Comparison of whole versus partial vertebral body stereotactic body radiation therapy for spinal metastases

Shifting the Landscape of Spine and Non-Spine Bone Metastases: A Review of Stereotactic Body Radiotherapy

ABSTRACT

Both spine and nonspine bone metastases are frequent sites of spread from solid organ malignancies. As bone metastases frequently cause significant morbidity for patients, it is critical to offer a treatment that can achieve rapid and durable symptomatic relief and local control, without being associated with serious risks of toxicity. Conventional palliative radiation therapy has a key treatment component in the multidisciplinary management of these patients; however, over the past decade, it has evolved to routinely deliver high biologically effective doses with precision in the form of stereotactic body radiation therapy. This change in paradigm is a result of the shifting landscape in cancer care, such that short-term pain relief is no longer the sole therapeutic aim for selected patients, and durable symptom relief and local tumor control are the goals. This review discusses the randomized prospective evidence, ongoing trials, approach to surveillance imaging, and treatment delivery for stereotactic body radiation therapy, to both spine and nonspine bone metastases, with a specific section on sacral metastases.

The Role of CT and MR Imaging in Stereotactic Body Radiotherapy of the Spine: From Patient Selection and Treatment Planning to Post-Treatment Monitoring

Spine metastases (SMs) are common, arising in 70% of the cases of the most prevalent malignancies in males (prostate cancer) and females (breast cancer). Stereotactic body radiotherapy, or SBRT, has been incorporated into clinical treatment algorithms over the past decade. SBRT has shown promising rates of local control for oligometastatic spinal lesions with low radiation dose to adjacent critical tissues, particularly the spinal cord. Imaging is critically important in SBRT planning, guidance, and response monitoring. This paper reviews the roles of imaging in spine SBRT, including conventional and advanced imaging approaches for SM detection, treatment planning, and post-SBRT follow-up.

Stereotactic Body Radiation Therapy for Sacral Metastases: Deviation From Recommended Target Volume Delineation Increases the Risk of Local Failure

PURPOSE

Although spine stereotactic body radiation therapy (SBRT) is considered a standard of care in the mobile spine, mature evidence reporting outcomes specific to sacral metastases is lacking. Furthermore, there is a need to validate the existing sacral SBRT international consensus contouring guidelines to define the optimal contouring approach. We report mature rates of local failure (LF), adverse events, and the effect of contouring deviations in the largest experience to date specific to sacrum SBRT.

METHODS AND MATERIALS

Consecutive patients who underwent sacral SBRT from 2010 to 2021 were retrospectively reviewed. The primary endpoint was magnetic resonance imaging-based LF with a focus on adherence to target volume contouring recommendations. Secondary endpoints included vertebral compression fracture and neural toxicity.

RESULTS

Of the 215 sacrum segments treated in 112 patients, most received 30 Gy/4 fractions (51%), 24 Gy/2 fractions (31%), or 30 Gy/5 fractions (10%). Sixteen percent of segments were nonadherent to the consensus guideline with a more restricted target volume (undercontoured). The median follow-up was 21.4 months (range, 1.5-116.9 months). The cumulative incidence of LF at 1 and 2 years was 18.4% and 23.1%, respectively. In those with guideline adherent versus nonadherent contours, the LF rate at 1 year was 15.1% versus 31.4% and at 2 years 18.8% versus 40.0% (hazard ratio [HR], 2.5; 95% CI, 1.4-4.6; P = .003), respectively. On multivariable analysis, guideline nonadherence (HR, 2.4; 95% CI, 1.3-4.7; P = .008), radioresistant histology (HR, 2.4; 95% CI, 1.4-4.1; P < .001), and extraosseous extension (HR, 2.5; 95% CI, 1.3-4.7; P = .005) predicted for an increased risk of LF. The cumulative incidence of vertebral compression fracture was 7.1% at 1 year and 12.3% at 2 years. Seven patients (6.3%) developed peripheral nerve toxicity, of whom 4 had been previously radiated.

CONCLUSIONS

Sacral SBRT is associated with high efficacy rates and an acceptable toxicity profile. Adhering to consensus guidelines for target volume delineation is recommended to reduce the risk of LF.

Volumetric Intensity-Modulated Arc Stereotactic Radiosurgery Boost in Oligometastatic Patients with Spine Metastases: a Dose-escalation Study

AIMS

To report the final results of a dose-escalation study of volumetric intensity-modulated arc stereotactic radiosurgery (VMAT-SRS) boost after three-dimensional conformal radiation therapy in patients with spine metastases.

MATERIALS AND METHODS

Oligometastatic cancer patients bearing up to five synchronous metastases (visceral or bone, including vertebral ones) and candidates for surgery or radiosurgery were considered for inclusion. 25 Gy was delivered in 10 daily fractions (2 weeks) to the metastatic lesion, affected vertebrae and adjacent ones (one cranial and one caudal vertebra). Sequentially, the dose to spinal metastases was progressively increased (8 Gy, 10 Gy, 12 Gy) in the patient cohorts. Dose-limiting toxicities were defined as any treatment-related non-hematologic acute adverse effects rated as grade ≥3 or any acute haematological toxicity rated as ≥ 4 by the Radiation Therapy Oncology Group scale.

RESULTS

Fifty-two lesions accounting for 40 consecutive patients (male/female: 29/11; median age: 71 years; range 40-85) were treated from April 2011 to September 2020. Most patients had a primary prostate (65.0%) or breast cancer (22.5%). Thirty-two patients received 8 Gy VMAT-SRS boost (total BED _α/β10: 45.6 Gy), 14 patients received 10 Gy (total BED _α/β10: 51.2 Gy) and six patients received 12 Gy (total BED _α/β10: 57.6 Gy). The median follow-up time was over 70 months (range 2-240 months). No acute toxicities > grade 2 and no late toxicities > grade 1 were recorded. The overall response rate based on computed tomography/positron emission tomography-computed tomography/magnetic resonance was 78.8%. The 24-month actuarial local control, distant metastases-free survival and overall survival rates were 88.5%, 27.1% and 90.3%, respectively.

CONCLUSION

A 12 Gy spine metastasis SRS boost following 25 Gy to the affected and adjacent vertebrae was feasible with an excellent local control rate and toxicity profile.

Deviation from consensus contouring guidelines predicts inferior local control after spine stereotactic body radiotherapy

BACKGROUND AND PURPOSE

To analyze the impact of target delineation on local control (LC) after stereotactic body radiotherapy (SBRT) for spine metastasis.

MATERIALS AND METHODS

Patients with de novo metastasis of the spine treated with SBRT, excluding those with prostate or hematologic malignancies, were retrospectively reviewed. Deviations from consensus contouring guidelines included incomplete coverage of involved vertebral compartments, omission of adjacent compartments, or unnecessary circumferential coverage. Univariable and multivariable Cox proportional hazard analyses were performed using death as a competing risk.

RESULTS

283 patients with 360 discrete lesions were included with a median follow up of 14.6 months (range 1.2-131.3). The prescription dose was 24-27Gy in 2-3 fractions for the majority of lesions. Median survival after SBRT was 18.3 months (95% confidence interval [CI]: 14.8-22.8). The 1 and 2-year LC rates were 81.1% (95% CI: 75.5-85.6%) and 70.6% (95% CI: 63.2-76.8%), respectively. In total, 60 deviations (16.7%) from consensus contouring guidelines were identified. Deviation from guidelines was associated with inferior LC (1-year LC 63.0% vs 85.5%, p<0.001). GI primary, epidural extension, and paraspinal extension were all associated with inferior LC on univariable analyses. After adjusting for confounding factors, deviation from guidelines was the strongest predictor of inferior LC (HR 3.52, 95% CI: 2.11-5.86, p<0.001). Among guideline-compliant treatments, progressions were mainly in field (61%) and/or epidural (49%), while marginal (42%) and/or epidural progressions (58%) were most common for those with deviations.

CONCLUSIONS

Adherence to consensus contouring guidelines for spine SBRT is associated with superior LC and fewer marginal misses.

Stereotactic body radiotherapy for spinal oligometastases: a review on patient selection and the optimal methodology

Stereotactic body radiotherapy (SBRT) has excellent local control and low toxicity for spinal metastases and is widely performed for spinal oligometastases. However, its additional survival benefit to standard of care, including systemic therapy, is unknown because the results of large-scale randomized controlled trials regarding SBRT for oligometastases have not been reported. Consequently, the optimal patient population among those with spinal oligometastases and the optimal methodology for spine SBRT remain unclear. The present review article discusses two topics: evidence-based optimal patient selection and methodology. The following have been reported to be good prognostic factors: young age, good performance status, slow-growing disease with a long disease-free interval, minimal disease burden, and mild fluorodeoxyglucose accumulation in positron emission tomography. In addition, we proposed four measures as the optimal SBRT method for achieving excellent local control: (i) required target delineation; (ii) recommended dose fraction schedule (20 or 24 Gy in a single fraction for spinal oligometastases and 35 Gy in five fractions for lesions located near the spinal cord); (iii) optimizing dose distribution for the target; (iv) dose constraint options for the spinal cord.

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

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

Stereotactic Body Radiation Therapy for Spinal Metastases: Tumor Control Probability Analyses and Recommended Reporting Standards

PURPOSE

We sought to investigate the tumor control probability (TCP) of spinal metastases treated with stereotactic body radiation therapy (SBRT) in 1 to 5 fractions.

METHODS AND MATERIALS

PubMed-indexed articles from 1995 to 2018 were eligible for data extraction if they contained SBRT dosimetric details correlated with actuarial 2-year local tumor control rates. Logistic dose-response models of collected data were compared in terms of physical dose and 3-fraction equivalent dose.

RESULTS

Data were extracted from 24 articles with 2619 spinal metastases. Physical dose TCP modeling of 2-year local tumor control from the single-fraction data were compared with data from 2 to 5 fractions, resulting in an estimated α/β = 6 Gy, and this was used to pool data. Acknowledging the uncertainty intrinsic to the data extraction and modeling process, the 90% TCP corresponded to 20 Gy in 1 fraction, 28 Gy in 2 fractions, 33 Gy in 3 fractions, and (with extrapolation) 40 Gy in 5 fractions. The estimated TCP for common fractionation schemes was 82% at 18 Gy, 90% for 20 Gy, and 96% for 24 Gy in a single fraction, 82% for 24 Gy in 2 fractions, and 78% for 27 Gy in 3 fractions.

CONCLUSIONS

Spinal SBRT with the most common fractionation schemes yields 2-year estimates of local control of 82% to 96%. Given the heterogeneity in the tumor control estimates extracted from the literature, with variability in reporting of dosimetry data and the definition of and statistical methods of reporting tumor control, care should be taken interpreting the resultant model-based estimates. Depending on the clinical intent, the improved TCP with higher dose regimens should be weighed against the potential risks for greater toxicity. We encourage future reports to provide full dosimetric data correlated with tumor local control to allow future efforts of modeling pooled data.

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

OBJECTIVE

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

METHODS

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

RESULTS

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

CONCLUSIONS

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

Decision Making in Patients With Metastatic Spine. The Role of Minimally Invasive Treatment Modalities

Spine metastases affect more than 70% of terminal cancer patients that eventually suffer from severe pain and neurological symptoms. Nevertheless, in the overwhelming majority of the cases, a spinal metastasis represents just one location of a diffuse systemic disease. Therefore, the best practice for treatment of spinal metastases depends on many different aspects of an oncological disease, including the assessment of neurological status, pain, location, and dissemination of the disease as well as the ability to predict the risk of disease progression with neurological worsening, benefits and risks associated to treatment and, eventually, expected survival. To address this need for a framework and algorithm that takes all aspects of care into consideration, we reviewed available evidence on the multidisciplinary management of spinal metastases. According to the latest evidence, the use of stereotactic radiosurgery (SRS) or stereotactic body radiotherapy (SBRT) for spinal metastatic disease is rapidly increasing. Indeed, aggressive surgical resection may provide the best results in terms of local control, but carries a significant rate of post-surgical morbidity whose incidence and severity appears to be correlated to the extent of resection. The multidisciplinary management represents, according to current evidence, the best option for the treatment of spinal metastases. Noteworthy, according to the recent literature evidence, cases that once required radical surgical resection followed by low-dose conventional radiotherapy, can now be more effectively treated by minimally invasive spinal surgery (MISS) followed by spine SRS with decreased morbidity, improved local control, and more durable pain control. This combination allows also extending this standard of care to patients that would be too sick for an aggressive surgical treatment.

Spinal metastasis: diagnosis, management and follow-up

Spine metastatic disease is an increasingly common occurrence in cancer patients due to improved patient survival. Close proximity of the bony spinal column to the spinal cord limits many conventional treatments for metastatic disease. In the past decade, we have witnessed dramatic advancements in therapies, with improvements in surgical techniques and recent adoption of spine stereotactic radiotherapy techniques leading to improved patient outcomes. Multidisciplinary approaches to patient evaluation, treatment and follow-up are essential. Imaging plays an ever increasing role in disease detection, pre-treatment planning and assessment of patient outcomes. It is important for the radiologist to be familiar with imaging algorithms, best practices for surgery and/or radiotherapy and imaging findings in the post-treatment period that may indicate disease recurrence. In this review, we present a multidisciplinary discussion of spine metastases, with specific focus on pre-treatment imaging, planning, current treatment approaches, and post-treatment assessment.

Treatment planning for spinal radiosurgery : A competitive multiplatform benchmark challenge

PURPOSE

To investigate the quality of treatment plans of spinal radiosurgery derived from different planning and delivery systems. The comparisons include robotic delivery and intensity modulated arc therapy (IMAT) approaches. Multiple centers with equal systems were used to reduce a bias based on individual's planning abilities. The study used a series of three complex spine lesions to maximize the difference in plan quality among the various approaches.

METHODS

Internationally recognized experts in the field of treatment planning and spinal radiosurgery from 12 centers with various treatment planning systems participated. For a complex spinal lesion, the results were compared against a previously published benchmark plan derived for CyberKnife radiosurgery (CKRS) using circular cones only. For two additional cases, one with multiple small lesions infiltrating three vertebrae and a single vertebra lesion treated with integrated boost, the results were compared against a benchmark plan generated using a best practice guideline for CKRS. All plans were rated based on a previously established ranking system.

RESULTS

All 12 centers could reach equality (n = 4) or outperform (n = 8) the benchmark plan. For the multiple lesions and the single vertebra lesion plan only 5 and 3 of the 12 centers, respectively, reached equality or outperformed the best practice benchmark plan. However, the absolute differences in target and critical structure dosimetry were small and strongly planner-dependent rather than system-dependent. Overall, gantry-based IMAT with simple planning techniques (two coplanar arcs) produced faster treatments and significantly outperformed static gantry intensity modulated radiation therapy (IMRT) and multileaf collimator (MLC) or non-MLC CKRS treatment plan quality regardless of the system (mean rank out of 4 was 1.2 vs. 3.1, p = 0.002).

CONCLUSIONS

High plan quality for complex spinal radiosurgery was achieved among all systems and all participating centers in this planning challenge. This study concludes that simple IMAT techniques can generate significantly better plan quality compared to previous established CKRS benchmarks.

Inverse treatment planning for spinal robotic radiosurgery: an international multi-institutional benchmark trial

Stereotactic radiosurgery (SRS) is the accurate, conformal delivery of high‐dose radiation to well‐defined targets while minimizing normal structure doses via steep dose gradients. While inverse treatment planning (ITP) with computerized optimization algorithms are routine, many aspects of the planning process remain user‐dependent. We performed an international, multi‐institutional benchmark trial to study planning variability and to analyze preferable ITP practice for spinal robotic radiosurgery. 10 SRS treatment plans were generated for a complex‐shaped spinal metastasis with 21 Gy in 3 fractions and tight constraints for spinal cord (V14Gy<2 cc, V18Gy<0.1 cc) and target (coverage >95%). The resulting plans were rated on a scale from 1 to 4 (excellent‐poor) in five categories (constraint compliance, optimization goals, low‐dose regions, ITP complexity, and clinical acceptability) by a blinded review panel. Additionally, the plans were mathematically rated based on plan indices (critical structure and target doses, conformity, monitor units, normal tissue complication probability, and treatment time) and compared to the human rankings. The treatment plans and the reviewers' rankings varied substantially among the participating centers. The average mean overall rank was 2.4 (1.2‐4.0) and 8/10 plans were rated excellent in at least one category by at least one reviewer. The mathematical rankings agreed with the mean overall human rankings in 9/10 cases pointing toward the possibility for sole mathematical plan quality comparison. The final rankings revealed that a plan with a well‐balanced trade‐off among all planning objectives was preferred for treatment by most participants, reviewers, and the mathematical ranking system. Furthermore, this plan was generated with simple planning techniques. Our multi‐institutional planning study found wide variability in ITP approaches for spinal robotic radiosurgery. The participants', reviewers', and mathematical match on preferable treatment plans and ITP techniques indicate that agreement on treatment planning and plan quality can be reached for spinal robotic radiosurgery.

PACS number(s): 87.55.de

Prognostic factors associated with pain palliation after spine stereotactic body radiation therapy

OBJECT The number of patients with spinal tumors is rapidly increasing; spinal metastases develop in more than 30% of cancer patients during the course of their illness. Such lesions can significantly decrease quality of life, often necessitating treatment. Stereotactic radiosurgery has effectively achieved local control and symptomatic relief for these patients. The authors determined prognostic factors that predicted pain palliation and report overall institutional outcomes after spine stereotactic body radiation therapy (SBRT). METHODS Records of patients who had undergone treatment with SBRT for either primary spinal tumors or spinal metastases from June 2008 through June 2013 were retrospectively reviewed. Data were collected at the initial visit just before treatment and at 1-, 3-, 6-, and 12-month follow-up visits. Collected clinical data included Karnofsky Performance Scale scores, pain status, presence of neurological deficits, and prior radiation exposure at the level of interest. Radiation treatment plan parameters (dose, fractionation, and target coverage) were recorded. To determine the initial extent of epidural spinal cord compression (ESCC), the authors retrospectively reviewed MR images, assessed spinal instability according to the Bilsky scale, and evaluated lesion progression after treatment. RESULTS The study included 99 patients (mean age 60.4 years). The median survival time was 9.1 months (95% CI 6.9-17.2 months). Significant decreases in the proportion of patients reporting pain were observed at 3 months (p < 0.0001), 6 months (p = 0.0002), and 12 months (p = 0.0019) after treatment. Significant decreases in the number of patients reporting pain were also observed at the last follow-up visit (p = 0.00020) (median follow-up time 6.1 months, range 1.0-56.6 months). Univariate analyses revealed that significant predictors of persistent pain after intervention were initial ESCC grade, stratified by a Bilsky grade of 1c (p = 0.0058); initial American Spinal Injury Association grade of D (p = 0.011); initial Karnofsky Performance Scale score, stratified by a score of 80 (p = 0.002); the presence of multiple treated lesions (p = 0.044); and prior radiation at the site of interest (p < 0.0001). However, when multivariate analyses were performed on all variables with p values less than 0.05, the only predictor of pain at last follow-up visit was a prior history of radiation at the site of interest (p = 0.0038), although initial ESCC grade trended toward significance (p = 0.073). Using pain outcomes at 3 months, at this follow-up time point, pain could be predicted by receipt of radiation above a threshold biologically effective dose of 66.7 Gy. CONCLUSIONS Pain palliation occurs as early as 3 months after treatment; significant differences in pain reporting are also observed at 6 and 12 months. Pain palliation is limited for patients with spinal tumors with epidural extension that deforms the cord and for patients who have previously received radiation to the same site. Further investigation into the optimal dose and fractionation schedule are needed, but improved outcomes were observed in patients who received radiation at a biologically effective dose (with an a/b of 3.0) of 66.7 Gy or higher.

The era of stereotactic body radiotherapy for spinal metastases and the multidisciplinary management of complex cases

Spinal metastases are increasingly becoming a focus of attention with respect to treating with locally "ablative" intent, as opposed to locally "palliative" intent. This is due to increasing survival rates among patients with metastatic disease, early detection as a result of increasing availability of spinal MRI, the recognition of the oligometastatic state as a distinct sub-group of favorable metastatic patients and the advent of stereotactic body radiotherapy (SBRT). Although conventionally fractionated radiation therapy has been utilized for decades, the rates of complete pain relief and local control for complex tumors are sub-optimal. SBRT has the advantage of delivering high total doses in few fractions (typically, 24 Gy in 1 or 2 fractions to 30-45 Gy in 5 fractions) that can be considered "ablative". With mature clinical experience emerging among early adopters, we are realizing beyond efficacy the limitations of spine SBRT. In particular, toxicities such as vertebral compression fracture, and epidural disease progression as the most common pattern of local tumor progression. As a result, the multidisciplinary evaluation of cases prior to SBRT is emphasized with the intent to identify patients who could benefit from surgical stabilization or down-staging of epidural disease. The purpose of this review is to provide an overview of the current literature with respect to outcomes, technical details for safe delivery, patient selection criteria, common and uncommon side effects of therapy, and the increasing use of minimally invasive surgical techniques that can improve both safety and local control.

Stereotactic body radiotherapy: a new paradigm in the management of spinal metastases

Spine stereotactic body radiotherapy is based on delivering high biologically effective doses to spinal metastases, with the intent to maximize both tumor and pain control. The purpose of this review is to outline the technical details of spine stereotactic body radiotherapy, contrast clinical outcomes to low biologically effective dose conventional palliative radiotherapy, discuss the role of surgery in the era of spine stereotactic body radiotherapy, and summarize the major serious adverse events that patients would otherwise not be at risk of with conventional radiotherapy.

Effective local control of vertebral metastases by simultaneous integrated boost radiotherapy: preliminary results

BACKGROUND

The primary endpoint was to improve local tumour control of patients with metastatic spinal tumours by stereotactic body radiotherapy (SBRT) and dose escalation by simultaneous, integrated boost (PTV-boost). We used a whole vertebral body (PTV-elective) contouring approach. Secondary endpoints were severity of acute and chronic adverse effects and overall survival.

METHODS

In all, 33 patients with metastases of the vertebral column were treated at Erlangen University Hospital. SBRT was given in 12 or 10 fractions. The metastatic lesion (PTV-boost) received 3.6 Gy (range 3.0-4.51 Gy) per fraction for a total of 42.0 Gy (24.36-48.0 Gy) and the whole vertebra (PTV-elective) received 2.85 Gy (range 1.8-3.6 Gy) per fraction for a total of 32.39 Gy (range 21.60-38.0 Gy). Patients were followed up every 3 months.

RESULTS

Local control rate of all patients was 93% at 12 and 24 months. The overall survival rate was 54% at 12 months, 38% at 24 months and 18% at 36 months. No radiation myelopathy occurred. The most frequently observed adverse events in 3 cases was oesophagitis grade 2.

CONCLUSION

SBRT with simultaneous, integrated boost was associated with excellent local control of 93% after 24 months. This result shows the possibility of delivering escalated doses to the target while still keeping the incidence of side effects low. This study forms the basis for a future randomised controlled trial comparing conventional radiotherapy (10 fractions of 3 Gy) with hypofractionated dose intensified SBRT (12 fractions of 3 Gy + integrated boost 12 fractions of 4 Gy) for improvement of local tumour control and pain.

Stereotactic radiosurgery for spinal metastases: a literature review

OBJECTIVE

The spine is the most common location for bone metastases. Since cure is not possible, local control and relief of symptoms is the basis for treatment, which is grounded on the use of conventional radiotherapy. Recently, spinal radiosurgery has been proposed for the local control of spinal metastases, whether as primary or salvage treatment. Consequently, we carried out a literature review in order to analyze the indications, efficacy, and safety of radiosurgery in the treatment of spinal metastases.

METHODS

We have reviewed the literature using the PubMed gateway with data from the MEDLINE library on studies related to the use of radiosurgery in treatment of bone metastases in spine. The studies were reviewed by all the authors and classified as to level of evidence, using the criterion defined by Wright.

RESULTS

The indications found for radiosurgery were primary control of epidural metastases (evidence level II), myeloma (level III), and metastases known to be poor responders to conventional radiotherapy--melanoma and renal cell carcinoma (level III). Spinal radiosurgery was also proposed for salvage treatment after conventional radiotherapy (level II). There is also some evidence as to the safety and efficacy of radiosurgery in cases of extramedullar and intramedullar intradural metastatic tumors (level III) and after spinal decompression and stabilization surgery.

CONCLUSION

Radiosurgery can be used in primary or salvage treatment of spinal metastases, improving local disease control and patient symptoms. It should also be considered as initial treatment for radioresistant tumors, such as melanoma and renal cell carcinoma.

[Advances in radiation oncology for metastatic bone disease]

INTRODUCTION

Irradiation of bone metastases primarily aims at alleviating pain, preventing fracture in the short term. The higher doses and more conformal dose distribution achievable while saving healthy tissue with new irradiation techniques have induced a paradigm shift in the management of bone metastases in a growing number of clinical situations.

MATERIALS AND METHODS

A search of the English and French literature was conducted using the keywords: bone metastases, radiotherapy, interventional radiology, vertebroplasty, radiofrequency, chemoembolization. RESULTS-DISCUSSION: Stereotactic irradiation yields pain relief rates greater than 90% in Phase I/II and retrospective studies. IMRT (static, rotational, helical) and stereotactic irradiation yield local control rates of 75-90% at 2 years. Some situations previously evaluated as palliative are currently treated more aggressively with optimized radiation sometimes combined modality interventional radiology.

CONCLUSION

A recommendation can only be made for stereotactic irradiation in vertebral oligometastases or reirradiation. In the absence of a sufficient level of evidence, the increasing use of conformal irradiation techniques can only reflect the daily practice and the patient benefit while integrating economic logic care. The impact of these aggressive approaches on survival remains to be formally demonstrated by interventional prospective studies or observatories including quality of life items and minimal 2-year follow-up.

Vertebral compression fracture after stereotactic body radiotherapy for spinal metastases

The use of stereotactic body radiotherapy for metastatic spinal tumours is increasing. Serious adverse events for this treatment include vertebral compression fracture (VCF) and radiation myelopathy. Although VCF is a fairly low-risk adverse event (approximately 5% risk) after conventional radiotherapy, crude risk estimates for VCF after spinal SBRT range from 11% to 39%. In this Review, we summarise the evidence and predictive factors for VCF induced by spinal SBRT, review the pathophysiology of VCF in the metastatic spine, and discuss strategies used to prevent and manage this potentially disabling complication.