Stereotactic body radiotherapy for de novo spinal metastases: systematic review

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

PURPOSE

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

METHODS

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

RESULTS

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

CONCLUSIONS

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

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.

Magnetic Resonance Imaging Frequency After Stereotactic Body Radiation Therapy for Spine Metastases

PURPOSE

Stereotactic body radiation therapy (SBRT) is increasingly being used to treat spine metastases. Current post-SBRT imaging surveillance strategies in this patient population may benefit from a more data-driven and personalized approach. The objective of this study was to develop risk-stratified post-SBRT magnetic resonance imaging (MRI) surveillance strategies using quantitative methods.

METHODS AND MATERIALS

Adult patients with bony spine metastases treated with SBRT between 2008 and 2021 and who had at least 2 follow-up spine MRIs were reviewed retrospectively. A recursive partitioning analysis model was developed to separate patients into different risk categories for post-SBRT progression anywhere within the spine. Imaging intervals were derived for each risk category using parametric survival regression based on multiple expected spine progression rates per scan.

RESULTS

A total of 446 patients and 1039 vertebral segments were included. Cumulative incidence of spine progression was 19.2% at 1 year, 26.7% at 2 years, and 35.3% at 4 years. The internally validated risk stratification model was able to divide patients into 3 risk categories based on epidural disease, paraspinal disease, and Spinal Instability Neoplastic Score category. The 4-year risk of spine progression was 23.4%, 39.0%, and 51.8%, respectively, for the low-, intermediate-, and high-risk groups. Using an expected per-scan spine progression rate of 3.75%, the low-risk group would require follow-up scans every 6.0 months (95% CI, 4.9-7.6) and the intermediate-risk group would require surveillance every 3.1 months (95% CI, 2.6-3.7). At an expected spine progression rate of 5%, the high-risk group would require surveillance every 1.3 months (95% CI, 1.1-1.6) during the first 13.2 months after SBRT and every 5.9 months thereafter (95% CI, 2.8-12.3).

CONCLUSIONS

Data-driven follow-up MRI surveillance intervals at a range of expected spine progression rates have been determined for patients at different risks of spine progression based on an internally validated, single-institution risk stratification model.

Meta-Analysis of Stereotactic Body Radiation ThERapy in Nonspine BONE Metastases (MASTER-BONES)

PURPOSE

The efficacy and safety of stereotactic body radiation therapy (SBRT) for patients with nonspine bone metastases remains in question. A systematic review and meta-analysis were performed to evaluate SBRT treatment outcomes in nonspine bone metastases.

METHODS AND MATERIALS

Eligible studies were retrieved from MEDLINE, Embase, Scielo, the Cochrane Library, and annual meeting proceedings through July 6, 2023. We adhered to the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) and Meta-analysis of Observational Studies in Epidemiology (MOOSE) guideline recommendations. Quantitative synthesis was performed using a random-effects model. Meta-regression was performed to determine correlation between clinical and treatment factors with the local failure (LF) and fracture rate. P values ≤.05 were deemed statistically significant.

RESULTS

Seven retrospective studies, with a total of 807 patients (1048 lesions) treated with SBRT were included, with median follow-up ranging from 7.6 to 26.5 months. The most common SBRT sites were pelvis (39.2%), ribs (25.8%), femur (16.7%), and humerus/shoulder region (8.7%). At 1 year, the LF and fracture rate were 7% (95% CI, 5.5%-8.5%; I2 = 0; n = 75/1048) and 5.3% (95% CI, 3%-7.5%; I2 = 0; n = 65/1010). The 2-year cumulative LF incidence was 12.1% (95% CI, 10%-15.5%). The overall survival and progression-free survival at 1 year were 82% (95% CI, 75%-88%; I2 = 82%; n = 746/867) and 33.5% (95% CI, 26%-41%; I2 = 0%; n = 51/152), with a median of 20.2 months (95% CI, 10.9-49.1 months) and 8.3 months (95% CI, 6.3-10.3 months) for overall survival and progression-free survival, respectively. Meta-regression analysis revealed a significant relationship between planning target volume and fracture rate (P < .05). Ribs (2.5%) followed by the femur (1.9%; 95% CI, 0%-6.1%) were the most common fracture sites. The occurrence of pain flare, fatigue, and dermatitis were 7%, 5.4%, and 0.65%, respectively.

CONCLUSIONS

Stereotactic body radiation proves both safety and efficacy for non-spine bone metastases, and although serious complications (grade 3) are rare, one case of grade 5 complication was reported. Careful consideration of target volume is crucial due to its link with a higher fracture risk.

Management of Metastatic Spinal Disease - A Practical Approach

STUDY DESIGN

Narrative review.

OBJECTIVE

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

METHODS

N/A.

RESULTS

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

CONCLUSION

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

Palliative Care Needs of Patients with Musculoskeletal Malignancies

PURPOSE OF REVIEW

This review aims to assess the literature regarding current treatment options for the palliative care of patients with advanced musculoskeletal malignancies whether primary or metastatic.

RECENT FINDINGS

The inclusion of specialized palliative care physicians, in conjunction with surgeons, medical oncologists, radiation oncologists, interventional radiologists, and mental health professionals, results in better control of end-of-life symptoms in both children and adults with terminal musculoskeletal malignancies. The palliative care of patients with musculoskeletal malignancies requires a multi-disciplinary team and benefits from specialized palliative care physicians. The unique impacts of musculoskeletal malignancies on ambulation and independence creates additional mental and physical burdens on patients and care-takers alike. Palliative care should focus on preserving ambulatory function and patient independence, in addition to managing chronic pain and other end-of-life symptoms common to these malignancies.

Imaging protocols for non-traumatic spinal cord injury: current state of the art and future directions

INTRODUCTION

Non-traumatic spinal cord injury (NTSCI) is a term used to describe damage to the spinal cord from sources other than trauma. Neuroimaging techniques such as computerized tomography (CT) and magnetic resonance imaging (MRI) have improved our ability to diagnose and manage NTSCIs. Several practice guidelines utilize MRI in the diagnostic evaluation of traumatic and non-traumatic SCI to direct surgical intervention.

AREAS COVERED

The authors review practices surrounding the imaging of various causes of NTSCI as well as recent advances and future directions for the use of novel imaging modalities in this realm. The authors also present discussions around the use of simple radiographs and advanced MRI modalities in clinical settings, and briefly highlight areas of active research that seek to advance our understanding and improve patient care.

EXPERT OPINION

Although several obstacles must be overcome, it appears highly likely that novel quantitative imaging features and advancements in artificial intelligence (AI) as well as machine learning (ML) will revolutionize degenerative cervical myelopathy (DCM) care by providing earlier diagnosis, accurate localization, monitoring for deterioration and neurological recovery, outcome prediction, and standardized practice. Some intriguing findings in these areas have been published, including the identification of possible serum and cerebrospinal fluid biomarkers, which are currently in the early phases of translation.

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

STUDY DESIGN

Retrospective Cohort.

OBJECTIVE

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

METHODS

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

RESULTS

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

CONCLUSION

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

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

PURPOSE

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

METHODS

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

RESULTS

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

CONCLUSIONS

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

Patient-Reported and Clinical Outcomes of Surgically Treated Patients With Symptomatic Spinal Metastases: Results From Epidemiology, Process, and Outcomes of Spine Oncology (EPOSO), a Prospective, Multi-Institutional and International Study

BACKGROUND AND OBJECTIVES

The palliative impact of spine surgery for metastatic disease is evolving with improvements in surgical technique and multidisciplinary cancer care. The goal of this study was to prospectively evaluate long-term clinical outcomes including health-related quality-of-life (HRQOL) measures, using spine cancer-specific patient-reported-outcome (PRO) measures, in patients with symptomatic spinal metastases who underwent surgical management.

METHODS

The Epidemiology, Process, and Outcomes of Spine Oncology (EPOSO, ClinicalTrials.gov identifier: NCT01825161) trial is a prospective-observational cohort study that included 10 specialist centers in North America and Europe. Patients aged 18 to 75 years who underwent surgery for spinal metastases were included. Prospective assessments included both spine tumor-specific and generic PRO tools which were collected for a minimum of 2 years post-treatment or until death.

RESULTS

Two hundred and eighty patients (51.8% female, mean age 57.9 years) were included. At presentation, the mean Charlson Comorbidity Index was 6.0, 35.7% had neurological deficits as defined by the American Spinal Cord Injury Association scores, 47.2% had high-grade epidural spinal cord compression (2-3), and 89.6% had impending or frank instability as measured by a Spinal Instability Neoplastic Score of ≥7. The most common primary tumor sites were breast (20.2%), lung (18.8%), kidney (16.2%), and prostate (6.5%). The median overall survival postsurgery was 501 days, and the 2-year progression-free-survival rate was 38.4%. Compared with baseline, significant and durable improvements in HRQOL were observed at the 6-week, 12-week, 26-week, 1-year, and 2-year follow-up assessments from a battery of PRO questionnaires including the spine cancer-specific, validated, Spine Oncology Study Group Outcomes Questionnaire v2.0, the Short Form 36 version 2, EuroQol-5 Dimension (3L), and pain numerical rating scale score.

CONCLUSION

Multi-institutional, prospective-outcomes data confirm that surgical decompression and/or stabilization provides meaningful and durable improvements in multiple HRQOL domains, including spine-specific outcomes based on the Spine Oncology Study Group Outcomes Questionnaire v2.0, for patients with metastatic spine disease.

Validation of complex radiotherapy techniques using polymer gel dosimetry

Modern radiotherapy delivers highly conformal dose distributions to irregularly shaped target volumes while sparing the surrounding normal tissue. Due to the complex planning and delivery techniques, dose verification and validation of the whole treatment workflow by end-to-end tests became much more important and polymer gel dosimeters are one of the few possibilities to capture the delivered dose distribution in 3D. The basic principles and formulations of gel dosimetry and its evaluation methods are described and the available studies validating device-specific geometrical parameters as well as the dose delivery by advanced radiotherapy techniques, such as 3D-CRT/IMRT and stereotactic radiosurgery treatments, the treatment of moving targets, online-adaptive magnetic resonance-guided radiotherapy as well as proton and ion beam treatments, are reviewed. The present status and limitations as well as future challenges of polymer gel dosimetry for the validation of complex radiotherapy techniques are discussed.

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.

A study on short-term efficacy and safety of Iodine-125 brachytherapy coupled with preoperative arterial chemoembolization for hypervascular spinal metastasis

PURPOSE

Hypervascular spinal metastatic malignancies can cause severe pain and intraoperative bleeding and selection of appropriate treatment can be challenging. This study aimed to observe the short-term efficacy and safety of Iodine-125 brachytherapy (125I BT) combined with preoperative transcatheter arterial chemoembolization (TACE) for hypervascular spinal metastasis.

METHODS

This study included a total of 33 patients (39 lesions) with hypervascular spinal metastasis. All of them carried out a regimen of TACE followed by 125I BT under CT guidance. A brachytherapy planning system has been utilized for the purpose of designing treatment plans and optimizing dose distribution. Pain relief was evaluated using a numeric rating scale (NRS) and intraoperative bleeding was recorded. Follow-up was conducted for 6 months to observe the local control rate and clinical complications.

RESULTS

All patients tolerated combined treatment well and intraoperative blood loss of every patient was not more than 10 ml. The 2- and 6- month local disease control rates were 92.3% and 83.8%. The NRS scores for thirty-three tumor patients before surgery and after one week, two, and six months of surgery were recorded as 7.33 ± 1.80, 7.39 ± 1.89, 3.15 ± 2.35, and 4.16 ± 2.15, respectively. The NRS score 2 months after treatment was found considerably lower in comparison to the NRS score before operation (p < 0.05).

CONCLUSIONS

According to our findings, 125I BT as well as preoperative TACE leads to perioperative hemostasis, pain alleviation, and reduced tumor burden, indicating that this combined treatment could be effective and promising for hypervascular spinal metastases.

[Acute spinal cord compression under systemic therapy - radiotherapy or surgery?]

Vertebral bodies are one of the most common metastasis sites found in advanced prostate cancer and have a significant impact on patients' quality of life. Spinal metastases frequently cause severe back pain and in some occasions can lead to secondary complications, with serious neurological deficits and loss of function. The main treatment goals include adequate pain management, controlling tumour growth and restoring spinal stability. Publications on the role of surgery - both conventional and stereotactic radiotherapy, and either as an individual modality or in combination - have been inconclusive. The NOMS score has proven to be useful in making treatment decisions. Existing data show better outcomes in patients with surgical therapy, both when performed in isolation and also combined with radiotherapy, in which some of the cohorts studied including patients with primary cancer other than prostate cancer. Comparative studies that specifically investigate the superiority of specific therapy modalities for metastatic prostate carcinoma are scarce. Similarly, there are limited data on microsurgical interventions for spinal metastases. Radiotherapy alone is crucial in the setting of palliation, especially for pain relief, and its effectiveness has been shown in many studies. The patient's life expectancy plays a crucial role in deciding the most appropriate treatment approach. Given the complexity of the patient population, a multimodal therapy approach is necessary. Current trends in therapy favour greater use of surgical interventions, particularly in the early detection of spinal metastases.

Stereotactic body radiation therapy (SBRT) for spinal metastases: 12 years of a single center experience

OBJECTIVE

To assess the clinical outcomes of patients with spine metastases treated with SBRT at our institution.

MATERIALS AND METHODS

Patients with spine metastases treated with SBRT (1 fraction/18 Gy or 5 fractions/7 Gy) during the last 12 years have been analyzed. All patients were simulated supine in a vacuum cushion or with a shoulder mask. CT scans and MRI image registration were performed. Contouring was based on International Spine-Radiosurgery-Consortium-Consensus-Guidelines. Highly conformal-techniques (IMRT/VMAT) were used for treatment planning. Intra and interfraction (CBCT or X-Ray-ExacTrac) verification were mandatory.

RESULTS

From February 2010 to January 2022, 129 patients with spinal metastases were treated with SBRT [1 fraction/18 Gy (75%) or 5 fractions/7 Gy] (25%). For patients with painful metastases (74/129:57%), 100% experienced an improvement in pain after SBRT. With a median follow-up of 14.2 months (average 22.9; range 0.5-140) 6 patients (4.6%) experienced local relapse. Local progression-free survival was different, considering metastases's location (p < 0.04). The 1, 2 and 3 years overall survival (OS) were 91.2%, 85.1% and 83.2%, respectively. Overall survival was significantly better for patients with spine metastases of breast and prostate cancers compared to other tumors (p < 0.05) and significantly worse when visceral metastases were present (p < 0.05), when patients were metastatic de novo (p < 0.05), and in those patients receiving single fraction SBRT (p: 0.01).

CONCLUSIONS

According to our experience, SBRT for patients with spinal metastases was effective in terms of local control and useful to reach pain relief. Regarding the intent of the treatment, an adequate selection of patients is essential to propose this ablative approach.

MRI feature-based radiomics models to predict treatment outcome after stereotactic body radiotherapy for spinal metastases

OBJECTIVE

This study aimed to extract radiomics features from MRI using machine learning (ML) algorithms and integrate them with clinical features to build response prediction models for patients with spinal metastases undergoing stereotactic body radiotherapy (SBRT).

METHODS

Patients with spinal metastases who were treated using SBRT at our hospital between July 2018 and April 2023 were recruited. We assessed their response to treatment using the revised Response Evaluation Criteria in Solid Tumors (version 1.1). The lesions were categorized into progressive disease (PD) and non-PD groups. Radiomics features were extracted from T1-weighted image (T1WI), T2-weighted image (T2WI), and fat-suppression T2WI sequences. Feature selection involved intraclass correlation coefficients, minimal-redundancy-maximal-relevance, and least absolute shrinkage and selection operator methods. Thirteen ML algorithms were employed to construct the radiomics prediction models. Clinical, conventional imaging, and radiomics features were integrated to develop combined models. Model performance was evaluated using receiver operating characteristic (ROC) curve analysis, and the clinical value was assessed using decision curve analysis.

RESULTS

We included 194 patients with 142 (73.2%) lesions in the non-PD group and 52 (26.8%) in the PD group. Each region of interest generated 2264 features. The clinical model exhibited a moderate predictive value (area under the ROC curve, AUC = 0.733), while the radiomics models demonstrated better performance (AUC = 0.745-0.825). The combined model achieved the best performance (AUC = 0.828).

CONCLUSION

The MRI-based radiomics models exhibited valuable predictive capability for treatment outcomes in patients with spinal metastases undergoing SBRT.

CRITICAL RELEVANCE STATEMENT

Radiomics prediction models have the potential to contribute to clinical decision-making and improve the prognosis of patients with spinal metastases undergoing SBRT.

KEY POINTS

• Stereotactic body radiotherapy effectively delivers high doses of radiation to treat spinal metastases. • Accurate prediction of treatment outcomes has crucial clinical significance. • MRI-based radiomics models demonstrated good performance to predict treatment outcomes.

Incidence and Prognostic Factors of Painful Vertebral Compression Fracture Caused by Spine Stereotactic Body Radiotherapy

Most studies of vertebral compression fractures (VCF) caused by stereotactic body radiotherapy (SBRT) do not discuss the symptoms of this complication. In this paper, we aimed to determine the rate and prognostic factors of painful VCF caused by SBRT for spinal metastases. Spinal segments with VCF in patients treated with spine SBRT between 2013 and 2021 were retrospectively reviewed. The primary endpoint was the rate of painful VCF (grades 2-3). Patient demographic and clinical characteristics were evaluated as prognosticators. In total, 779 spinal segments in 391 patients were analyzed. The median follow-up after SBRT was 18 (range: 1-107) months. Sixty iatrogenic VCFs (7.7%) were identified. The rate of painful VCF was 2.4% (19/779). Eight (1.0%) VCFs required surgery for internal fixation or spinal canal decompression. The painful VCF rate was significantly higher in patients with no posterolateral tumor involvement than in those with bilateral or unilateral involvement (50% vs. 23%; p = 0.042); it was also higher in patients with spine without fixation than in those with fixation (44% vs. 0%; p < 0.001). Painful VCFs were confirmed in only 2.4% of all the irradiated spinal segments. The absence of posterolateral tumor involvement and no fixation was significantly associated with painful VCF.

Quantification of six-degree-of-freedom motion during beam delivery in spine stereotactic body radiotherapy using intra-irradiation cone-beam computed tomography imaging technique

PURPOSE

Quantifying intra-fractional six-degree-of-freedom (6DoF) residual errors or motion from approved patient setups is necessary for accurate beam delivery in spine stereotactic body radiotherapy. However, previously reported errors were not acquired during beam delivery. Therefore, we aimed to quantify the 6DoF residual errors and motions during arc beam delivery using a concurrent cone-beam computed tomography (CBCT) imaging technique, intra-irradiation CBCT.

METHODS

Consecutive 15 patients, 19 plans for various treatment sites, and 199 CBCT images were analyzed. Pre-irradiation CBCT was performed to verify shifts from the initial patient setup using the ExacTrac system. During beam delivery by two or three co-planar full-arc rotations, CBCT imaging was performed concurrently. Subsequently, an intra-irradiation CBCT image was reconstructed. Pre- and intra-irradiation CBCT images were rigidly registered to a planning CT image based on the bone to quantify 6DoF residual errors.

RESULTS

6DoF residual errors quantified using pre- and intra-irradiation CBCTs were within 2.0 mm/2.0°, except for one measurement. The mean elapsed time (mean ± standard deviation [min:sec]) after pre-irradiation CBCT to the end of the last arc beam delivery was 6:08 ± 1:25 and 7:54 ± 2:14 for the 2- and 3-arc plans, respectively. Root mean squares of residual errors for several directions showed significant differences; however, they were within 1.0 mm/1.0°. Time-dependent analysis revealed that the residual errors tended to increase with elapsed time.

CONCLUSION

The errors represent the optimal intra-fractional error compared with those acquired using the pre-, inter-beam, and post-6DoF image guidance and can be acquired within a standard treatment timeslot.

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.

Evaluation of a dedicated software for semi-automated VMAT planning of spine Stereotactic Body Radiotherapy (SBRT)

PURPOSE

To determine whether SBRT of spinal metastasis using a dedicated treatment planning system (TPS) and delivered with a gantry-based LINAC could provide plans of similar quality to the Cyberknife technology. Additional comparison was also done with other commercial TPS used for volumetric modulated arc therapy (VMAT) planning.

MATERIALS AND METHODS

Thirty Spine SBRT patients, previously treated in our institution with CyberKnife (Accuray, Sunnyvale) using Multiplan TPS, were replanned in VMAT with an dedicated TPS (Elements Spine SRS, Brainlab, Munich) and our clinical TPS (Monaco, Elekta LTD, Stockholm), using exactly the same arc geometry. The comparison was done by assessing differences in dose delivered to PTV, CTV and spinal cord, calculating modulation complexity scores (MCS) and performing quality control (QA) of the plans.

RESULTS

Regardless of the vertebra level, in general, no statistical difference was found in PTV coverage between all TPS. Conversely, PTV and CTV D_50% were found significantly higher for the dedicated TPS compared to others. In addition, the dedicated TPS also resulted in better gradient index (GI) than clinical VMAT TPS, whatever the vertebral level, and better GI than Cyberknife TPS for the thoracic level only. The D_2% to the spinal cord was generally significantly lower with the dedicated TPS compared with others. No significant difference was found in the MCS between both VMAT TPS. All QA were clinically acceptable.

CONCLUSION

The Elements Spine SRS TPS offers very effective and user-friendly semi-automated planning tools and is secure and promising for gantry-based LINAC spinal SBRT.

Spinal tumours: recommendations of the Polish Society of Spine Surgery, the Polish Society of Oncology, the Polish Society of Neurosurgeons, the Polish Society of Oncologic Surgery, the Polish Society of Oncologic Radiotherapy, and the Polish Society of Orthopaedics and Traumatology

PURPOSE

The purpose of these recommendations is to spread the available evidence for evaluating and managing spinal tumours among clinicians who encounter such entities.

METHODS

The recommendations were developed by members of the Development Recommendations Group representing seven stakeholder scientific societies and organizations of specialists involved in various forms of care for patients with spinal tumours in Poland. The recommendations are based on data yielded from systematic reviews of the literature identified through electronic database searches. The strength of the recommendations was graded according to the North American Spine Society's grades of recommendation for summaries or reviews of studies.

RESULTS

The recommendation group developed 89 level A-C recommendations and a supplementary list of institutions able to manage primary malignant spinal tumours, namely, spinal sarcomas, at the expert level. This list, further called an appendix, helps clinicians who encounter spinal tumours refer patients with suspected spinal sarcoma or chordoma for pathological diagnosis, surgery and radiosurgery. The list constitutes a basis of the network of expertise for the management of primary malignant spinal tumours and should be understood as a communication network of specialists involved in the care of primary spinal malignancies.

CONCLUSION

The developed recommendations together with the national network of expertise should optimize the management of patients with spinal tumours, especially rare malignancies, and optimize their referral and allocation within the Polish national health service system.

Patterns of Failure After Stereotactic Body Radiotherapy to Sacral Metastases

AIMS

Stereotactic body radiotherapy (SBRT) is increasingly used to treat sacral metastases. We analysed our centre's local relapse rates and patterns of failure after sacral SBRT and assessed whether using the consensus contouring recommendation (CCR) may have prevented local relapse.

MATERIALS AND METHODS

We conducted a single-centre retrospective review of patients treated with sacral SBRT between February 2012 and December 2021. The cumulative incidence of local relapse, patterns of failure and overall survival were determined. Two investigators reviewed planning computed tomography scans and imaging at relapse to determine if local relapse was potentially preventable with a larger CCR-derived radiotherapy field.

RESULTS

In total, 34 patients received sacral SBRT, with doses ranging from 24 to 40 Gy over three to five fractions. The most frequently used schedule was 30 Gy in three fractions. Common primaries treated included prostate (n = 16), breast (n = 6), lung (n = 3) and renal (n = 3) cancers. The median follow-up was 20 months (interquartile range 13-55 months). The cumulative incidence of local relapse (4/34) was 2.9% (95% confidence interval 0.2-13.2), 6.3% (95% confidence interval 1.1-18.5) and 16.8% (95% confidence interval 4.7-35.4) at 6 months, 1 year and 2 years, respectively. The patterns of failure were local-only (1/34), local and distant (3/34) and distant relapse (10/34). The overall survival was 96.7% (95% confidence interval 90.5-100) and 90.6% (95% confidence interval 78.6-100) at 1 and 2 years, respectively. For prostate/breast primaries, the cumulative incidence of local relapse was 4.5% (95% confidence interval 0.3-19.4), 4.5% (95% confidence interval 0.3-19.4) and 12.5% (95% confidence interval 1.7-34.8) at 6 months, 1 and 2 years, respectively. Twenty-nine cases (85.3%) deviated from the CCR. Sacral relapse was potentially preventable if the CCR was used in one patient (2.9% of the whole cohort and 25% of the relapsed cohort).

DISCUSSION

We have shown excellent local control rates with sacral SBRT, which was largely planned with a margin expansion approach.

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.

Stereotactic body radiotherapy versus conventional radiotherapy for painful bone metastases: a systematic review and meta-analysis of randomised controlled trials

BACKGROUND

Stereotactic body radiotherapy (SBRT) is a promising approach in treating painful bone metastases. However, the superiority of SBRT over conventional external beam radiotherapy (cEBRT) remains controversial. Therefore, this systematic review and meta-analysis of randomised controlled trials was conducted to compare SBRT and cEBRT for the treatment of bone metastases.

METHODS

A search was conducted using PubMed on January 22, 2022, with the following inclusion criteria: (i) randomised controlled trials comparing SBRT with cEBRT for bone metastases and (ii) endpoint including pain response. Effect sizes across studies were pooled using random-effects models in a meta-analysis of risk ratios.

RESULTS

A total of 1246 articles were screened, with 7 articles comprising 964 patients (522 and 442 patients in the SBRT and cEBRT arms, respectively) meeting the inclusion criteria. The overall pain response (OR) rates of bone metastases at 3 months were 45% and 36% in the SBRT and cEBRT arms, respectively. The present analyses showed no significant difference between the two groups. In four studies included for the calculation of OR rates of spinal metastases at three months, the OR rates were 40% and 35% in the SBRT and cEBRT arms, respectively, with no significant difference between the two groups. The incidence of severe adverse effects and health-related quality of life outcomes were comparable between the two arms.

CONCLUSIONS

The superiority of SBRT over cEBRT for pain palliation in bone metastases was not confirmed in this meta-analysis. Although SBRT is a standard of care for bone metastases, patients receiving SBRT should be selected appropriately.

Application of Artificial Intelligence Methods for Imaging of Spinal Metastasis

Spinal metastasis is the most common malignant disease of the spine. Recently, major advances in machine learning and artificial intelligence technology have led to their increased use in oncological imaging. The purpose of this study is to review and summarise the present evidence for artificial intelligence applications in the detection, classification and management of spinal metastasis, along with their potential integration into clinical practice. A systematic, detailed search of the main electronic medical databases was undertaken in concordance with the PRISMA guidelines. A total of 30 articles were retrieved from the database and reviewed. Key findings of current AI applications were compiled and summarised. The main clinical applications of AI techniques include image processing, diagnosis, decision support, treatment assistance and prognostic outcomes. In the realm of spinal oncology, artificial intelligence technologies have achieved relatively good performance and hold immense potential to aid clinicians, including enhancing work efficiency and reducing adverse events. Further research is required to validate the clinical performance of the AI tools and facilitate their integration into routine clinical practice.

Palliative Efficacy of High-Dose Stereotactic Body Radiotherapy Versus Conventional Radiotherapy for Painful Non-Spine Bone Metastases: A Propensity Score-Matched Analysis

(1) Background: The superiority of stereotactic body radiotherapy (SBRT) over conventional external beam radiotherapy (cEBRT) in terms of pain palliation for bone metastases remains controversial. (2) Methods: This propensity score-matched study compared the overall pain response (OR) 3 months after radiotherapy among patients with painful (≥2 points on a 0-to-10 scale) non-spine bone metastases. Patients with lesions that were treated with SBRT or cEBRT and whose pain scores were evaluated 3 months after radiotherapy were included in this study. Pain response was evaluated according to the International Consensus Criteria. (3) Results: A total of 234 lesions (SBRT, n = 129; cEBRT, n = 105) were identified in our institutional database. To reduce the confounding effects, 162 patients were selected using a propensity score-matched analysis (n = 81 for each treatment). The OR rate at 3 months after SBRT was significantly higher than that after cEBRT (76.5% vs. 56.8%; p = 0.012). A noteworthy finding of our study is that the same trend was observed even after 6 months (75.9% vs. 50.0%; p = 0.011). The 1-year local failure rates after SBRT and cEBRT were 10.2% and 33.3% (p < 0.001), respectively. (4) Conclusions: Our findings suggest that SBRT is superior to cEBRT for pain palliation in patients with non-spine bone metastases.

Single and multi-fraction spine stereotactic body radiation therapy and the risk of radiation induced myelopathy

Purpose

This study reports on the risk of radiation-induced myelitis (RM) of the spinal cord from a large single-institutional experience with 1 to 5 fraction stereotactic body radiation therapy (SBRT) to the spine.

Methods and Materials

A retrospective review of patients who received spine SBRT to a radiation naïve level at or above the conus medullaris between 2007 and 2019 was performed. Local failure determination was based on SPIne response assessment in Neuro-Oncology criteria. RM was defined as neurologic symptoms consistent with the segment of cord irradiated in the absence of neoplastic disease recurrence and graded by Common Toxicity Criteria for Adverse Events, version 4.0. Rates of adverse events were estimated and dose-volume statistics from delivered treatment plans were extracted for the planning target volumes and spinal cord.

Results

A total of 353 lesions in 277 patients were identified that met the specified criteria, for which 270, 70, and 13 lesions received 1-, 3-, and 5-fraction treatments, respectively, with a median follow-up of 46 months (95% confidence interval [CI], 41-52 months) for all surviving patients. The median overall survival was 33.0 months (95% CI, 29-43). The median D0.03cc to the spinal cord was 11.7 Gy (interquartile range [IQR], 10.5-12.4), 16.7 Gy (IQR, 12.8-20.6), and 26.0 Gy (IQR, 24.1-28.1), for 1-, 3-, 5-fractions. Using an a/b = 2Gy for the spinal cord, the median single-fraction equivalent-dose (SFED₂) was 11.7 Gy (IQR, 10.2-12.5 Gy) and the normalized biological equivalent dose (nBED_2/2) was 19.9 Gy (IQR, 15.4-22.8 Gy). One patient experienced grade 2 RM after a single-fraction treatment. The cumulative probability of RM was 0.3% (95% CI, 0%-2%).

Conclusions

Spine SBRT is safe while limiting the spinal cord (as defined on treatment planning magnetic resonance imaging or computed tomography myelogram) D0.03cc to less than 14 Gy, 21.9 Gy, and 30 Gy, for 1, 3, and 5-fractions, consistent with standard guidelines.

Stereotactic Body Radiation Therapy versus Conventional External Beam Radiation Therapy for Painful Bone Metastases: A Systematic Review and Meta-analysis of Randomized Trials

PURPOSE

To compare the efficacy and safety of stereotactic body radiation therapy (SBRT) and conventional external beam radiation therapy (cEBRT) in patients with previously unirradiated painful bone metastases (BM).

METHODS

We searched biomedical databases for eligible randomized trials (RCTs). The outcomes of interest were pain response, local progression, overall survival (OS) and adverse events. We used established tools to assess the quality of the individual trials and certainty of the pooled evidence. We performed meta-analyses using random effects models.

RESULTS

Six RCTs were identified. SBRT improved complete pain response rates at 3 months (OR, 3.38; 95% CI, 1.88-6.07; high certainty), reduced local progression rates (OR, 0.19; 95% CI, 0.06-0.62; high certainty) and increase pain flare rates. There were no differences for other outcomes.

CONCLUSION

Among patients with previously unirradiated painful BM, SBRT significantly improved complete pain response rates at 3 months, delayed local progression and increase pain flare rates.

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.

Narrative Review of Synergistics Effects of Combining Immunotherapy and Stereotactic Radiation Therapy

Stereotactic radiotherapy (SRT) has become an attractive treatment modality in full bloom in recent years by presenting itself as a safe, noninvasive alternative to surgery to control primary or secondary malignancies. Although the focus has been on local tumor control as the therapeutic goal of stereotactic radiotherapy, rare but intriguing observations of abscopal (or out-of-field) effects have highlighted the exciting possibility of activating antitumor immunity using high-dose radiation. Furthermore, immunotherapy has revolutionized the treatment of several types of cancers in recent years. However, resistance to immunotherapy often develops. These observations have led researchers to combine immunotherapy with SRT in an attempt to improve outcomes. The benefits of this combination would come from the stimulation and suppression of various immune pathways. Thus, in this review, we will first discuss the immunomodulation induced by SRT with the promising results of preclinical studies on the changes in the immune balance observed after SRT. Then, we will discuss the opportunities and risks of the combination of SRT and immunotherapy with the preclinical and clinical data available in the literature. Furthermore, we will see that many perspectives are conceivable to potentiate the synergistic effects of this combination with the need for prospective studies to confirm the encouraging data.

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.

Multi-Omics Approaches for the Prediction of Clinical Endpoints after Immunotherapy in Non-Small Cell Lung Cancer: A Comprehensive Review

Immune checkpoint inhibitors (ICI) have revolutionized the management of locally advanced and advanced non-small lung cancer (NSCLC). With an improvement in the overall survival (OS) as both first- and second-line treatments, ICIs, and especially programmed-death 1 (PD-1) and programmed-death ligands 1 (PD-L1), changed the landscape of thoracic oncology. The PD-L1 level of expression is commonly accepted as the most used biomarker, with both prognostic and predictive values. However, even in a low expression level of PD-L1, response rates remain significant while a significant number of patients will experience hyperprogression or adverse events. The dentification of such subtypes is thus of paramount importance. While several studies focused mainly on the prediction of the PD-L1 expression status, others aimed directly at the development of prediction/prognostic models. The response to ICIs depends on a complex physiopathological cascade, intricating multiple mechanisms from the molecular to the macroscopic level. With the high-throughput extraction of features, omics approaches aim for the most comprehensive assessment of each patient. In this article, we will review the place of the different biomarkers (clinical, biological, genomics, transcriptomics, proteomics and radiomics), their clinical implementation and discuss the most recent trends projecting on the future steps in prediction modeling in NSCLC patients treated with ICI.

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

BACKGROUND AND PURPOSE

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

MATERIALS AND METHODS

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

RESULTS

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

CONCLUSION

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

Risk of radiculopathy caused by second course of spine stereotactic body radiotherapy

Objective

Stereotactic body radiotherapy is used to treat spinal metastases; however, 10% of patients experience local failure. We aimed to clarify the outcomes of the second course of stereotactic body radiotherapy for spinal metastases with a uniform fractionation schedule at our institution.

Methods

Data of patients treated with a second salvage stereotactic body radiotherapy course at the same spinal level or adjacent level from July 2018 to December 2020 were retrospectively reviewed. The initial prescribed dose was 24 Gy in two fractions, and the second dose 30 or 35 Gy in five fractions. The spinal cord dose constraint at the second course was 15.5 Gy at the maximum point dose. The endpoints were local failure and adverse effects. Local failure was defined as tumor progression using imaging.

Results

We assessed 19 lesions in 17 patients, with radioresistant lesions in 14 (74%) cases, the second stereotactic body radiotherapy to the same/adjacent spinal level in 13/6 cases, the median interval between stereotactic body radiotherapy of 23 (range, 6–52) months, and lesions compressing the cord in 5 (26%) cases. The median follow-up period was 19 months. The 12- and 18-month local failure rates were 0% and 8%, respectively. Radiation-induced myelopathy, radiculopathy and vertebral compression fractures were observed in 0 (0%), 4 (21%) and 2 (11%) lesions, respectively. Three patients with radiculopathy experienced almost complete upper or lower limb paralysis.

Conclusions

The second course of salvage stereotactic body radiotherapy for spinal metastases achieved good local control with a reduced risk of myelopathy. However, a high occurrence rate of radiation-induced radiculopathy has been confirmed.

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.

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.

Spine Stereotactic Body Radiotherapy for Prostate Cancer Metastases and the Impact of Hormone Sensitivity Status on Local Control

BACKGROUND

Stereotactic body radiotherapy (SBRT) is used to deliver ablative dose of radiation to spinal metastases.

OBJECTIVE

To report the first dedicated series of spine SBRT specific to prostate cancer (PCa) metastases with outcomes reported according to hormone sensitivity status.

METHODS

A prospective database was reviewed identifying patients with PCa treated with spine SBRT. This included those with hormone-sensitive PCa (HSPC) and castrate-resistant PCa (CRPC). The primary end point was MRI-based local control (LC).

RESULTS

A total of 183 spine segments in 93 patients were identified; 146 segments had no prior radiation and 37 had been previously radiated; 27 segments were postoperative. The median follow-up was 31 months. At the time of SBRT, 50 patients had HSPC and the remaining 43 had CRPC. The most common fractionation scheme was 24-28 Gy in 2 SBRT fractions (76%). LC rates at 1 and 2 years were 99% and 95% and 94% and 78% for the HSPC and CRPC cohorts, respectively. For patients treated with de novo SBRT, a higher risk of local failure was observed in patients with CRPC (P = .0425). The 1-year and 2-year overall survival rates were significantly longer at 98% and 95% in the HSPC cohort compared with 79% and 65% in the CRPC cohort (P = .0005). The cumulative risk of vertebral compression fracture at 2 years was 10%.

CONCLUSION

Favorable LC rates were observed after spine SBRT for PCa metastases; strategies to improve long-term LC in patients with CRPC require further investigation.

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

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

Cost-effectiveness of treatment strategies for spinal metastases

PURPOSE

We analyze the cost-effectiveness of standard palliative external beam radiation (EBRT, 8 Gy in 1 fraction), stereotactic body radiation therapy (SBRT, 24 Gy in 2 fractions), and radiofrequency ablation (RFA) for painful spinal metastases. Single-fraction SBRT (delivering 24 Gy) is also assessed.

METHODS AND MATERIALS

A Markov state transition model was constructed. Key model parameters were derived from prospective clinical trial data. Strategies were compared using the incremental cost-effectiveness ratio (ICER), with effectiveness in quality-adjusted life years (QALYs) and a willingness-to-pay (WTP) threshold of $100,000 per QALY gained. Costs included both hospital and professional costs using 2020 Medicare reimbursement.

RESULTS

The base case demonstrated that 2-fraction SBRT was not cost-effective compared to single-fraction EBRT, with an ICER of $194,145/QALY gained. RFA was a dominated treatment strategy (more costly and less effective) in this model. Probabilistic sensitivity analysis demonstrated that EBRT was favored in 66% of model iterations. If median survival were improved after SBRT, two-fraction SBRT became cost-effective, with ICER of $80,394, $57,062, and $47,038 for 3, 6, and 9-month improvements in survival. Because two-fraction SBRT data reported 18% of patients with indeterminant pain response at 3 months, and two-fraction SBRT is infrequently used in clinical practice, single-fraction SBRT data was also assessed. Single-fraction SBRT delivering 24 Gy was cost-effective compared to single-fraction EBRT, with an ICER of $92,833/QALY gained.

CONCLUSIONS

For appropriately chosen patients, single-fraction SBRT is more cost-effective than conventional EBRT or RFA. Conventional EBRT remains a cost-effective treatment for patients with poor expected survival.

Percutaneous image-guided cryoablation of spinal metastases: over 10-year experience in two academic centers

OBJECTIVES

To report on safety and clinical effectiveness of cryoablation for the treatment of spinal metastases (SM) in patients needing pain palliation or local tumor control (LTC).

METHODS

All consecutive patients with SM who underwent cryoablation from May 2008 to September 2020 in two academic centers were retrospectively identified and included in the present analysis. Patient characteristics, goal of treatment (curative/palliative), SM characteristics, procedural details, and clinical outcomes (pain relief; local tumor control [LTC]) were analyzed.

RESULTS

There were 74 patients (35 women; median age 61 years) accounting for 105 SM. Additional cementoplasty was used for 76 SM (76/105; 72.4%). There were 9 complications (out of 105 SM [8.5%]; 2 major and 7 minor) in 8 patients. Among the 64 (64/74; 86.5%) patients with painful SM, the mean Numerical Pain Rating Scale dropped from 6.8 ± 2.2 (range, 0-10) at the baseline to 4.1 ± 2.4 (range, 0-9; p < 0.0001) at 24 h, 2.5 ± 2.6 (range, 0-9; p < 0.0001) at 1 month, and 2.4 ± 2.5 (range, 0-9; p < 0.0001) at the last available follow-up (mean 14.7 ± 19.6 months; median 6). Thirty-four patients (34/64; 53.1%) were completely pain-free at the last follow-up. At mean 25.9 ± 21.2 months (median 16.5) of follow-up, LTC was achieved in 23/28 (82.1%) SM in 21 patients undergoing cryoablation with curative intent.

CONCLUSION

Cryoablation of SM, often performed in combination with vertebral augmentation, is safe, achieves fast and sustained pain relief, and provides high rates of LTC at mean 2-year follow-up.

KEY POINTS

•Cryoablation of spinal metastases is safe. •Cryoablation of spinal metastases allows rapid and sustained pain relief. •The mean 2-year rate of local tumor control after cryoablation of spinal metastases is 82.1%.

Fracture risk following stereotactic body radiotherapy for long bone metastases

BACKGROUND

Stereotactic body radiotherapy is a new treatment modality for long bone metastasis and has not been discussed in literature. We aimed to clarify stereotactic body radiotherapy outcomes for long bone metastases.

METHODS

Data of patients receiving stereotactic body radiotherapy for long bone metastases (July 2016-November 2020) were retrospectively reviewed. The prescribed dose was 30 or 35 Gy in five fractions. The endpoints were local failure and adverse effects. Local failure was defined as radiological tumor growth within the irradiation field. Adverse effects were evaluated according to the National Cancer Institute Common Terminology Criteria for Adverse Events, version 5.

RESULTS

Nineteen osseous lesions in 17 patients were assessed. The target lesions included 13 femoral, 4 humeral and 2 radial lesions. The median follow-up duration was 14 (range, 3-62) months. The 12- and 18-month local failure rates were 0 and 11%, respectively. Following 2 and 46 months of stereotactic body radiotherapy, two lesions (11%) resulted in painful femoral fractures (grade 3). Both patients underwent bipolar hip arthroplasty and could walk normally after surgery. In the late phase, one patient developed radiculopathy (almost complete paralysis of grasp) and another developed grade 2 limb edema. Other grade 2 or more severe acute and late toxicities were not observed during the follow-up period.

CONCLUSIONS

Stereotactic body radiotherapy for long bone metastases achieved excellent local control and caused two femoral fractures. We argue that stereotactic body radiotherapy for curative intent should not be contraindicated in long bone oligometastasis because fractures do not directly contribute to life expectancy.

Reduction of inter-observer differences in the delineation of the target in spinal metastases SBRT using an automatic contouring dedicated system

BACKGROUND

Approximately one third of cancer patients will develop spinal metastases, that can be associated with back pain, neurological symptoms and deterioration in performance status. Stereotactic radiosurgery (SRS) and stereotactic body radiotherapy (SBRT) have been offered in clinical practice mainly for the management of oligometastatic and oligoprogressive patients, allowing the prescription of high total dose delivered in one or few sessions to small target volumes, minimizing the dose exposure of normal tissues. Due to the high delivered doses and the proximity of critical organs at risk (OAR) such as the spinal cord, the correct definition of the treatment volume becomes even more important in SBRT treatment, thus making it necessary to standardize the method of target definition and contouring, through the adoption of specific guidelines and specific automatic contouring tools. An automatic target contouring system for spine SBRT is useful to reduce inter-observer differences in target definition. In this study, an automatic contouring tool was evaluated.

METHODS

Simulation CT scans and MRI data of 20 patients with spinal metastases were evaluated. To evaluate the advantage of the automatic target contouring tool (Elements SmartBrush Spine), which uses the identification of different densities within the target vertebra, we evaluated the agreement of the contours of 20 spinal target (2 cervical, 9 dorsal and 9 lumbar column), outlined by three independent observers using the automatic tool compared to the contours obtained manually, and measured by DICE similarity coefficient.

RESULTS

The agreement of GTV contours outlined by independent operators was superior with the use of the automatic contour tool compared to manually outlined contours (mean DICE coefficient 0.75 vs 0.57, p = 0.048).

CONCLUSIONS

The dedicated contouring tool allows greater precision and reduction of inter-observer differences in the delineation of the target in SBRT spines. Thus, the evaluated system could be useful in the setting of spinal SBRT to reduce uncertainties of contouring increasing the level of precision on target delivered doses.

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.

Current Overview of Treatment for Metastatic Bone Disease

The number of patients with bone metastasis increases as medical management and surgery improve the overall survival of patients with cancer. Bone metastasis can cause skeletal complications, including bone pain, pathological fractures, spinal cord or nerve root compression, and hypercalcemia. Before initiation of treatment for bone metastasis, it is important to exclude primary bone malignancy, which would require a completely different therapeutic approach. It is essential to select surgical methods considering the patient’s prognosis, quality of life, postoperative function, and risk of postoperative complications. Therefore, bone metastasis treatment requires a multidisciplinary team approach, including radiologists, oncologists, and orthopedic surgeons. Recently, many novel palliative treatment options have emerged for bone metastases, such as stereotactic body radiation therapy, radiopharmaceuticals, vertebroplasty, minimally invasive spine stabilization with percutaneous pedicle screws, acetabuloplasty, embolization, thermal ablation techniques, electrochemotherapy, and high-intensity focused ultrasound. These techniques are beneficial for patients who may not benefit from surgery or radiotherapy.

A Prognostic Index for Predicting Survival of Patients Undergoing Radiation Therapy for Spine Metastasis Using Recursive Partitioning Analysis

Background: Physicians' estimate of life expectancy in patients with spine metastasis frequently impacts treatment decisions regarding surgery, radiation techniques, dose, and fractionation. Objective: We aimed to identify predictors of survival and generate a stratification schema that could guide clinical decision making. Materials and Methods: We identified 269 patients who have undergone surgery and/or radiation for spine metastasis from 2002 to 2013 at an academic medical institution in the United States. A univariate survival analysis was carried out using the Kaplan-Meier method. Differences in survival by histology were assessed using the log-rank test. Multivariate analysis was performed using the Cox proportional hazards model, then using the same variables, recursive partitioning analysis (RPA) was conducted to determine risk groups associated with survival. Results: The median overall survival was 4.76 months. Twenty percent, 40%, and 57% of patients died within one, three, and six months of radiation treatment, respectively. RPA analysis resulted in three classes; class I included patients with Karnofsky Performance Status (KPS) ≥80. Class II included patients with KPS <80 and radioresistant or favorable histologies. Class III included all other histologies. Median survival in months was 11.4, 6.3, and 2.0, respectively. Conclusion: We developed a stratification schema predictive of survival in patients with spine metastasis. This RPA classification should be validated in independent patient populations from several institutions and may ultimately identify patients who are good candidates for more complex treatment regimens, such as stereotactic body radiotherapy.

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.

Iodine-125 radioactive seed brachytherapy as a treatment for spine and bone metastases: A systematic review and meta-analysis

AIM

To evaluate the analgesic efficacy, safety, and local tumor control of iodine-125 (¹²⁵I) seed brachytherapy (BT) for the management of spine and bone metastases.

METHODS

A systematic literature search was conducted using PubMed, the Cochrane Library, and Scopus databases. Data regarding patient demographics, tumor characteristics, procedural parameters, and clinical outcomes were extracted and analyzed.

RESULTS

Fourteen studies (7 prospective, 7 retrospective) were included, accounting for 689 patients, in our review. Analgesic efficacy was assessed at baseline and various postoperative time points. Significant improvement in pain was noted at 4- and 24-week follow-ups (p < 0.01). Interestingly, all studies that combined ¹²⁵I seed BT with cement augmentation reported relatively higher levels of pain reduction (mean pain reduction ≥4 points) as compared to the studies which applied ¹²⁵I seed BT as a stand-alone therapy (mean pain reduction ≥2 points), at the last follow-up. Local tumor control rates ranged widely from 14% to 100% at varying follow-ups. Median overall survival ranged between 10 months and 25 months. The overall complication rate was 19% (130/689) and mainly included minor subcutaneous hemorrhage, fever, myelosuppression, and seed displacement. Metrics assessing performance and quality of life demonstrated significant improvements from baseline to posttreatment.

CONCLUSION

¹²⁵I seed BT, alone or in conjunction with cement augmentation, may be a viable salvage therapy in appropriately selected patients. However, further studies are needed to analyze the long-term efficacy of this intervention as a palliative and curative modality.