Single versus multiple session stereotactic body radiotherapy for spinal metastasis: the risk-benefit ratio

Transpedicular Corpectomy in Minimally Invasive Surgery for Metastatic Spinal Cord Compression: A Single-Center Series

Introduction The role of separation surgery in managing symptomatic spinal metastases has been increasing in recent years, and it represents a crucial part of the definitive management of this condition. Methods We report on a series of seven patients treated at the National Cancer Institute in Mexico using minimally invasive approaches to perform transpedicular corpectomy. The goal was to obtain a margin of tumor-free tissue, enabling the completion of oncological treatment with radiotherapy. Results We collected data from six cases. The mean age was 61.2 years. Surgical outcomes were good in 83.3% of patients. Ranging from minimally invasive instrumentations to total or partial corpectomies, these procedures achieved their intended function of generating healthy neural tissue free of tumor. This ensures that the radiation gradient does not affect this tissue. No surgical complications were reported. The objective of these surgeries was to establish a radiotherapy or radiosurgery regimen as soon as possible, thereby improving patients' quality of life (QoL). Conclusions Low-cost transpedicular corpectomy via minimally invasive surgery (MIS) is a safe and effective method that meets the goals of separation surgery. However, prospective studies are needed to directly compare open techniques with minimally invasive methods.

Stereotactic Body and Conventional Radiotherapy for Painful Bone Metastases: A Systematic Review and Meta-Analysis

Importance

Conventional external beam radiotherapy (cEBRT) and stereotactic body radiotherapy (SBRT) are commonly used treatment options for relieving metastatic bone pain. The effectiveness of SBRT compared with cEBRT in pain relief has been a subject of debate, and conflicting results have been reported.

Objective

To compare the effectiveness associated with SBRT vs cEBRT for relieving metastatic bone pain.

Data Sources

A structured search was performed in the PubMed, Embase, and Cochrane databases on June 5, 2023. Additionally, results were added from a new randomized clinical trial (RCT) and additional unpublished data from an already published RCT.

Study Selection

Comparative studies reporting pain response after SBRT vs cEBRT in patients with painful bone metastases.

Data Extraction and Synthesis

Two independent reviewers extracted data from eligible studies. Data were extracted for the intention-to-treat (ITT) and per-protocol (PP) populations. The study is reported following the Preferred Reporting Items for Systematic Reviews and Meta-analyses (PRISMA) reporting guideline.

Main Outcomes and Measures

Overall and complete pain response at 1, 3, and 6 months after radiotherapy, according to the study's definition. Relative risk ratios (RRs) with 95% CIs were calculated for each study. A random-effects model using a restricted maximum likelihood estimator was applied for meta-analysis.

Results

There were 18 studies with 1685 patients included in the systematic review and 8 RCTs with 1090 patients were included in the meta-analysis. In 7 RCTs, overall pain response was defined according to the International Consensus on Palliative Radiotherapy Endpoints in clinical trials (ICPRE). The complete pain response was reported in 6 RCTs, all defined according to the ICPRE. The ITT meta-analyses showed that the overall pain response rates did not differ between cEBRT and SBRT at 1 (RR, 1.14; 95% CI, 0.99-1.30), 3 (RR, 1.19; 95% CI, 0.96-1.47), or 6 (RR, 1.22; 95% CI, 0.96-1.54) months. However, SBRT was associated with a higher complete pain response at 1 (RR, 1.43; 95% CI, 1.02-2.01), 3 (RR, 1.80; 95% CI, 1.16-2.78), and 6 (RR, 2.47; 95% CI, 1.24-4.91) months after radiotherapy. The PP meta-analyses showed comparable results.

Conclusions and Relevance

In this systematic review and meta-analysis, patients with painful bone metastases experienced similar overall pain response after SBRT compared with cEBRT. More patients had complete pain alleviation after SBRT, suggesting that selected subgroups will benefit from SBRT.

High-Dose Rate Interstitial Spine Brachytherapy Using an Intraoperative Mobile Computed Tomography-Guided Surgical Navigation System

BACKGROUND

Up to 15% of previously irradiated metastatic spine tumors will progress. Re-irradiation of these tumors poses a significant risk of exceeding the radiation tolerance to the spinal cord. High-dose rate (HDR) brachytherapy is a treatment alternative.

OBJECTIVE

To develop a novel HDR spine brachytherapy technique using an intraoperative computed tomography-guided navigation (iCT navigation).

METHODS

Patients with progressive metastatic spine tumors were included in the study. HDR brachytherapy catheters were placed under iCT navigation. CT-based planning with magnetic resonance imaging fusion was performed to ensure conformal dose delivery to the target while sparing normal tissue, including the spinal cord. Patients received single fraction radiation treatment.

RESULTS

Five patients with thoracolumbar tumors were treated with HDR brachytherapy. Four patients previously received radiotherapy to the same spinal level. Preimplant plans demonstrated median clinical target volume (CTV) D90 of 116.5% (110.8%-147.7%), V100 of 95.7% (95.5%-99.6%), and Dmax of 8.08 Gy (7.65-9.8 Gy) to the spinal cord/cauda equina. Postimplant plans provided median CTV D90 of 113.8% (93.6%-120.1%), V100 of 95.9% (87%-99%), and Dmax of 9.48 Gy (6.5-10.3 Gy) to cord/cauda equina. Patients who presented with back pain (n = 3) noted symptomatic improvement at a median follow-up of 22 d after treatment. Four patients demonstrated local tumor control of spinal metastatic tumor at a median follow-up of 92 d after treatment. One patient demonstrated radiographic evidence of local tumor progression 2.7 mo after treatment.

CONCLUSION

HDR spine brachytherapy with iCT navigation is a promising treatment alternative to induce local tumor control and reduce pain symptoms associated with metastatic spine disease.

High-dose hypofractionated stereotactic body radiotherapy for spinal chordoma

OBJECTIVE

Spinal chordoma is locally aggressive and has a high rate of recurrence, even after en bloc resection. Conventionally fractionated adjuvant radiation leads to suboptimal tumor control, and data regarding hypofractionated regimens are limited. The authors hypothesized that neoadjuvant stereotactic body radiotherapy (SBRT) may overcome its intrinsic radioresistance, improve surgical margins, and allow preservation of critical structures during surgery. The purpose of this study is to review the feasibility and early outcomes of high-dose hypofractionated SBRT, with a focus on neoadjuvant SBRT.

METHODS

Electronic medical records of patients with spinal chordoma treated using image-guided SBRT between 2009 and 2019 at a single institution were retrospectively reviewed.

RESULTS

Twenty-eight patients with 30 discrete lesions (24 in the mobile spine) were included. The median follow-up duration was 20.8 months (range 2.3-126.3 months). The median SBRT dose was 40 Gy (range 15-50 Gy) in 5 fractions (range 1-5 fractions). Seventeen patients (74% of those with newly diagnosed lesions) received neoadjuvant SBRT, of whom 15 (88%) underwent planned en bloc resection, all with negative margins. Two patients (12%) developed surgical wound-related complications after neoadjuvant SBRT and surgery, and 4 (two grade 3 and two grade 2) experienced postoperative complications unrelated to the surgical site. Of the remaining patients with newly diagnosed lesions, 5 received adjuvant SBRT for positive or close surgical margins, and 1 received SBRT alone. Seven recurrent lesions were treated with SBRT alone, including 2 after failure of prior conventional radiation. The 2-year overall survival rate was 92% (95% confidence interval [CI] 71%-98%). Patients with newly diagnosed chordoma had longer median survival (not reached) than those with recurrent lesions (27.7 months, p = 0.006). The 2-year local control rate was 96% (95% CI 74%-99%). Among patients with radiotherapy-naïve lesions, no local recurrence was observed with a biologically effective dose ≥ 140 Gy, maximum dose of the planning target volume (PTV) ≥ 47 Gy, mean dose of the PTV ≥ 39 Gy, or minimum dose to 80% of the PTV ≥ 36 Gy (5-fraction equivalent doses). All acute toxicities from SBRT were grade 1-2, and no myelopathy was observed.

CONCLUSIONS

Neoadjuvant high-dose, hypofractionated SBRT for spinal chordoma is safe and does not increase surgical morbidities. Early outcomes at 2 years are promising, although long-term follow-up is pending.

Patient outcomes and tumor control in single-fraction versus hypofractionated stereotactic body radiation therapy for spinal metastases

OBJECTIVE

Stereotactic body radiation therapy (SBRT) offers efficient, noninvasive treatment of spinal neoplasms. Single-fraction (SF) high-dose SBRT has a relatively narrow therapeutic window, while hypofractionated delivery of SBRT may have an improved safety profile with similar efficacy. Because the optimal approach of delivery is unknown, the authors examined whether hypofractionated SBRT improves pain and/or functional outcomes and results in better tumor control compared with SF-SBRT.

METHODS

This is a single-institution retrospective study of adult patients with spinal metastases treated with SF- or three-fraction (3F) SBRT from 2008 to 2019. Demographics and baseline characteristics, radiographic data, and posttreatment outcomes at a minimum follow-up of 3 months are reported.

RESULTS

Of the 156 patients included in the study, 70 (44.9%) underwent SF-SBRT (median total dose 1700 cGy) and 86 (55.1%) underwent 3F-SBRT (median total dose 2100 cGy). At baseline, a higher proportion of patients in the 3F-SBRT group had a worse baseline profile, including severity of pain (p < 0.05), average use of pain medication (p < 0.001), and functional scores (p < 0.05) compared with the SF-SBRT cohort. At the 3-month follow-up, the 3F-SBRT cohort experienced a greater frequency of improvement in pain compared with the SF-SBRT group (p < 0.05). Furthermore, patients treated with 3F-SBRT demonstrated a higher frequency of improved Karnofsky Performance Scale (KPS) scores (p < 0.05) compared with those treated with SF-SBRT, with no significant difference in the frequency of improvement in modified Rankin Scale scores. Local tumor control did not differ significantly between the two cohorts.

CONCLUSIONS

Patients who received spinal 3F-SBRT more frequently achieved significant pain relief and an increased frequency of improvement in KPS compared with those treated with SF-SBRT. Local tumor control was similar in the two groups. Future work is needed to establish the relationship between fractionation schedule and clinical outcomes.

Single-Fraction Stereotactic Body Radiation Therapy: A Paradigm During the Coronavirus Disease 2019 (COVID-19) Pandemic and Beyond?

PURPOSE

Owing to the coronavirus disease 2019 (COVID-19) pandemic, radiation oncology departments have adopted various strategies to deliver radiation therapy safely and efficiently while minimizing the risk of severe acute respiratory syndrome coronavirus-2 transmission among patients and health care providers. One practical strategy is to deliver stereotactic body radiation therapy (SBRT) in a single fraction, which has been well established for treating bone metastases, although it has been infrequently used for other extracranial sites.

METHODS AND MATERIALS

A PubMed search of published articles in English related to single-fraction SBRT was performed. A critical review was performed of the articles that described clinical outcomes of single-fraction SBRT for treatment of primary extracranial cancers and oligometastatic extraspinal disease.

RESULTS

Single-fraction SBRT for peripheral early-stage non-small cell lung cancer is supported by randomized data and is strongly endorsed during the COVID-19 pandemic by the European Society for Radiotherapy and Oncology-American Society for Radiation Oncology practice guidelines. Prospective and retrospective studies supporting a single-fraction regimen are limited, although outcomes are promising for renal cell carcinoma, liver metastases, and adrenal metastases. Data are immature for primary prostate cancer and demonstrate excess late toxicity in primary pancreatic cancer.

CONCLUSIONS

Single-fraction SBRT should be strongly considered for peripheral early-stage non-small cell lung cancer during the COVID-19 pandemic to mitigate the potentially severe consequences of severe acute respiratory syndrome coronavirus-2 transmission. Although single-fraction SBRT is promising for the definitive treatment of other primary or oligometastatic cancers, multi-fraction SBRT should be the preferred regimen owing to the need for additional prospective evaluation to determine long-term efficacy and safety.

Stereotactic Radiation for Treating Primary and Metastatic Neoplasms of the Spinal Cord

Stereotactic radiation treatment can be used to treat spinal cord neoplasms in patients with either unresectable lesions or residual disease after surgical resection. While treatment guidelines have been suggested for epidural lesions, the utility of stereotactic radiation for intradural and intramedullary malignancies is still debated. Prior reports have suggested that stereotactic radiation approaches can be used for effective tumor control and symptom management. Treatment-related toxicity has been documented in rare subsets of patients, though the incidences of injury are not directly correlated with higher radiation doses. Further studies are needed to assess the factors that influence the risk of radiation-induced myelopathy when treating spinal cord neoplasms with stereotactic radiation, which can include, but may not be limited to, maximum dose, dose-fractionation, irradiated volume, tumor location, histology and treatment history. This review will discuss evidence for current treatment approaches.

Evolving Role of Stereotactic Body Radiation Therapy in the Management of Spine Metastases: Defining Dose and Dose Constraints

When treating solid tumor spine metastases, stereotactic high-dose-per-fraction radiation, given in a single fraction or in a hypofractionated approach, has proved to be a highly effective and safe therapeutic option for any tumor histology, in the setting of de novo therapy, as salvage treatment of local progression after previous radiation, and in the postoperative setting. There are variations in practice based on the clinical presentation, goals of therapy, as well as institutional preferences. As a biologically potent therapy, a thoughtful and careful attention to detail with patient selection, treatment planning, and delivery is crucial for treatment success.

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.

Stereotactic Body Radiotherapy (SBRT) for Oligometastatic Spine Metastases: An Overview

The oligometastatic state is hypothesized to represent an intermediary state of cancer between widely metastatic disease and curable, localized disease. Advancements in radiotherapy have allowed for delivery of high precision, dose escalated treatment known as stereotactic body radiotherapy (SBRT) to targets throughout the body with excellent rates of local control. Recently, the first phase II randomized trial comparing conventional radiotherapy to comprehensive SBRT of oligometastatic disease demonstrated an overall survival and progression free survival advantage. The spine is a common site of metastasis, and a complex site for SBRT given the adjacent spinal cord and the tumor embedded within the bone tissue putting the patient at risk of fracture. Although there are expert spine SBRT guidelines for practice, there are as yet no reported randomized trials that proves superiority as compared to conventional radiation. The use of SBRT in patients with oligometastatic disease and spinal metastases is the focus of this review.

Outcomes in the radiosurgical management of metastatic spine disease

Purpose

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

Methods and Materials

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

Results

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

Conclusions

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

Instability and impending instability in patients with vertebral metastatic disease

Metastatic disease commonly involves the spine with an increasing incidence due to a worldwide rise of cancer incidence and a longer survival of patients with osseous metastases. Metastases compromise the mechanical integrity of the vertebra and make it susceptible to fracture. Patients with pathological vertebral fracture often become symptomatic, with mechanical pain generally due to intervertebral instability, and may develop spinal cord compression and neurological deficits. Advances in imaging, radiotherapy, as well as in spinal surgery techniques, have allowed the evolution from conventional palliative external beam radiotherapy to modern stereotactic radiosurgery and from traditional open surgery to less-invasive, and sometimes prophylactic stabilization surgical treatments. It is therefore clear that fracture risk prediction, and maintenance or restoration of intervertebral stability, are important objectives in the management of these patients. Correlation between imaging findings and clinical manifestations is crucial, and a common knowledge base for treatment team members rather than a compartmentalized view is very important. This article reviews the literature on the imaging and clinical diagnosis of intervertebral instability and impending instability in the setting of spine metastatic disease, including the spinal instability neoplastic score, which is a reliable tool for diagnosing unstable or potentially unstable metastatic spinal lesions, and on the different elements considered for treatment.

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

BACKGROUND

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

METHODS

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

RESULTS

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

CONCLUSION

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

Consensus guidelines for postoperative stereotactic body radiation therapy for spinal metastases: results of an international survey

OBJECTIVE Although postoperative stereotactic body radiation therapy (SBRT) for spinal metastases is increasingly performed, few guidelines exist for this application. The purpose of this study is to develop consensus guidelines to promote safe and effective treatment for patients with spinal metastases. METHODS Fifteen radiation oncologists and 5 neurosurgeons, representing 19 centers in 4 countries and having a collective experience of more than 1300 postoperative spine SBRT cases, completed a 19-question survey about postoperative spine SBRT practice. Responses were defined as follows: 1) consensus: selected by ≥ 75% of respondents; 2) predominant: selected by 50% of respondents or more; and 3) controversial: no single response selected by a majority of respondents. RESULTS Consensus treatment indications included: radioresistant primary, 1-2 levels of adjacent disease, and previous radiation therapy. Contraindications included: involvement of more than 3 contiguous vertebral bodies, ASIA Grade A status (complete spinal cord injury without preservation of motor or sensory function), and postoperative Bilsky Grade 3 residual (cord compression without any CSF around the cord). For treatment planning, co-registration of the preoperative MRI and postoperative T1-weighted MRI (with or without gadolinium) and delineation of the cord on the T2-weighted MRI (and/or CT myelogram in cases of significant hardware artifact) were predominant. Consensus GTV (gross tumor volume) was the postoperative residual tumor based on MRI. Predominant CTV (clinical tumor volume) practice was to include the postoperative bed defined as the entire extent of preoperative tumor, the relevant anatomical compartment and any residual disease. Consensus was achieved with respect to not including the surgical hardware and incision in the CTV. PTV (planning tumor volume) expansion was controversial, ranging from 0 to 2 mm. The spinal cord avoidance structure was predominantly the true cord. Circumferential treatment of the epidural space and margin for paraspinal extension was controversial. Prescription doses and spinal cord tolerances based on clinical scenario, neurological compromise, and prior overlapping treatments were controversial, but reasonable ranges are presented. Fifty percent of those surveyed practiced an integrated boost to areas of residual tumor and density override for hardware within the beam path. Acceptable PTV coverage was controversial, but consensus was achieved with respect to compromising coverage to meet cord constraint and fractionation to improve coverage while meeting cord constraint. CONCLUSIONS The consensus by spinal radiosurgery experts suggests that postoperative SBRT is indicated for radioresistant primary lesions, disease confined to 1-2 vertebral levels, and/or prior overlapping radiotherapy. The GTV is the postoperative residual tumor, and the CTV is the postoperative bed defined as the entire extent of preoperative tumor and anatomical compartment plus residual disease. Hardware and scar do not need to be included in CTV. While predominant agreement was reached about treatment planning and definition of organs at risk, future investigation will be critical in better understanding areas of controversy, including whether circumferential treatment of the epidural space is necessary, management of paraspinal extension, and the optimal dose fractionation schedules.