Quantitative Evaluation of Local Control and Wound Healing Following Surgery and Stereotactic Spine Radiosurgery for Spine Tumors

Oncologic and Functional Outcomes After Stereotactic Body Radiation Therapy for High-Grade Malignant Spinal Cord Compression

Purpose

Although surgical decompression is the gold standard for metastatic epidural spinal cord compression (MESCC) from solid tumors, not all patients are candidates or undergo successful surgical Bilsky downgrading. We report oncologic and functional outcomes for patients treated with stereotactic body radiation therapy (SBRT) to high-grade MESCC.

Methods and Materials

Patients with Bilsky grade 2 to 3 MESCC from solid tumor metastases treated with SBRT at a single institution from 2009 to 2020 were retrospectively reviewed. Patients who received upfront surgery before SBRT were included only if postsurgical Bilsky grade remained ≥2. Neurologic examinations, magnetic resonance imaging, pain assessments, and analgesic usage were assessed every 3 to 4 months post-SBRT. Cumulative incidence of local recurrence was calculated with death as a competing risk, and overall survival was estimated by Kaplan-Meier.

Results

One hundred forty-three patients were included. The cumulative incidence of local recurrence was 5.1%, 7.5%, and 14.1% at 6, 12, and 24 months, respectively. At first post-SBRT imaging, 16.2% of patients with initial Bilsky grade 2 improved to grade 1, and 53.8% of patients were stable. Five of 13 patients (38.4%) with initial Bilsky grade 3 improved to grade 1 to 2. Pain response at 3 and 6 months post-SBRT was complete in 45.4% and 55.7%, partial in 26.9% and 13.1%, stable in 24.1% and 27.9%, and worse in 3.7% and 3.3% of patients, respectively. At 3 and 6 months after SBRT, 17.8% and 25.0% of patients had improved ambulatory status and 79.7% and 72.4% had stable status.

Conclusions

We report the largest series to date of patients with high-grade MESCC treated with SBRT. The excellent local control and functional outcomes suggest SBRT is a reasonable approach in inoperable patients or cases unable to be successfully surgically downgraded.

The Evolution of Minimally Invasive Spine Tumor Resection and Stabilization: From K-Wires to Navigated One-Step Screws

Minimization of the surgical approaches to spinal extradural metastases resection and stabilization was advocated by the 2012 Oncological Guidelines for Spinal Metastases Management. Minimally invasive approaches to spine oncology surgery (MISS) are continually advancing. This paper will describe the evolution of minimally invasive surgical techniques for the resection of metastatic spinal lesions and stabilization in a single institute. A retrospective analysis of patients who underwent minimally invasive extradural spinal metastases resection during the years 2013-2019 by a single surgeon was performed. Medical records, imaging studies, operative reports, rates of screw misplacement, operative time and estimated blood loss were reviewed. Detailed description of the surgical technique is provided. Of 138 patients operated for extradural spinal tumors during the study years, 19 patients were treated in a minimally invasive approach and met the inclusion criteria for this study. The mortality rate was significantly improved over the years with accordance of improve selection criteria to better prognosis patients. The surgical technique has evolved over the study years from fluoroscopy to intraoperative 3D imaging and navigation guidance and from k-wire screw insertion technique to one-step screws. Minimally invasive spinal tumor surgery is an evolving technique. The adoption of assistive devices such as intraoperative 3D imaging and one-step screw insertion systems was safe and efficient. Oncologic patients may particularly benefit from the minimization of surgical decompression and fusion in light of the frailty of this population and the mitigated postoperative outcomes associated with MIS oncological procedures.

A quantitative and comparative evaluation of stereotactic spine radiosurgery local control: proposing a consistent measurement methodology

OBJECTIVE

Stereotactic body radiotherapy (SBRT) is a precise and conformal treatment modality used in the management of metastatic spine tumors. Multiple studies have demonstrated its safety and efficacy for pain and tumor control. However, no uniform quantitative imaging methodology exists to evaluate response to treatment in these patients. This study presents radiographic local control rates post-SBRT, systematically compares measurements acquired according to WHO and Response Evaluation Criteria in Solid Tumors (RECIST) criteria, and explores the relationship to patient outcome.

METHODS

The authors performed a retrospective review of prospectively obtained data from a cohort of 59 consecutive patients (81 metastatic isocenters) treated with SBRT and followed with serial MRI scans. Measurements were performed by a neuroradiologist blinded to the patients’ clinical course. Local control status was determined according to both WHO and RECIST measurements, and agreement between the measuring methodologies was calculated and reported.

RESULTS

Eighty-one isocenters (111 vertebral bodies) were treated with SBRT. The mean treatment dose was 13.96 Gy and the median follow-up duration was 10.8 months, during which 408 MRI scans were evaluated with both WHO and RECIST criteria for each scan point. Imaging demonstrated a mean unidimensional size decrease of 0.2 cm (p = 0.14) and a mean area size decrease of 0.99 cm2 (p = 0.03). Although 88% of the case classifications were concordant and the agreement was significant, WHO criteria were found to be more sensitive to tumor size change. The local control rates according to WHO and RECIST were 95% and 98%, respectively.

CONCLUSIONS

Although WHO volumetric measurements are admittedly superior for tumor size measurement, RECIST is simpler, reproducible, and for the first time is shown here to be comparable to WHO criteria. Thus, the application of RECIST methodology appears to be a suitable standard for evaluating post-SBRT treatment response. Moreover, using comprehensive and consistent measuring approaches, this study substantiates the efficacy of SBRT in the treatment of spine metastases.

Comparison of Surgical Outcomes Between Separation Surgery and Piecemeal Spondylectomy for Spinal Metastasis: A Retrospective Analysis

Objective: This study aimed to compare the outcomes between piecemeal spondylectomy and separation surgery for patients with spinal metastasis.

Summary of Background Data: Piecemeal spondylectomy and separation surgery are two widely-used treatment options for spinal metastasis. However, no studies have compared the surgical outcomes between both treatment modalities.

Methods: Patients with spinal metastasis who underwent piecemeal spondylectomy or separation surgery between August 2017 and April 2020 at our spine center were recruited. Demographic, preoperative, perioperative, and follow-up data were collected and analyzed. Kaplan–Meier analysis and the log-rank test were used to analyze overall survival (OS) and progression-free survival (PFS) in patients with spinal metastasis.

Results: Overall, 26 patients were treated with piecemeal spondylectomy, and 29 underwent separation surgery with postoperative stereotactic radiosurgery. Both groups showed significant postoperative improvements in neurological status. The piecemeal spondylectomy group had significantly more blood loss (1784.62 ± 833.64 vs. 1165.52 ± 307.38 ml) and required longer operative time (4.76 ± 0.93 vs. 3.73 ± 1.15 h) than the separation surgery group. No significant difference in OS was found between the groups (P = 0.064); however, patients in the separation surgery group experienced less local recurrence than those in the piecemeal spondylectomy group (P = 0.0014). Notably, significant differences were detected in the development of complications between the groups (P = 0.029).

Conclusion: Separation surgery led to less blood loss and reduced complications and had shorter operation time than piecemeal spondylectomy. Although no significant differences were found in OS between the groups, separation surgery was associated with better PFS compared with piecemeal spondylectomy. These findings suggest that separation surgery has some advantages over piecemeal spondylectomy for patients with spinal metastatic disease.

Stereotactic Radiosurgery for Postoperative Spine Malignancy: A Systematic Review and International Stereotactic Radiosurgery Society (ISRS) Practice Guidelines

PURPOSE

To determine safety and efficacy of postoperative spine stereotactic body radiation therapy (SBRT) in the published literature, and to present practice recommendations on behalf of the International Stereotactic Radiosurgery Society (ISRS).

MATERIALS AND METHODS

A systematic review of the literature was performed, specific to postoperative spine SBRT, using PubMed and Embase databases. A meta-analysis for 1-year local control (LC), overall survival (OS) and vertebral compression fracture (VCF) probability was conducted.

RESULTS

The literature search revealed 251 potentially relevant articles after duplicates were removed. Of these 56 were reviewed in-depth for eligibility and 12 met all the inclusion criteria for analysis. 7 studies were retrospective, 2 prospective observational and 3 were prospective phase I/II clinical trials. Outcomes for a total of 461 patients and 499 spinal segments were reported. 10 studies used an MRI fused to CT-simulation for treatment planning, 2 investigations reported on all patients receiving a CT-myelogram at the time of planning. Meta-analysis for 1 year LC and OS was 88.9% and 57%, respectively. The crude reported VCF rate was 5.6%. One case of myelopathy was described in a patient with a previously irradiated spinal segment. One patient developed an esophageal fistula requiring surgical repair.

CONCLUSIONS

Postoperative spine SBRT delivers a high 1-year LC with acceptably low toxicity. Patients that may benefit from this include those with oligometastatic disease, radioresistant histology, paraspinal masses and/or those with a history of prior irradiation to the affected spinal segment. The ISRS recommends a minimum interval of 8 to 14 days after invasive surgery prior to simulation for SBRT, with initiation of radiotherapy within 4 weeks of surgery. An MRI fused to the planning CT, and/or the use of a CT-myelogram, are necessary for target and organ-at-risk delineation. A planning organ-at-risk volume (PRV) of 1.5 to 2mm for the spinal cord is advised.

Drivers of Readmission and Reoperation After Surgery for Vertebral Column Metastases

OBJECTIVE

To determine those clinical, demographic, and operative factors that predict 30-day unplanned reoperation and readmission within a population of adults who underwent spinal metastasis surgery at a comprehensive cancer center.

METHODS

Adults who underwent spinal metastasis surgery at a comprehensive cancer center were analyzed. Data included baseline laboratory values, cancer history, demographics, operative characteristics and medical comorbidities. Medical comorbidities were quantified using the modified Charlson Comorbidity Index (CCI). Values associated with the outcomes of interest were then subjected to multivariable logistic regression to identify independent predictors of readmission and reoperation.

RESULTS

A total of 345 cases were identified. Mean age was 59.4 ± 11.7 years, 56% were male, and the racial makeup was 64% white, 29% black, and 7.3% other. Forty-two patients (12.2%) had unplanned readmissions, most commonly for wound infection with dehiscence (14.2%), venous thromboembolism (14.2%), and bowel obstruction/complication (11.9%). Thirteen patients required reoperation (4%), most commonly for wound infection with dehiscence (39%) or local recurrence (23%). Multivariable analysis showed that the modified CCI (odds ratio [OR], 1.25; 95% confidence interval [CI] 1.03-1.52; P = 0.03) was an independent predictor of 30-day readmission. Independent predictors of 30-day unplanned reoperation were: black (vs. white) race (OR, 0.08; 95% CI, 0.01-0.41; P < 0.01), length of stay (OR, 1.05 per day; 95% CI, 1.00-1.09; P = 0.04), and CCI (OR, 1.72 per point; 95% CI, 1.29-2.28; P < 0.01).

CONCLUSIONS

Increasing medical comorbidities is independently predictive of both 30-day unplanned readmission and reoperation after spinal metastasis surgery. Unplanned reoperation is also positively predicted by a longer index admission. Neither tumor pathology nor age predicted outcome, suggesting that poor wound-healing factors and increased surgical morbidity may best predict these adverse outcomes.

Hypofractionated spinal stereotactic body radiation therapy for high-grade epidural disease

OBJECTIVE

To characterize the clinical outcomes when stereotactic body radiation therapy (SBRT) alone is used to treat high-grade epidural disease without prior surgical decompression, the authors conducted a retrospective cohort study of patients treated at the Memorial Sloan Kettering Cancer Center between 2014 and 2018. The authors report locoregional failure (LRF) for a cohort of 31 cases treated with hypofractionated SBRT alone for grade 2 epidural spinal cord compression (ESCC) with radioresistant primary cancer histology.

METHODS

High-grade epidural disease was defined as grade 2 ESCC, which is notable for radiographic deformation of the spinal cord by metastatic disease. Kaplan-Meier survival curves and cumulative incidence functions were generated to examine the survival and incidence experiences of the sample level with respect to overall survival, LRF, and subsequent requirement of vertebral same-level surgery (SLS) due to tumor progression or fracture. Associations with dosimetric analysis were also examined.

RESULTS

Twenty-nine patients undergoing 31 episodes of hypofractionated SBRT alone for grade 2 ESCC between 2014 and 2018 were identified. The 1-year and 2-year cumulative incidences of LRF were 10.4% (95% CI 0-21.9) and 22.0% (95% CI 5.5-38.4), respectively. The median survival was 9.81 months (95% CI 8.12-18.54). The 1-year cumulative incidence of SLS was 6.8% (95% CI 0-16.0) and the 2-year incidence of SLS was 14.5% (95% CI 0.6-28.4). All patients who progressed to requiring surgery had index lesions at the thoracic apex (T5-7).

CONCLUSIONS

In carefully selected patients, treatment of grade 2 ESCC disease with hypofractionated SBRT alone offers a 1-year cumulative incidence of LRF similar to that in low-grade ESCC and postseparation surgery adjuvant hypofractionated SBRT. Use of SBRT alone has a favorable safety profile and a low cumulative incidence of progressive disease requiring open surgical intervention (14.5%).

Local Tumor Control for Metastatic Epidural Spinal Cord Compression Following Separation Surgery with Adjuvant CyberKnife Stereotactic Radiotherapy or Image-Guided Intensity-Modulated Radiotherapy

BACKGROUND

We sought to compare local tumor control after conventionally fractionated image-guided intensity-modulated radiotherapy (IMRT) versus adjuvant CyberKnife stereotactic body radiotherapy (SBRT) in patients who underwent separation surgery for metastatic epidural spinal cord compression (MESCC).

METHODS

We retrospectively reviewed patients with MESCC who were treated at our hospital. The Kaplan-Meier method was used to estimate local progression and overall survival.

RESULTS

Fifty-six patients with MESCC underwent separation surgery between 2013 and 2018, among whom 6 were lost to follow-up, 24 received conventionally fractionated image-guided IMRT, and 26 were treated with CyberKnife SBRT. The median follow-up was 16.5 months (range, 2.1-47.5 months). Eleven patients experienced local failure including 9 and 2 from the IMRT and SBRT groups, respectively. The local progression-free survival rates were significantly higher in the SBRT group than IMRT group at 6 months (95.5% vs. 82.0%), 1 year (90.9% vs. 71.8%), and 2 years (90.9% vs. 57.6%) (P = 0.035). Multivariate Cox proportional hazards regression analysis identified radiotherapy method (P = 0.034) and receipt of preoperative radiotherapy (P = 0.047) as significant predictors of local control, while visceral metastasis (P = 0.048) and high-malignancy primary tumor type (P = 0.002) were negative predictors of overall survival. Moreover, postoperative SBRT was noninferior to IMRT in terms of pain control, adverse effects, and performance in treating irradiated spinal metastases.

CONCLUSIONS

Hybrid surgery-radiosurgery therapy is a safe and effective treatment option for patients with MESCC. SBRT provided higher local control rates compared with IMRT. Thus postoperative SBRT should be considered for patients expected to have relatively long survival.

Stereotactic Radiotherapy Followed by Surgical Stabilization Within 24 h for Unstable Spinal Metastases; A Stage I/IIa Study According to the IDEAL Framework

Background: Routine treatment for unstable spinal metastases consists of surgical stabilization followed by external beam radiotherapy (EBRT) or stereotactic body radiotherapy (SBRT) after a minimum of 1–2 weeks to allow for initial wound healing. Although routine treatment, there are several downsides. First, radiotherapy induced pain relief is delayed by the time interval required for wound healing. Second, EBRT often requires multiple hospital visits and only 60% of the patients experience pain relief. Third, spinal implants cause imaging artifacts hindering SBRT treatment planning and delivery. Reversing the order of surgery and radiotherapy, with dose sparing of the surgical area by SBRT, could overcome these disadvantages and by eliminating the interval between the two treatments, recovery, and palliation may occur earlier.

Design: The safety of SBRT followed by surgical stabilization within 24 h for the treatment of unstable spinal metastases was investigated. Safety was evaluated using the Common-Toxicity-Criteria-Adverse-Events-4.0, with the occurrence of wound complications within 90-days being the primary concern.

Results: Between June-2015 and January-2017, 13 patients underwent SBRT followed by surgical stabilization for unstable spinal metastases. The median time between SBRT and surgery was 17-h (IQR 5–19). None of the patients experienced wound complications. Improvements in pain and quality of life were observed over time for all patients.

Conclusion: SBRT followed by surgical stabilization within 24 h for the treatment of unstable spinal metastases is safe. Palliation may be experienced earlier and with both treatments being performed in one hospital admission the treatment burden decreases.

Impact of cervicothoracic region stereotactic spine radiosurgery on adjacent organs at risk

OBJECTIVE

Stereotactic radiosurgery (SRS) of the spine is a conformal method of delivering a high radiation dose to a target in a single or few (usually ≤ 5) fractions with a sharp fall-off outside the target volume. Although efforts have been focused on evaluating spinal cord tolerance when treating spinal column metastases, no study has formally evaluated toxicity to the surrounding organs at risk (OAR), such as the brachial plexus or the oropharynx, when performing SRS in the cervicothoracic region. The aim of this study was to evaluate the radiation dosimetry and the acute and delayed toxicities of SRS on OAR in such patients.

METHODS

Fifty-six consecutive patients (60 procedures) with a cervicothoracic spine tumor involving segments within C5–T1 who were treated using single-fraction SRS between February 2006 and July 2014 were included in the study. Each patient underwent CT simulation and high-definition MRI before treatment. The clinical target volume and OAR were contoured on BrainScan and iPlan software after image fusion. Radiation toxicity was evaluated using the common toxicity criteria for adverse events and correlated to the radiation doses delivered to these regions. The incidence of vertebral body compression fracture (VCF) before and after SRS was evaluated also.

RESULTS

Metastatic lesions constituted the majority (n = 52 [93%]) of tumors treated with SRS. Each patient was treated with a median single prescription dose of 16 Gy to the target. The median percentage of tumor covered by SRS was 93% (maximum target dose 18.21 Gy). The brachial plexus received the highest mean maximum dose of 17 Gy, followed by the esophagus (13.8 Gy) and spinal cord (13 Gy). A total of 14 toxicities were encountered in 56 patients (25%) during the study period. Overall, 14% (n = 8) of the patients had Grade 1 toxicity, 9% (n = 5) had Grade 2 toxicity, 2% (n = 1) had Grade 3 toxicity, and none of the patients had Grade 4 or 5 toxicity. The most common (12%) toxicity was dysphagia/odynophagia, followed by axial spine pain flare or painful radiculopathy (9%). The maximum radiation dose to the brachial plexus showed a trend toward significance (p = 0.066) in patients with worsening post-SRS pain. De novo and progressive VCFs after SRS were noted in 3% (3 of 98) and 4% (4 of 98) of vertebral segments, respectively.

CONCLUSIONS

From the analysis, the current SRS doses used at the Cleveland Clinic seem safe and well tolerated at the cervicothoracic junction. These preliminary data provide tolerance benchmarks for OAR in this region. Because the effect of dose-escalation SRS strategies aimed at improving local tumor control needs to be balanced carefully with associated treatment-related toxicity on adjacent OAR, larger prospective studies using such approaches are needed.

Spine radiosurgery: lessons learned from the first 100 treatment sessions

OBJECTIVE

Local therapy to spine tumors has been shown to be effective in selected cases. Spinal radiosurgery (SRS) is an evolving radiotherapy regimen allowing for noninvasive, highly efficacious local treatment. The learning curve can compromise the results of any newly employed technology and should be studied to minimize its effects. In this paper the first 100 SRSs performed at several medical centers are presented and analyzed for the effects of the learning curve on outcome.

METHODS

A retrospective analysis was undertaken to evaluate data from patients treated with SRS at Sheba Medical Center and Assuta Medical Centers in the period from September 2011 to February 2016. Medical history, clinical and neurological findings, pathological diagnoses, SRS variables, complications, and follow-up data were collected and analyzed. Local control rates were calculated, and local treatment failure cases were qualitatively studied.

RESULTS

One hundred treatment sessions were performed for 118 lesions at 179 spinal levels in 80 patients. The complication rate was low and did not correlate with a learning curve. Mean follow-up time was 302 days, and the overall local control rate was 95%. The local control rate was dose dependent and increased from 87% (among 35 patients receiving a dose of 16 Gy) to 97% (among 65 patients receiving a dose of 18 Gy). The 6 treatment failure cases are discussed in detail.

CONCLUSIONS

Spinal radiosurgery is a safe and effective treatment. Comprehensive education of the treating team and continuous communication are essential to limit the effects of the learning curve on outcome.

Consensus Contouring Guidelines for Postoperative Stereotactic Body Radiation Therapy for Metastatic Solid Tumor Malignancies to the Spine

PURPOSE

To develop consensus contouring guidelines for postoperative stereotactic body radiation therapy (SBRT) for spinal metastases.

METHODS AND MATERIALS

Ten spine SBRT specialists representing 10 international centers independently contoured the clinical target volume (CTV), planning target volume (PTV), spinal cord, and spinal cord planning organ at risk volume (PRV) for 10 representative clinical scenarios in postoperative spine SBRT for metastatic solid tumor malignancies. Contours were imported into the Computational Environment for Radiotherapy Research. Agreement between physicians was calculated with an expectation minimization algorithm using simultaneous truth and performance level estimation with κ statistics. Target volume definition guidelines were established by finding optimized confidence level consensus contours using histogram agreement analyses.

RESULTS

Nine expert radiation oncologists and 1 neurosurgeon completed contours for all 10 cases. The mean sensitivity and specificity were 0.79 (range, 0.71-0.89) and 0.94 (range, 0.90-0.99) for the CTV and 0.79 (range, 0.70-0.95) and 0.92 (range, 0.87-0.99) for the PTV), respectively. Mean κ agreement, which demonstrates the probability that contours agree by chance alone, was 0.58 (range, 0.43-0.70) for CTV and 0.58 (range, 0.37-0.76) for PTV (P<.001 for all cases). Optimized consensus contours were established for all patients with 80% confidence interval. Recommendations for CTV include treatment of the entire preoperative extent of bony and epidural disease, plus immediately adjacent bony anatomic compartments at risk of microscopic disease extension. In particular, a "donut-shaped" CTV was consistently applied in cases of preoperative circumferential epidural extension, regardless of extent of residual epidural extension. Otherwise more conformal anatomic-based CTVs were determined and described. Spinal instrumentation was consistently excluded from the CTV.

CONCLUSIONS

We provide consensus contouring guidelines for common scenarios in postoperative SBRT for spinal metastases. These consensus guidelines are subject to clinical validation.