Stereotactic Body Radiotherapy for Spinal Metastases: What are the Risks and How Do We Minimize Them?

Management of Metastatic Spinal Disease - A Practical Approach

STUDY DESIGN

Narrative review.

OBJECTIVE

This review presents a comprehensive approach to the management of spinal metastases.

METHODS

N/A.

RESULTS

The wide spectrum of clinical presentation in spinal metastases necessitates a personalized approach to treatment planning. This includes a comprehensive diagnostic workup, oncological management, palliation of symptoms, and surgical intervention if appropriate. A systematic and multidisciplinary approach allows optimal shared decision making to reach an evidence-informed and value-congruent treatment plan for the patient. We highlight how advances in stereotactic body radiotherapy (SBRT) and separation surgery may be incorporated into clinical management from a spine surgeon's perspective.

CONCLUSION

This review summarizes the approach and management of spinal metastases, its outcomes and complications.

Tumor treating fields suppress tumor cell growth and neurologic decline in models of spinal metastases

Spinal metastases can result in severe neurologic compromise and decreased overall survival. Despite treatment advances, local disease progression is frequent, highlighting the need for novel therapies. Tumor treating fields (TTFields) impair tumor cell replication and are influenced by properties of surrounding tissue. We hypothesized that bone's dielectric properties will enhance TTFields-mediated suppression of tumor growth in spinal metastasis models. Computational modeling of TTFields intensity was performed following surgical resection of a spinal metastasis and demonstrated enhanced TTFields intensity within the resected vertebral body. Additionally, luciferase-tagged human KRIB osteosarcoma and A549 lung adenocarcinoma cell lines were cultured in demineralized bone grafts and exposed to TTFields. Following TTFields exposure, the bioluminescence imaging (BLI) signal decreased to 10%-80% of baseline, while control cultures displayed a 4.48- to 9.36-fold increase in signal. Lastly, TTFields were applied in an orthotopic murine model of spinal metastasis. After 21 days of treatment, control mice demonstrated a 5-fold increase in BLI signal compared with TTFields-treated mice. TTFields similarly prevented tumor invasion into the spinal canal and development of neurologic symptoms. Our data suggest that TTFields can be leveraged as a local therapy within minimally conductive bone of spinal metastases. This provides the groundwork for future studies investigating TTFields for patients with treatment-refractory spinal metastases.

Dosimetric impact of CT metal artifact reduction for spinal implants in stereotactic body radiotherapy planning

Background

Metal artifacts due to spinal implants may affect the accuracy of dose calculation for radiotherapy. However, the dosimetric impact of metal artifact reduction (MAR) for spinal implants in stereotactic body radiotherapy (SBRT) plans has not been well studied. The objective of this study was to evaluate the dosimetric impact of MAR in spinal SBRT planning with three clinically common dose calculation algorithms.

Methods

Gammex phantom and 10 patients' computed tomography (CT) images were studied to investigate the effects of titanium implants. A commercial orthopedic MAR algorithm was employed to reduce artifacts. Dose calculations for SBRT were conducted on both artifact-corrected and uncorrected images using three commercial algorithms [analytical anisotropic algorithm (AAA), Acuros XB (AXB), and Monte Carlo (MC)]. Dose discrepancies between artifact-corrected and uncorrected cases were appraised using a dose-volume histogram (DVH) and 3-dimensional (3D) gamma analysis with different distance to agreement (DTA) and dose difference criteria. The gamma agreement index (GAI) was denoted as G(∆D, DTA). Statistical analysis of t-test was utilized to evaluate the dose differences of different algorithms.

Results

The phantom study demonstrated that titanium metal artifacts can be effectively reduced. The patient cases study showed that dose differences between the artifact-corrected and uncorrected datasets were small evaluated by gamma index and DVH. Gamma analysis found that even the strict criterion local G(1,1) had average values ≥93.9% for the three algorithms. For all DVH metrics, average differences did not exceed 0.7% in planning target volume (PTV) and 2.1% in planning risk volume of spinal cord (PRV-SC). Statistical analysis showed that the observed dose differences of MC method were significantly larger than those of AAA (P<0.01 for D98% of PTV and P<0.001 for D0.1cc of spinal cord) and AXB methods (P<0.001 for D98% and P<0.0001 for D0.1cc).

Conclusions

Dosimetric impact of artifacts caused by titanium implants is not significant in spinal SBRT planning, which indicates that dose calculation algorithms might not be very sensitive to CT number variation caused by titanium inserts.

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.

Radiation myelopathy following stereotactic body radiation therapy for spine metastases

PURPOSE

Stereotactic body radiation therapy (SBRT) is now considered a standard of care treatment option in the management of spine metastases. One of the most feared complications of spine SBRT is radiation myelopathy (RM).

METHODS

We provided a narrative review of RM following spine SBRT based on review of the published literature, including data on spinal cord dose constraints associated with the risk of RM, strategies to mitigate the risk, and management options for RM.

RESULTS

There are limited published data of cases of RM following spine SBRT with detailed spinal cord dosimetry. The HyTEC report provided recommendations for the point maximal dose (Dmax) for the spinal cord that is associated with a < 5% risk of RM for 1-5 fractions spine SBRT. In the setting of spine SBRT reirradiation after previous conventional external beam radiation therapy (cEBRT), factors associated with RM are: SBRT spinal cord Dmax, cumulative spinal cord Dmax, and the time interval between previous RT and SBRT reirradiation. There are various strategies to mitigate the risk of RM, including accurate delineation of the spinal cord (or thecal sac), strict adherence to the recommended spinal cord dose constraints, and robust treatment immobilisation set-up and delivery. Limited effective treatment options are available for patients who develop RM, and these include corticosteroids, hyperbaric oxygen, and bevacizumab; however, none have been supported by high quality evidence.

CONCLUSION

RM is a rare but devastating complication following SBRT for spine metastases. There are strategies to minimise the risk of RM to ensure safe delivery of spine SBRT.

Extranodal classical Hodgkin lymphoma involving the spinal cord: case report and review of the literature

Primary CNS involvement is very rare in Hodgkin lymphoma. Here we present two cases of spinal cord dissemination. Two women of 40 and 65 years of age presented symptoms of spinal cord injury; imaging showed an intramedullary mass in T10 and T2, respectively, without vertebral involvement and upper diaphragmatic lymph nodes. Lymph-node biopsy confirmed the diagnosis of classical Hodgkin lymphoma in both patients. The first patient received four cycles of chemotherapy (escalated BEACOPP and ABVD) with intrathecal therapy, and the second four cycles of doxorubicin, vinblastine, dacarbazine (AVD) and local irradiation after surgery decompression. Complete metabolic response was obtained at the end of treatment. After 5 and 7 years of follow-up respectively, neurological deficits persisted in both.

Lymph-node infiltration is the most common presentation in Hodgkin lymphoma at diagnosis. Primary extranodal involvement is rare and spinal cord infiltration exceptional. Back pain, tingling and vesico-sphincter dysfunctions are the main symptoms. 18F-fluorodeoxyglucose (FDG) PET and MRI can detect the location and extension of neurological involvement. We present here two cases of tumoral myelitis and a review of the literature. Local treatment (surgery/radiotherapy) is often administered together with chemotherapy to optimize local control and to avoid long-term sequelae.

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.

Personalized Automation of Treatment Planning for Linac-Based Stereotactic Body Radiotherapy of Spine Cancer

Purpose/Objective(s)

Stereotactic ablative body radiotherapy (SBRT) for vertebral metastases is a challenging treatment process. Planning automation has recently reported the potential to improve plan quality and increase planning efficiency. We performed a dosimetric evaluation of the new Personalized engine implemented in Pinnacle3 for full planning automation of SBRT spine treatments in terms of plan quality, treatment efficiency, and delivery accuracy.

Materials/Methods

The Pinnacle3 treatment planning system was used to reoptimize six patients with spinal metastases, employing two separate automated engines. These two automated engines, the existing Autoplanning and the new Personalized, are both template-based algorithms that employ a wishlist to construct planning goals and an iterative technique to replicate the planning procedure performed by skilled planners. The boost tumor volume (BTV) was defined as the macroscopically visible lesion on RM examination, and the planning target volume (PTV) corresponds with the entire vertebra. Dose was prescribed according to simultaneous integrated boost strategy with BTV and PTV irradiated simultaneously over 3 fractions with a dose of 30 and 21 Gy, respectively. Dose-volume histogram (DVH) metrics and conformance indices were used to compare clinically accepted manual plans (MP) with automated plans developed using both Autoplanning (AP) and Personalized engines (Pers). All plans were evaluated for planning efficiency and dose delivery accuracy.

Results

For similar spinal cord sparing, automated plans reported a significant improvement of target coverage and dose conformity. On average, Pers plans increased near-minimal dose D98% by 10.4% and 8.9% and target coverage D95% by 8.0% and by 4.6% for BTV and PTV, respectively. Automated plans provided significantly superior dose conformity and dose contrast by 37%–47% and by 4.6%–5.7% compared with manual plans. Overall planning times were dramatically reduced to about 15 and 23 min for Pers and AP plans, respectively. The average beam-on times were found to be within 3 min for all plans. Despite the increased complexity, all plans passed the 2%/2 mm γ-analysis for dose verification.

Conclusion

Automated planning for spine SBRT through the new Pinnacle3 Personalized engine provided an overall increase of plan quality in terms of dose conformity and a major increase in efficiency. In this complex anatomical site, Personalized strongly reduce the tradeoff between optimal accurate dosimetry and planning time.

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.

Comparison of Surgical Outcomes Between Separation Surgery and Piecemeal Spondylectomy for Spinal Metastasis: A Retrospective Analysis

Objective: This study aimed to compare the outcomes between piecemeal spondylectomy and separation surgery for patients with spinal metastasis.

Summary of Background Data: Piecemeal spondylectomy and separation surgery are two widely-used treatment options for spinal metastasis. However, no studies have compared the surgical outcomes between both treatment modalities.

Methods: Patients with spinal metastasis who underwent piecemeal spondylectomy or separation surgery between August 2017 and April 2020 at our spine center were recruited. Demographic, preoperative, perioperative, and follow-up data were collected and analyzed. Kaplan–Meier analysis and the log-rank test were used to analyze overall survival (OS) and progression-free survival (PFS) in patients with spinal metastasis.

Results: Overall, 26 patients were treated with piecemeal spondylectomy, and 29 underwent separation surgery with postoperative stereotactic radiosurgery. Both groups showed significant postoperative improvements in neurological status. The piecemeal spondylectomy group had significantly more blood loss (1784.62 ± 833.64 vs. 1165.52 ± 307.38 ml) and required longer operative time (4.76 ± 0.93 vs. 3.73 ± 1.15 h) than the separation surgery group. No significant difference in OS was found between the groups (P = 0.064); however, patients in the separation surgery group experienced less local recurrence than those in the piecemeal spondylectomy group (P = 0.0014). Notably, significant differences were detected in the development of complications between the groups (P = 0.029).

Conclusion: Separation surgery led to less blood loss and reduced complications and had shorter operation time than piecemeal spondylectomy. Although no significant differences were found in OS between the groups, separation surgery was associated with better PFS compared with piecemeal spondylectomy. These findings suggest that separation surgery has some advantages over piecemeal spondylectomy for patients with spinal metastatic disease.

Fundamentals of Radiation Oncology for Treatment of Vertebral Metastases

The fields of both radiology and radiation oncology have evolved considerably in the past few decades, resulting in an increased ability to delineate between tumor and normal tissue to precisely target and treat vertebral metastases with radiation therapy. These scientific advances have also led to improvements in assessing treatment response and diagnosing toxic effects related to radiation treatment. However, despite technological innovations yielding greatly improved rates of palliative relief and local control of osseous spinal metastases, radiation therapy can still lead to a number of acute and delayed posttreatment complications. Treatment-related adverse effects may include pain flare, esophageal toxic effects, dermatitis, vertebral compression fracture, radiation myelopathy, and myositis, among others. The authors provide an overview of the multidisciplinary approach to the treatment of spinal metastases, indications for surgical management versus radiation therapy, various radiation technologies and techniques (along with their applications for spinal metastases), and current principles of treatment planning for conventional and stereotactic radiation treatment. Different radiologic criteria for assessment of treatment response, recent advances in radiologic imaging, and both common and rare complications related to spinal irradiation are also discussed, along with the imaging characteristics of various adverse effects. Familiarity with these topics will not only assist the diagnostic radiologist in assessing treatment response and diagnosing treatment-related complications but will also allow more effective collaboration between diagnostic radiologists and radiation oncologists to guide management decisions and ensure high-quality patient care. ^©RSNA, 2021.

The emergence of new prognostic scores in lung cancer patients with spinal metastasis: A 12-year single-center retrospective study

Objective: Lung cancer patients exhibit spinal metastases from a specific population, and with this study, we aimed to develop a model that can predict this particular group's survival.

Methods: Data were retrospectively collected from 83 lung cancer patients who underwent spinal metastasis surgery at our center from 2009 to 2021. After the initial assessment of treatment and scoring effects, a nomogram for survival prediction was created by identifying and integrating critical prognostic factors, followed by a consistency index (C-index) to measure consistency, and finally, a subject working characteristic curve (ROC) to compare the predictive accuracy of the three existing models.

Results: The mean postoperative survival was 14.7 months. Surgical treatment significantly improved the VAS and Frankel scores in lung cancer patients with spinal metastases. The revised Tokuhashi score underestimated the life expectancy of these patients. Six independent prognostic factors, including age, extraspinal bone metastasis foci, visceral metastasis, Frankel score, targeted therapy, and radiotherapy, were identified and incorporated into the model. Calibration curves for 3-, 6-, and 12-month overall survival showed a good concordance between predicted and actual risk. The nomogram C-index for the cohort study was 0.800 (95% confidence interval [CI]: 0.757-0.843). Model comparisons showed that the nomogram's prediction accuracy was better than revised Tokuhashi and Bauer's scoring systems.

Conclusions: Spine surgery offered patients the possibility of regaining neurological function. Having identified shortcomings in existing scoring systems, we have recreated and validated a new nomogram that can be used to predict survival outcomes in patients with spinal metastases from lung cancer, thereby assisting spinal surgeons in making surgical decisions and personalizing treatment for these patients.

Paraspinal Myosistis After Stereotactic Radiation Surgery

Myositis of the paraspinal muscles can be a clinically significant side effect of spinal radiation surgery. This report describes the typical clinical scenario, relevant radiologic findings, treatment, and management with the best available evidence.

Stereotactic body radiation therapy for spinal metastases: a novel local control stratification by spinal region

OBJECTIVE

This study evaluated a large cohort of patients treated with stereotactic body radiation therapy for spinal metastases and investigated predictive factors for local control, local progression-free survival (LPFS), overall survival, and pain response between the different spinal regions.

METHODS

The study was undertaken via retrospective review at a single institution. Patients with a tumor metastatic to the spine were included, while patients with benign tumors or primary spinal cord cancers were excluded. Statistical analysis involved univariate analysis, Cox proportional hazards analysis, the Kaplan-Meier method, and machine learning techniques (decision-tree analysis).

RESULTS

A total of 165 patients with 190 distinct lesions met all inclusion criteria for the study. Lesions were distributed throughout the cervical (19%), thoracic (43%), lumbar (19%), and sacral (18%) spines. The most common treatment regimen was 24 Gy in 3 fractions (44%). Via the Kaplan-Meier method, the 24-month local control was 80%. Sacral spine lesions demonstrated decreased local control (p = 0.01) and LPFS (p < 0.005) compared with those of the thoracolumbar spine. The cervical spine cases had improved local control (p < 0.005) and LPFS (p < 0.005) compared with the sacral spine and trended toward improvement relative to the thoracolumbar spine. The 36-month local control rates for cervical, thoracolumbar, and sacral tumors were 86%, 73%, and 44%, respectively. Comparably, the 36-month LPFS rates for cervical, thoracolumbar, and sacral tumors were 85%, 67%, and 35%, respectively. A planning target volume (PTV) > 50 cm3 was also predictive of local failure (p = 0.04). Fewer cervical spine cases had disease with PTV > 50 cm3 than the thoracolumbar (p = 5.87 × 10-8) and sacral (p = 3.9 × 10-3) cases. Using decision-tree analysis, the highest-fidelity models for predicting pain-free status and local failure demonstrated the first splits as being cervical and sacral location, respectively.

CONCLUSIONS

This study presents a novel risk stratification for local failure and LPFS by spinal region. Patients with metastases to the sacral spine may have decreased local control due to increased PTV, especially with a PTV of > 50 cm3. Multidisciplinary care should be emphasized in these patients, and both surgical intervention and radiotherapy should be strongly considered.

Vertebral compression fracture during stereotactic body radiotherapy for spinal metastasis: A rare case of tracking failure

Spinal metastasis are a daily challenge in clinical practice. Stereotactic body radiotherapy (SBRT) allows delivery of definitive treatment with excellent long-term control rates. Its implementation needs dedicated devices and day-to-day image-guided radiotherapy (IGRT). The XSight™ spine tracking system, integrates with the CyberKnife® (Accuray™), provides a fiducial-free tracking system for spinal SBRT. We report a rare case of tracking failure during treatment due to the occurrence of a vertebral compression fracture (VCF).

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.

Systematic Review of the Role of Stereotactic Radiotherapy for Bone Metastases

Background

Stereotactic radiotherapy (SBRT) might improve pain and local control in patients with bone metastases compared to conventional radiotherapy, although an overall estimate of these outcomes is currently unknown.

Methods

A systematic review was carried out following Preferred Reporting Items for Systematic Reviews and Meta-Analyses guidelines. Pubmed, Embase, and Cochrane databases were systematically searched to identify studies reporting pain response and local control among patients with bone metastases from solid-organ tumors who underwent SBRT in 1–6 fractions. All studies prior to April 15, 2017, were included. Study quality was assessed by predefined criteria, and pain response and local control rates were extracted.

Results

A total of 2619 studies were screened; 57 were included (reporting outcomes for 3995 patients) of which 38 reported pain response and 45 local control rates. Local control rates were high with pain response rates above those previously reported for conventional radiotherapy. Marked heterogeneity in study populations and delivered treatments were identified such that quantitative synthesis was not appropriate. Reported toxicity was limited. Of the pain response studies, 73.7% used a retrospective cohort design and only 10.5% used the international consensus endpoint definitions of pain response. The median survival within the included studies ranged from 8 to 30.4 months, suggesting a high risk of selection bias in the included observational studies.

Conclusions

This review demonstrates the potential benefit of SBRT over conventional palliative radiotherapy in improving pain due to bone metastases. Given the methodological limitations of the published literature, however, large randomized trials are now urgently required to better quantify this benefit.

Vertebral fractures following stereotactic body radiotherapy for spine metastases

Stereotactic body radiotherapy has emerged as one of the preferred treatments for patients with spine metastases, with the potential for long-term control from lesion irradiation. Post-treatment vertebral compression fractures are a known complication of this therapy, contributing to worsening pain and reduced quality of life, sometimes requiring surgical intervention. This review explores the current knowledge of post-radiotherapy fractures, in terms of the rates and associated predictive factors. A search of databases including Medline, Embase and the Cochrane Library was conducted using keywords such as 'vertebral compression fracture', 'stereotactic body radiotherapy' and 'spine metastases'. The search was limited to published studies up to March 2019, reporting clinical outcomes including both the post-treatment fracture rate and statistical identification of associated risk factors. Rates of post-treatment fractures ranged from 4 to 39%. A variety of factors were found to increase the risk, including the appearance of lytic vertebral disease, degree of pre-existing compression, spinal malalignment, increased dose per fraction and a Spinal Instability Neoplastic Score >6. This knowledge can enable clinicians to counsel patients when considering management options for spine metastases, maintaining the balance between local tumour control and the risk of subsequent fracture.

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.

Precision Radiation Therapy for Metastatic Spinal Cord Compression: Final Results of the PRE-MODE Trial

OBJECTIVE

To investigate precision radiation therapy for metastatic spinal cord compression and compare it to conventional radiation therapy.

METHODS AND MATERIALS

In a multicenter phase 2 study, 40 patients received 5 Gy × 5 fractions of precision radiation therapy (38 volume modulated arc therapy, 2 intensity modulated radiation therapy) for metastatic spinal cord compression and were evaluated for local progression-free survival (LPFS), motor function, ambulatory status, sensory function, sphincter dysfunction, pain, distress, overall survival (OS), and toxicity. Maximum spinal cord dose was 101.5% (myelopathy risk, <0.03%) of the prescription dose. Patients were compared with a historical control group conventionally irradiated with 4 Gy × 5 fractions (propensity score analysis). The equivalent dose in 2 Gy-fractions of 5 Gy × 5 fractions is similar to 3 Gy × 10 fractions, which results in better LPFS than 4 Gy × 5 fractions. It was assumed that 5 Gy × 5 fractions is also superior to 4 Gy × 5 fractions for LPFS. (ClinicalTrials.gov-identifier: NCT03070431) RESULTS: Six-month rates of LPFS and OS were 95.0% and 42.6%, respectively. Improvement of motor function occurred in 24 patients (60%). Thirty-three patients (82.5%) were ambulatory after radiation therapy. Eight of 16 patients (50.0%) with sensory deficits improved. Pain and distress relief were reported by 61.9% and 54.2% of patients 1 month after radiation therapy. Grade 3 toxicities occurred in 1 patient and grade 2 toxicities in another 3 patients. Of the control group, 664 patients qualified for the propensity score analysis; 5 Gy × 5 fractions was significantly superior to 4 Gy × 5 fractions with regard to LPFS (P = .026) but not motor function (P = .51) or OS (P = .82).

CONCLUSIONS

Precision radiation therapy with 5 Gy × 5 fractions was well tolerated and effective and appeared superior to 4 Gy × 5 fractions in terms of LPFS. The retrospective nature of the historic control group, which might have led to a hidden selection bias, needs to be considered when interpreting the results.

Radiotherapy for metastatic spinal cord compression with increased radiation doses (RAMSES-01): a prospective multicenter study

BACKGROUND

Patients with metastatic spinal cord compression (MSCC) and favorable survival prognoses can benefit from radiation doses greater than 30Gy in 10 fractions in terms of improved local progression-free survival (LPFS) and overall survival (OS).

METHODS/DESIGN

This prospective study mainly investigates LPFS after precision radiotherapy (volumetric modulated arc therapy or stereotactic body radiotherapy) with 18 × 2.33Gy in 3.5 weeks. LPFS is defined as freedom from progression of motor deficits during radiotherapy and an in-field recurrence of MSCC following radiotherapy. The maximum relative dose allowed to the spinal cord is 101.5% of the prescribed dose, resulting in an equivalent dose in 2Gy-fractions (EQD2) for radiation myelopathy is 45.5Gy, which is below the tolerance dose of 50Gy according to the Quantitative Analyses of Normal Tissue Effects in the Clinic (QUANTEC). The EQD2 of this regimen for tumor cell kill is 43.1Gy, which is 33% higher than for 30Gy in 10 fractions (EQD2 = 32.5Gy). Primary endpoint is LPFS at 12 months after radiotherapy. Secondary endpoints include the effect of 18 × 2.33Gy on motor function, ambulatory status, sensory function, sphincter dysfunction, LPFS at other follow-up times, overall survival, pain relief, relief of distress and toxicity. Follow-up visits for all endpoints will be performed directly and at 1, 3, 6, 9 and 12 months after radiotherapy. A total of 65 patients are required for the prospective part of the study. These patients will be compared to a historical control group of at least 235 patients receiving conventional radiotherapy with 10x3Gy in 2 weeks.

DISCUSSION

If precision radiotherapy with 18 × 2.33Gy results in significantly better LPFS than 10x3Gy of conventional radiotherapy, this regimen should be strongly considered for patients with MSCC and favorable survival prognoses.

TRIAL REGISTRATION

Clinicaltrials.gov NCT04043156. Registered 30-07-2019.

Dosimetric study for spine stereotactic body radiation therapy: magnetic resonance guided linear accelerator versus volumetric modulated arc therapy

Background Stereotactic body radiation therapy (SBRT) given in 1-5 fractions is an effective treatment for vertebral metastases. Real-time magnetic resonance-guided radiotherapy (MRgRT) improves soft tissue contrast, which translates into accurate delivery of spine SBRT. Here we report on clinical implementation of MRgRT for spine SBRT, the quality of MRgRT plans compared to TrueBeam based volumetric modulated arc therapy (VMAT) plans in the treatment of spine metastases and benefits of MRgRT MR scan. Patients and methods Ten metastatic lesions were included in this study for plan comparison. Lesions were spread across thoracic spine and lumbosacral spine. Three fraction spine SBRT plans: 27Gy to planning target volume (PTV) and 30Gy to gross tumor volume (GTV) were generated on the ViewRay MRIdian Linac system and compared to TrueBeamTM STx based VMAT plans. Plans were compared using metrics such as minimum dose, maximum dose, mean dose, ratio of the dose to 50% of the volume (R50), conformity index, homogeneity index and dose to the spinal cord. Results MRIdian plans achieved equivalent target coverage and spinal cord dose compared to VMAT plans. The maximum and minimum PTV doses and homogeneity index were equivalent for both planning systems. R50 was lower for MRIdian plans compared to VMAT plans, indicating a lower spread of intermediate doses with MRIdian system (5.16 vs. 6.11, p = 0.03). Conclusions MRgRT can deliver high-quality spine SBRT plans comparable to TrueBeam volumetric modulated arc therapy (VMAT) plans.

Outcomes in the radiosurgical management of metastatic spine disease

Purpose

Stereotactic body radiation therapy (SBRT) is a common treatment option for patients with metastatic tumors of the spine. The optimal treatment-, tumor-, and patient-specific characteristics necessary to achieve durable outcomes remain less well understood given the heterogeneous nature of the patient population this modality typically serves. The objective of this analysis was to better understand the determinants underlying SBRT spine treatment outcomes.

Methods and Materials

A total of 127 patients with 287 spine tumors were treated between March 2010 and May 2015. The median total doses for single-fraction and hypofractionated courses of treatment were 16 Gy (range, 16-20 Gy) and 24 Gy (range, 16-40 Gy), respectively. Radiologic local control and numeric pain score data were measured, and univariate and multivariate analyses were done to determine factors predictive of treatment response.

Results

Median follow-up was 5.9 months (range, 1-61 months). Radiologic local control was achieved in 84.7% of patients at 6 months and in 74.7% of patients at 1 year. Local control was found to be affected by the Spinal Instability Neoplastic Score, and was worse in patients with scores ≥7 (hazard ratio [HR]: 4.25; 95% confidence interval [CI], 1.57-11.51). Patients who required upfront surgical intervention to alleviate spinal cord compression, address mechanical spinal instability, or both had worse local control than those who did not require surgery (HR: 2.32; 95% CI, 1.04-5.17). Patients treated with a hypofractionated course compared with a single fraction had worse radiologic local control (HR: 2.63; 95% CI, 1.27-5.45). No patients developed radiation-induced myelitis after treatment, and the vertebral compression fracture rate was 9.1% after SBRT.

Conclusions

Patients with potentially unstable spines or needing upfront spinal surgery before SBRT are less likely to achieve durable radiologic local control. Additionally, patients treated with single-fraction regimens have improved local control compared with those treated with hypofractionated radiation.

Local control and vertebral compression fractures following stereotactic body radiotherapy for spine metastases

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SBRT provides a satisfying local control rate of 88% in patients with spMets.

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Post-SBRT vertebral compression rate of 4% corresponds to the current literature.

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>6 months of bisphosphonates use is associated with lower fracture-free survival.

Purpose

We aimed to retrospectively assess the incidence of vertebral compression fractures (VCF), examine clinicopathologic factors potentially associated with VCF, and evaluate treatment response in patients who received stereotactic body radiotherapy (SBRT) for spine metastases (spMets).

Methods and Materials

We identified 78 patients with 125 spMets at baseline and subsequent assessments. Patients received SBRT doses of 16 or 18 Gy. Patients with pre-existing VCF and co-existing local progression were excluded. Spine instability neoplastic score (SINS) was used for spMets categorization. Response to SBRT and VCF were assessed according to the Positron Emission tomography Response Criteria In Solid Tumors (PERCIST) and Genant scores, respectively. Kaplan–Meier analyses were used to assess local control of disease and vertebral compression fracture-free survival (FFS).

Results

We treated 103 cases with single spMets and 11 cases involving double spMets with SBRT. Progressive disease was reported in 3.2% and 8.2% of the cases in the first and last PET/CT reports, respectively. The distribution of treatment response in the remaining patients was: complete response in 30.6% of patients, partial response in 47.1% of patients, and stable disease in 22.3% of patients in the first PET/CT; complete response in 62.3% of patients, partial response in 16.7% of patients, and stable disease in 21% of patients at the last monitoring. Local failures were observed in 15 (12%) of cases. Median SINS was 5 (range: 1−13); majority of patients in our cohort (70.4%) were categorized as stable according to SINS, five (4%) patients had Grade 3 VCF at a median time of 16 months after SBRT (range: 2−22 months), and 60% of VCF occurred after an interval of at least 12 months after SBRT. No bisphosphonate usage was significantly associated with VCF (r = −0.204; p = 0.022). Median FFS was 21 months. Univariate analyses indicated that female gender (p < 0.001), bisphosphonate use (p = 0.005), >6 months of bisphosphonates use (p = 0.002), and the lowest vertebral body collapse score (p = 0.023) were associated with higher FFS. Female gender (p = 0.007), >6 months of bisphosphonates usage (p = 0.018), and the lowest vertebral body collapse score (p = 0.044) retained independent significance.

Conclusions

This study demonstrated that spine SBRT with doses of 16–18 Gy promises good local control of disease with acceptable VCF rates. Lowest vertebral body collapse score, female gender, and >6 months of bisphosphonate use were significantly associated with longer FFS.

Management - spinal metastases

Due to a worldwide increase of cancer incidence and a longer life expectancy of patients with metastatic cancer, a rise in the incidence of symptomatic vertebral metastases has been observed. Metastatic spinal disease is one of the most dreaded complications of cancer as it is not only associated with severe pain, but also with paralysis, sensory loss, sexual dysfunction, urinary and fecal incontinency when the neurologic elements are compressed. Rapid diagnosis and treatment have been shown to improve both the quality and length of remaining life. This chapter on vertebral metastases with epidural disease and intramedullary spinal metastases will be discussed in terms of epidemiology, pathophysiology, demographics, clinical presentation, diagnosis, and management. With respect to treatment options, our review will summarize the evolution of conventional palliative radiation to modern stereotactic body radiotherapy for spinal metastases and the surgical evolution from traditional open procedures to minimally invasive spine surgery. Lastly, we will review the most common clinical prediction and decision rules, framework and algorithms, and guidelines that have been developed to guide treatment decision making.

Vertebral Compression Fracture After Spine Stereotactic Body Radiation Therapy: A Review of the Pathophysiology and Risk Factors

BACKGROUND

Vertebral compression fracture (VCF) is a challenging and not infrequent complication observed following spine stereotactic body radiation therapy (SBRT).

OBJECTIVE

To summarize the data from the multiple studies that have been published, addressing the risk and predictive factors for VCF post-SBRT.

METHODS

A systematic literature review was conducted. Studies were selected if they specifically addressed risk factors for post-SBRT VCF in their analyses.

RESULTS

A total of 11 studies were identified, reporting both the risk of VCF post-SBRT and an analysis of risk factors based on univariate and multivariate analysis. A total of 2911 spinal segments were treated with a crude VCF rate of 13.9%. The most frequently identified risk factors on multivariate analysis were: lytic disease (hazard ratio [HR] range, 2.76-12.2), baseline VCF prior to SBRT (HR range, 1.69-9.25), higher dose per fraction SBRT (HR range, 5.03-6.82), spinal deformity (HR range, 2.99-11.1), older age (HR range, 2.15-5.67), and more than 40% to 50% of vertebral body involved by tumor (HR range, 3.9-4.46). In the 9 studies that specifically reported on the use of post-SBRT surgical procedures, 37% of VCF had undergone an intervention (range, 11%-60%).

CONCLUSION

VCF is an important adverse effect following SBRT. Risk factors have been identified to guide the selection of high-risk patients. Evidence-based algorithms with respect to patient selection and intervention are needed.

Diagnostic algorithm, prognostic factors and surgical treatment of metastatic cancer diseases of the long bones and spine

Oncological management of skeletal metastases has changed dramatically in the last few decades. A significant number of patients survive for many years with their metastases.

Surgeons are more active and the technical repertoire is broader, from plates to intramedullary devices to (tumour) endoprostheses.

The philosophy of treatment should be different in the case of a trauma-related fracture and a pathological fracture. A proper algorithm for establishing a diagnosis and evaluation of prognostic factors helps in planning the surgical intervention.

The aim of palliative surgery is usually to eliminate pain and to allow the patient to regain his/her mobility as well as to improve the quality of life through minimally invasive techniques using life-long durable devices.

In a selected group of patients with an oncologically controlled primary tumour site and a solitary bone metastasis with positive prognostic factors, which meet the criteria for radical excision (approximately 10% to 15% of the cases), a promising three to five years of survival may be achieved, especially in cases of metastases from breast and kidney cancer.

Spinal metastases require meticulous evaluation because decisions on treatment mostly depend on the tumour type, segmental stability, the patient’s symptoms and general state of health.

Advanced radiotherapy combined with minimally invasive surgical techniques (minimally invasive stabilisation and separation surgery) provides durable local control with a low complication rate in a number of patients.

Cite this article: EFORT Open Rev 2017;2:372-381.

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

BACKGROUND

Stereotactic body radiotherapy (SBRT) is an emerging treatment option for spinal metastases with demonstrated efficacy in the upfront, postoperative, and re-treatment settings, as well as for tumor histologies considered radioresistant. Uncertainty exists regarding the optimal dose and fractionation schedule, with single and multifraction regimens commonly utilized.

METHODS

A literature search of the PubMed and Medline databases was conducted to identify papers specific to spine SBRT and the effect of varying dose/fractionation regimens on outcomes. Bibliographies of relevant papers were searched for further references, and international spine SBRT experts were consulted.

RESULTS

Local control rates generally exceed 80% at 1 year, while high rates of pain control have been attained. There is insufficient evidence to suggest superiority of either single or multiple fraction regimens with respect to local control and pain control. Low rates of toxicity have been reported, assuming strict dose constraints are respected. Radiation myelopathy may be the most morbid toxicity, although the rates are low. The risk of vertebral compression fracture appears to be associated with higher doses per fraction such as those used in single-fraction regimens. The Spinal Instability Neoplastic Score should be considered when evaluating patients for spine SBRT, and prophylactic stabilisation may be warranted. Pain flare is a relatively common toxicity which may be mediated with prophylactic dexamethasone. Because of the treatment complexity and potentially serious toxicities, strict quality assurance should occur at the organizational, planning, dosimetric, and treatment delivery levels.

CONCLUSION

Both single and multifraction regimens are safe and efficacious in spine SBRT for spinal metastases. There may be advantages to hypofractionated treatment over single-fraction regimens with respect to toxicity. Ongoing investigation is underway to define optimal dose and fractionation schedules.