Vertebral compression fracture risk after stereotactic body radiotherapy for spinal metastases

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

INTRODUCTION

Sarcoma spinal metastases (SSM) are particularly difficult to manage given their poor response rates to chemotherapy and inherent radioresistance. We evaluated outcomes in a cohort of patients with SSM uniformly treated using single-fraction simultaneous-integrated-boost (SIB) spine stereotactic radiosurgery (SSRS).

MATERIALS AND METHODS

A retrospective review was conducted at a single tertiary institution treated with SSRS for SSM between April 2007-April 2023. 16-24 Gy was delivered to the GTV and 16 Gy uniformly to the CTV. Kaplan-Meier analysis was conducted to assess time to progression of disease (PD) with proportionate hazards modelling used to determine hazard ratios (HR) and respective 95 % confidence intervals (CI).

RESULTS

70 patients with 100 lesions underwent SSRS for SSM. Median follow-up was 19.3 months (IQR 7.7-27.8). Median age was 55 years (IQR42-63). Median GTV and CTVs were 14.5 cm3 (IQR 5-32) and 52.7 cm3 (IQR 29.5-87.5) respectively. Median GTV prescription dose and biologically equivalent dose (BED) [α/β = 10] was 24 Gy and 81.6 Gy respectively. 85 lesions received 24 Gy to the GTV. 27 % of patients had Bilsky 1b or greater disease. 16 of 100 lesions recurred representing a crude local failure rate of 16 % with a median time to failure of 10.4 months (IQR 5.7-18) in cases which failed locally. 1-year actuarial local control (LC) was 89 %. Median overall survival (OS) was 15.3 months (IQR 7.7-25) from SSRS. Every 1 Gy increase in GTV absolute minimum dose (DMin) across the range (5.8-25 Gy) was associated with a reduced risk of local failure (HR = 0.871 [95 % CI 0.782-0.97], p = 0.009). 9 % of patients developed vertebral compression fractures at a median of 13 months post SSRS (IQR 7-25).

CONCLUSION

This study represents one of the most homogenously treated and the largest cohorts of patients with SSM treated with single-fraction SSRS. Despite inherent radioresistance, SSRS confers durable and high rates of local control in SSM without unexpected long-term toxicity rates.

Clinical Outcomes Among Patients Treated With Stereotactic Body Radiation Therapy to Femur Metastases for Oligometastatic Disease Control or Reirradiation: Results From a Large Single-Institution Experience

Purpose

There are limited data regarding outcomes after stereotactic body radiation therapy (SBRT) for femur metastases, which was an exclusion criteria for the Stereotactic Ablative Radiotherapy for the Comprehensive Treatment of Oligometastatic Cancers (SABR-COMET) trial. We aimed to characterize clinical outcomes from a large single institution experience.

Methods and Materials

Forty-eight patients with 53 lesions were consecutively treated with femur SBRT from May 2017 to June 2022. The Kaplan-Meier method and Cox proportional hazard models were used to characterize time-to-event endpoints and associations between baseline factors and clinical outcomes, respectively. Local control and locoregional control were defined as the absence of tumor progression within the radiation treatment field or within the treated femur, respectively.

Results

Most patients had Eastern Cooperative Oncology Group performance status 0 to 1 (90%), prostate (52%) or breast/lung (17%) cancer, and 1 to 3 lesions (100%), including 29 proximal and 5 distal. Fifty-seven percent of the lesions were treated with concurrent systemic therapy. Median planning target volume was 49.1 cc (range, 6.6-387 cc). Planning target volume V100 (%) was 99% (range, 90-100). Fractionation included 18 to 20 Gy/1F, 27 to 30 Gy/3F, and 28.5-40 Gy/5F. Forty-two percent had Mirels score ≥7 and most (94%) did not have extraosseous extension. Acute toxicities included grade 1 fatigue (15%), pain flare (7.5%), nausea (3.8%), and decreased blood counts (1.9%). Late toxicities included fracture (1.9%) at 1.5 years and osteonecrosis (4%) from dose of 40 Gy in 5F and 30 Gy in 5F (after prior 30 Gy/10F). One patient (2%) required fixation postradiation for progressive pain. With median follow-up 19.4 months, 1- and 2-year rates of local control were 94% and 89%, locoregional control was 83% and 67%, progression-free survival were 56% and 25%, and overall survival were 91% and 73%. Fifty percent of local regional recurrence events occurred within 5 cm of gross tumor volume.

Conclusions

Femur SBRT for oligometastatic disease control in well-selected patients was associated with good outcomes with minimal rates of acute and late toxicity. Patterns of local regional recurrence warrant consideration of larger elective volume coverage. Additional prospective study is needed.

Efficacy of flattening filter-free beams with the acuros XB algorithm in thoracic spine stereotactic body radiation therapy

This study aimed to determine the dosimetric value of flattening filter-free (FFF) beams compared to flattening filter (FF) beams using different algorithms in the treatment planning of thoracic spine stereotactic body radiation therapy (SBRT). A total of 120 plans were created for 15 patients using the Anisotropic Analytical Algorithm (AAA) and the Acuros External Beam (AXB) algorithm with FF and FFF beams at 6 MV and 10 MV energies. Various dosimetric parameters were evaluated, including target coverage, dose spillage, and organs-at-risk sparing of the spinal cord and esophagus. Treatment delivery parameters, such as the monitor units (MUs), modulation factors (MFs), beam-on time (BOT), and dose calculation time (DCT), were also collected. Significant differences were observed in the dosimetric parameters when AXB was used for all energies (P < 0.05). 6 XFFF energy was the best option for target coverage, dose spillage, and organs-at-risk sparing. In contrast, dosimetric parameters had no significant difference when using the AAA. The AAA and AXB calculations showed that the 6 XFFF beam had the shortest DCT. The treatment delivery parameters indicated that 10 XFF beam required the fewest MUs and MFs. In addition, the 10 XFFF beam demonstrated the shortest BOT. For effective treatment of the thoracic spine using SBRT, it is recommended to use the 10 XFFF beam because of the short BOT. Moreover, the AXB algorithm should be used because of its accurate dose calculation in regions with tissue heterogeneity.

ESTRO clinical practice guideline: Stereotactic body radiotherapy for spine metastases

BACKGROUND AND PURPOSE

Recent progress in diagnostics and treatment of metastatic cancer patients have improved survival substantially. These developments also affect local therapies, with treatment aims shifting from short-term palliation to long-term symptom or disease control. There is consequently a need to better define the value of stereotactic body radiotherapy (SBRT) for the treatment of spinal metastases.

METHODS

This ESTRO clinical practice guideline is based on a systematic literature review conducted according to PRISMA standards, which formed the basis for answering four key questions about the indication and practice of SBRT for spine metastases.

RESULTS

The analysis of the key questions based on current evidence yielded 22 recommendations and 5 statements with varying levels of endorsement, all achieving a consensus among experts of at least 75%. In the majority, the level of evidence supporting the recommendations and statements was moderate or expert opinion, only, indicating that spine SBRT is still an evolving field of clinical research. Recommendations were established concerning the selection of appropriate patients with painful spine metastases and oligometastatic disease. Recommendations about the practice of spinal SBRT covered technical planning aspects including dose and fractionation, patient positioning, immobilization and image-guided SBRT delivery. Finally, recommendations were developed regarding quality assurance protocols, including description of potential SBRT-related toxicity and risk mitigation strategies.

CONCLUSIONS

This ESTRO clinical practice guideline provides evidence-based recommendations and statements regarding the selection of patients with spinal metastases for SBRT and its safe implementation and practice. Enrollment of patients into well-designed prospective clinical trials addressing clinically relevant questions is considered important.

Risk Factors for Radiotherapy Failure in the Treatment of Spinal Metastases

STUDY DESIGN

Retrospective cohort study.

OBJECTIVE

To build a predictive model for risk factors for failure of radiation therapy, hypothesizing a higher SINS would correlate with failure.

METHODS

Patients with spinal metastasis being treated with radiation at a tertiary care academic center between September 2014 and October 2018 were identified. The primary outcome measure was radiation therapy failure as defined by persistent pain, need for re-irradiation, or surgical intervention. Risk factors were primary tumor type, Karnofsky and ECOG scores, time to treatment, biologically effective dose (BED) calculations using α/β ratio = 10, and radiation modality. A logistic regression was used to construct a prediction model for radiation therapy failure.

RESULTS

One hundred and seventy patients were included. Median follow up was 91.5 days. Forty-three patients failed radiation therapy. Of those patients, 10 required repeat radiation and 7 underwent surgery. Thirty-six patients reported no pain relief, including some that required re-irradiation and surgery. Total SINS score for those who failed reduction therapy was <7 for 27 patients (62.8%), between 7-12 for 14 patients (32.6%), and >12 for 2 patients (4.6%). In the final prediction model, BED (OR .451 for BED > 43 compared to BED ≤ 43; P = .174), Karnofksy score (OR .736 for every 10 unit increase in Karnofksy score; P = .008), and gender (OR 2.147 for male compared to female; P = .053) are associated with risk of radiation failure (AUC .695). A statistically significant association between SINS score and radiation therapy failure was not found.

CONCLUSIONS

In the multivariable model, BED ≤ 43, lower Karnofksy score, and male gender are predictive for radiotherapy failure. SINS score was among the candidate risk factors included in multivariable model building procedure, but it was not selected in the final model.

LEVEL OF EVIDENCE

Prognostic level III.

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

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

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

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

A Cancer Care Ontario Consensus-Based Organizational Guideline for the Planning and Delivery of Spine Stereotactic Body Radiation Therapy Treatment in Ontario

The proposed recommendations are primarily based on the consensus opinion and in-field experience of the Ontario Health/Cancer Care Ontario stereotactic body radiation therapy (SBRT) for Spine Metastasis Guideline Development Group and published literature when available. Primary consideration was given to the perceived benefits for patients and the small likelihood of harm arising from recommendation implementation. Apart from the magnetic resonance imaging (MRI) follow-up strategy, all evidence was considered indirect and was provided by the working group in conjunction with their collective expertise in the field of SBRT. The application of an SBRT program requires a multidisciplinary team consisting of a radiation oncologist, spine surgeon, neuroradiologist, medical physicist, medical dosimetrist, and radiation therapist. In Canada, linear accelerators are the most used treatment delivery units and should follow technology-specific quality assurance procedures. Immobilization technique is location dependant. Treatment planning MRI sequences should be acquired no more than 14 days from the date of treatment. In the case of epidural disease, simulation MRI should be completed no more than 7 days from the date of treatment. After treatment, patients should be followed with routine clinical visits every 3 months for the first year, every 3 to 6 months during years 2 and 3, and every 4 to 6 months thereafter. The recommendations enclosed provide a framework for the minimum requirements for a cancer center in Ontario, Canada to offer SBRT for spine metastases.

Predicting vertebral compression fracture prior to spinal SBRT using radiomics from planning CT

PURPOSE

The purpose of the study was to develop a predictive model for vertebral compression fracture (VCF) prior to spinal stereotactic body radiation therapy (SBRT) using radiomics features extracted from pre-treatment planning CT images.

METHODS

A retrospective analysis was conducted on 85 patients (114 spinal lesions) who underwent spinal SBRT. Radiomics features were extracted from pre-treatment planning CT images and used to develop a predictive model using a classification algorithm selected from nine different machine learning algorithms. Four different models were trained, including clinical features only, clinical and radiomics features, radiomics and dosimetric features, and all features. Model performance was evaluated using accuracy, precision, recall, F1-score, and area under the curve (AUC).

RESULTS

The model that used all features (radiomics, clinical, and dosimetric) showed the highest performance with an AUC of 0.871. The radiomics and dosimetric features model had the superior performance in terms of accuracy, precision, recall, and F1-score.

CONCLUSION

The developed predictive model based on radiomics features extracted from pre-treatment planning CT images can accurately predict the likelihood of VCF prior to spinal SBRT. This model has significant implications for treatment planning and preventive measures for patients undergoing spinal SBRT. Future research can focus on improving model performance by incorporating new data and external validation using independent data sets.

30 Gy in 4 Stereotactic Body Radiotherapy Fractions for Complex Spinal Metastases: Mature Outcomes Supporting This Novel Regimen

BACKGROUND AND OBJECTIVES

We designed a 30 Gy in 4 fractions stereotactic body radiotherapy protocol, as an alternative option to our standard 2-fraction approach, for primarily large volume, multilevel, or previously radiated spinal metastases. We report imaging-based outcomes of this novel fractionation scheme.

METHODS

The institutional database was reviewed to identify all patients who underwent 30 Gy/4 fractions from 2010 to 2021. Primary outcomes were magnetic resonance-based vertebral compression fracture (VCF) and local failure per treated vertebral segment.

RESULTS

We reviewed 245 treated segments in 116 patients. The median age was 64 years (range, 24-90). The median number of consecutive segments within the treatment volume was 2 (range, 1-6), and the clinical target volume (CTV) was 126.2 cc (range, 10.4-863.5). Fifty-four percent had received at least 1 previous course of radiotherapy, and 31% had previous spine surgery at the treated segment. The baseline Spinal Instability Neoplastic Score was stable, potentially unstable, and unstable for 41.6%, 51.8%, and 6.5% of segments, respectively. The cumulative incidence of local failure was 10.7% (95% CI 7.1-15.2) at 1 year and 16% (95% CI 11.5-21.2) at 2 years. The cumulative incidence of VCF was 7.3% (95% CI 4.4-11.2) at 1 year and 11.2% (95% CI 7.5-15.8) at 2 years. On multivariate analysis, age ≥68 years ( P = .038), CTV volume ≥72 cc ( P = .021), and no previous surgery ( P = .021) predicted an increased risk of VCF. The risk of VCF for CTV volumes <72 cc/≥72 cc was 1.8%/14.6% at 2 years. No case of radiation-induced myelopathy was observed. Five percent of patients developed plexopathy.

CONCLUSION

30 Gy in 4 fractions was safe and efficacious despite the population being at increased risk of toxicity. The lower risk of VCF in previously stabilized segments highlights the potential for a multimodal treatment approach for complex metastases, especially for those with a CTV volume of ≥72 cc.

Does re-ossification after palliative radiotherapy for spinal bone metastases help maintain vertebral body height?

BACKGROUND CONTEXT

After palliative radiotherapy of spinal bone metastases, re-ossification is sometimes observed in bone with osteolytic changes. However, it remains unknown whether the re-ossification that is observed after radiotherapy is associated with preservation of vertebral body height.

PURPOSE

To investigate whether re-ossification observed after palliative radiotherapy can contribute to the preservation of vertebral body height.

STUDY DESIGN

This is a retrospective observational study.

PATIENTS SAMPLE

We investigated 111 vertebral bodies in 54 patients that underwent palliative radiotherapy at a single center for painful osteolytic/mixed metastatic spinal tumors in solid tumors between 2016 and 2020.

OUTCOME MEASURES

The outcome measures were the presence of re-ossification and vertebral body height reduction on the CT image.

METHODS

Re-ossification was evaluated according to the MD Anderson response classification criteria, and sagittal CT images were used to evaluate vertebral body height. A vertebral body ID was assigned to the irradiated vertebral body, and continuous CT images obtained for each vertebral body ID were evaluated. The median number of evaluation periods for each vertebral body was 4, and the total number of periods was 463. Logistic regression analysis was performed to investigate factors related to the occurrence of vertebral body height reduction before the subsequent CT. As a subanalysis, factors related to re-ossification were investigated.

RESULTS

The following primary cancer types were observed: lung cancer, 41 vertebral bodies; breast cancer, 19; renal cell cancer, 15; other, 36. A total of 62.2% showed re-ossification. The median time to confirmation of re-ossification by CT was 2 months. Factors significantly associated with vertebral body height reduction were presence of vertebral body height reduction before radiotherapy (odds ratio [OR] 6.8, 95% confidence interval [CI] 2.0-63, p=.01) and no re-ossification (OR 137, 95% CI 22-3469, p<.01). Factors associated with re-ossification were the type of cancer and total radiation dose. Those with lung cancer and those with a total radiation dose of 20 Gy or less were more prone to re-ossification.

CONCLUSIONS

Re-ossification was observed in 62.2% of vertebral bodies after palliative radiotherapy for painful osteolytic/mixed metastatic spinal tumors. The re-ossification group demonstrated significantly less vertebral body height reduction when compared with the non-re-ossification group. The presence of re-ossification may potentially serve an important role in maintaining vertebral body height.

Vertebral compression fracture after stereotactic ablative radiotherapy in patients with oligometastatic bone lesions from hepatocellular carcinoma

Background and purpose

Stereotactic ablative radiotherapy (SABR) is popularly used to treat bone metastasis. Despite its efficacy, adverse events, including vertebral compression fracture (VCF), are frequently observed. Here, we investigated VCF risk after SABR for oligometastatic vertebral bone metastasis from hepatocellular carcinoma.

Materials and methods

A total of 84 patients with 144 metastatic bone lesions treated at three institutions between 2009 and 2019 were retrospectively reviewed. The primary endpoint was VCF development, either new or progression of a pre-existing VCF. VCFs were assessed using the spinal instability neoplastic score (SINS).

Results

Among 144 spinal segments, 26 (18%) had pre-existing VCF and 90 (63%) had soft tissue extension. The median biologically effective dose (BED) was 76.8 Gy. VCF developed in 14 (12%) of 118 VCF-naïve patients and progressed in 20 of the 26 with pre-existing VCF. The median time to VCF development was 6 months (range, 1-12 months). The cumulative incidence of VCF at 12 months with SINS class I, II and III was 0%, 26% and 83%, respectively (p < 0.001). Significant factors for VCF development were pre-existing VCF, soft tissue extension, high BED, and SINS class in univariate analysis, and pre-existing VCF in multivariate analysis. Of the six components of SINS, pain, type of bone lesion, spine alignment, vertebral body collapse, and posterolateral involvement were identified as predictors of VCF development.

Conclusion

SABR for oligometastatic vertebral bone lesions from HCC resulted in a substantial rate of new VCF development and pre-existing VCF progression. Pre-existing VCF was significant risk factor for VCF development, which require special attention in patient care. Patients with SINS class III should be considered surgical treatment rather than upfront SABR.

Beyond the Knife in Renal Cell Carcinoma: A Systematic Review-To Ablate or Not to Ablate?

Intensified systemic therapy in metastatic renal cell carcinoma (mRCC) has led to improved patient outcomes. Patients commonly require local control of one or a few metastases. The aim was to evaluate metastasis-directed ablative therapies in extracranial mRCC. Two databases and one registry were searched, using the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) approach, for all prospective and matched-pair case-control mRCC studies of radiofrequency ablation (RFA), cryotherapy, microwave ablation (MWA), and stereotactic body radiotherapy (SBRT). Eighteen studies were identified. Fourteen investigated SBRT in 424 patients. Four thermal ablation studies were identified: two cryotherapy (56 patients) and two RFA studies (90 patients). The median participant number was 30 (range 12-69). The combined median follow-up was 17.3 months (range 8-52). Four SBRT studies reported local control (LC) at 12 months, median 84.4% (range 82.5-93). Seven studies (six SBRT and one cryotherapy) reported an LC rate of median 87% (79-100%). Median overall survival (OS) was reported in eight studies (five SBRT, two cryotherapy, and one RFA) with a median of 22.7 months (range 6.7-not reached). Median progression-free survival was reported in seven studies (five SBRT, one cryotherapy, and one RFA); the median was 9.3 months (range 3.0-22.7 months). Grade ≥ 3 toxicity ranged from 1.7% to 10%. SBRT has excellent local control outcomes and acceptable toxicity. Only four eligible thermal ablative studies were identified and could not be compared with SBRT. Translationally rich definitive studies are warranted.

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.

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.

Independent predictors of vertebral compression fracture following radiation for metastatic spine disease

OBJECTIVE

The goal of this study was to determine independent risk factors for vertebral compression fracture (VCF) following radiation for metastatic spine disease, including low bone mineral density as estimated by Hounsfield units (HU).

METHODS

A retrospective chart review identified patients with a single vertebral column metastasis treated with radiation therapy, a pretreatment CT scan, and a follow-up CT scan at least 6 weeks after treatment. Patients with primary spine tumors, preradiation vertebroplasty, preradiation spine surgery, prior radiation to the treatment field, and proton beam treatment modality were excluded. The HU were measured in the vertebral bodies at the level superior to the metastasis, within the tumor and medullary bone of the metastatic level, and at the level inferior to the metastasis. Variables collected included basic demographics, Spine Instability Neoplastic Score (SINS), presenting symptoms, bone density treatment, primary tumor pathology, Weinstein-Boriani-Biagini (WBB) classification, Enneking stage, radiation treatment details, chemotherapy regimen, and prophylactic vertebroplasty.

RESULTS

One hundred patients with an average age of 63 years and average follow-up of 18 months with radiation treatment dates ranging from 2017 to 2020 were included. Fifty-nine patients were treated with external-beam radiation therapy, with a median total dose of 20 Gy (range 8-40 Gy). Forty-one patients were treated with stereotactic body radiation therapy, with a median total dose of 24 Gy (range 18-39 Gy). The most common primary pathologies included lung (n = 22), prostate (n = 21), and breast (n = 14). Multivariable logistic regression analysis (area under the curve 0.89) demonstrated pretreatment HU (p < 0.01), SINS (p = 0.02), involvement of ≥ 3 WBB sectors (p < 0.01), primary pathology other than prostate (p = 0.04), and ongoing chemotherapy treatment (p = 0.04) to be independent predictors of postradiation VCF. Patients with pretreatment HU < 145 (n = 32), 145-220 (n = 31), and > 220 (n = 37) had a fracture rate of 59%, 39%, and 11%, respectively. An HU cutoff of 157 was found to maximize sensitivity (71%) and specificity (75%) in predicting postradiation VCF.

CONCLUSIONS

Low preradiation HU, higher SINS, involvement of ≥ 3 WBB sectors, ongoing chemotherapy, and nonprostate primary pathology were independent predictors of postradiation VCF in patients with metastatic spine disease. Low bone mineral density, as estimated by HU, is a novel and potentially modifiable risk factor for VCF.

Multidisciplinary management of spinal metastases: what the radiologist needs to know

The modern management of spinal metastases requires a multidisciplinary approach that includes radiation oncologists, surgeons, medical oncologists, and diagnostic and interventional radiologists. The diagnostic radiologist can play an important role in the multidisciplinary team and help guide assessment of disease and selection of appropriate therapy. The assessment of spine metastases is best performed on MRI, but imaging from other modalities is often needed. We provide a review of the clinical and imaging features that are needed by the multidisciplinary team caring for patients with spine metastases and stress the importance of the spine radiologist taking responsibility for synthesizing imaging features across multiple modalities to provide a report that advances patient care.

Evaluation of Load-To-Strength Ratios in Metastatic Vertebrae and Comparison With Age- and Sex-Matched Healthy Individuals

Vertebrae containing osteolytic and osteosclerotic bone metastases undergo pathologic vertebral fracture (PVF) when the lesioned vertebrae fail to carry daily loads. We hypothesize that task-specific spinal loading patterns amplify the risk of PVF, with a higher degree of risk in osteolytic than in osteosclerotic vertebrae. To test this hypothesis, we obtained clinical CT images of 11 cadaveric spines with bone metastases, estimated the individual vertebral strength from the CT data, and created spine-specific musculoskeletal models from the CT data. We established a musculoskeletal model for each spine to compute vertebral loading for natural standing, natural standing + weights, forward flexion + weights, and lateral bending + weights and derived the individual vertebral load-to-strength ratio (LSR). For each activity, we compared the metastatic spines' predicted LSRs with the normative LSRs generated from a population-based sample of 250 men and women of comparable ages. Bone metastases classification significantly affected the CT-estimated vertebral strength (Kruskal-Wallis, p < 0.0001). Post-test analysis showed that the estimated vertebral strength of osteosclerotic and mixed metastases vertebrae was significantly higher than that of osteolytic vertebrae (p = 0.0016 and p = 0.0003) or vertebrae without radiographic evidence of bone metastasis (p = 0.0010 and p = 0.0003). Compared with the median (50%) LSRs of the normative dataset, osteolytic vertebrae had higher median (50%) LSRs under natural standing (p = 0.0375), natural standing + weights (p = 0.0118), and lateral bending + weights (p = 0.0111). Surprisingly, vertebrae showing minimal radiographic evidence of bone metastasis presented significantly higher median (50%) LSRs under natural standing (p < 0.0001) and lateral bending + weights (p = 0.0009) than the normative dataset. Osteosclerotic vertebrae had lower median (50%) LSRs under natural standing (p < 0.0001), natural standing + weights (p = 0.0005), forward flexion + weights (p < 0.0001), and lateral bending + weights (p = 0.0002), a trend shared by vertebrae with mixed lesions. This study is the first to apply musculoskeletal modeling to estimate individual vertebral loading in pathologic spines and highlights the role of task-specific loading in augmenting PVF risk associated with specific bone metastatic types. Our finding of high LSRs in vertebrae without radiologically observed bone metastasis highlights that patients with metastatic spine disease could be at an increased risk of vertebral fractures even at levels where lesions have not been identified radiologically.

Stereotactic radiotherapy (SRT) for differentiated thyroid cancer (DTC) oligometastases: an AIRO (Italian association of radiotherapy and clinical oncology) systematic review

PURPOSE

The aim of this systematic review was to examine efficacy of stereotactic radiotherapy (SRT) in patients with oligometastatic thyroid cancer.

MATERIALS AND METHODS

A systematic search was conducted by means of PubMed, Scopus, and Cochrane library.

CLINICALTRIALS

gov was searched for ongoing or recently completed trials, and PROSPERO was searched for ongoing or recently completed systematic reviews. We analyzed only clinical studies as full text carried out on patients with oligometastatic thyroid cancer treated with SRT. Conference papers, surveys, letters, editorials, book chapters, and reviews were excluded. Time of publication was restricted to the years 1990-2021.

RESULTS

The number of evaluated patients was 146 (267 lesions), and the median age was 58 years. The median 1-year local control (LC) was 82% (range 67.0%-97.1%); the median disease-free survival (DFS) was 12 months (range 4-53); the median 1-year overall survival was 72% (range 66.6%-85.0%); the 3-year cancer-specific survival was 75.0%; and the 4-year cancer-specific survival was 37.5%. No grade 3-5 acute toxicity was reported. No late effects were recorded.

CONCLUSIONS

SRT for oligometastases from thyroid cancer as salvage therapy is well tolerated and yields high rates of LC and prolonged DFS.

CIRSE Standards of Practice on Thermal Ablation of Bone Tumours

Background

Percutaneous thermal ablation is an effective, minimally invasive means of treating a variety of focal benign and malignant osseous lesions. To determine the role of ablation in individual cases, multidisciplinary team (MDT) discussion is required to assess the suitability and feasibility of a thermal ablative approach, to select the most appropriate technique and to set the goals of treatment i.e. curative or palliative.

Purpose

This document will presume the indication for treatment is clear and approved by the MDT and will define the standards required for the performance of each modality. CIRSE Standards of Practice documents are not intended to impose a standard of clinical patient care, but recommend a reasonable approach to, and best practices for, the performance of thermal ablation of bone tumours.

Methods

The writing group was established by the CIRSE Standards of Practice Committee and consisted of five clinicians with internationally recognised expertise in thermal ablation of bone tumours. The writing group reviewed the existing literature on thermal ablation of bone tumours, performing a pragmatic evidence search using PubMed to search for publications in English and relating to human subjects from 2009 to 2019. Selected studies published in 2020 and 2021 during the course of writing these standards were subsequently included. The final recommendations were formulated through consensus.

Results

Recommendations were produced for the performance of thermal ablation of bone tumours taking into account the biologic behaviour of the tumour and the therapeutic intent of the procedure. Recommendations are provided based on lesion characteristics and thermal modality, for the use of tissue monitoring and protection, and for the appropriately timed application of adjunctive procedures such as osseus consolidation and transarterial embolisation.

Results

Percutaneous thermal ablation has an established role in the successful management of bone lesions, with both curative and palliative intent. This Standards of Practice document provides up-to-date recommendations for the safe performance of thermal ablation of bone tumours.

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.

Radiomic modeling to predict risk of vertebral compression fracture after stereotactic body radiation therapy for spinal metastases

OBJECTIVE

In the treatment of spinal metastases with stereotactic body radiation therapy (SBRT), vertebral compression fracture (VCF) is a common and potentially morbid complication. Better methods to identify patients at high risk of radiation-induced VCF are needed to evaluate prophylactic measures. Radiomic features from pretreatment imaging may be employed to more accurately predict VCF. The objective of this study was to develop and evaluate a machine learning model based on clinical characteristics and radiomic features from pretreatment imaging to predict the risk of VCF after SBRT for spinal metastases.

METHODS

Vertebral levels C2 through L5 containing metastases treated with SBRT were included if they were naive to prior surgery or radiation therapy, target delineation was based on consensus guidelines, and 1-year follow-up data were available. Clinical features, including characteristics of the patient, disease, and treatment, were obtained from chart review. Radiomic features were extracted from the planning target volume (PTV) on pretreatment CT and T1-weighted MRI. Clinical and radiomic features selected by least absolute shrinkage and selection operator (LASSO) regression were included in random forest classification models, which were trained to predict VCF within 1 year after SBRT. Model performance was assessed with leave-one-out cross-validation.

RESULTS

Within 1 year after SBRT, 15 of 95 vertebral levels included in the analysis demonstrated new or progressive VCF. Selected clinical features included BMI, performance status, total prescription dose, dose to 99% of the PTV, lumbar location, and 2 components of the Spine Instability Neoplastic Score (SINS): lytic tumor character and spinal misalignment. Selected radiomic features included 5 features from CT and 3 features from MRI. The best-performing classification model, derived from a combination of selected clinical and radiomic features, demonstrated a sensitivity of 0.844, specificity of 0.800, and area under the receiver operating characteristic (ROC) curve (AUC) of 0.878. This model was significantly more accurate than alternative models derived from only selected clinical features (AUC = 0.795, p = 0.048) or only components of the SINS (AUC = 0.579, p < 0.0001).

CONCLUSIONS

In the treatment of spinal metastases with SBRT, a machine learning model incorporating both clinical features and radiomic features from pretreatment imaging predicted VCF at 1 year after SBRT with excellent sensitivity and specificity, outperforming models developed from clinical features or components of the SINS alone. If validated, these findings may allow more judicious selection of patients for prophylactic interventions.

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.

Improved estimates of strength and stiffness in pathologic vertebrae with bone metastases using CT-derived bone density compared with radiographic bone lesion quality classification

OBJECTIVE

The aim of this study was to compare the ability of 1) CT-derived bone lesion quality (classification of vertebral bone metastases [BM]) and 2) computed CT-measured volumetric bone mineral density (vBMD) for evaluating the strength and stiffness of cadaver vertebrae from donors with metastatic spinal disease.

METHODS

Forty-five thoracic and lumbar vertebrae were obtained from cadaver spines of 11 donors with breast, esophageal, kidney, lung, or prostate cancer. Each vertebra was imaged using microCT (21.4 μm), vBMD, and bone volume to total volume were computed, and compressive strength and stiffness experimentally measured. The microCT images were reconstructed at 1-mm voxel size to simulate axial and sagittal clinical CT images. Five expert clinicians blindly classified the images according to bone lesion quality (osteolytic, osteoblastic, mixed, or healthy). Fleiss' kappa test was used to test agreement among 5 clinical raters for classifying bone lesion quality. Kruskal-Wallis ANOVA was used to test the difference in vertebral strength and stiffness based on bone lesion quality. Multivariable regression analysis was used to test the independent contribution of bone lesion quality, computed vBMD, age, gender, and race for predicting vertebral strength and stiffness.

RESULTS

A low interrater agreement was found for bone lesion quality (κ = 0.19). Although the osteoblastic vertebrae showed significantly higher strength than osteolytic vertebrae (p = 0.0148), the multivariable analysis showed that bone lesion quality explained 19% of the variability in vertebral strength and 13% in vertebral stiffness. The computed vBMD explained 75% of vertebral strength (p < 0.0001) and 48% of stiffness (p < 0.0001) variability. The type of BM affected vBMD-based estimates of vertebral strength, explaining 75% of strength variability in osteoblastic vertebrae (R2 = 0.75, p < 0.0001) but only 41% in vertebrae with mixed bone metastasis (R2 = 0.41, p = 0.0168), and 39% in osteolytic vertebrae (R2 = 0.39, p = 0.0381). For vertebral stiffness, vBMD was only associated with that of osteoblastic vertebrae (R2 = 0.44, p = 0.0024). Age and race inconsistently affected the model's strength and stiffness predictions.

CONCLUSIONS

Pathologic vertebral fracture occurs when the metastatic lesion degrades vertebral strength, rendering it unable to carry daily loads. This study demonstrated the limitation of qualitative clinical classification of bone lesion quality for predicting pathologic vertebral strength and stiffness. Computed CT-derived vBMD more reliably estimated vertebral strength and stiffness. Replacing the qualitative clinical classification with computed vBMD estimates may improve the prediction of vertebral fracture risk.

Current Management of Bone Metastases from Differentiated Thyroid Cancer

Simple Summary

Patients with bone metastases (BMs) from differentiated thyroid carcinoma (DTC) can live longer than those with BMs from other cancers. BMs from DTC create destructive lesions and easily cause intractable pain and neurological symptoms, including paralysis. These symptoms related to BMs affect mortality directly and indirectly by hampering the application of systemic therapies. Therefore, long-term local control of BMs in patients with DTC is desired, especially in patients with single or a small number of metastases. Local treatments for BMs have recently become advanced and sophisticated in surgery, radiotherapy, and percutaneous procedures. These therapies, either alone or in combination with other treatments, can effectively improve, or prevent the deterioration of, the performance status and quality of life of patients with DTC-BM. Among local therapies, complete surgical resection and stereotactic radiosurgery are the mainstay for achieving long-term control of DTC-BM.

Abstract

After the lung, the skeleton is the second most common site of distant metastases in differentiated thyroid carcinoma (DTC). Patients with osteolytic bone metastases (BMs) from thyroid carcinoma often have significantly reduced performance status and quality of life. Recent advancements in cancer therapy have improved overall survival in multiple cancer subtypes, including thyroid cancer. Therefore, long-term local control of thyroid BMs is desired, especially in patients with a single metastasis or oligometastases. Here, we reviewed the current management options for DTC-BMs and especially focused on local treatments for long-term local tumor control from an orthopedic tumor surgeon’s point of view. Metastasectomy and stereotactic radiosurgery can be performed either alone or in combination with radioiodine therapy and kinase inhibitors to cure skeletal lesions in selected patients. Percutaneous procedures have been developed in recent years, and they can also have a curative role in small BMs. Recent advancements in local therapies have the potential to provide not only long-term local tumor control but also a better prognosis.

A Volumetric Dosimetry Analysis of Vertebral Body Fracture Risk after Single Fraction Spine Stereotactic Body Radiotherapy

PURPOSE

Vertebral compression fractures (VCF) are a common and severe complication of spine stereotactic body radiotherapy (SBRT). We sought to analyze how volumetric dosimetry and clinical factors were associated with the risk of VCF.

METHODS AND MATERIALS

We evaluated 173 spinal segments undergoing single fraction SBRT in 85 patients from a retrospective database. Vertebral bodies were contoured and dosimetric values were calculated. Competing risk models were used to evaluate the effect of clinical and dosimetry variables on the risk of VCF.

RESULTS

Our primary endpoint was development of a post SBRT VCF. New or progressive fractures were noted in 21/173 vertebrae (12.1%); the median time to fracture was 322 days. Median follow up time was 426 days. Upon multivariable analysis, the percentages of vertebral body volume receiving >20 Gy and >24 Gy were significantly associated with increased risk of VCF (HR: 1.036, 1.104; p = 0.029, 0.044 respectively). No other patient or treatment factors were found to be significant on multivariable analysis. Sensitivity analysis revealed that the percentages of vertebral body volume receiving >20 Gy and >24 Gy required to obtain 90% sensitivity for predicting vertebral body fracture were 24% and 0%, respectively.

CONCLUSIONS

VCF is a common complication after SBRT with a crude incidence of 12.1%. Treatment plans that permit higher volumes receiving doses >20 Gy and >24 Gy to the vertebral body are associated with increased risk of VCF. In order to achieve 90% sensitivity for predicting VCF post SBRT, the percentage of vertebral volume receiving >20 Gy should be <24% and maximum point dose should be <24 Gy. These results may help guide clinicians when evaluating spine SBRT treatment plans to minimize the risk of developing post-treatment VCF.

Effects of Single-Dose Versus Hypofractionated Focused Radiation on Vertebral Body Structure and Biomechanical Integrity: Development of a Rabbit Radiation-Induced Vertebral Compression Fracture Model

PURPOSE

Vertebral compression fracture is a common complication of spinal stereotactic body radiation therapy. Development of an in vivo model is crucial to fully understand how focal radiation treatment affects vertebral integrity and biology at various dose fractionation regimens. We present a clinically relevant animal model to analyze the effects of localized, high-dose radiation on vertebral microstructure and mechanical integrity. Using this model, we test the hypothesis that fractionation of radiation dosing can reduce focused radiation therapy's harmful effects on the spine.

METHODS AND MATERIALS

The L5 vertebra of New Zealand white rabbits was treated with either a 24-Gy single dose of focused radiation or 3 fractionated 8-Gy doses over 3 consecutive days via the Small Animal Radiation Research Platform. Nonirradiated rabbits were used as controls. Rabbits were euthanized 6 months after irradiation, and their lumbar vertebrae were harvested for radiologic, histologic, and biomechanical testing.

RESULTS

Localized single-dose radiation led to decreased vertebral bone volume and trabecular number and a subsequent increase in trabecular spacing and thickness at L5. Hypofractionation of the radiation dose similarly led to reduced trabecular number and increased trabecular spacing and thickness, yet it preserved normalized bone volume. Single-dose irradiated vertebrae displayed lower fracture loads and stiffness compared with those receiving hypofractionated irradiation and with controls. The hypofractionated and control groups exhibited similar fracture load and stiffness. For all vertebral samples, bone volume, trabecular number, and trabecular spacing were correlated with fracture loads and Young's modulus (P < .05). Hypocellularity was observed in the bone marrow of both irradiated groups, but osteogenic features were conserved in only the hypofractionated group.

CONCLUSIONS

Single-dose focal irradiation showed greater detrimental effects than hypofractionation on the microarchitectural, cellular, and biomechanical characteristics of irradiated vertebral bodies. Correlation between radiologic measurements and biomechanical properties supported the reliability of this animal model of radiation-induced vertebral compression fracture, a finding that can be applied to future studies of preventative measures.

Clinical and dosimetric risk factors for vertebral compression fracture after single-fraction stereotactic body radiation therapy for spine metastases

Objectives

This analysis was performed to evaluate the incidence of vertebral compression fracture (VCF) and determine the contributing factors for VCF in patients undergoing single-fraction stereotactic body radiotherapy (SBRT) for spinal bone metastases (SBM).

Methods

A retrospective review of medical records was conducted for patients undergoing SBRT for SBM at our institution between January 2010 and December 2018. Patients who had undergone neither pre-SBRT surgical excision nor post-SBRT prophylactic fixation were included. The effects of clinical and dosimetric parameters were analyzed with respect to VCF risk. The following dosimietric parameters of the planning target volume (PTV) were calculated: mean/minimum/maximum dose, radiation dose to 10-90% volume, and irradiated volume receiving more than 10-25 Gy (PTV_V_{10 - 25 Gy}).

Results

Among 163 patients (179 vertebrae), 21 (12.8%) experienced VCF. The 1-year and 2-year VCF rates were 12.1% and 13.2%, respectively. Among dosimetric parameters, PTV_V15 Gy was the most significant for VCF prediction. In a univariate analysis, breast or prostate primary, no vertebral body collapse, and PTV_V_{15 Gy} ≤42 cm³ were significantly associated with a lower incidence rate of VCF. In a multivariate analysis, PTV_V_{15 Gy} was the only significant factor for VCF risk. The 1-year VCF rate was 3.8% in patients with PTV_V_{15 Gy} ≤42 cm³, while it was 22.1% in those with PTV_V_{15 Gy} > 42 cm³ (p < 0.01).

Conclusions

SBRT-related VCF was found in 12% of patients in our institution. The PTV_V_{15 Gy} is a significant factor for VCF prediction.

Vertebral compression fracture rate following stereotactic ablative body radiotherapy for spine oligometastases: a UK experience

Aim:

Stereotactic ablative body radiotherapy (SABR) for spine metastases is associated with a risk of vertebral compression fracture (VCF). The aim of this study was to determine the rate of VCF at one UK institution and evaluate the use of the Spinal Instability Neoplastic Score (SINS) to predict these.

Materials and methods:

A retrospective analysis of all patients who underwent SABR for spinal metastases between 2014 and 2018 at one UK institution was performed. Basic demographic data were collected, and SINS prior to SABR was calculated. The primary outcome was VCF rate. Secondary outcomes included time to VCF and need for surgical intervention following VCF.

Results:

A total of 48 oligometastases were treated with a median follow-up of 20·5 months. A maximum of two vertebral bodies were treated. The median baseline SINS was calculated as 3. The median dose was 26 Gy in three fractions. Two patients were reported to have VCF and both were successfully conservatively managed.

Findings:

SABR for spine oligometastases is being performed safely with low VCF rates which are comparable with those in international publications. This may be as a result of strict adherence to criteria for delivery of SABR with low pre-treatment SINS.

Percutaneous bipolar radiofrequency ablation for spine metastatic lesions

PURPOSE

The purpose of this review is to become familiar with the most common indications for imaging guided percutaneous bipolar radiofrequency ablation, to learn about different technical considerations during performance providing the current evidence. Controversies concerning products will be addressed.

METHODS

We performed a literature review excluding non-English studies and case reports. All references of the obtained articles were also evaluated for any additional information.

RESULTS

RFA achieves cytotoxicity by raising target area temperatures above 60 °C, and may be used to achieve total necrosis of lesions smaller than 3 cm in diameter, to debulk and reduce the pain associated with larger lesions, to prevent pathological fractures due to progressive osteolysis or for cavity creation aiming for targeted cement delivery in case of posterior vertebral wall breaching. Protective ancillary techniques should be used in order to increase safety and augment efficacy of RFA in the spine.

CONCLUSION

Percutaneous radiofrequency ablation of vertebral lesions is a reproducible, successful and safe procedure. Ablation should be combined with vertebral augmentation in all cases. In order to optimize maximum efficacy a patient- and a lesion-tailored approach should both be offered focusing upon clinical and performance status along with life expectancy of the patient as well as upon lesion characteristics.

Accuracy and precision of the spinal instability neoplastic score (SINS) for predicting vertebral compression fractures after radiotherapy in spinal metastases: a meta-analysis

Radiotherapy has played an important role in the treatment of spinal metastases. One of the major complications of radiotherapy is vertebral compression fracture (VCF). Although the spinal instability neoplastic score (SINS) was developed for evaluating spinal instability in patients with spinal metastases, it is also commonly used to predict VCF after radiotherapy in patients with spinal metastases. However, its accuracy for predicting radiotherapy-induced VCF and precision remain controversial. The aim of this study was to clarify the diagnostic value of the SINS to predict radiotherapy-induced VCF and to make recommendations for improving its diagnostic power. We searched core databases and identified 246 studies. Fourteen studies were analyzed, including 7 studies (with 1269 segments) for accuracy and 7 studies (with 280 patients) for precision. For accuracy, the area under the summary receiver operating characteristic curve was 0.776. When a SINS cut-off value of 7 was used, as was done in the included studies, the pooled sensitivity was 0.790 and the pooled specificity was 0.546. For precision, the summary estimate of interobserver agreement was the highest dividing 2 categories based on a cut-off value of 7, and the value was 0.788. The body collapse showed moderate relationship and precision with the VCF. The lytic tumor of bone lesion showed high accuracy and fair reliability, while location had excellent reliability, but low accuracy. The SINS system can be used to predict the occurrence of VCF after radiotherapy in spinal metastases with moderate accuracy and substantial reliability. Increasing the cut-off value and revising the domains may improve the diagnostic performance to predict the VCF of the SINS.

Bone metastases from differentiated thyroid carcinoma: current knowledge and open issues

Bone represents the second most common site of distant metastases in differentiated thyroid cancer (DTC). The clinical course of DTC patients with bone metastases (BM) is quite heterogeneous, but generally associated with low survival rates. Skeletal-related events might be a serious complication of BM, resulting in high morbidity and impaired quality of life. To achieve disease control and symptoms relief, multimodal treatment is generally required: radioiodine therapy, local procedures-including surgery, radiotherapy and percutaneous techniques-and systemic therapies, such as kinase inhibitors and antiresorptive drugs. The management of DTC with BM is challenging: a careful evaluation and a personalized approach are essential to improve patients' outcomes. To date, prospective studies focusing on the main clinical aspects of DTC with BM are scarce; available analyses mainly include cohorts assembled over multiple decades, small samples sizes and data about BM not always separated from those regarding other distant metastases. The aim of this review is to summarize the most recent evidences and the unsolved questions regarding BM in DTC, analyzing several key issues: pathophysiology, prognostic factors, role of anatomic and functional imaging, and clinical management.

Biomechanical Properties of Metastatically Involved Osteolytic Bone

PURPOSE OF REVIEW

Skeletal metastasis involves the uncoupling of physiologic bone remodeling resulting in abnormal bone turnover and radical changes in bony architecture, density, and quality. Bone strength assessment and fracture risk prediction are critical in clinical treatment decision-making. This review focuses on bone tissue and structural mechanisms altered by osteolytic metastasis and the resulting changes to its material and mechanical behavior.

RECENT FINDINGS

Both organic and mineral phases of bone tissue are altered by osteolytic metastatic disease, with diminished bone quality evident at multiple length-scales. The mechanical performance of bone with osteolytic lesions is influenced by a combination of tissue-level and structural changes. This review considers the effects of osteolytic metastasis on bone biomechanics demonstrating its negative impact at tissue and structural levels. Future studies need to assess the cumulative impact of cancer treatments on metastatically involved bone quality, and its utility in directing multimodal treatment planning.

Early palliative radiation versus observation for high-risk asymptomatic or minimally symptomatic bone metastases: study protocol for a randomized controlled trial

Background

In patients with metastatic cancer, the bone is the third-most common site of involvement. Radiation to painful bone metastases results in high rates of pain control and is an integral part of bone metastases management. Up to one-third of inpatient consults are requested for painful bone metastases, and up to 60% of these patients had evidence of these lesions visible on prior imaging. Meanwhile recent advances have reduced potential side effects of radiation. Therefore, there is an opportunity to further improve outcomes for patients using prophylactic palliative radiation to manage asymptomatic bone metastases.

Methods/study design

In this trial, 74 patients with metastatic solid tumors and high-risk asymptomatic or minimally symptomatic bone metastases will be enrolled and randomized to early palliative radiation or standard of care. This will be the first trial to assess the efficacy of prophylactic palliative radiation in preventing skeletal related events (SREs), the primary endpoint. This endpoint was selected to encompass patient-centered outcomes that impact quality of life including pathologic fracture, spinal cord compression, and intervention with surgery or radiation. Secondary endpoints include hospitalizations, Bone Pain Index, pain-free survival, pain-related quality of life, and side effects of radiation therapy.

Discussion

In this study, we propose a novel definition of high-risk bone metastases most likely to benefit from preventive radiation and use validated questionnaires to assess pain and impact on quality of life and health resource utilization. Observations from early patient enrollment have demonstrated robustness of the primary endpoint and need for minor modifications to Bone Pain Index and data collection for opioid use and hospitalizations. With increasing indications for radiation in the oligometastatic setting, this trial aims to improve patient-centered outcomes in the polymetastatic setting.

Trial registration

ISRCTN Number/Clinical trials.gov, ID:NCT03523351. Registered on 14 May 2018.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12885-020-07591-w.

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.

CT based quantitative measures of the stability of fractured metastatically involved vertebrae treated with spine stereotactic body radiotherapy

Mechanical instability secondary to vertebral metastases can lead to pathologic vertebral compression fracture (VCF) mechanical pain, neurological compromise, and the need for surgical stabilization. Stereotactic body radiation therapy (SBRT) as a treatment for spinal metastases is effective for pain and local tumor control, it has been associated with an increased risk of VCF. This study quantified computed tomography (CT) based stability measures in metastatic vertebrae with VCF treated with spine SBRT. It was hypothesized that semi-automated quantification of VCF based on CT metrics would be related to clinical outcomes. 128 SBRT treated spinal metastases patients were identified from a prospective database. Of these, 18 vertebral segments were identified with a VCF post-SBRT. A semi-automated system for quantifying VCF was developed based on CT imaging before and after SBRT. The system identified and segmented SBRT treated vertebral bodies, calculated stability metrics at single time points and changes over time. In the vertebrae that developed a new (n = 7) or progressive (n = 11) VCF following SBRT, the median time to VCF/VCF progression was 1.74 months (range 0.53-7.79 months). Fractured thoracolumbar vertebrae that went on to be stabilized (cemented and/or instrumented), had greater fractured vertebral body volume progression over time (12%) compared to those not stabilized (0.4%, p < 0.05). Neither the spinal instability neoplastic score (SINS) or any single timepoint stability metrics in post-hoc analyses correlated with future stabilization. This pilot study presents a quantitative semi-automated method assessing fractured thoracolumbar vertebrae based on CT. Increased fractured vertebral body volume progression post-SBRT was shown to predict those patients who were subsequently stabilized, motivating study of methods that assess temporal radiological changes toward augmenting existing clinical management in the metastatic spine.

The effects of metastatic lesion on the structural determinants of bone: Current clinical and experimental approaches

Metastatic bone disease is incurable with an associated increase in skeletal-related events, particularly a 17-50% risk of pathologic fractures. Current surgical and oncological treatments are palliative, do not reduce overall mortality, and therefore optimal management of adults at risk of pathologic fractures presents an unmet medical need. Plain radiography lacks specificity and may result in unnecessary prophylactic fixation. Radionuclide imaging techniques primarily supply information on the metabolic activity of the tumor or the bone itself. Magnetic resonance imaging and computed tomography provide excellent anatomical and structural information but do not quantitatively assess bone matrix. Research has now shifted to developing unbiased data-driven tools that can predict risk of impending fractures and guide individualized treatment decisions. This review discusses the state-of-the-art in clinical and experimental approaches for prediction of pathologic fractures with bone metastases. Alterations in bone matrix quality are associated with an age-related increase in skeletal fragility but the impact of metastases on the intrinsic material properties of bone is unclear. Engineering-based analyses are non-invasive with the capability to evaluate oncological treatments and predict failure due to the progression of metastasis. The combination of these approaches may improve our understanding of the underlying deterioration in mechanical performance.

Vertebral body fracture rates after stereotactic body radiation therapy compared with external-beam radiation therapy for metastatic spine tumors

OBJECTIVE

Stereotactic body radiation therapy (SBRT) is utilized to deliver highly conformal, dose-escalated radiation to a target while sparing surrounding normal structures. Spinal SBRT can allow for durable local control and palliation of disease while minimizing the risk of damage to the spinal cord; however, spinal SBRT has been associated with an increased risk of vertebral body fractures. This study sought to compare the fracture rates between SBRT and conventionally fractionated external-beam radiation therapy (EBRT) in patients with metastatic spine tumors.

METHODS

Records from patients treated at the University of California, San Francisco, with radiation therapy for metastatic spine tumors were retrospectively reviewed. Vertebral body fracture and local control rates were compared between SBRT and EBRT. Ninety-six and 213 patients were identified in the SBRT and EBRT groups, respectively. Multivariate analysis identified the need to control for primary tumor histology (p = 0.003 for prostate cancer, p = 0.0496 for renal cell carcinoma). The patient-matched EBRT comparison group was created by matching SBRT cases using propensity scores for potential confounders, including the Spinal Instability Neoplastic Score (SINS), the number and location of spine levels treated, sex, age at treatment, duration of follow-up (in months) after treatment, and primary tumor histology. Covariate balance following group matching was confirmed using the Student t-test for unequal variance. Statistical analysis, including propensity score matching and multivariate analysis, was performed using R software and related packages.

RESULTS

A total of 90 patients met inclusion criteria, with 45 SBRT and 45 EBRT matched cases. Balance of the covariates, SINS, age, follow-up time, and primary tumor histology after the matching process was confirmed between groups (p = 0.062, p = 0.174, and 0.991, respectively, along with matched tumor histology). The SBRT group had a higher 5-year rate of vertebral body fracture at 22.22% (n = 10) compared with 6.67% (n = 3) in the EBRT group (p = 0.044). Survival analysis was used to adjust for uneven follow-up time and showed a significant difference in fracture rates between the two groups (p = 0.044). SBRT also was associated with a higher rate of local control (86.67% vs 77.78%).

CONCLUSIONS

Patients with metastatic cancer undergoing SBRT had higher rates of vertebral body fractures compared with patients undergoing EBRT, and this difference held up after survival analysis. SBRT also had higher rates of initial local control than EBRT but this difference did not hold up after survival analysis, most likely because of a high percentage of radiosensitive tumors in the EBRT cohort.

Conventional Radiotherapy and Stereotactic Radiosurgery in the Management of Metastatic Spine Disease

Spinal metastases are a common manifestation of malignant tumors that can cause severe pain, spinal cord compression, pathological fractures, and hypercalcemia, and these clinical manifestations will ultimately reduce the health-related quality of life and even shorten life expectancy in patient with cancer. Effective management of spinal bone metastases requires multidisciplinary collaboration, including radiologists, surgeons, radiation oncologists, medical oncologists, and pain specialists. In the past few decades, conventional radiotherapy has been the most common form of radiotherapy, which can achieve favorable local control and pain relief; however, it lacks precise methods of delivering radiation and thus cannot provide sufficient tumoricidal dose. The advent of stereotactic radiosurgery has changed this situation by using highly focused radiation beams guided by 3-dimensional imaging to deliver a high biologic equivalent dose to the target region, and the spinal cord can be identified and excluded from the target volume to reduce the risk of radiation-induced myelopathy. Separation surgery can provide a 2- to 3-mm safe separation of tumor and spinal cord to avoid radiation-induced damage to the spinal cord. Targets for separation surgery include decompression of metastatic epidural spinal cord compression and spinal stabilization without partial or en bloc tumor resection. Combined with conventional radiotherapy, stereotactic radiosurgery can provide better local tumor control and pain relief. Several scoring systems have been developed to estimate the life expectancy of patients with spinal metastases treated with radiotherapy. Thorough understanding of radiotherapy-related knowledge including the dose-fractionation schedule, separation surgery, efficacy and safety, scoring systems, and feasibility of combination with other treatment methods is critical to providing optimal patient care.

Normal tissue complication probability of vertebral compression fracture after stereotactic body radiotherapy for de novo spine metastasis

OBJECTIVE

Stereotactic body radiotherapy (SBRT) for spine metastases is associated with post-treatment vertebral compression fracture (VCF). The purpose of this study is to identify clinical and radiation planning characteristics that predict post-SBRT VCF through a novel normal tissue complication probability (NTCP) analysis.

METHODS

Patients with de novo spine metastases treated with SBRT between 2009 and 2018 at a single institution were included. Those who had surgical stabilization or radiation to the same site prior to SBRT were excluded. VCF was defined as new development or progression of existing vertebral body height loss not attributable to tumor growth. Probit NTCP models were constructed and fitted using a maximum likelihood approach. A multivariate proportional hazard model was used to estimate time to VCF using the Fine and Gray method.

RESULTS

Three hundred and two vertebral segments from 193 patients were treated with a median dose of 24 Gy in 3 fractions (range 15-30 Gy in 1-5 fractions). With a median follow up of 13.9 months, local control was 89.3% at 1 year. A total of 26 SBRT-induced VCFs were observed, with 1 and 2-year cumulative incidences of 4.6% and 6.7%. NTCP modeling demonstrated a steep response of VCF risk to the dose to 80% and 50% volume of the planning target volume (PTV D80% and D50%), but not maximum dose or dose to 1 cc or 10% of PTV. D80% of 25 Gy and D50% of 28 Gy in 3 fractions corresponded to 10% VCF risk. On multivariate analysis, lower body mass index (HR 0.90 per unit increase, p = 0.04), total spinal instability neoplastic score (SINS, HR 2.44 unstable vs stable, p = 0.04), and PTV D80% (HR 1.11 for every Gy increase, p = 0.003) were associated with increased VCF risk.

CONCLUSIONS

SBRT provides excellent tumor control for spinal metastases and is associated with low rate of VCF in our cohort. NTCP modeling suggests that the larger volume of spine receiving lower doses are more closely associated with post-SBRT VCF than high dose regions. Under current target delineation methods, common SBRT regimens such as 24 Gy in 2 fractions or 27 Gy in 3 fractions may be inherently associated with VCF risk of 10% or greater. Consensus contouring guidelines should be reevaluated to minimize the volume of irradiated spine in light of these new data.

CT Derived Hounsfield Unit: An Easy Way to Determine Osteoporosis and Radiation Related Fracture Risk in Irradiated Patients

Background: We aimed to evaluate osteoporosis, bone mineral density, and fracture risk in irradiated patients by computerized tomography derived Hounsfield Units (HUs) calculated from radiation treatment planning system.

Methods: Fifty-seven patients operated for gastric adenocarcinoma who received adjuvant abdominal radiotherapy were included in the study group. Thirty-four patients who were not irradiated after surgery comprised the control group. HUs of T12, L1, L2 vertebral bodies were measured from the computerized tomographies imported to the treatment planning system for all the patients. While the measurements were obtained just after surgery and 1 year later after surgery in the control group, the same measurements were obtained just before irradiation and 1 year after radiotherapy in the study group. Percent change in HU values (Δ%HU) was determined for each group. Vertebral compression fractures, which are the consequence of radiation induced osteoporosis and bone toxicity were assessed during follow-up.

Results: There was no statistical significant difference in HU values measured for all the vertebrae between the study and the control group at the onset of the study. While HU values decreased significantly in the study group, there was no significant reduction in HU values in the control group after 1 year. significant correlation was found between Δ%HU and the radiation dose received by each vertebra. Insufficiency fractures (IFs) were observed only in the irradiated patients (4 out of 57 patients) with the cumulative incidence of 7%.

Conclusions: HU values are very valuable in determining bone mineral density and fracture risk. Radiation treatment planning system can be utilized to determine HU values. IFs are common after abdominal radiotherapy in patients with low vertebral HU values detected during radiation treatment planning. Radiation dose to the vertebral bones with low HU values should be limited below 20 Gy to prevent late radiation related bone toxicity.

Imaging response assessment following stereotactic body radiotherapy for solid tumour metastases of the spine: Current challenges and future directions

Patients with metastatic disease are routinely serially imaged to assess disease burden and response to systemic and local therapies, which places ever-expanding demands on our healthcare resources. Image interpretation following stereotactic body radiotherapy (SBRT) for spine metastases can be challenging; however, appropriate and accurate assessment is critical to ensure patients are managed correctly and resources are optimised. Here, we take a critical review of the merits and pitfalls of various imaging modalities, current response assessment guidelines, and explore novel imaging approaches and the potential for radiomics to add value in imaging assessment.

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.

Vertebral Fractures Following Stereotactic Body Radiotherapy for Spine Oligometastases: A Multi-institutional Analysis of Patient Outcomes

AIMS

Stereotactic body radiotherapy (SBRT) is a locally ablative therapy used for the treatment of patients with spine metastases. However, it is associated with higher rates of vertebral compression fractures (VCF) than conventionally fractionated palliative radiotherapy. The purpose of this study was to determine the rate of VCF following spine SBRT and to identify the risk factors associated with this outcome.

MATERIALS AND METHODS

We retrospectively reviewed patients treated at two Australian institutions from January 2015 to March 2019. Descriptive statistics were used to assess patient, tumour and treatment factors. The Log-rank test and Cox proportional hazards model were applied in univariate and multivariable analyses to identify factors associated with VCF, local control and overall survival.

RESULTS

We evaluated 113 spinal segments from 84 patients, with a median follow-up time of 11.9 months. The median dose and fractionation utilised was 30 Gy in three fractions (67.3%), with a single-fraction rate of 0.9%. The median Spinal Instability Neoplastic Score (SINS) of the lesions was 4/18, with most (84.1%) being SINS stable, scoring between 0 and 6. Five VCFs were observed (three progression of pre-existing fractures and two de novo), a cumulative VCF risk of 4.4%. Four of five fractures occurred within the first year after treatment, with a median time to VCF of 9.2 months. A pre-existing VCF (P = 0.011) was associated with subsequent fracture on multivariable analysis, whereas all VCF segments displayed lytic disease appearance. All fractures were managed conservatively with analgesia, without requirement for subsequent surgical intervention.

CONCLUSION

SBRT to spine metastases is safe with respect to VCF, with rates around the lower limit observed in similar studies. Knowledge of factors that predispose to post-treatment fracture, such as pre-existing compression, lytic vertebral disease and SINS >6 will aid in the counselling and selection of patients for this therapy.

Histopathological Findings After Reirradiation Compared to First Irradiation of Spinal Bone Metastases With Stereotactic Body Radiotherapy: A Cohort Study

BACKGROUND

Stereotactic body radiotherapy (SBRT) of the spine provides superior tumor control, but vertebral compression fractures are increased and the pathophysiological process underneath is not well understood. Data on histopathological changes, particularly after salvage SBRT (sSBRT) following conventional irradiation, are scarce.

OBJECTIVE

To investigate surgical specimens after sSBRT and primary SBRT (pSBRT) regarding histopathological changes.

METHODS

We assessed 704 patients treated with spine SBRT 2006 to 2012. Thirty patients underwent salvage surgery; 23 histopathological reports were available. Clinical and histopathological findings were analyzed for sSBRT (69.6%) and pSBRT (30.4%).

RESULTS

Mean time to surgery after sSBRT/pSBRT was 8.3/10.3 mo (P = .64). Reason for surgery included pain (sSBRT/pSBRT: 12.5%/71.4%, P = .25), fractures (sSBRT/pSBRT: 37.5%/28.6%, P = .68), and neurological symptoms (sSBRT/pSBRT: 68.8%/42.9%, P = .24). Radiological tumor progression after sSBRT/pSBRT was seen in 71.4%/42.9% (P = .2). Most specimens displayed viable/proliferative tumor (sSBRT/pSBRT: 62.5%/71.4%, P = .68 and 56.3%/57.1%, P = .97). Few specimens showed soft tissue necrosis (sSBRT/pSBRT: 20%/28.6%, P = .66), osteonecrosis (sSBRT/pSBRT: 14.3%/16.7%, P = .89), or bone marrow fibrosis (sSBRT/pSBRT: 42.9%/33.3%, P = .69). Tumor bed necrosis was more common after sSBRT (81.3%/42.9%, P = .066). Radiological tumor progression correlated with viable/proliferative tumor (P = .03/P = .006) and tumor bed necrosis (P = .03). Fractures were increased with bone marrow fibrosis (P = .07), but not with osteonecrosis (P = .53) or soft tissue necrosis (P = .19). Neurological symptoms were common with radiological tumor progression (P = .07), but not with fractures (P = .18).

CONCLUSION

For both, sSBRT and pSBRT, histopathological changes were similar. Neurological symptoms were attributable to tumor progression and pathological fractures were not associated with osteonecrosis or tumor progression.

Importance of Spinal Alignment in Primary and Metastatic Spine Tumors

Spinal alignment, particularly with respect to spinopelvic parameters, is highly correlated with morbidity and health-related quality-of-life outcomes. Although the importance of spinal alignment has been emphasized in the deformity literature, spinopelvic parameters have not been considered in the context of spine oncology. Because the aim of oncologic spine surgery is mostly palliative, consideration of spinopelvic parameters could improve postoperative outcomes in both the primary and metastatic tumor population by taking overall vertebral stability into account. This review highlights the relevance of focal and global spinal alignment, particularly related to spinopelvic parameters, in the treatment of spine tumors.

Single-Fraction Radiotherapy (SFRT) For Bone Metastases: Patient Selection And Perspectives

Bone metastases are a frequent and important source of morbidity in cancer patients. Stereotactic body radiation therapy (SBRT) is an established treatment option for local control and pain relief of bone metastases, and it is increasingly used as upfront treatment, postoperative consolidation or salvage treatment after prior RT. However, heterogeneity of dose schedules described in literature represents a severe limitation in the definition of the role of SBRT as a standard of care. No consensus is available on the use of single versus multiple fraction SBRT for bone metastases. Advantages of single-fraction SBRT include shorter overall duration of treatment, absence of inter-fraction uncertainty, improved compliance, theoretical increased efficacy, and lower costs. However, caution has been advised due to reports of severe late toxicities, in particular, vertebral collapse fracture (VCF). The aim of this paper is to review dose fractionation and indications for the management of bone metastases using SBRT.