterial Embolization of Spine Metastases Associated With Improved Local Control in Patients Receiving Surgical Decompression and Stereotactic Body Radiotherapy

BACKGROUND

Spine metastases often cause significant pain, instability, and/or neurological morbidity. Local control (LC) of spine metastases has been augmented with advances in systemic therapies, radiation, and surgical technique. Prior reports suggest an association between preoperative arterial embolization and improved LC and palliative pain control.

OBJECTIVE

To further elucidate the role of neoadjuvant embolization on LC of spine metastases and the potential for improved pain control in patients receiving surgery and stereotactic body radiotherapy (SBRT).

METHOD

A retrospective single-center review between 2012 and 2020 identified 117 patients with spinal metastases from various solid tumor malignancies managed with surgery and adjuvant SBRT with or without preoperative spinal arterial embolization. Demographic information, radiographic studies, treatment characteristics, Karnofsky Performance Score, Defensive Veterans Pain Rating Scale, and mean daily doses of analgesic medications were reviewed. LC was assessed using magnetic resonance imaging obtained at a median 3-month interval and defined as progression at the surgically treated vertebral level.

RESULTS

Of 117 patients, 47 (40.2%) underwent preoperative embolization, followed by surgery and SBRT and 70 (59.8%) underwent surgery and SBRT alone. Within the embolization cohort, the median LC was 14.2 months compared with 6.3 months among the nonembolization cohort ( P = .0434). Receiver operating characteristic analysis suggests ≥82.5% embolization predicted significantly improved LC (area under the curve = 0.808; P < .0001). Defensive Veterans Pain Rating Scale mean and maximum scores significantly decreased immediately after embolization ( P < .001).

CONCLUSION

Preoperative embolization was associated with improved LC and pain control suggesting a novel role for its use. Additional prospective study is warranted.

Impact of Postoperative Stereotactic Body Radiation Therapy on Survival of Patients with Spinal Metastases in the Context of Additional Systemic Adjuvant Therapy

BACKGROUND

Stereotactic body radiotherapy (SBRT) has been established as a safe and effective treatment modality for control of long-term pain and tumor growth. However, few studies have investigated the efficacy of postoperative SBRT versus conventional external beam radiation therapy (EBRT) in extending survival within the context of systemic therapy.

METHODS

A retrospective chart review of patients who underwent surgery for spinal metastasis at our institution was conducted. Demographic, treatment, and outcome data were collected. SBRT was compared with EBRT and non-SBRT, and analyses were stratified by whether patients received systemic therapy. Survival analysis was conducted using propensity score matching.

RESULTS

Bivariate analysis in the nonsystemic therapy group revealed longer survival with SBRT compared with EBRT and non-SBRT. Further analysis also showed that primary cancer type and preoperative mRS significantly affected survival. Within patients who received systemic therapy, overall median survival for patients receiving SBRT was 22.7 months (95% confidence interval [CI] 12.1-52.3) versus 16.1 months (95% CI 12.7-44.0; P = 0.28) for patients who received EBRT and 16.1 months (95% CI: 12.2-21.9; P = 0.07) for patients without SBRT. Within patients who did not receive systemic therapy, overall median survival for patients with SBRT was 62.1 months (95% CI 18.1-unknown) versus 5.3 months (95% CI 2.8-unknown; P = 0.08) for patients with EBRT and 6.9 months (95% CI 5.0-45.6; P = 0.02) for patients without SBRT.

CONCLUSIONS

In patients who do not receive systemic therapy, treatment with postoperative SBRT may increase survival time compared with patients not receiving SBRT.

Dosimetric analysis on computed tomography myelography based treatment planning in stereotactic body radiotherapy for spinal metastases

This study aimed to quantitatively evaluate the influence of enhanced contrast on the CT myelography image of the spinal cord and/or cauda equina in addition to the target volume in spine SBRT treatment planning. In total, 19 patients who had previously undergone spine SBRT were randomly selected. The rigid image registration accuracy of CT myelography that aligned with the treatment planning CT was evaluated by calculating the normalized mutual information (NMI) and Pearson's correlation coefficient for the vertebral landmarks. At postregistration, the contrast-enhanced region of the CT myelography image was replaced with water-mass density, and the original treatment plan was recalculated on this image. For comparison, the dose was also recalculated on the contrast-enhanced CT myelography images. The NMI and Pearson's correlation coefficients for landmarks were 0.39 ± 0.12 and 0.97 ± 0.04, respectively. The mean D_0.035cc of the spinal cord and/or cauda equina on the CT myelography image with the contrast-enhanced region replaced by water-mass density showed -0.37% ± 0.64% changes compared with that of the treatment planning CT. Conversely, the mean D_0.035cc in contrast-enhanced CT myelography changed by -1.39% ± 0.51%. The percentage change in D_98% for the planning target volume was confirmed to be small by replacing the contrast-enhanced region with water-mass density (p < 0.01). The dose calculation of the target volume, spinal cord, and/or cauda equina using the CT myelography image that replaced the contrast-enhanced region with water-mass density could be a more appropriate procedure with less dose calculation uncertainty.

Stereotactic Body Radiation Therapy for Spinal Metastases: Benefits and Limitations

Progress in biological cancer characterization, targeted systemic therapies and multimodality treatment strategies have shifted the goals of radiotherapy for spinal metastases from short-term palliation to long-term symptom control and prevention of compilations. This article gives an overview of the spine stereotactic body radiotherapy (SBRT) methodology and clinical results of SBRT in cancer patients with painful vertebral metastases, metastatic spinal cord compression, oligometastatic disease and in a reirradiation situation. Outcomes after dose-intensified SBRT are compared with results of conventional radiotherapy and patient selection criteria will be discussed. Though rates of severe toxicity after spinal SBRT are low, strategies to minimize the risk of vertebral compression fracture, radiation induced myelopathy, plexopathy and myositis are summarized, to optimize the use of SBRT in multidisciplinary management of vertebral metastases.

Current and Emerging Approaches for Spine Tumor Treatment

Spine tumors represent a significant social and medical problem, affecting the quality of life of thousands of patients and imposing a burden on healthcare systems worldwide. Encompassing a wide range of diseases, spine tumors require prompt multidisciplinary treatment strategies, being mainly approached through chemotherapy, radiotherapy, and surgical interventions, either alone or in various combinations. However, these conventional tactics exhibit a series of drawbacks (e.g., multidrug resistance, tumor recurrence, systemic adverse effects, invasiveness, formation of large bone defects) which limit their application and efficacy. Therefore, recent research focused on finding better treatment alternatives by utilizing modern technologies to overcome the challenges associated with conventional treatments. In this context, the present paper aims to describe the types of spine tumors and the most common current treatment alternatives, further detailing the recent developments in anticancer nanoformulations, personalized implants, and enhanced surgical techniques.

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

OBJECTIVE

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.

METHODS

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.

RESULTS

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.

CONCLUSIONS

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.

Separation surgery followed by stereotactic ablative radiotherapy for metastatic epidural spinal cord compression: A systematic review and meta-analysis for local progression rate

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The pooled 1-year local progression rate of hybrid therapy in spinal metastasis was 10.2%.

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The pooled 2-year local progression rate of hybrid therapy in spinal metastasis was 13.7%.

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A lower radiation dose per fraction showed a significant association with the 1-year local progression rate of hybrid therapy in spinal metastasis.

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History of prior radiotherapy showed a significant association with the 1-year local progression rate of hybrid therapy in spinal metastasis.

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Colorectal cancer showed a significant association with the 1-year local progression rate of hybrid therapy in spinal metastasis.

Introduction

Spinal metastasis is the most common metastatic skeletal disease in cancer patients. Metastatic epidural spinal cord compression (MESCC), which occurs in 5–14% of cancer patients, is an oncological emergency because it may cause a permanent neurological deficit. Separation surgery followed by stereotactic ablative radiotherapy (SABR), so-called “hybrid therapy,” has shown effectiveness in local control of spinal metastasis and has become an integral treatment option for patients with MESCC. Therefore, we performed a meta-analysis and meta-regression analysis to clarify the local progression rate of hybrid therapy and the risk factors for local progression.

Methods

We searched PubMed, EMBASE, Scopus, Cochrane Library, and Web of Science databases from inception to December 2021. Meta-analyses of proportions were used to analyze the data using a random-effects model to calculate the pooled 1-year local progression rate and confidence interval. Subgroup analyses were performed using meta-analyses of odds ratio (OR) for comparisons between groups. We also conducted a meta-regression analysis to identify the factors that caused heterogeneity.

Results

A total of 661 patients from 13 studies (10 retrospective and 3 prospective) were included in the final meta-analysis. The quality of the included studies assessed using the Newcastle − Ottawa scale ranged from poor to fair (range, 4–6). The pooled local progression rate was 10.2 % (95 % confidence interval [CI], 7.8–12.8 %; I² = 30 %) and 13.7 % (95 % CI, 9.3–18.8 %; I² = 55 %) at postoperative 1 and 2 years, respectively. The subgroup analysis indicated that patients with a history of prior radiotherapy (OR, 5.14; 95 % CI, 1.71–15.51) and lower radiation dose per fraction (OR, 4.57; 95 % CI, 1.88–11.13) showed significantly higher pooled 1-year local progression rates. In the moderator analysis, the 1-year local progression rate was significantly associated with the proportion of patients with a history of prior radiotherapy (p = 0.036) and those with colorectal cancer as primary origin (p < 0.001).

Conclusions

The pooled 1-year local progression rate of hybrid therapy for MESCC was 10.2%. In subgroup and moderator analyses, a lower radiation dose per fraction, history of prior radiotherapy, and colorectal cancer showed a significant association with the 1-year local progression rate.

Practice Patterns and Perspectives on Stereotactic Body Radiation Therapy for the Metastatic Spine From Lower- and Middle-Income Countries

PURPOSE

We wanted to understand the current practice patterns and stereotactic body radiation therapy (SBRT) utilization for spine metastases in lower- and middle-income countries (LMICs).

METHODS

A questionnaire was designed to identify the current practice patterns of treating spine metastases, uptake of spine SBRT in routine care, dose fractionations commonly used, and the perceived benefits and toxicities of using ablative doses. Individuals registering for a spine SBRT workshop were requested to answer the questionnaire.

RESULTS

We received 395 responses from radiation oncologists (ROs) working in 12 different LMICs. The majority of respondents were from an academic institute (57.5%). Two hundred seventy-four respondents further identified themselves from the government/public sector (44.89%), corporate/private sector (47.89%), not-for-profit organization (5.4%), or public-private partnership (5.4%). The respondents indicated that 8.43%, 27.46%, 41.73%, and 10.04% of the spine metastases patients are treated using clinical marking, X-ray-based, 3D conformal radiation therapy, and SBRT, respectively. A third of the respondents did not have any experience of spine SBRT; those with high-volume practice were predominantly from an academic institute. The majority of respondents would use spine SBRT to reduce pain severity (71.9%) and achieve durable pain control (61.01%) in the setting of oligometastases (92.73%) and reirradiation (56.69%). Respondents preferred 3- to 5-fraction regimens (64.9%) over 1-2 fractions (33.68%). The top three reasons for not using spine SBRT were resource constraints (50%), lack of machine (37.11%), and lack of training (27.34%).

CONCLUSION

There is heterogeneity in spine SBRT practice and utilization between academic and nonacademic institutes. Resource and infrastructure constraints along with lack of training are limiting the use of SBRT among ROs from LMICs. Collaborative studies from LMICs will help in resolving unique challenges posed by resource constraints.

Feasibility of postoperative spine stereotactic body radiation therapy in proximity of carbon and titanium hybrid implants using a robotic radiotherapy device

BACKGROUND AND PURPOSE

To assess the feasibility of postoperative stereotactic body radiation therapy (SBRT) for patients with hybrid implants consisting of carbon fiber reinforced polyetheretherketone and titanium (CFP-T) using CyberKnife.

MATERIALS AND METHODS

All essential steps within a radiation therapy (RT) workflow were evaluated. First, the contouring process of target volumes and organs at risk (OAR) was done for patients with CFP-T implants. Second, after RT-planning, the accuracy of the calculated dose distributions was tested in a slab phantom and an anthropomorphic phantom using film dosimetry. As a third step, the accuracy of the mandatory image guided radiation therapy (IGRT) including automatic matching was assessed using the anthropomorphic phantom. For this goal, a standard quality assurance (QA) test was modified to carry out its IGRT part in presence of CFP-T implants.

RESULTS

Using CFP-T implants, target volumes could precisely delineated. There was no need for compromising the contours to overcome artifact obstacles. Differences between measured and calculated dose values were below 11% for the slab phantom, and at least 95% of the voxels were within 5% dose difference. The comparisons for the anthropomorphic phantom showed a gamma-passing rate (5%, 1 mm) of at least 97%. Additionally the test results with and without CFP-T implants were comparable. No issues concerning the IGRT were detected. The modified machine QA test resulted in a targeting error of 0.71 mm, which corresponds to the results of the unmodified standard tests.

CONCLUSION

Dose calculation and delivery of postoperative spine SBRT is feasible in proximity of CFP-T implants using a CyberKnife system.

Utility of expanded anterior column resection versus decompression-alone for local control in the management of carcinomatous vertebral column metastases undergoing adjuvant stereotactic radiotherapy

BACKGROUND CONTEXT

With improvements in adjuvant radiotherapy and minimally invasive surgical techniques, separation surgery has become the default surgical intervention for spine metastases at many centers. However, it is unclear if there is clinical benefit from anterior column resection in addition to simple epidural debulking prior to stereotactic body radiotherapy (SBRT).

PURPOSE

To examine the effect of anterior column debulking versus epidural disease resection alone in the local control of metastases to the bony spine.

STUDY DESIGN

Retrospective cohort study.

PATIENT SAMPLE

Ninety-seven patients who underwent open surgery followed by SBRT for spinal metastases at a single comprehensive cancer center.

OUTCOME MEASURES

Local tumor recurrence following surgery and SBRT.

METHODS

Data were collected regarding radiation dose, cancer histology, extent of anterior column resection, and recurrence. Tumor involvement was categorized using the International Spine Radiosurgery Consortium guidelines. Univariable analyses were conducted to determine predictors of local recurrence and time to local recurrence.

RESULTS

Among the 97 included patients, mean age was 60.5±11.4 years and 51% of patients were male. The most common primary tumor types were lung (20.6%), breast (17.5%), kidney (13.4%) and prostate (12.4%). Recurrence was seen in 17 patients (17.5%) and local control rates were: 85.5% (1-year), 81.1% (2-year), and 54.9% (5-year). Overall predictors of local recurrence were tumor pathology (p<.01; renal cell carcinoma and colorectal adenocarcinoma associated with poorest PFS) and undergoing anterior column debulking versus epidural decompression-alone (p=.03). Only tumor pathology predicted time to local recurrence (p<.01), though inspection of Kaplan-Meier functions showed superior long-term local control in patients with radiosensitive tumor pathologies, no previous irradiation of the metastasis, and who underwent anterior column resection versus epidural removal alone. Median time to recurrence was 288 days with 100% of lesions showing anterior column recurrence and recurrence in the epidural space.

CONCLUSIONS

With the increasing shift towards surgery as a neoadjuvant to radiotherapy for patients with spinal column metastases, the role for surgical debulking has become less clear. In the present study, we find that anterior column debulking as opposed to epidural debulking-alone decreases the odds of local recurrence and improves long-term local control.

Development and Assessment of a Predictive Score for Vertebral Compression Fracture After Stereotactic Body Radiation Therapy for Spinal Metastases

IMPORTANCE

Vertebral compression fracture (VCF) is a potential adverse effect following treatment with stereotactic body radiation therapy (SBRT) for spinal metastases.

OBJECTIVE

To develop and assess a risk stratification model for VCF after SBRT.

DESIGN, SETTING, AND PARTICIPANTS

This retrospective cohort study conducted at a high-volume referral center included 331 patients who had undergone 464 spine SBRT treatments from December 2007 through October 2019. Data analysis was conducted from November 1, 2020, to August 17, 2021. Exclusions included proton therapy, prior surgical intervention, vertebroplasty, or missing data.

EXPOSURES

One and 3 fraction spine SBRT treatments were most commonly delivered. Single-fraction treatments generally involved prescribed doses of 16 to 24 Gy (median, 20 Gy; range, 16-30 Gy) to gross disease compared with multifraction treatment that delivered a median of 30 Gy (range, 21-50 Gy).

MAIN OUTCOMES AND MEASURES

The VCF and radiography components of the spinal instability neoplastic score were determined by a radiologist. Recursive partitioning analysis was conducted using separate training (70%), internal validation (15%), and test (15%) sets. The log-rank test was the criterion for node splitting.

RESULTS

Of the 331 participants, 88 were women (27%), and the mean (IQR) age was 63 (59-72) years. With a median follow-up of 21 months (IQR, 11-39 months), we identified 84 VCFs (18%), including 65 (77%) de novo and 19 (23%) progressive fractures. There was a median of 9 months (IQR, 3-21 months) to developing a VCF. From 15 candidate variables, 6 were identified using the backward selection method, feature importance testing, and a correlation heatmap. Four were selected via recursive partitioning analysis: epidural tumor extension, lumbar location, gross tumor volume of more than 10 cc, and a spinal instability neoplastic score of more than 6. One point was assigned to each variable, and the resulting multivariable Cox model had a concordance of 0.760. The hazard ratio per 1-point increase for VCF was 1.93 (95% CI, 1.62-2.30; P < .001). The cumulative incidence of VCF at 2 years (with death as a competing risk) was 6.7% (95% CI, 4.2%-10.7%) for low-risk (score, 0-1; 273 [58.3%]), 17.0% (95% CI, 10.8%-26.7%) for intermediate-risk (score, 2; 99 [21.3%]), and 35.4% (95% CI, 26.7%-46.9%) for high-risk cases (score, 3-4; 92 [19.8%]) (P < .001). Similar results were observed for freedom from VCF using stratification.

CONCLUSIONS AND RELEVANCE

The results of this cohort study identify a subgroup of patients with high risk for VCF following treatment with SBRT who may potentially benefit from undergoing prophylactic spinal stabilization or vertebroplasty.

Fully automated rigid image registration versus human registration in postoperative spine stereotactic body radiation therapy: a multicenter non-inferiority study

To confirm the fully automated rigid image registration (A-RIR) accuracy in postoperative spine stereotactic body radiation therapy (SBRT), we conducted a multicenter non-inferiority study compared to the human rigid image registration (H-RIR). Twenty-eight metastatic cancer patients who underwent postoperative spine SBRT are enrolled-image registration (IR) of planning computed tomography (CT) and CT-myelogram for delineating the spinal cord. The adopted A-RIR workflow is a contour-focused algorithm performing a rigid registration by maximizing normalized mutual information (NMI) restricted to the data contained within the automatically extracted contour. Three radiation oncologists (ROs) from multicenters were prompted to review two blinded registrations and choose one for clinical use. Indistinguishable cases were allowed to vote equivalent, counted A-RIR side. A-RIR is considered non-inferior to H-RIR if the lower limit of the 95% confidence interval (CI) of A-RIR preferable/equivalent is greater than 0.45. We also evaluated the NMI improvement from the baseline and the translational/rotational errors between A-RIR and H-RIR. The A-RIR preferable/equivalent was selected in 21 patients (0.75, 95% CI: 0.55-0.89), demonstrating non-inferiority to H-RIR. The A-RIR's NMI improvement was greater than H-RIR in 24 patients: the mean value ± SD was 0.225 ± 0.115 in A-RIR and 0.196 ± 0.114 in H-RIR (P < 0.001). The absolute translational error was 0.38 ± 0.31 mm. The rotational error was -0.03 ± 0.20, 0.05 ± 0.19, -0.04 ± 0.20 degrees in axial, coronal, and sagittal planes (range: -0.66-0.52). In conclusion, A-RIR shows non-inferior to H-RIR in CT and CT-myelogram registration for postoperative spine SBRT planning.

Focused versus conventional radiotherapy in spinal oncology: is there any difference in fusion rates and pseudoarthrosis?

INTRODUCTION

Radiotherapy is considered standard of care for adjuvant peri-operative treatment of many spinal tumors, including those with instrumented fusion. Unfortunately, radiation treatment has been linked to increased risk of pseudoarthrosis. Newer focused radiotherapy strategies with enhanced conformality could offer improved fusion rates for these patients, but this has not been confirmed.

METHODS

We performed a retrospective analysis of patients at three tertiary care academic institutions with primary and secondary spinal malignancies that underwent resection, instrumented fusion, and peri-operative radiotherapy. Two board certified neuro-radiologists used the Lenke fusion score to grade fusion status at 6 and 12-months after surgery. Secondary outcomes included clinical pseudoarthrosis, wound complications, the effect of radiation timing and radiobiological dose delivered, the use of photons versus protons, tumor type, tumor location, and use of autograft on fusion outcomes.

RESULTS

After review of 1252 spinal tumor patients, there were 60 patients with at least 6 months follow-up that were included in our analyses. Twenty-five of these patients received focused radiotherapy, 20 patients received conventional radiotherapy, and 15 patients were treated with protons. There was no significant difference between the groups for covariates such as smoking status, obesity, diabetes, intraoperative use of autograft, and use of peri-operative chemotherapy. There was a significantly higher rate of fusion for patients treated with focused radiotherapy compared to those treated with conventional radiotherapy at 6-months (64.0% versus 30.0%, Odds ratio: 4.15, p = 0.036) and 12-months (80.0% versus 42.1%, OR: 5.50, p = 0.022). There was a significantly higher rate of clinical pseudoarthrosis in the conventional radiotherapy cohort compared to patients in the focused radiotherapy cohort (19.1% versus 0%, p = 0.037). There was no difference in fusion outcomes for any of the secondary outcomes except for use of autograft. The use of intra-operative autograft was associated with an improved fusion at 12-months (66.7% versus 37.5%, OR: 3.33, p = 0.043).

CONCLUSION

Focused radiotherapy may be associated with an improved rate of fusion and clinical pseudoarthrosis when compared to conventional radiation delivery strategies in patients with spinal tumors. Use of autograft at the time of surgery may be associated with improved 12-month fusion rates. Further large-scale prospective and randomized controlled studies are needed to better stratify the effects of radiation delivery modality in these patients.

Local control of 1-5 fraction radiotherapy regimens for spinal metastases: an analysis of the impacts of biologically effective dose and primary histology

BACKGROUND

This analysis evaluates the impacts of biologically effective dose (BED) and histology on local control (LC) of spinal metastases treated with highly conformal radiotherapy to moderately-escalated doses.

MATERIALS AND METHODS

Patients were treated at two institutions from 2010-2020. Treatments with less than 5 Gy per fraction or 8 Gy in 1 fraction were excluded. The dataset was divided into three RPA classes predictive of survival (1). The primary endpoint was LC.

RESULTS

223 patients with 248 treatments met inclusion criteria. Patients had a median Karnofsky Performance Status (KPS ) of 80, and common histologies included breast (29.4%), non-small cell lung cancer (15.7%), and prostate (13.3%). A median 24 Gy was delivered in 3 fractions (BED: 38.4 Gy) to a median planning target volume (PTV) of 37.3 cc. 2-year LC was 75.7%, and 2-year OS was 42.1%. Increased BED was predictive of improved LC for primary prostate cancer (HR = 0.85, 95% CI: 0.74-0.99). Patients with favorable survival (RPA class 1) had improved LC with BED ≥ 40 Gy (p = 0.05), unlike the intermediate and poor survival groups. No grade 3-5 toxicities were reported.

CONCLUSIONS

Moderately-escalated treatments were efficacious and well-tolerated. BED ≥ 40 Gy may improve LC, particularly for prostate cancer and patients with favorable survival.

Failure mode and effect analysis for linear accelerator-based paraspinal stereotactic body radiotherapy

Introduction

Paraspinal stereotactic body radiotherapy (SBRT) involves risks of severe complications. We evaluated the safety of the paraspinal SBRT program in a large academic hospital by applying failure modes and effects analysis.

Methods

The analysis was conducted by a multidisciplinary committee (two therapists, one dosimetrist, four physicists, and two radiation oncologists). The paraspinal SBRT workflow was segmented into four phases (simulation, treatment planning, delivery, and machine quality assurance (QA)). Each phase was further divided into a sequence of sub‐processes. Potential failure modes (PFM) were identified from each subprocess and scored in terms of the frequency of occurrence, severity and detectability, and a risk priority number (RPN). High‐risk PFMs were identified based on RPN and were studied for root causes using fault tree analysis.

Results

Our paraspinal SBRT process was characterized by eight simulations, 11 treatment planning, nine delivery, and two machine QA sub‐processes. There were 18, 29, 19, and eight PFMs identified from simulation, planning, treatment, and machine QA, respectively. The median RPN of the PFMs was 62.9 for simulation, 68.3 for planning, 52.9 for delivery, and 22.0 for machine QA. The three PFMs with the highest RPN were: previous radiotherapy outside the institution is not accurately evaluated (RPN: 293.3), incorrect registration between diagnostic magnetic resonance imaging and simulation computed tomography causing incorrect contours (273.0), and undetected patient movement before ExacTrac baseline (217.8). Remedies to the high RPN failures were implemented, including staff education, standardized magnetic resonance imaging acquisition parameters, and an image fusion process, and additional QA on beam steering.

Conclusions

A paraspinal SBRT workflow in a large clinic was evaluated using a multidisciplinary and systematic risk analysis, which led to feasible solutions to key root causes. Treatment planning was a major source of PFMs that systematically affect the safety and quality of treatments. Accurate evaluation of external treatment records remains a challenge.

Stereotactic Radiosurgery for Postoperative Spine Malignancy: A Systematic Review and International Stereotactic Radiosurgery Society (ISRS) Practice Guidelines

PURPOSE

To determine safety and efficacy of postoperative spine stereotactic body radiation therapy (SBRT) in the published literature, and to present practice recommendations on behalf of the International Stereotactic Radiosurgery Society (ISRS).

MATERIALS AND METHODS

A systematic review of the literature was performed, specific to postoperative spine SBRT, using PubMed and Embase databases. A meta-analysis for 1-year local control (LC), overall survival (OS) and vertebral compression fracture (VCF) probability was conducted.

RESULTS

The literature search revealed 251 potentially relevant articles after duplicates were removed. Of these 56 were reviewed in-depth for eligibility and 12 met all the inclusion criteria for analysis. 7 studies were retrospective, 2 prospective observational and 3 were prospective phase I/II clinical trials. Outcomes for a total of 461 patients and 499 spinal segments were reported. 10 studies used an MRI fused to CT-simulation for treatment planning, 2 investigations reported on all patients receiving a CT-myelogram at the time of planning. Meta-analysis for 1 year LC and OS was 88.9% and 57%, respectively. The crude reported VCF rate was 5.6%. One case of myelopathy was described in a patient with a previously irradiated spinal segment. One patient developed an esophageal fistula requiring surgical repair.

CONCLUSIONS

Postoperative spine SBRT delivers a high 1-year LC with acceptably low toxicity. Patients that may benefit from this include those with oligometastatic disease, radioresistant histology, paraspinal masses and/or those with a history of prior irradiation to the affected spinal segment. The ISRS recommends a minimum interval of 8 to 14 days after invasive surgery prior to simulation for SBRT, with initiation of radiotherapy within 4 weeks of surgery. An MRI fused to the planning CT, and/or the use of a CT-myelogram, are necessary for target and organ-at-risk delineation. A planning organ-at-risk volume (PRV) of 1.5 to 2mm for the spinal cord is advised.

Recent advances and new discoveries in the pipeline of the treatment of primary spinal tumors and spinal metastases: A scoping review

The field of spinal oncology has substantially evolved over the past decades. This review synthesizes and appraises what was learned and what will potentially be discovered from the recently completed and ongoing clinical studies related to the treatment of primary and secondary spinal neoplasms. This scoping review included all clinical studies on the treatment of spinal neoplasms registered in the ClinicalTrials.gov website from February/2000 to December/2020. The terms "spinal cord tumor", "spinal metastasis", and "metastatic spinal cord compression" were used. Of the 174 registered clinical studies on primary spinal tumors and spinal metastasis, most of the clinical studies registered in this American registry were interventional studies led by single institutions in North America (n=101), Europe (n=43), Asia (n=24) or other continents (n=6). The registered clinical studies mainly focused on treatment strategies for spinal neoplasms (90.2%) that included investigating stereotactic radiosurgery (n=33), radiotherapy (n=21), chemotherapy (n=20), and surgical technique (n=11). Of the 69 completed studies, the results from 44 studies were published in the literature. In conclusion, this review highlights the key features of the 174 clinical studies on spinal neoplasms that were registered from 2000 to 2020. Clinical trials were heavily skewed towards the metastatic population as opposed to the primary tumours which likely reflects the rarity of the latter condition and associated challenges in undertaking prospective clinical studies in this population. This review serves to emphasize the need for a focused approach to enhancing translational research in spinal neoplasms with a particular emphasis on primary tumors.

The current knowledge concerning solid cancer and therapy

Solid cancers comprise a large number of new cases and deaths from cancer each year globally. There are a number of strategies for addressing tumors raised from solid organs including surgery, chemotherapy, radiotherapy, targeted therapy, immunotherapy, combinational therapy, and stem cell and extracellular vesicle (EV) therapy. Surgery, radiotherapy, and chemotherapy are the dominant cures, but are not always effective, in which even in a localized tumor there is a possibility of tumor relapse after surgical resection. Over half of the cancer patients will receive radiotherapy as a part of their therapeutic schedule. Radiotherapy can cause an abscopal response for boosting the activity of the immune system outside the local field of radiation, but it may also cause an unwanted bystander effect, predisposing nonradiated cells into carcinogenesis. In the context of immunotherapy, immune checkpoint inhibition is known as the standard-of-care, but the major concern is in regard with cold cancers that show low responses to such therapy. Stem-cell therapy can be used to send prodrugs toward the tumor area; this strategy, however, has its own predicaments, such as unwanted attraction toward the other sites including healthy tissues and its instability. A substitute to such therapy and quite a novel strategy is to use EVs, by virtue of their stability and potential to cross biological barriers and long-term storage of contents. Combination therapy is the current focus. Despite advances in the field, there are still unmet concerns in the area of effective cancer therapy, raising challenges and opportunities for future investigations.

Spinal metastases 2021: a review of the current state of the art and future directions

Spinal metastases are an increasing societal health burden secondary to improvements in systemic therapy. Estimates indicate that 100,000 or more people have symptomatic spine metastases requiring management. While open surgery and external beam radiotherapy have been the pillars of treatment, there is growing interest in more minimally invasive technologies (eg separation surgery) and non-operative interventions (eg percutaneous cementoplasty, stereotactic radiosurgery). The great expansion of these alternatives to open surgery and the prevalence of adjuvant therapeutic options means that treatment decision making is now complex and reliant upon multidisciplinary collaboration. To help facilitate construction of care plans that meet patient goals and expectations, clinical decision aids and prognostic scores have been developed. These have been shown to have superior predictive value relative to more classic prediction models and may become an increasingly important aspect of the clinical practice of spinal oncology. Here we overview current therapeutic advances in the management of spine metastases and highlight emerging areas for research. Given the rapid advancements in surgical technologies and adjuvants, the field is likely to undergo further transformative changes in the coming decade.

Phase II clinical trial of separation surgery followed by stereotactic body radiotherapy for metastatic epidural spinal cord compression

BACKGROUND

Stereotactic body radiotherapy (SBRT) is a postoperative treatment option for spinal metastases. As data on surgery with SBRT are limited to retrospective studies, this single-center, single-arm, phase II study aimed to prospectively evaluate the outcomes of separation surgery and SBRT for metastatic epidural spinal cord compression (MESCC).

METHODS

Patients with symptomatic MESCC due to a solid carcinoma were enrolled. The protocol for treatments comprised preoperative embolization, separation surgery, and spine SBRT. Surgical procedures were performed via the posterior approach, with decompression and a fixation procedure. The prescribed dose for spine SBRT was 24 Gy in two fractions. The primary endpoint was the 12-month local failure (LF) rate. The secondary endpoints were ambulatory functions and adverse effects.

RESULTS

Thirty-three patients were registered between November 2017 and October 2019. All patients satisfied the inclusion criteria, and all but one completed the protocol treatment. Twenty-three patients (70%) had radioresistant lesions. The Bilsky grade at registration was 1c, 2, and 3 in 4, 8, and 21 patients, respectively. The median follow-up duration after registration was 15 (range 3-35) months. Three months after the administration of treatments according to the protocol, 90% of the patients (26/29) had diseases of Bilsky grade ≤ 1. The 12-month LF rate was 13%. Twenty patients could walk normally or with a cane 12 months after registration. Radiation-induced myelopathy, radiculopathy, and vertebral compression fracture were observed in zero, one, and six patients, respectively.

CONCLUSIONS

Separation surgery with SBRT for MESCC was effective in decompression and long-term local control. These findings warrant larger randomized controlled trials to compare SBRT with conventional radiotherapy.

Factors associated with adjacent-level tumor progression in patients receiving surgery followed by radiosurgery for metastatic epidural spinal cord compression

OBJECTIVE

Separation surgery followed by spine stereotactic radiosurgery (SSRS) has been shown to achieve favorable rates of local tumor control and patient-reported outcomes in patients with metastatic epidural spinal cord compression (MESCC). However, rates and factors associated with adjacent-level tumor progression (ALTP) in this population have not yet been characterized. The present study aimed to identify factors associated with ALTP and examine its association with overall survival (OS) in patients receiving surgery followed by radiosurgery for MESCC.

METHODS

Thirty-nine patients who underwent separation surgery followed by SSRS for MESCC were identified using a prospectively collected database and were retrospectively reviewed. Radiological measurements were collected from preoperative, postoperative, and post-SSRS MRI. Statistical analysis was conducted using the Kaplan-Meier product-limit method and Cox proportional hazards test. Subgroup analysis was conducted for patients who experienced ALTP into the epidural space (ALTP-E).

RESULTS

The authors' cohort included 39 patients with a median OS of 14.7 months (range 2.07-96.3 months). ALTP was observed in 16 patients (41.0%) at a mean of 6.1 ± 5.4 months postradiosurgery, of whom 4 patients (10.3%) experienced ALTP-E. Patients with ALTP had shorter OS (13.0 vs 17.1 months, p = 0.047) compared with those without ALTP. Factors associated with an increased likelihood of ALTP included the amount of bone marrow infiltrated by tumor at the index level, amount of residual epidural disease following separation surgery, and prior receipt of radiotherapy at the index level (p < 0.05). Subgroup analysis revealed that primary tumor type, amount of preoperative epidural disease, time elapsed between surgery and radiosurgery, and prior receipt of radiotherapy at the index level were significantly associated with ALTP-E (p < 0.05).

CONCLUSIONS

To the authors' knowledge, this study is the first to identify possible risk factors for ALTP, and they suggest that it may be associated with shorter OS in patients receiving surgery followed by radiosurgery for MESCC. Future studies with higher power should be conducted to further characterize factors associated with ALTP in this population.

Electron beam intraoperative radiotherapy for metastatic epidural spinal cord compression: a prospective observational study

To assess the additional effects of intraoperative radiotherapy (IORT) with decompression surgery and adjuvant external beam radiotherapy (EBRT) for metastatic epidural spinal cord compression (MESCC). This single-arm institutional prospective observational study recruited patients between June 2017 and March 2020 and included those with symptoms of spinal cord compression owing to metastases, who were diagnosed using MRI. Patients with radiation-sensitive primary tumors and those who could not tolerate surgery were excluded. The treatment protocol comprised decompression surgery and electron beam IORT of 20 Gy in a single fraction followed by EBRT of 30 Gy in 10 fractions. The primary endpoints included the 1-year local failure rate and ambulatory functions. The study was closed in May 2019 owing to changes in treatment policies at our institution. Twenty patients were registered between June 2017 and May 2019. Although all patients completed surgery and IORT, 2 did not receive postoperative EBRT. Patients most commonly had colorectal cancer (4 patients), followed by thyroid cancer, renal cell carcinoma, lung cancer, breast cancer, sarcomas, and other cancers (3, 3, 2, 2, 2, and 4 patients, respectively). The median follow-up duration was 16 months (range 2-30 months); the 1-year local failure rate was 16%. On comparing ambulatory functions pre-treatment and at 1 year after treatment, improvement, no change, and worsening were observed in 3, 9, and 0 patients, respectively. This study's findings suggest that decompression surgery and IORT followed by EBRT are effective in achieving local control and maintaining ambulation in patients with MESCC.

Patient outcomes and tumor control in single-fraction versus hypofractionated stereotactic body radiation therapy for spinal metastases

OBJECTIVE

Stereotactic body radiation therapy (SBRT) offers efficient, noninvasive treatment of spinal neoplasms. Single-fraction (SF) high-dose SBRT has a relatively narrow therapeutic window, while hypofractionated delivery of SBRT may have an improved safety profile with similar efficacy. Because the optimal approach of delivery is unknown, the authors examined whether hypofractionated SBRT improves pain and/or functional outcomes and results in better tumor control compared with SF-SBRT.

METHODS

This is a single-institution retrospective study of adult patients with spinal metastases treated with SF- or three-fraction (3F) SBRT from 2008 to 2019. Demographics and baseline characteristics, radiographic data, and posttreatment outcomes at a minimum follow-up of 3 months are reported.

RESULTS

Of the 156 patients included in the study, 70 (44.9%) underwent SF-SBRT (median total dose 1700 cGy) and 86 (55.1%) underwent 3F-SBRT (median total dose 2100 cGy). At baseline, a higher proportion of patients in the 3F-SBRT group had a worse baseline profile, including severity of pain (p < 0.05), average use of pain medication (p < 0.001), and functional scores (p < 0.05) compared with the SF-SBRT cohort. At the 3-month follow-up, the 3F-SBRT cohort experienced a greater frequency of improvement in pain compared with the SF-SBRT group (p < 0.05). Furthermore, patients treated with 3F-SBRT demonstrated a higher frequency of improved Karnofsky Performance Scale (KPS) scores (p < 0.05) compared with those treated with SF-SBRT, with no significant difference in the frequency of improvement in modified Rankin Scale scores. Local tumor control did not differ significantly between the two cohorts.

CONCLUSIONS

Patients who received spinal 3F-SBRT more frequently achieved significant pain relief and an increased frequency of improvement in KPS compared with those treated with SF-SBRT. Local tumor control was similar in the two groups. Future work is needed to establish the relationship between fractionation schedule and clinical outcomes.

Hypofractionated spinal stereotactic body radiation therapy for high-grade epidural disease

OBJECTIVE

To characterize the clinical outcomes when stereotactic body radiation therapy (SBRT) alone is used to treat high-grade epidural disease without prior surgical decompression, the authors conducted a retrospective cohort study of patients treated at the Memorial Sloan Kettering Cancer Center between 2014 and 2018. The authors report locoregional failure (LRF) for a cohort of 31 cases treated with hypofractionated SBRT alone for grade 2 epidural spinal cord compression (ESCC) with radioresistant primary cancer histology.

METHODS

High-grade epidural disease was defined as grade 2 ESCC, which is notable for radiographic deformation of the spinal cord by metastatic disease. Kaplan-Meier survival curves and cumulative incidence functions were generated to examine the survival and incidence experiences of the sample level with respect to overall survival, LRF, and subsequent requirement of vertebral same-level surgery (SLS) due to tumor progression or fracture. Associations with dosimetric analysis were also examined.

RESULTS

Twenty-nine patients undergoing 31 episodes of hypofractionated SBRT alone for grade 2 ESCC between 2014 and 2018 were identified. The 1-year and 2-year cumulative incidences of LRF were 10.4% (95% CI 0-21.9) and 22.0% (95% CI 5.5-38.4), respectively. The median survival was 9.81 months (95% CI 8.12-18.54). The 1-year cumulative incidence of SLS was 6.8% (95% CI 0-16.0) and the 2-year incidence of SLS was 14.5% (95% CI 0.6-28.4). All patients who progressed to requiring surgery had index lesions at the thoracic apex (T5-7).

CONCLUSIONS

In carefully selected patients, treatment of grade 2 ESCC disease with hypofractionated SBRT alone offers a 1-year cumulative incidence of LRF similar to that in low-grade ESCC and postseparation surgery adjuvant hypofractionated SBRT. Use of SBRT alone has a favorable safety profile and a low cumulative incidence of progressive disease requiring open surgical intervention (14.5%).

Separation surgery for metastatic epidural spinal cord compression: A qualitative review

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Separation surgery is a new concept for metastatic spinal cord compression treatment.

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Stereotactic radiosurgery increased local control, overcoming radio-resistance’s idea.

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The surgery goal shifted towards creating targets for radiations avoiding cord damages.

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Minimal invasive strategies could allow quick return to systemic therapies.

Introduction

The new concept of separation surgery has changed the surgical paradigms for the treatment of metastatic epidural spinal cord compression (MESCC), shifting from aggressive cytoreductive surgery towards less invasive surgery with the aim to achieve circumferential separation of the spinal cord and create a safe target for high dose Stereotactic Body Radiation Therapy (SBRT), which turned out to be the real game-changer for disease’s local control.

Discussion

In this review a qualitative analysis of the English literature has been performed according to the rating of evidence, with the aim to underline the increasingly role of the concept of separation surgery in MESCC treatment. A review of the main steps in the evolution of both radiotherapy and surgery fields have been described, highlighting the important results deriving from their integration.

Conclusion

Compared with more aggressive surgical approaches, the concept of separation surgery together with the advancements of radiotherapy and the use of SBRT for the treatment of MESCC showed promising results in order to achieve a valuable local control while reducing surgical related morbidities and complications.

Treatment Strategy for Metastatic Spinal Tumors: A Narrative Review

Metastatic spinal tumors are common, and their rising incidence can be attributed to the expanding aging population and increased survival rates among cancer patients. The decision-making process in the treatment of spinal metastasis requires a multidisciplinary approach that includes medical and radiation oncology, surgery, and rehabilitation. Various decision-making systems have been proposed in the literature in order to estimate survival and suggest appropriate treatment options for patients experiencing spinal metastasis. However, recent advances in treatment modalities for spinal metastasis, such as stereotactic radiosurgery and minimally invasive surgical techniques, have reshaped clinical practices concerning patients with spinal metastasis, making a demand for further improvements on current decision-making systems. In this review, recent improvements in treatment modalities and the evolution of decision-making systems for metastatic spinal tumors are discussed.

Precision Stereotactic Radiotherapy for Spinal Tumors: Mechanism, Efficacy, and Issues

Stereotactic ablative radiotherapy (SABR/SBRT) is a revolutionary technique for tumor therapy. Its advantages are especially beneficial for the treatment spinal tumors. It has a wide range of indications in radiotherapy alone and in preoperative and postoperative treatments for spinal tumor. The mechanism of stereotactic radiotherapy for spinal tumors is special, and completely different from traditional radiotherapy. Compared with traditional radiotherapy, SBRT creates more DNA double-strand breaks, leads to less DNA damage repair, and also has anti-vascular effects, in situ vaccine effects and abscopal effect. In the present study, the literature regarding SABR for the treatment of spinal tumors is summarized, and we reviewed characteristics of SABR and spinal tumors, as well as the clinical efficacy and toxicity of SABR in treating spinal tumors. In addition, we proposed several issues around the SABR treatment of spinal tumor, the standard of treatment dose, and the post-treatment follow-up. We also made predictions with respect to future management of spinal tumors, SABR development, multi-modality integration between SABR and other treatments, and other future development trends, thereby providing future research directions as a contribution to the field.

Evolving Role of Stereotactic Body Radiation Therapy in the Management of Spine Metastases: Defining Dose and Dose Constraints

When treating solid tumor spine metastases, stereotactic high-dose-per-fraction radiation, given in a single fraction or in a hypofractionated approach, has proved to be a highly effective and safe therapeutic option for any tumor histology, in the setting of de novo therapy, as salvage treatment of local progression after previous radiation, and in the postoperative setting. There are variations in practice based on the clinical presentation, goals of therapy, as well as institutional preferences. As a biologically potent therapy, a thoughtful and careful attention to detail with patient selection, treatment planning, and delivery is crucial for treatment success.

A comparison of stereotactic body radiation therapy for metastases to the sacral spine and treatment of the thoracolumbar spine

Background: This study compares the outcomes of stereotactic body radiation therapy (SBRT) for sacral and thoracolumbar spine metastases. Methods: This analysis considered each sacral spine SBRT treatment at a single institution and a cohort of consecutive thoracolumbar treatments. Results: 28 patients with 35 sacral treatments and 41 patients with 49 thoracolumbar treatments were included. Local control was 63% and 90%, respectively. The sacral cohort contained more lesions with ≥2 vertebrae and epidural and paraspinal involvement. Sacral patients had larger treatment volumes, increased rates of subsequent SBRT, decreased propensity for pain improvement, and decreased local control (p=0.02 on Kaplan-Meier analysis). Multivariate analysis demonstrated that PTV > 50 cc and epidural involvement were correlated with decreased local control. No cases had grade ≥3 toxicity. Conclusion: SBRT for sacral spine metastases is a distinct disease process than metastases to the thoracolumbar spine, resulting in lower rates of local control and pain improvement.