Risk of fracture after single fraction image-guided intensity-modulated radiation therapy to spinal metastases

Spinal chordoma and chondrosarcoma treatment experiences - a 20-year retrospective study from databases of two medical centers

The research retrospectively analyzed cases of spinal chordoma and chondrosarcoma involving patients who received treatment at the two hospitals between 2001 and 2023. Among the 48 patients studied (39 chordoma and 9 chondrosarcoma cases), the average age was 53.9 ± 15.8 years, with a range of 17 to 86 years. Out of these patients, 43 underwent excision surgery and were categorized based on tumor margin into negative (R0) or microscopically positive (R1) margin (n = 14) and macroscopically positive (R2) margin (n = 29) groups. The mean overall survival (OS) for R0/R1 and R2 groups was 156.5 ± 19.3 and 79.2 ± 11.9 months, respectively (p value = 0.012). The mean progression-free survival (PFS) for R0/R1 and R2 was 112.9 ± 24.4 and 25.5 ± 5.5 months (p value < 0.001). The study showed that regardless of whether patients in the R0/R1 or R2 groups received radiation therapy (RT) or not, there was no significant improvement in OS or PFS. Specifically, the OS and PFS for the RT only group were 75.9 ± 16.6 and 73.3 ± 18.0 months. In conclusion, the recommended treatment approach for spinal chordoma and chondrosarcoma remains en bloc resection surgery with an appropriate margin. Patients who are unsuitable for or decline surgery may find a beneficial disease control rate with traditional external beam photon/proton therapy.

Vertebral body collapse after spine stereotactic body radiation therapy: a single-center institutional experience

BACKGROUND

Spine stereotactic body radiation therapy (SBRT) for the treatment of metastatic disease is increasingly utilized owing to improved pain and local control over conventional regimens. Vertebral body collapse (VBC) is an important toxicity following spine SBRT. We investigated our institutional experience with spine SBRT as it relates to VBC and spinal instability neoplastic score (SINS).

PATIENTS AND METHODS

Records of 83 patients with 100 spinal lesions treated with SBRT between 2007 and 2022 were reviewed. Clinical information was abstracted from the medical record. The primary endpoint was post-treatment VBC. Logistic univariate analysis was performed to identify clinical factors associated with VBC.

RESULTS

Median dose and number of fractions used was 24 Gy and 3 fractions, respectively. There were 10 spine segments that developed VBC (10%) after spine SBRT. Median time to VBC was 2.4 months. Of the 11 spine segments that underwent kyphoplasty prior to SBRT, none developed subsequent VBC. No factors were associated with VBC on univariate analysis.

CONCLUSIONS

The rate of vertebral body collapse following spine SBRT is low. Prophylactic kyphoplasty may provide protection against VBC and should be considered for patients at high risk for fracture.

Stereotactic Radiosurgery in Metastatic Spine Disease-A Systemic Review of the Literature

BACKGROUND

This study investigated the efficacy of stereotactic radiosurgery (SRS) in managing spinal metastasis. Traditionally, surgery was the primary approach, but SRS has emerged as a promising alternative.

OBJECTIVE

The study aims to evaluate the efficacy of stereotactic radiosurgery in the management of spinal metastasis in terms of local tumor control, patient survival, and quality of life, identifying both advantages and limitations of SRS.

METHODS

Through an extensive literature search in PubMed with cross-referencing, relevant full-text-available papers published between 2012 and 2022 in English or German were included. The search string used was "metastatic spine diseases AND SRS OR stereotactic radiosurgery".

RESULTS

There is growing evidence of SRS as a precise and effective treatment. SRS delivers high radiation doses while minimizing exposure to critical neural structures, offering benefits like pain relief, limited tumor growth, and a low complication rate, even for tumors resistant to traditional radiation therapies. SRS can be a primary treatment for certain metastatic cases, particularly those without spinal cord compression.

CONCLUSIONS

SRS appears to be a preferable option for oligometastasis and radioresistant lesions, assuming there are no contraindications. Further research is necessary to refine treatment protocols, determine optimal radiation dose and fractionation schemes, and assess the long-term effects of SRS on neural structures.

40 Gray in 5 Fractions for Salvage Reirradiation of Spine Lesions Previously Treated With Stereotactic Body Radiotherapy

BACKGROUND AND PURPOSE

A retrospective single-center analysis of the safety and efficacy of reirradiation to 40 Gy in 5 fractions (reSBRT) in patients previously treated with stereotactic body radiotherapy to the spine was performed.

METHODS

We identified 102 consecutive patients treated with reSBRT for 105 lesions between 3/2013 and 8/2021. Sixty-three patients (61.8%) were treated to the same vertebral level, and 39 (38.2%) to overlapping immediately adjacent levels. Local control was defined as the absence of progression within the treated target volume. The probability of local progression was estimated using a cumulative incidence curve. Death without local progression was considered a competing risk.

RESULTS

Most patients had extensive metastatic disease (54.9%) and were treated to the thoracic spine (53.8%). The most common regimen in the first course of stereotactic body radiotherapy was 27 Gy in 3 fractions, and the median time to reSBRT was 16.4 months. At the time of simulation, 44% of lesions had advanced epidural disease. Accordingly, 80% had myelogram simulations. Both the vertebral body and posterior elements were treated in 86% of lesions. At a median follow-up time of 13.2 months, local failure occurred in 10 lesions (9.5%). The 6- and 12-month cumulative incidences of local failure were 4.8% and 6%, respectively. Seven patients developed radiation-related neuropathy, and 1 patient developed myelopathy. The vertebral compression fracture rate was 16.7%.

CONCLUSION

In patients with extensive disease involvement, reSBRT of spine metastases with 40 Gy in 5 fractions seems to be safe and effective. Prospective trials are needed to determine the optimal dose and fractionation in this clinical scenario.

Stereotactic Body Radiation Therapy Versus Conventional Radiation Therapy for Painful Spinal Metastases: A Comparative Analysis of Randomized Trials and Practical Considerations

PURPOSE

Recent randomized trials have compared the efficacy and safety of stereotactic body radiation therapy (SBRT) with those of standard conventional external beam radiation therapy (cEBRT) for the treatment of painful spinal metastases. We conducted a composite analysis of these trials in order to inform current practice using pooled outcomes.

METHODS AND MATERIALS

Data from each randomized trial were abstracted from the final publications with biologically effective doses (BEDs) recalculated for SBRT and cEBRT. Primary outcome measures were overall pain response (OR) and complete pain response (CR) rates at 1, 3, and 6 months and rates of vertebral compression fracture. Random effects models were used to estimate primary outcome measures, and meta-regression assessed the effect of BED.

RESULTS

Four prospective randomized clinical trials published between 2018 and 2024 were included, with a total of 686 patients (383 and 303 in the SBRT and cEBRT groups, respectively). Dose and fraction (fx) number ranged from 24 Gy/1 fx to 48.5 Gy/10 fx for the SBRT group (median BED using an α-to-β ratio of 10, 50 Gy) and from 8 Gy/1 fx to 30 Gy/10 fx for the cEBRT group (median BED using an α-to-β ratio of 10, 28 Gy). The 1-, 3-, and 6-month OR rates for SBRT and cEBRT were similar: 53.6%, 52.4%, and 58.8% versus 48.4%, 47.9%, and 43.8%, respectively (p > .05). The 3-month CR rate was significantly higher for SBRT than for cEBRT (31.9% vs 14.8%; risk ratio, 2.26; 95% CI, 1.48-3.45; p < .001), but not the 6-month rate (34.4% vs 16.3%; risk ratio, 1.83; 95% CI, 0.74-4.53; p = .194). Vertebral compression fracture rates were similar at 17.3% and 18.4% for SBRT and cEBRT, respectively. No significant dose-dependent effect was observed with increasing BED for any efficacy or safety outcomes.

CONCLUSIONS

OR rates are similar, but CR rates appear higher with SBRT than with cEBRT, yet no dose-dependent effects were identified despite approximately 1.8 × BED dose with SBRT.

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.

A new era in the management of spinal metastasis

Despite the recent advances in cancer treatment, the incidence of patients with spinal metastases continues to grow along with the total number of cancer patients. Spinal metastases can significantly impair activities of daily living (ADL) and quality of life (QOL), compared with other types of bone metastases, as they are characterized with severe pain and paralysis caused by skeletal-related events. Reduced ADL can also lead to treatment limitations as certain anticancer agents and radiation therapy are not compatible treatments; thus, leading to a shorter life expectancy. Consequently, maintaining ADLs in patients with spinal metastases is paramount, and spine surgeons have an integral role to play in this regard. However, neurosurgeon, orthopedic and spinal surgeons in Japan do not have a proactive treatment approach to spinal metastases, which may prevent them from providing appropriate treatment when needed (clinical inertia). To overcome such endemic inertia, it is essential for 1) spine surgeons to understand and be more actively involved with patients with musculoskeletal disorders (cancer locomo) and cancer patients; 2) the adoption of a multidisciplinary approach (coordination and meetings not only with the attending oncologist but also with spine surgeons, radiologists, rehabilitation specialists, and other professionals) to preemptive treatment such as medication, radiotherapy, and surgical treatment; and 3) the integration of the latest findings associated with minimally invasive spinal treatments that have expanded the indications for treatment of spinal metastases and improved treatment outcomes. This heralds a new era in the management of 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.

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

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

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

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

Treatment affects load to failure and microdamage accumulation in healthy and osteolytic rat vertebrae

Bone turnover and microdamage are impacted by the presence of skeletal metastases which can contribute to increased fracture risk. Treatments for metastatic disease may further impact bone quality. This exploratory study aimed to establish an initial understanding of microdamage accumulation and load to failure in healthy and osteolytic rat vertebrae following focal and systemic cancer treatment (docetaxel (DTX), stereotactic body radiotherapy (SBRT), or zoledronic acid (ZA)). Osteolytic spine metastases were developed in 6-week-old athymic female rats via intracardiac injection of HeLa human cervical cancer cells (day 0). Additional rats served as healthy controls. Rats were either untreated, received SBRT to the T10-L6 vertebrae on day 14 (15 Gy, two fractions), DTX on day 7 or 14, or ZA on day 7. Rats were euthanized on day 21. Tumor burden was assessed with bioluminescence images acquired on day 14 and 21, histology of the excised T11 and L5 vertebrae, and ex-vivo μCT images of the T13-L4. Microstructural parameters (bone volume/total volume, trabecular number, spacing, thickness, and bone mineral density) were measured from L2 vertebrae. Load to failure was measured with axial compressive loading of the L1-L3 motion segments. Microdamage accumulation was labeled in T13 vertebrae with BaSO4 staining and was visualized with high resolution μCT imaging. Microdamage volume fraction was defined as the ratio of BaSO4 to bone volume. DTX administered on day 7 reduced tumor growth significantly (p < 0.05). Microdamage accumulation was found to be increased by the presence of metastases but was reduced by all treatments with ZA showing the largest improvement in HeLa cell injected rats. Load to failure was decreased in untreated and SBRT HeLa cell injected rats compared to healthy controls (p < 0.01). There was a moderate negative correlation between load to failure and microdamage volume fraction in vertebrae from rats injected with HeLa cells (R = -0.35, p = 0.031). Strong correlations were also found between microstructural parameters and load to failure and microdamage accumulation. Several factors, including the presence of osteolytic lesions and use of cancer therapies, influence microdamage accumulation and load to failure in rat vertebrae. Understanding the impact of these treatments on fracture risk of metastatic vertebrae is important to improve management of patients with spinal metastases.

Fracture rate after conventional external beam radiation therapy to the spine in multiple myeloma patients

BACKGROUND CONTEXT

Conventional external beam radiation therapy (cEBRT) is used in multiple myeloma (MM) to treat severe pain, spinal cord compression, and disease-related bone disease. However, radiation may be associated with an increased risk of vertebral compression fractures (VCFs), which could substantially impair survival and quality of life. Additionally, the use of the Spinal Instability Neoplastic Score (SINS) in MM is debated in MM.

PURPOSE

To determine the incidence of VCFs after cEBRT in patients with MM and to assess the applicability of the SINS score in the prediction of VCFs in MM.

STUDY DESIGN

Retrospective multicenter cohort study.

PATIENT SAMPLE

MM patients with spinal myeloma lesions who underwent cEBRT between January 2010 and December 2021.

OUTCOME MEASURES

Frequency of new or progressed VCFs and subdistribution hazard ratios for potentially associated factors.

METHODS

Patient and treatment characteristics were manually collected from the patients' electronic medical records. Computed tomography (CT) scans from before and up to 3 years after the start of radiation were used to score radiographic variables at baseline and at follow-up. Multivariable Fine and Gray competing risk analyses were performed to evaluate the diagnostic value of the SINS score to predict the postradiation VCF rate.

RESULTS

A total of 127 patients with 427 eligible radiated vertebrae were included in this study. The mean age at radiation was 64 years, and 66.1% of them were male. At the start of radiation, 57 patients (44.9%) had at least one VCF. There were 89 preexisting VCFs (18.4% of 483 vertebrae). Overall, 39 of 127 patients (30.7%) reported new fractures (number of vertebrae (n)=12) or showed progression of existing fractures (n=36). This number represented 11.2% of all radiated vertebrae. Five of the 39 (12.8%) patients with new or worsened VCFs received an unplanned secondary treatment (augmentation [n=2] or open surgery [n=3]) within 3 years. Both the total SINS score (SHR 1.77; 95% confidence interval (CI) 1.54-2.03; p<.001) and categorical SINS score (SHR 10.83; 95% CI 4.20-27.94; p<.001) showed an independent association with higher rates of new or progressed VCFs in adjusted analyses. The use of bisphosphonates was independently associated with a lower rate of new or progressed VCFs (SHR 0.47 [95% CI 0.24-0.92; p=.027]).

CONCLUSIONS

This study demonstrated that new or progressed VCFs occurred in 30.7% of patients within 3 years, in a total of 11.2% of vertebrae. The SINS score was found to be independently associated with the development or progression of VCFs and could thus be applied in MM for fracture prediction and possibly prevention.

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.

Stereotactic body radiation therapy versus conventional external beam radiotherapy for spinal metastases: A systematic review and meta-analysis of randomized controlled trials

INTRODUCTION

This study aimed to compare SBRT and cEBRT for treating spinal metastases through a systematic review and meta-analysis of randomized controlled trials (RCTs).

METHODS

PubMed, EMBASE and Cochrane Library were searched up to 6 May 2023 for RCTs comparing SBRT and cEBRT for spinal metastases. Overall and complete pain response, local progression, overall survival, quality of life and adverse events were extracted. Data were pooled using random-effects models. Results were reported as risk ratios (RRs) for dichotomous outcomes, and hazard ratios (HRs) for time-to-event outcomes, along with their 95% confidence intervals (CIs). Heterogeneity was evaluated using the I2 statistic.

RESULTS

Three RCTs were identified involving 642 patients. No differences were seen in overall pain response comparing SBRT and cEBRT (RR at 3 months: 1.12, 95% CI, 0.74-1.70, p = 0.59; RR at 6 months: 1.29, 95% CI, 0.97-1.72, p = 0.08). Only two of three studies presented complete pain response data. SBRT demonstrated a statistically significant improvement in complete pain response compared to cEBRT (RR at 3 months: 2.52; 95% CI, 1.58-4.01; P < 0.0001; RR at 6 months: 2.48; 95% CI, 1.23-4.99; P = 0.01). There were no significant differences in local progression and overall survival. Adverse events were similar, except for any grade radiation dermatitis, which was significantly lower in SBRT arm (RR 0.17, 95% CI 0.03-0.96, P = 0.04).

CONCLUSION

SBRT is a safe treatment option for spine metastases. It may provide better complete pain response compared to cEBRT. Additional trials are needed to determine the potential benefits of SBRT in specific patient subsets.

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.

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.

Musculoskeletal Interventional Oncology: A Contemporary Review

Musculoskeletal interventional oncology is an emerging field that addresses the limitations of conventional therapies for bone and soft-tissue tumors. The field's growth has been driven by evolving treatment paradigms, expanding society guidelines, mounting supportive literature, technologic advances, and cross-specialty collaboration with medical, surgical, and radiation oncology. Safe, effective, and durable pain palliation, local control, and stabilization of musculoskeletal tumors are increasingly achieved through an expanding array of contemporary minimally invasive percutaneous image-guided treatments, including ablation, osteoplasty, vertebral augmentation (with or without mechanical reinforcement via implants), osseous consolidation via percutaneous screw fixation (with or without osteoplasty), tumor embolization, and neurolysis. These interventions may be used for curative or palliative indications and can be readily combined with systemic therapies. Therapeutic approaches include the combination of different interventional oncology techniques as well as the sequential application of such techniques with other local treatments, including surgery or radiation. This article reviews the current practice of interventional oncology treatments for the management of patients with bone and soft-tissue tumors with a focus on emerging technologies and techniques.

Predictors of pathologic fracture and local recurrence following stereotactic body radiation therapy to 505 non-spine bone metastases

PURPOSE

Stereotactic Body Radiation Therapy (SBRT) is increasingly applied to treat non-spine bone metastases (NSBM) though data remains limited on this approach. In this retrospective study, we report outcomes and predictors of local failure (LF) and pathological fracture (PF) post-SBRT for NSBM using a mature single-institution database.

METHODS

Patients with NSBM treated with SBRT between 2011 and 2021 were identified. The primary objective was to assess the rates of radiographic LF. Secondary objectives were to assess the rates of in-field PF, overall survival (OS), and late grade ≥ 3 toxicity. Competing risks analysis was used to assess rates of LF and PF. Univariable regression and multivariable regression (MVR) were performed to investigate predictors of LF and PF.

RESULTS

A total of 373 patients with 505 NSBM were included in this study. Median follow-up was 26.5 months. The cumulative incidence of LF at 6, 12, and 24 months were 5.7%, 7.9%, and 12.6%, respectively. The cumulative incidence of PF at 6, 12, and 24 months were 3.8%, 6.1%, and 10.9%, respectively. Lytic NSBM (HR = 2.18; p < 0.01), a lower biologically effective dose (HR = 1.11 per 5 Gy10 decrease; p = 0.04), and a PTV ≥ 54 cc (HR = 4.32; p < 0.01) predicted for a higher risk of LF on MVR. Lytic NSBM (HR = 3.43; p < 0.01), mixed (lytic/sclerotic) lesions (HR = 2.70; p = 0.04), and rib metastases (HR = 2.68; p < 0.01) predicted for a higher risk of PF on MVR.

CONCLUSION

SBRT is an effective modality to treat NSBM with high rates of radiographic local control with an acceptable rate of PF. We identify predictors of both LF and PF that can serve to inform practice and trial design.

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

PURPOSE

The management of chordoma or chondrosarcoma involving the spine is often challenging due to adjacent critical structures and tumor radioresistance. Spine stereotactic radiosurgery (SSRS) has radiobiologic advantages compared with conventional radiotherapy, though there is limited evidence on SSRS in this population. We sought to characterize the long-term local control (LC) of patients treated with SSRS.

METHODS

We retrospectively reviewed patients with chordoma or chondrosarcoma treated with dose-escalated SSRS, defined as 24 Gy in 1 fraction to the gross tumor volume. Overall survival (OS) was calculated by Kaplan-Meier functions. Competing risk analysis using the cause-specific hazard function estimated LC time.

RESULTS

Fifteen patients, including 12 with chordoma and 3 with chondrosarcoma, with 22 lesions were included. SSRS intent was definitive, single-modality in 95% of cases (N = 21) and post-operative in 1 case (5%). After a median censored follow-up time of 5 years (IQR 4 to 8 years), median LC time was not reached (IQR 8 years to not reached), with LC rates of 100%, 100%, and 90% at 1 year, 2 years, and 5 years. The median OS was 8 years (IQR 3 years to not reached). Late grade 3 toxicity occurred after 23% of treatments (N = 5, fracture), all of which were managed successfully with stabilization.

CONCLUSION

Definitive dose-escalated SSRS to 24 Gy in 1 fraction appears to be a safe and effective treatment for achieving durable local control in chordoma or chondrosarcoma involving the spine, and may hold particular importance as a low-morbidity alternative to surgery in selected cases.

Spine Patient Optimal Radiosurgery Treatment for Symptomatic Metastatic Neoplasms (SPORTSMEN): a randomized phase II study protocol

Background

Approximately 40% of patients with metastatic cancer will have spinal metastatic disease. Historically treated with external beam radiation therapy (EBRT) with limited durability in pain control, the increased lifespan of this patient population has necessitated more durable treatment results via spine radiosurgery/stereotactic body radiation therapy (SBRT). The goal of this study is to assess three-month pain freedom rates via the Spine Patient Optimal Radiosurgery Treatment for Symptomatic Metastatic Neoplasms (SPORTSMEN) randomized trial.

Materials and methods

This study is a prospective randomized three-arm phase II trial which will recruit patients with symptomatic spine metastases. All patients will be randomized to standard-of care SBRT (24 Gy in 2 fractions), single-fraction SBRT (19 Gy in 1 fraction), or EBRT (8 Gy in 1 fraction), with the primary endpoint of three-month pain freedom (using the Brief Pain Inventory). We expect that SPORTSMEN will help definitively answer the efficacy of spine SBRT versus EBRT for achieving pain freedom, while defining the safety and efficacy of 19 Gy single-fraction spine SBRT. Local control will be defined according to Spine Response Assessment in Neuro-Oncology (SPINO) criteria.

Discussion

This is the first phase II trial to objectively assess optimal spine SBRT dosing in the treatment of symptomatic spine metastatic disease, while assessing spine SBRT versus EBRT. Findings should allow for better determination of the efficacy of two-fraction spine SBRT versus EBRT in the United States, as well as for the novel single-fraction 19 Gy spine SBRT regimen in patients with symptomatic spine metastases.

Trial Registration

Clinicaltrials.gov identifier: NCT05617716 (registration date: November 14, 2022).

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 radiotherapy for spine metastases: a review of 24 Gy in 2 daily fractions

PURPOSE

Stereotactic body radiotherapy (SBRT) has proven to be a highly effective treatment for selected patients with spinal metastases. Randomized evidence shows improvements in complete pain response rates and local control with lower retreatment rates favoring SBRT, compared to conventional external beam radiotherapy (cEBRT). While there are several reported dose-fractionation schemes for spine SBRT, 24 Gy in 2 fractions has emerged with Level 1 evidence providing an excellent balance between minimizing treatment toxicity while respecting patient convenience and financial strain.

METHODS

We provide an overview of the 24 Gy in 2 SBRT fraction regimen for spine metastases, which was developed at the University of Toronto and tested in an international Phase 2/3 randomized controlled trial.

RESULTS

The literature summarizing global experience with 24 Gy in 2 SBRT fractions suggests 1-year local control rates ranging from 83-93.9%, and 1-year rates of vertebral compression fracture ranging from 5.4-22%. Reirradiation of spine metastases that failed prior cEBRT is also feasible with 24 Gy in 2 fractions, and 1-year local control rates range from 72-86%. Post-operative spine SBRT data are limited but do support the use of 24 Gy in 2 fractions with reported 1-year local control rates ranging from 70-84%. Typically, the rates of plexopathy, radiculopathy and myositis are under 5% in those series reporting mature follow up, with no cases of radiation myelopathy (RM) reported in the de novo setting when the spinal cord avoidance structure is limited to 17 Gy in 2 fractions. However, re-irradiation RM has been observed following 2 fraction SBRT. More recently, 2-fraction dose escalation with 28 Gy, with a higher dose constraint to the critical neural tissues, has been reported suggesting improved rates of local control. This regimen may be important in those patients with radioresistant histologies, high grade epidural disease, and/or paraspinal disease.

CONCLUSION

The dose-fractionation of 24 Gy in 2 fractions is well-supported by published literature and is an ideal starting point for centers looking to establish a spine SBRT program.

Radiofrequency Ablation Provides Rapid and Durable Pain Relief for the Palliative Treatment of Lytic Bone Metastases Independent of Radiation Therapy: Final Results from the OsteoCool Tumor Ablation Post-Market Study

PURPOSE

The OsteoCool Tumor Ablation Post-Market Study (OPuS One) was a prospective, multi-national, single-arm study to investigate safety and effectiveness of radiofrequency ablation (RFA) for palliation of painful lytic bone metastases with 12 months of follow-up. RFA has demonstrated effective palliation of osseous metastases in small clinical studies with short-term follow-up; however, a long-term assessment with robust subject numbers is lacking.

MATERIALS AND METHODS

Prospective assessments were conducted at Baseline, 3 days, 1 week, and 1, 3, 6, and 12-months. Pain and quality of life were measured prior to RFA and postoperatively using the Brief Pain Inventory, European Quality of Life-5 Dimension, and European Organization for Research and Treatment of Cancer Care Quality of Life Questionnaire for palliative care. Radiation, chemotherapy and opioid usage, and related adverse events were collected.

RESULTS

206 subjects were treated with RFA at 15 institutions in OPuS One. Worst pain, average pain, pain interference and quality of life significantly improved at all visits starting 3 days post-RFA and sustained to 12 months (P < 0.0001). Post hoc analysis found neither systemic chemotherapy nor local radiation therapy at the index site of RFA influenced worst pain, average pain, or pain interference. Six subjects had device/procedure-related adverse events.

CONCLUSION

RFA for lytic metastases provides rapid (within 3 days) and statistically significant pain and quality of life improvements with sustained long-term relief through 12 months and a high degree of safety, independent of radiation.

LEVEL OF EVIDENCE

2B, PROSPECTIVE, NON-RANDOMIZED, POST-MARKET STUDY: This journal requires that authors assign a level of evidence to each article. For a full description of these Evidence-Based Medicine ratings, please refer to the Table of Contents or the online Instructions to Authors www.springer.com/00266 .

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.

Dose-Escalated 2-Fraction Spine Stereotactic Body Radiation Therapy: 28 Gy Versus 24 Gy in 2 Daily Fractions

PURPOSE

Stereotactic body radiation therapy (SBRT) for spine metastases improves pain response rates compared with conventional external beam radiation therapy; however, the optimal fractionation schedule is unclear. We report local control and toxicity outcomes after dose-escalated 2-fraction spine SBRT.

METHODS AND MATERIALS

A prospectively maintained institutional database of over 600 patients and 1400 vertebral segments treated with spine SBRT was reviewed to identify those prescribed 28 or 24 Gy in 2 daily fractions. The primary endpoint was magnetic resonance imaging based local failure (LF), and secondary endpoints included overall survival and vertebral compression fracture (VCF).

RESULTS

A total of 947 treated vertebral segments in 482 patients were identified, of which 301 segments in 159 patients received 28 Gy, and 646 segments in 323 patients received 24 Gy in 2 fractions. Median follow-up per patient was 23.5 months, and median overall survival was 49.1 months. In the 28 Gy cohort, the 6-, 12-, and 24-month cumulative incidences of LF were 3.5%, 5.4%, and 11.1%, respectively, versus 6.0%, 12.5%, and 17.6% in the 24 Gy cohort, respectively (P = .008). On multivariable analysis, 24 Gy (hazard ratio [HR], 1.525; 95% confidence interval, 1.039-2.238; P = .031), paraspinal disease extension (HR, 1.422; 95% confidence interval, 1.010-2.002; P = .044), and epidural extension in either radioresistant or radiosensitive histologies (HR, 2.117 and 1.227, respectively; P = .003) were prognostic for higher rates of LF. Risk of VCF was 5.5%, 7.6%, and 10.7% at 6, 12, and 24 months, respectively, and was similar between cohorts (P = .573). Spinal malalignment (P < .001), baseline VCF (P = .003), junctional spine location (P = .030), and greater minimum dose to 90% of planning target volume were prognostic for higher rates of VCF.

CONCLUSIONS

Dose escalation to 28 Gy in 2 daily fractions was associated with improved local control without increasing the risk of VCF. The 2-year local control rates are consistent with those predicted by the Hypofractionated Treatment Effects in the Clinic spine tumor control probability model, and these data will inform a proposed dose escalation randomized trial.

Fifty-year history of the evolution of spinal metastatic disease management

Spine metastases are a significant source of morbidity in oncology. Treatment of these spine metastases largely remains palliative, but advances over the past 50 years have improved the effectiveness of interventions for preserving functional status and obtaining local control while minimizing morbidity. While the field began with conventional external beam radiation as the primary treatment modality, a series of paradigm shifts and technological advances in the 2000s led to a change in treatment patterns. These advances allowed for an increased role of surgical decompression of neural elements, a shift in the stereotactic capabilities of radiation oncologists, and an improved understanding of the radiobiology of metastatic disease. The result was improved local control while minimizing treatment morbidity. These advances fit within the larger framework of metastatic spine tumor management known as the Neurologic, Oncologic, Mechanical, and Systemic disease decision framework. This dynamic framework takes into account the neurological function of the patient, the radiobiology of their tumor, their degree of mechanical instability, and their systemic disease control and treatment options to help determine appropriate interventions based on the individual patient. Herein, we describe the 50-year evolution of metastatic spine tumor management and the impact of various advances on the field.

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.

State-of-the-Art Imaging Techniques in Metastatic Spinal Cord Compression

Metastatic Spinal Cord Compression (MSCC) is a debilitating complication in oncology patients. This narrative review discusses the strengths and limitations of various imaging modalities in diagnosing MSCC, the role of imaging in stereotactic body radiotherapy (SBRT) for MSCC treatment, and recent advances in deep learning (DL) tools for MSCC diagnosis. PubMed and Google Scholar databases were searched using targeted keywords. Studies were reviewed in consensus among the co-authors for their suitability before inclusion. MRI is the gold standard of imaging to diagnose MSCC with reported sensitivity and specificity of 93% and 97% respectively. CT Myelogram appears to have comparable sensitivity and specificity to contrast-enhanced MRI. Conventional CT has a lower diagnostic accuracy than MRI in MSCC diagnosis, but is helpful in emergent situations with limited access to MRI. Metal artifact reduction techniques for MRI and CT are continually being researched for patients with spinal implants. Imaging is crucial for SBRT treatment planning and three-dimensional positional verification of the treatment isocentre prior to SBRT delivery. Structural and functional MRI may be helpful in post-treatment surveillance. DL tools may improve detection of vertebral metastasis and reduce time to MSCC diagnosis. This enables earlier institution of definitive therapy for better outcomes.

Effects of Radiation on the Bone Strength of Spinal Vertebrae in Rats

STUDY DESIGN

A controlled laboratory study.

OBJECTIVE

The aim of this study was to examine bone damage caused by irradiation to spinal vertebrae in rats.

SUMMARY OF BACKGROUND DATA

Radiotherapy is widely used in the treatment of malignant spine tumors. However, a few studies have reported vertebral fractures following radiotherapy as an adverse reaction. There are no reports on irradiation- induced changes in bone fragility, mechanical and structural changes focusing on the spine, and the mechanism of irradiation-induced bone osteoporosis.

METHODS

Eighty-four female Wistar rats were randomly allocated to the 20 Gy irradiated or the nonirradiated (control) group. The lumbar vertebrae were irradiated with an external focal radiation dose of 20 Gy. Biomechanical, structural, and histological analyses were performed at 0, 2, 4, 6, 8, 12, and 24 weeks after irradiation. Structural analysis and bone density measurement of vertebral trabecular bone were performed by μCT. Histopathological evaluation was performed by hematoxylin and eosin staining and immunostaining.

RESULTS

The bone strength at 2 weeks after irradiation (311 ± 23 N) was 22% lower than that before irradiation (398 ± 34 N) (P  < 0.05). The trabecular spacing increased, and trabecular connectivity and width decreased significantly in the irradiated group compared with those in the non-irradiated group. The three-dimensional structure model became coarse, and the trabecular structure continued to thin and disrupt after irradiation. There was no significant change in the bone mineral density in both groups.

CONCLUSION

A decrease in bone strength was observed 2 weeks after irradiation. Bone mineral density remained unaltered, whereas the microstructure of trabecular bone changed, suggesting bone damage by irradiation.Level of Evidence: N/A.

Toward an artificial intelligence-assisted framework for reconstructing the digital twin of vertebra and predicting its fracture response

This article presents an effort toward building an artificial intelligence (AI) assisted framework, coined ReconGAN, for creating a realistic digital twin of the human vertebra and predicting the risk of vertebral fracture (VF). ReconGAN consists of a deep convolutional generative adversarial network (DCGAN), image-processing steps, and finite element (FE) based shape optimization to reconstruct the vertebra model. This DCGAN model is trained using a set of quantitative micro-computed tomography (micro-QCT) images of the trabecular bone obtained from cadaveric samples. The quality of synthetic trabecular models generated using DCGAN are verified by comparing a set of its statistical microstructural descriptors with those of the imaging data. The synthesized trabecular microstructure is then infused into the vertebra cortical shell extracted from the patient's diagnostic CT scans using an FE-based shape optimization approach to achieve a smooth transition between trabecular to cortical regions. The final geometrical model of the vertebra is converted into a high-fidelity FE model to simulate the VF response using a continuum damage model under compression and flexion loading conditions. A feasibility study is presented to demonstrate the applicability of digital twins generated using this AI-assisted framework to predict the risk of VF in a cancer patient with spinal metastasis.

Stereotactic Body Radiation Therapy (SBRT) for Spinal Metastases: Real-world Outcomes From an International Multi-institutional SBRT Registry

OBJECTIVE

The objective of this study was to compare clinical outcomes following single fraction versus fractionated stereotactic body radiotherapy (SBRT) for spinal metastases.

MATERIALS AND METHODS

A multi-institutional registry was queried for patients with spinal metastases treated with single-fraction or fractionated SBRT. Potential predictive factors of local control (LC) and overall survival were evaluated. Pretreatment and posttreatment Visual Analog Scale scores were analyzed to examine initial and durable pain responses and complete response (CR) rates. Logistic regression was utilized to assess potential correlations between pain response, biologically effective dose (BED), and fractionation.

RESULTS

Four hundred sixty-six patients with 514 lesions treated with SBRT were identified; 209 and 104 lesions had information on LC and pain, respectively. The median pain score of patients with symptoms was 6 (range: 3 to 10). The median follow-up was 8.9 months (range: 0.4 to 125.5 mo). Utilizing Karnofsky Performance Score, age, and primary site (lung and/or nonbreast), 1-year overall survival rates were 76.1%, 59.1%, 54.9%, 37.2%, and 23.5% for patients with 0 to 4 of these factors, respectively (P<0.0001). One- and 2-year LC rates were 79.9% and 73.6%, respectively. Eighty-six patients (82.7%) had an initial pain response with a median decline of 3.5 and a CR rate of 47.1%. Sixty-five patients (62.5%) had a durable pain response with a median decline of 2 and a CR rate of 20.2%. Higher initial CR rates were observed with BED10 ≥51 Gy10 (58.7% vs. 37.9%; P=0.04).

CONCLUSIONS

Following SBRT, encouraging palliative responses with >80% and 60% of patients having initial and durable pain responses, respectively. Dose escalation may result in improved initial CR rates. Performance status, age, and primary histology are factors to consider in the absence of pain.

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.

A preliminary safety assessment of vertebral augmentation with 32P brachytherapy bone cement

Comprehensive treatment for vertebral metastatic lesions commonly involves vertebral augmentation (vertebroplasty or kyphoplasty) to relieve pain and stabilize the spine followed by multiple sessions of radiotherapy. We propose to combine vertebral augmentation and radiotherapy into a single treatment by adding 32P, a β-emitting radionuclide, to bone cement, thereby enabling spinal brachytherapy to be performed without irradiating the spinal cord. The goal of this study was to address key dosimetry and safety questions prior to performing extensive animal studies. The 32P was in the form of hydroxyapatite powder activated by neutron bombardment in a nuclear reactor. We performed ex vivo dosimetry experiments to establish criteria for safe placement of the cement within the sheep vertebral body. In an in vivo study, we treated three control ewes and three experimental ewes with brachytherapy cement containing 2.23–3.03 mCi 32P ml−1 to identify the preferred surgical approach, to determine if 32P leaches from the cement and into the blood, urine, or feces, and to identify unexpected adverse effects. Our ex vivo experiments showed that cement with 4 mCi 32P ml−1 could be safely implanted in the vertebral body if the cement surface is at least 4 mm from the spinal cord in sheep and 5 mm from the spinal cord in humans. In vivo, a lateral retroperitoneal surgical approach, ventral to the transverse processes, was identified as easy to perform while allowing a safe distance to the spinal cord. The blood, urine, and feces of the sheep did not contain detectable levels of 32P, and the sheep did not experience any neurologic or other adverse effects from the brachytherapy cement. These results demonstrate, on a preliminary level, the relative safety of this brachytherapy cement and support additional development and testing.

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.

Response assessment after stereotactic body radiation therapy for spine and non-spine bone metastases: results from a single institutional study

Background

The use of stereotactic body radiation therapy (SBRT) for tumor and pain control in patients with bone metastases is increasing. We report response assessment after bone SBRT using radiological changes through time and clinical examination of patients.

Methods

We analyzed retrospectively oligo-metastatic/progressive patients with bony lesions treated with SBRT between 12/2008 and 10/2018, without in-field re-irradiation, in our institution. Radiological data were obtained from imaging modalities used for SBRT planning and follow-up purposes in picture archiving and communication system and assessed by two independent radiologists blind to the time of treatment. Several radiological changes were described. Radiographic response assessment was classified according to University of Texas MD Anderson Cancer Center criteria. Pain response and the neurological deficit were captured before and at least 6 months after SBRT.

Results

A total of 35 of the 74 reviewed patients were eligible, presenting 43 bone metastases, with 51.2% (n = 22) located in the vertebral column. Median age at the time of SBRT was 66 years (range 38–84) and 77.1% (n = 27) were male. Histology was mainly prostate (51.4%, n = 18) and breast cancer (14.3%, n = 5). Median total radiation dose delivered was 24 Gy (range 24–42), in three fractions (range 2–7), prescribed to 70–90% isodose-line. After a median follow-up of 1.8 years (range < 1–8.2) for survivors, complete or partial response, stable, and progressive disease occurred in 0%, 11.4% (n = 4), 68.6% (n = 24), and 20.0% (n = 7) of the patients, respectively. Twenty patients (57.1%) died during the follow-up time, all from disease progression, yet 70% (n = 14) from this population with local stable disease after SBRT. From patients who were symptomatic and available for follow-up, almost half (44.4%) reported pain reduction after SBRT.

Conclusions

Eighty percent of the patients showed local control after SBRT for bone metastases. Pain response was favorable. For more accurate response assessment, comparing current imaging modalities with advanced imaging techniques such as functional MRI and PET/CT, in a prospective and standardized way is warranted.

Trial registration Retrospectively registered.

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.

[Stereotactic body radiation therapy for spine bone oligometastatic disease]

Stereotactic radiotherapy is an ever more common technique, regardless of the location treated. However, spinal stereotactic radiotherapy requires a particular technicality in order to ensure its proper realization. There is now a large literature defining the type of imaging to be used, the dose to be delivered and the delineation of target volumes. This technique can achieve a significant local control and an interesting analgesic efficiency. However, its place in relation to conventional radiotherapy remains limited because it requires MRI imaging and a significantly longer patient management during the treatment fraction. In this context, it is currently mainly restricted to oligometastatic patients or for re-irradiations.

Ablation Techniques in Cancer Pain

Painful bone metastases are a frequently encountered problem in oncology practice. The skeletal system is the third most common site of metastatic disease and up to 85% of patients with breast, prostate, and lung cancer may develop bone metastases during the course of their disease.

Photodynamic therapy outcome modelling for patients with spinal metastases: a simulation-based study

Spinal metastases often occur in the advanced stages of breast, lung or prostate cancer, resulting in a significant impact on the patient's quality of life. Current treatment modalities for spinal metastases include both systemic and localized treatments that aim to decrease pain, improve mobility and structural stability, and control tumour growth. With the development of non-toxic photosensitizer drugs, photodynamic therapy (PDT) has shown promise as a minimally invasive non-thermal alternative in oncology, including for spinal metastases. To apply PDT to spinal metastases, predictive algorithms that optimize tumour treatment and minimize the risk of spinal cord damage are needed to assess the feasibility of the treatment and encourage a broad acceptance of PDT in clinical trials. This work presents a framework for PDT modelling and planning, and simulates the feasibility of using a BPD-MA mediated PDT to treat bone metastases at two different wavelengths (690 nm and 565 nm). An open-source software for PDT planning, PDT-SPACE, is used to evaluate different configurations of light diffusers (cut-end and cylindrical) fibres with optimized power allocation in order to minimize the damage to spinal cord or maximize tumour destruction. The work is simulated on three CT images of metastatically involved vertebrae acquired from three patients with spinal metastases secondary to colorectal or lung cancer. Simulation results show that PDT at a 565 nm wavelength has the ability to treat 90% of the metastatic lesion with less than 17% damage to the spinal cord. However, the energy required, and hence treatment time, to achieve this outcome with the 565 nm is infeasible. The energy required and treatment time for the longer wavelength of 690 nm is feasible ([Formula: see text] min), but treatment aimed at 90% of the metastatic lesion would severely damage the proximal spinal cord. PDT-SPACE provides a simulation platform that can be used to optimize PDT delivery in the metastatic spine. While this work serves as a prospective methodology to analyze the feasibility of PDT for tumour ablation in the spine, preclinical studies in an animal model are ongoing to elucidate the spinal cord damage extent as a function of PDT dose, and the resulting short and long term functional impairments. These will be required before there can be any consideration of clinical trials.

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.

Stereotactic body radiotherapy versus conventional external beam radiotherapy in patients with painful spinal metastases: an open-label, multicentre, randomised, controlled, phase 2/3 trial

BACKGROUND

Conventional external beam radiotherapy is the standard palliative treatment for spinal metastases; however, complete response rates for pain are as low as 10-20%. Stereotactic body radiotherapy delivers high-dose, ablative radiotherapy. We aimed to compare complete response rates for pain after stereotactic body radiotherapy or conventional external beam radiotherapy in patients with painful spinal metastasis.

METHODS

This open-label, multicentre, randomised, controlled, phase 2/3 trial was done at 13 hospitals in Canada and five hospitals in Australia. Patients were eligible if they were aged 18 years and older, and had painful (defined as ≥2 points with the Brief Pain Inventory) MRI-confirmed spinal metastasis, no more than three consecutive vertebral segments to be included in the treatment volume, an Eastern Cooperative Oncology Group performance status of 0-2, a Spinal Instability Neoplasia Score of less than 12, and no neurologically symptomatic spinal cord or cauda equina compression. Patients were randomly assigned (1:1) with a web-based, computer-generated allocation sequence to receive either stereotactic body radiotherapy at a dose of 24 Gy in two daily fractions or conventional external beam radiotherapy at a dose of 20 Gy in five daily fractions using standard techniques. Treatment assignment was done centrally by use of a minimisation method to achieve balance for the stratification factors of radiosensitivity, the presence or absence of mass-type tumour (extraosseous or epidural disease extension, or both) on imaging, and centre. The primary endpoint was the proportion of patients with a complete response for pain at 3 months after radiotherapy. The primary endpoint was analysed in the intention-to-treat population and all safety and quality assurance analyses were done in the as-treated population (ie, all patients who received at least one fraction of radiotherapy). The trial is registered with ClinicalTrials.gov, NCT02512965.

FINDINGS

Between Jan 4, 2016, and Sept 27, 2019, 229 patients were enrolled and randomly assigned to receive conventional external beam radiotherapy (n=115) or stereotactic body radiotherapy (n=114). All 229 patients were included in the intention-to-treat analysis. The median follow-up was 6·7 months (IQR 6·3-6·9). At 3 months, 40 (35%) of 114 patients in the stereotactic body radiotherapy group, and 16 (14%) of 115 patients in the conventional external beam radiotherapy group had a complete response for pain (risk ratio 1·33, 95% CI 1·14-1·55; p=0·0002). This significant difference was maintained in multivariable-adjusted analyses (odds ratio 3·47, 95% CI 1·77-6·80; p=0·0003). The most common grade 3-4 adverse event was grade 3 pain (five [4%] of 115 patients in the conventional external beam radiotherapy group vs five (5%) of 110 patients in the stereotactic body radiotherapy group). No treatment-related deaths were observed.

INTERPRETATION

Stereotactic body radiotherapy at a dose of 24 Gy in two daily fractions was superior to conventional external beam radiotherapy at a dose of 20 Gy in five daily fractions in improving the complete response rate for pain. These results suggest that use of conformal, image-guided, stereotactically dose-escalated radiotherapy is appropriate in the palliative setting for symptom control for selected patients with painful spinal metastases, and an increased awareness of the need for specialised and multidisciplinary involvement in the delivery of end-of-life care is needed.

FUNDING

Canadian Cancer Society and the Australian National Health and Medical Research Council.

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.

Dosimetric feasibility of hypofractionation for metastatic bone/bone marrow lesions from paediatric solid tumours

BACKGROUND AND PURPOSE

The aim of this study was to determine the feasibility of hypofractionated schedules for metastatic bone/bone marrow lesions in children and to investigate dosimetric differences to the healthy surrounding tissues compared to conventional schedules.

METHODS

27 paediatric patients (mean age, 7 years) with 50 metastatic bone/bone marrow lesions (n = 26 cranial, n = 24 extra-cranial) from solid primary tumours (neuroblastoma and sarcoma) were included. The PTV was a 2 mm expansion of the GTV. A prescription dose of 36 and 54 Gy EQD2_α/β=10 was used for neuroblastoma and sarcoma lesions, respectively. VMAT plans were optimized for each single lesion using different fractionation schedules: conventional (30/20 fractions, V_95% ≥ 99%, D_0.1cm³ ≤ 107%) and hypofractionated (15/10/5/3 fractions, V_100% ≥ 95%, D_0.1cm³ ≤ 120%)_. Relative EQD2 differences in OARs D_mean between the different schedules were compared.

RESULTS

PTV coverage was met for all plans independently of the fractionation schedule and for all lesions (V_95% range 95.5-100%, V_100% range 95.1-100%), with exception of the vertebrae (V_100% range 63.5-91.0%). For most OARs, relative mean reduction in the D_mean was seen for the hypofractionated plans compared to the conventional plans, with largest sparing in the 5 fractions (< 43%) followed by the 3 fractions schedule (< 40%). In case of PTV overlap with an OAR, a significant increase in dose for the OAR was observed with hypofractionation.

CONCLUSIONS

For the majority of the cases, iso-effective plans with hypofractionation were feasible with similar or less dose in the OARs. The most suitable fractionation schedule should be personalised depending on the spatial relationship between the PTV and OARs and the prescription dose.

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.

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.