Spot-Scanning-Based Proton Therapy for Extracranial Chordoma

Proton Therapy for Spinal Tumors: A Consensus Statement From the Particle Therapy Cooperative Group

PURPOSE

Proton beam therapy (PBT) plays an important role in the management of primary spine tumors. The purpose of this consensus statement was to summarize safe and optimal delivery of PBT for spinal tumors.

METHODS AND MATERIALS

The Particle Therapy Cooperative Group Skull Base/Central nervous system/Sarcoma Subcommittee consisting of radiation oncologists and medical physicists with specific expertise in spinal irradiation developed expert recommendations discussing treatment planning considerations and current approaches in the treatment of primary spinal tumors.

RESULTS

Computed tomography simulation: factors that require significant consideration include (1) patient comfort, (2) setup reproducibility and stability, and (3) accessibility of appropriate beam angles.

SPINE STABILIZATION HARDWARE

If present, hardware should be placed with cross-links well above/below the level of the primary tumor to reduce the metal burden at the level of the tumor bed. New materials that can reduce uncertainties include polyether-ether-ketone and composite polyether-ether-ketone-carbon fiber implants.

FIELD ARRANGEMENT

Appropriate beam selection is required to ensure robust target coverage and organ at risk sparing. Commonly, 2 to 4 treatment fields, typically from posterior and/or posterior-oblique directions, are used.

TREATMENT PLANNING METHODOLOGY

Robust optimization is recommended for all pencil beam scanning plans (the preferred treatment modality) and should consider setup uncertainty (between 3 and 7 mm) and range uncertainty (3%-3.5%). In the presence of metal hardware, use of an increased range uncertainty up to 5% is recommended.

CONCLUSIONS

The Particle Therapy Cooperative Group Skull Base/Central nervous system/Sarcoma Subcommittee has developed recommendations to enable centers to deliver PBT safely and effectively for the management of primary spinal tumors.

Robust IMPT and follow-up toxicity in skull base chordoma and chondrosarcoma-a single-institution clinical experience

BACKGROUND

Chordomas and chondrosarcomas of the skull base are rare, slowly growing malignant bone neoplasms. Despite their radioresistant properties, proton therapy has been successfully used as an adjunct to resection or as a definitive treatment. Herewith, we present our experience with robustly optimized intensity-modulated proton therapy (IMPT) and related toxicities in skull base chordoma and chondrosarcoma patients treated at HollandPTC, Delft, the Netherlands.

METHODS

Clinical data, treatment plans, and acute toxicities of patients treated between July 2019 and August 2021 were reviewed. CT and 3.0T MRI scans for treatment planning were performed in supine position in a thermoplastic mold. In total, 21 dose optimization and 28 dose evaluation scenarios were simulated. Acute toxicity was scored weekly before and during the treatment according to the CTCAE v4.0. Median follow-up was 35 months (range 12-36 months).

RESULTS

Overall, 9 chordoma and 3 chondrosarcoma patients with 1-3 resections prior to IMPT were included; 4 patients had titanium implants. Brainstem core and surface and spinal cord core and surface were used for nominal plan robust optimization in 11, 10, 8, and 7 patients, respectively. Middle ear inflammation, dry mouth, radiation dermatitis, taste disorder, and/or alopecia of grades 1-3 were noted at the end of treatment among 6 patients without similar complaints at inclusion; symptoms disappeared 3 months following the treatment.

CONCLUSION

Robustly optimized IMPT is clinically feasible as a postoperative treatment for skull base chordoma and chondrosarcoma patients. We observed acceptable early toxicities (grade 1-3) that disappeared within the first 3 months after irradiation.

Surgery and proton radiation therapy for pediatric base of skull chordomas: Long-term clinical outcomes for 204 patients

BACKGROUND

Data on clinical outcomes for base of skull (BOS) chordomas in the pediatric population is limited. We report patient outcomes after surgery and proton radiotherapy (PRT).

METHODS

Pediatric patients with BOS chordomas were treated with PRT or combined proton/photon approach (proton-based; for most, 80% proton/20% photon) at the Massachusetts General Hospital from 1981 to 2021. Endpoints of interest were overall survival (OS), disease-specific survival, progression-free survival (PFS), freedom from local recurrence (LC), and freedom from distant failure (DC).

RESULTS

Of 204 patients, median age at diagnosis was 11.1 years (range, 1-21). Chordoma location included 59% upper and/or middle clivus, 36% lower clivus, 4% craniocervical junction, and 1% nasal cavity. Fifteen (7%) received pre-RT chemotherapy. Forty-seven (23%) received PRT, and 157 (77%) received comboRT. Median total dose was 76.7 Gy (RBE) (range, 59.3-83.3). At a median follow-up of 10 years (interquartile range, 5-16 years), 56 recurred. Median OS and PFS were 26 and 25 years, with 5-, 10-, and 20-year OS and PFS rates of 84% and 74%, 78% and 69%, and 64% and 64%, respectively. Multivariable actuarial analyses showed poorly differentiated subtype, radiographical progression prior to RT, larger treatment volume, and lower clivus location to be prognostic factors for worse OS, PFS, and LC. RT was well tolerated at a median follow-up of 9 years (interquartile range, 4-16 years). Side effects included 166 patients (80%) with mild/moderate acute toxicities, 24 (12%) patients with late toxicities, and 4 (2%) who developed secondary radiation-related malignancies.

CONCLUSION

This is the largest cohort of BOS chordomas in the literature, pediatric and/or adult. High-dose PRT following surgical resection is effective with low rates of late toxicity.

Intensity-modulated radiotherapy for the management of primary and recurrent chordomas: a retrospective long-term follow-up study

Background

Chordomas have a high risk of recurrence. Radiotherapy (RT) is required as adjuvant therapy after resection. Sufficient radiation doses for local control (LC) can be achieved using either particle therapy, if this technology is available and feasible, or intensity-modulated radiotherapy.

Materials and methods

57 patients (age, 11.8-81.6 years) with chordomas of the skull base, spine and pelvis who received photon radiotherapy between 1995 and 2017 were enrolled in the study. Patients were treated at the time of initial diagnosis (68.4%) or during recurrence (31.6%). 44 patients received adjuvant radiotherapy and 13 received definitive radiotherapy. The median total dose to the physical target volume was 70 Gy equivalent dose in 2 Gy fractions (EQD2) (range: 54.7-82.5) in 22-36 fractions.

Results

LC was 76.4%, 58.4%, 46.7% and 39.9% and overall survival (OS) was 98.3%, 89%, 76.9% and 47.9% after 1, 3, 5 and 10 years, respectively, with a median follow-up period of 6.5 years (range, 0.5-24.3 years). Age, dose and treatment concept (post-operative or definitive) were significant prognostic factors for OS. Primary treatment, macroscopic tumour at RT and size of the irradiated volume were statistically significant prognostic factors for LC.

Conclusion

Photon treatment is a safe and effective treatment for chordomas if no particle therapy is available. The best results can be achieved against primary tumours if the application of curative doses is possible due to organs at risk in direct proximity. We recommend high-dose radiotherapy, regardless of the resection status, as part of the initial treatment of chordoma, using the high conformal radiation technique if particle therapy is not feasible.

Radiotherapy for Mobile Spine and Sacral Chordoma: A Critical Review and Practical Guide from the Spine Tumor Academy

Chordomas are rare tumors of the embryologic spinal cord remnant. They are locally aggressive and typically managed with surgery and either adjuvant or neoadjuvant radiation therapy. However, there is great variability in practice patterns including radiation type and fractionation regimen, and limited high-level data to drive decision making. The purpose of this manuscript was to summarize the current literature specific to radiotherapy in the management of spine and sacral chordoma and to provide practice recommendations on behalf of the Spine Tumor Academy. A systematic review of the literature was performed using the Preferred Reporting Items for Systematic reviews and Meta-Analyses (PRISMA) approach. Medline and Embase databases were utilized. The primary outcome measure was the rate of local control. A detailed review and interpretation of eligible studies is provided in the manuscript tables and text. Recommendations were defined as follows: (1) consensus: approved by >75% of experts; (2) predominant: approved by >50% of experts; (3) controversial: not approved by a majority of experts. Expert consensus supports dose escalation as critical in optimizing local control following radiation therapy for chordoma. In addition, comprehensive target volumes including sites of potential microscopic involvement improve local control compared with focal targets. Level I and high-quality multi-institutional data comparing treatment modalities, sequencing of radiation and surgery, and dose/fractionation schedules are needed to optimize patient outcomes in this locally aggressive malignancy.

Clinical outcomes and toxicities of 100 patients treated with proton therapy for chordoma on the proton collaborative group prospective registry

BACKGROUND

We present efficacy and toxicity outcomes among patients with chordoma treated on the Proton Collaborative Group prospective registry.

METHODS

Consecutive chordoma patients treated between 2010-2018 were evaluated. One hundred fifty patients were identified, 100 had adequate follow-up information. Locations included base of skull (61%), spine (23%), and sacrum (16%). Patients had a performance status of ECOG 0-1 (82%) and median age of 58 years. Eighty-five percent of patients underwent surgical resection. The median proton RT dose was 74 Gy (RBE) (range 21-86 Gy (RBE)) using passive scatter proton RT (PS-PBT) (13%), uniform scanning proton RT (US-PBT) (54%) and pencil beam scanning proton RT (PBS-PBT) (33%). Rates of local control (LC), progression-free survival (PFS), overall survival (OS) and acute and late toxicities were assessed.

RESULTS

2/3-year LC, PFS, and OS rates are 97%/94%, 89%/74%, and 89%/83%, respectively. LC did not differ based on surgical resection (p = 0.61), though this is likely limited by most patients having undergone a prior resection. Eight patients experienced acute grade 3 toxicities, most commonly pain (n = 3), radiation dermatitis (n = 2), fatigue (n = 1), insomnia (n = 1) and dizziness (n = 1). No grade ≥ 4 acute toxicities were reported. No grade ≥ 3 late toxicities were reported, and most common grade 2 toxicities were fatigue (n = 5), headache (n = 2), CNS necrosis (n = 1), and pain (n = 1).

CONCLUSIONS

In our series, PBT achieved excellent safety and efficacy outcomes with very low rates of treatment failure. CNS necrosis is exceedingly low (<1%) despite the high doses of PBT delivered. Further maturation of data and larger patient numbers are necessary to optimize therapy in chordoma.

A component method to delineate surgical spine implants for proton Monte Carlo dose calculation

PURPOSE

Metallic implants have been correlated to local control failure for spinal sarcoma and chordoma patients due to the uncertainty of implant delineation from computed tomography (CT). Such uncertainty can compromise the proton Monte Carlo dose calculation (MCDC) accuracy. A component method is proposed to determine the dimension and volume of the implants from CT images.

METHODS

The proposed component method leverages the knowledge of surgical implants from medical supply vendors to predefine accurate contours for each implant component, including tulips, screw bodies, lockers, and rods. A retrospective patient study was conducted to demonstrate the feasibility of the method. The reference implant materials and samples were collected from patient medical records and vendors, Medtronic and NuVasive. Additional CT images with extensive features, such as extended Hounsfield units and various reconstruction diameters, were used to quantify the uncertainty of implant contours.

RESULTS

For in vivo patient implant estimation, the reference and the component method differences were 0.35, 0.17, and 0.04 cm3 for tulips, screw bodies, and rods, respectively. The discrepancies by a conventional threshold method were 5.46, 0.76, and 0.05 cm3 , respectively. The mischaracterization of implant materials and dimensions can underdose the clinical target volume coverage by 20 cm3 for a patient with eight lumbar implants. The tulip dominates the dosimetry uncertainty as it can be made from titanium or cobalt-chromium alloys by different vendors.

CONCLUSIONS

A component method was developed and demonstrated using phantom and patient studies with implants. The proposed method provides more accurate implant characterization for proton MCDC and can potentially enhance the treatment quality for proton therapy. The current proof-of-concept study is limited to the implant characterization for lumbar spine. Future investigations could be extended to cervical spine and dental implants for head-and-neck patients where tight margins are required to spare organs at risk.

Efficacy and safety of carbon ion radiotherapy for bone sarcomas: a systematic review and meta-analysis

Objective

This study aimed to systematically evaluate and conduct a meta-analysis of the efficacy and safety of carbon ion radiotherapy for bone sarcomas.

Methods

We searched for articles using the PubMed, Embase, Cochrane Library, and the Web of Science databases from their inception to January 12, 2022. Two researchers independently screened the literature and extracted data based on the inclusion and exclusion criteria. Statistical analyses were performed using STATA version 14.0.

Results

We searched for 4378 candidate articles, of which 12 studies were included in our study according to the inclusion and exclusion criteria. Of the 897 BSs patients who received carbon ion radiotherapy in the studies, 526 patients had chordoma, 255 patients had chondrosarcoma, 112 patients had osteosarcoma, and 4 patients had other sarcomas. The local control rate at 1, 2, 3, 4, 5, and 10 years in these studies were 98.5% (95% confidence interval [CI] = 0.961–1.009, I² = 0%), 85.8% (95% CI = 0.687–1.030, I² = 91%), 86% (95% CI = 0.763–0.957, I² = 85.3%), 91.1% (95% CI = 0.849–0.974), 74.3% (95% CI = 0.666–0.820, I² = 85.2%), and 64.7% (95% CI = 0.451–0.843, I² = 95.3%), respectively. The overall survival rate at 1, 2, 3, 4, 5, and 10 years in these studies were 99.9% (95% CI = 0.995–1.004, I² = 0%), 89.6% (95% CI = 0.811–0.980, I² = 96.6%), 85% (95% CI = 0.750–0.950, I² = 89.4%), 92.4% (95% CI = 0.866–0.982), 72.7% (95% CI = 0.609–0.844, I² = 95.3%), and 72.1% (95% CI = 0.661–0.781, I² = 46.5%), respectively. Across all studies, the incidence of acute and late toxicities was mainly grade 1 to grade 2, and grade 1 to grade 3, respectively.

Conclusion

As an advanced radiotherapy, carbon ion radiotherapy is promising for patients with bone sarcomas that are unresectable or residual after incomplete surgery. The data indicated that carbon ion radiotherapy was safe and effective for bone sarcomas, showing promising results for local control, overall survival, and lower acute and late toxicity.

PROSPERO registration number

CRD42021258480.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13014-022-02089-0.

Outcomes and issues of 12 chordomas treated in a single center

Background

Chordomas stem from notochordal vestiges and rank as low-grade bone malignancies although fraught with high risk of recurrence. This study assesses the clinical outcomes of twelve chordoma cases treated in our clinic, in an effort to shed light on the often under-represented pool of results deriving from non-referral centers.

Methods

We reviewed the clinicopathological traits of all chordoma patients registered in our center since 1991. Major endpoints were overall survival (OS) and progression-free survival (PFS) estimated using the Kaplan–Meier and Nelson–Aalen methods.

Results

Twelve patients, aged on average 47.9 years, were treated for primary or recurrent disease. Seven had chordomas originating in the cranium, 5 in the spine, including a bifocal tumor, and the mean time lapse between the beginning of symptoms and diagnosis was 15.4 months, marked by dull ache. Subtotal resection was achieved in 5 cases, incomplete in 5, while in 2, only biopsy was accomplished. Conformal radiotherapy was administered to 5 and stereotactic radiosurgery to 2 in the setting of recurrence. Protons were used once and targeted agents induced no clinical response in 3 patients. Median OS and PFS were 36 and 12 months, respectively, with the best outlook linked to maximal resection, spinal location, and good preoperative functional status. In all, 6 patients died of chordoma, 4 are alive, and 1 was lost. Relapse was the rule for most cases, except 2, and pulmonary metastases were ascertained in 1.

Conclusions

Our cases were typical of chordomas, implying that inadequate surgical margins and successive recurrence are negative determinants of prognosis and that interinstitutional cooperation counterbalances shortages in non-referral institutes.

Clinical Outcome of Sacral Chordoma Patients Treated with Pencil Beam Scanning Proton Therapy

AIMS

Sacral chordomas are locally aggressive, radio-resistant tumours. Proton therapy has the potential to deliver high radiation doses, which may improve the therapeutic ratio when compared with conventional radiotherapy. We assessed tumour control and radiation-induced toxicity in a cohort of sacral chordoma patients treated with definitive or postoperative pencil beam scanning proton therapy.

METHODS AND MATERIALS

Sixty patients with histologically proven sacral chordoma treated between November 1997 and October 2018 at the Paul Scherrer Institute with postoperative (n = 50) or definitive proton therapy (n = 10) were retrospectively analysed. Only 10 (17%) patients received combined photon radiotherapy and proton therapy. Survival rates were calculated using the Kaplan-Meier actuarial method. The Log-rank test was used to compare different functions for local control, freedom from distant recurrence and overall survival. Acute and late toxicity were assessed according to the Common Terminology Criteria for Adverse Events (CTCAE) v5.0.

RESULTS

The median follow-up was 48 months (range 4-186). Local recurrence occurred in 20 (33%) patients. The 4-year local control, freedom from distant recurrence and overall survival rates were 77%, 89% and 85%, respectively. On univariate analysis, subtotal resection/biopsy (P = 0.02), tumour extension restricted to bone (P = 0.01) and gross tumour volume >130 ml (P = 0.04) were significant predictors for local recurrence. On multivariate analysis, tumour extension restricted to bone (P = 0.004) and gross total resection (P = 0.02) remained independent favourable prognostic factors for local recurrence. Twenty-four (40%), 28 (47%) and eight (11%) patients experienced acute grade 1, 2 and 3 toxicities, respectively. The 4-year late toxicity-free survival was 91%. Two patients developed secondary malignancies to the bladder 3-7 years after proton therapy.

CONCLUSIONS

Our data indicate that pencil beam scanning proton therapy for sacral chordomas is both safe and effective. Gross total resection, tumour volume <130 ml and tumour restricted to the bone are favourable prognostic factors for local tumour control.

Radiolucent Carbon Fiber-Reinforced Implants for Treatment of Spinal Tumors-Clinical, Radiographic, and Dosimetric Considerations

The management of spine tumors is multimodal and personalized to each individual patient. Patients often require radiation therapy after surgical fixation. Although titanium implants are used most commonly, they produce significant artifact, leading to decreased confidence in target-volume coverage and normal tissue sparing. Carbon-based materials have been found to have minimal effects on dose perturbation in postoperative radiation therapy and have shown biostability and biocompatibility that are comparable to titanium implants. Using the PubMed and Web of Sciences databases, we conducted a systematic review of carbon-based screw and rod fixation systems in the treatment of spinal tumors. We reviewed clinical studies regarding safety of spine fixation with carbon fiber-reinforced (CFR) implants and biomechanical studies, as well as radiation and dosimetric studies. The radiolucency of CFR-polyether ether ketone implants has the potential to benefit patients with spine tumor. Clinical studies have shown no increase in complications with implementation of CFR-polyether ether ketone implants, and these devices seem to have sufficient stiffness and pullout strength. However, further trials are necessary to determine if there is a clinically significant impact on local tumor control.

Systematic review of charged-particle therapy for chordomas and sarcomas of the mobile spine and sacrum

OBJECTIVE

Long-term local control in patients with primary chordoma and sarcoma of the spine and sacrum is increasingly reliant upon en bloc resection with negative margins. At many institutions, adjuvant radiation is recommended; definitive radiation is also recommended for the treatment of unresectable tumors. Because of the high off-target radiation toxicities associated with conventional radiotherapy, there has been growing interest in the use of proton and heavy-ion therapies. The aim of this study was to systematically review the literature regarding these therapies.

METHODS

The PubMed, OVID, Embase, and Web of Science databases were queried for articles describing the use of proton, combined proton/photon, or heavy-ion therapies for adjuvant or definitive radiotherapy in patients with primary sarcoma or chordoma of the mobile spine and sacrum. A qualitative synthesis of the results was performed, focusing on overall survival (OS), progression-free survival (PFS), disease-free survival (DFS), and disease-specific survival (DSS); local control; and postradiation toxicities.

RESULTS

Of 595 unique articles, 64 underwent full-text screening and 38 were included in the final synthesis. All studies were level III or IV evidence with a high risk of bias; there was also significant overlap in the reported populations, with six centers accounting for roughly three-fourths of all reports. Five-year therapy outcomes were as follows: proton-only therapies, OS 67%-82%, PFS 31%-57%, and DFS 52%-62%; metastases occurred in 17%-18% and acute toxicities in 3%-100% of cases; combined proton/photon therapy, local control 62%-85%, OS 78%-87%, PFS 90%, and DFS 61%-72%; metastases occurred in 12%-14% and acute toxicities in 84%-100% of cases; and carbon ion therapy, local control 53%-100%, OS 52%-86%, PFS (only reported for 3 years) 48%-76%, and DFS 50%-53%; metastases occurred in 2%-39% and acute toxicities in 26%-48%. There were no studies directly comparing outcomes between photon and charged-particle therapies or comparing outcomes between radiation and surgical groups.

CONCLUSIONS

The current evidence for charged-particle therapies in the management of sarcomas of the spine and sacrum is limited. Preliminary evidence suggests that with these therapies local control and OS at 5 years are comparable among various charged-particle options and may be similar between those treated with definitive charged-particle therapy and historical surgical cohorts. Further research directly comparing charged-particle and photon-based therapies is necessary.

Local Control After Proton Therapy for Pediatric Chordoma

PURPOSE

Due to the location and high dose required for disease control, pediatric chordomas are theoretically well-suited for treatment with proton therapy, but their low incidence limits the clinical outcome data available in the literature. We sought to report the efficacy and toxicity of proton therapy among a single-institution cohort.

METHODS AND MATERIALS

Between 2008 and 2019, 29 patients with a median age of 14.8 years (range, 3.8-21.8) received passive-scattered proton therapy for nonmetastatic chordoma. No patient received prior irradiation. Twenty-four tumors arose in the clivus/cervical spine region and 5 in the lumbosacral spine. Twenty-six tumors demonstrated classic well-differentiated histology and 3 were dedifferentiated or not otherwise specified. Approximately half of the tumors underwent specialized testing: 14 were brachyury-positive and 10 retained INI-1. Three patients had locally recurrent tumors after surgery alone (n = 2) or surgery + chemotherapy (n = 1), and 17 patients had gross disease at the time of radiation. The median radiation dose was 73.8 Gy relative biological effectivness (range, 69-75.6).

RESULTS

With a median follow-up of 4.3 years (range, 1.0-10.7), the 5-year estimates of local control, progression-free survival, and overall survival rates were 85%, 82%, and 86%, respectively. No disease progression was observed beyond 3 years. Excluding 3 patients with dedifferentiated/not-otherwise-specified chordoma, the 5-year local control, progression-free survival, and overall survival rates were 92%, 92%, and 91%, respectively. Serious toxicities included 3 patients with hardware failure or related infection requiring revision surgery, 2 patients with hormone deficiency, and 2 patients with Eustachian tube dysfunction causing chronic otitis media. No patient experienced brain stem injury, myelopathy, vision loss, or hearing loss after radiation.

CONCLUSIONS

In pediatric patients with chordoma, proton therapy is associated with a low risk of serious toxicity and high efficacy, particularly in well-differentiated tumors. Complete resection may be unnecessary for local control, and destabilizing operations requiring instrumentation may result in additional complications after therapy.

Impact of Carbon Ion Radiotherapy on Inoperable Bone Sarcoma

Simple Summary

The standard treatment for bone sarcoma is surgery with or without additional chemotherapy; however, complete resection of the tumor might not be possible in patients with locally advanced lesions. Management of patients with bone sarcoma who are unsuitable for surgery is challenging. Carbon ion radiotherapy (C-ion RT) was initiated in 1994 for treating various cancers in Japan and is being considered to be an effective treatment for unresectable bone sarcoma. However, there is a limited number of reports on the clinical outcomes of C-ion RT for bone sarcoma. Here, we aimed to analyze the clinical outcomes and prognostic factors among patients with unresectable bone sarcoma who were treated with C-ion RT. We found that C-ion RT had favorable overall survival and local control with low toxicity rates compared to surgery. Therefore, our results suggest a potential role for C-ion RT in the radical treatment of inoperable bone sarcoma.

Abstract

Management of patients with bone sarcoma who are unsuitable for surgery is challenging. We aimed to analyze the clinical outcomes among such patients who were treated with carbon ion radiotherapy (C-ion RT). We reviewed the medical records of the patients treated with C-ion RT between April 2011 and February 2019 and analyzed the data of 53 patients. Toxicities were classified using the National Cancer Institute’s Common Terminology Criteria for Adverse Events (Version 4.0). The median follow-up duration for all patients was 36.9 months. Histologically, 32 patients had chordoma, 9 had chondrosarcoma, 8 had osteosarcoma, 3 had undifferentiated pleomorphic sarcoma, and 1 had sclerosing epithelioid fibrosarcoma. The estimated 3-year overall survival (OS), local control (LC), and progression-free survival (PFS) rates were 79.7%, 88.6%, and 68.9%, respectively. No patients developed grade 3 or higher acute toxicities. Three patients developed both grade 3 radiation dermatitis and osteomyelitis, one developed both grade 3 radiation dermatitis and soft tissue infection, and one developed rectum-sacrum-cutaneous fistula. C-ion RT showed favorable clinical outcomes in terms of OS, LC, and PFS and low rates of toxicity in bone sarcoma patients. These results suggest a potential role for C-ion RT in the management of this population.

A novel proton counting detector and method for the validation of tissue and implant material maps for Monte Carlo dose calculation

The presence of artificial implants complicates the delivery of proton therapy due to inaccurate characterization of both the implant and the surrounding tissues. In this work, we describe a method to characterize implant and human tissue mimicking materials in terms of relative stopping power (RSP) using a novel proton counting detector. Each proton is tracked by directly measuring the deposited energy along the proton track using a fast, pixelated spectral detector AdvaPIX-TPX3 (TPX3). We considered three scenarios to characterize the RSPs. First, in-air measurements were made in the presence of metal rods (Al, Ti and CoCr) and bone. Then, measurements of energy perturbations in the presence of metal implants and bone in an anthropomorphic phantom were performed. Finally, sampling of cumulative stopping power (CSP) of the phantom were made at different locations of the anthropomorphic phantom. CSP and RSP information were extracted from energy spectra at each beam path. To quantify the RSP of metal rods we used the shift in the most probable energy (MPE) of CSP from the reference CSP without a rod. Overall, the RSPs were determined as 1.48, 2.06, 3.08, and 5.53 from in-air measurements; 1.44, 1.97, 2.98, and 5.44 from in-phantom measurements, for bone, Al, Ti and CoCr, respectively. Additionally, we sampled CSP for multiple paths of the anthropomorphic phantom ranging from 18.63 to 25.23 cm deriving RSP of soft tissues and bones in agreement within 1.6% of TOPAS simulations. Using minimum error of these multiple CSP, optimal mass densities were derived for soft tissue and bone and they are within 1% of vendor-provided nominal densities. The preliminary data obtained indicates the proposed novel method can be used for the validation of material and density maps, required by proton Monte Carlo Dose calculation, provided by competing multi-energy computed tomography and metal artifact reduction techniques.

Carbon fiber-reinforced PEEK versus titanium implants: an in vitro comparison of susceptibility artifacts in CT and MR imaging

Artifacts in computed tomography (CT) and magnetic resonance imaging (MRI) due to titanium implants in spine surgery are known to cause difficulties in follow-up imaging, radiation planning, and precise dose delivery in patients with spinal tumors. Carbon fiber–reinforced polyetheretherketon (CFRP) implants aim to reduce these artifacts. Our aim was to analyze susceptibility artifacts of these implants using a standardized in vitro model. Titanium and CFRP screw-rod phantoms were embedded in 3% agarose gel. Phantoms were scanned with Siemens Somatom AS Open and 3.0-T Siemens Skyra scanners. Regions of interest (ROIs) were plotted and analyzed for CT and MRI at clinically relevant localizations. CT voxel–based imaging analysis showed a significant difference of artifact intensity and central overlay between titanium and CFRP phantoms. For the virtual regions of the spinal canal, titanium implants (ti) presented − 30.7 HU vs. 33.4 HU mean for CFRP (p < 0.001), at the posterior margin of the vertebral body 68.9 HU (ti) vs. 59.8 HU (CFRP) (p < 0.001) and at the anterior part of the vertebral body 201.2 HU (ti) vs. 70.4 HU (CFRP) (p < 0.001), respectively. MRI data was only visually interpreted due to the low sample size and lack of an objective measuring system as Hounsfield units in CT. CT imaging of the phantom with typical implant configuration for thoracic stabilization could demonstrate a significant artifact reduction in CFRP implants compared with titanium implants for evaluation of index structures. Radiolucency with less artifacts provides a better interpretation of follow-up imaging, radiation planning, and more precise dose delivery.

The dosimetric impact of stabilizing spinal implants in radiotherapy treatment planning with protons and photons: standard titanium alloy vs. radiolucent carbon-fiber-reinforced PEEK systems

Background

Throughout the last years, carbon‐fibre‐reinforced PEEK (CFP) pedicle screw systems were introduced to replace standard titanium alloy (Ti) implants for spinal instrumentation, promising improved radiotherapy (RT) treatment planning accuracy. We compared the dosimetric impact of both implants for intensity modulated proton (IMPT) and volumetric arc photon therapy (VMAT), with the focus on uncertainties in Hounsfield unit assignment of titanium alloy.

Methods

Retrospective planning was performed on CT data of five patients with Ti and five with CFP implants. Carbon‐fibre‐reinforced PEEK systems comprised radiolucent pedicle screws with thin titanium‐coated regions and titanium tulips. For each patient, one IMPT and one VMAT plan were generated with a nominal relative stopping power (SP) (IMPT) and electron density (ρ) (VMAT) and recalculated onto the identical CT with increased and decreased SP or ρ by ±6% for the titanium components.

Results

Recalculated VMAT dose distributions hardly deviated from the nominal plans for both screw types. IMPT plans resulted in more heterogeneous target coverage, measured by the standard deviation σ inside the target, which increased on average by 7.6 ± 2.3% (Ti) vs 3.4 ± 1.2% (CFP). Larger SPs lead to lower target minimum doses, lower SPs to higher dose maxima, with a more pronounced effect for Ti screws.

Conclusions

While VMAT plans showed no relevant difference in dosimetric quality between both screw types, IMPT plans demonstrated the benefit of CFP screws through a smaller dosimetric impact of CT‐value uncertainties compared to Ti. Reducing metal components in implants will therefore improve dose calculation accuracy and lower the risk for tumor underdosage.

The sacral chordoma margin

OBJECTIVE

Aim of the manuscript is to discuss how to improve margins in sacral chordoma.

BACKGROUND

Chordoma is a rare neoplasm, arising in half cases from the sacrum, with reported local failure in >50% after surgery.

METHODS

A multidisciplinary meeting of the "Chordoma Global Consensus Group" was held in Milan in 2017, focusing on challenges in defining and achieving optimal margins in chordoma with respect to surgery, definitive particle radiation therapy (RT) and medical therapies. This review aims to report on the outcome of the consensus meeting and to provide a summary of the most recent evidence in this field. Possible new ways forward, including on-going international clinical studies, are discussed.

RESULTS

En-bloc tumor-sacrum resection is the cornerstone of treatment of primary sacral chordoma, aiming to achieve negative microscopic margins. Radical definitive particle therapy seems to offer a similar outcome compared to surgery, although confirmation in comparative trials is lacking; besides there is still a certain degree of technical variability across institutions, corresponding to different fields of treatment and different tumor coverage. To address some of these questions, a prospective, randomized international study comparing surgery versus definitive high-dose RT is ongoing. Available data do not support the routine use of any medical therapy as (neo)adjuvant/cytoreductive treatment.

CONCLUSION

Given the significant influence of margins status on local control in patients with primary localized sacral chordoma, the clear definition of adequate margins and a standard local approach across institutions for both surgery and particle RT is vital for improving the management of these patients.

Particle therapy tumour outcomes: An updated systematic review

Particle therapy (PT) offers the potential for reduced normal tissue damage as well as escalation of target dose, thereby enhancing the therapeutic ratio in radiation therapy. Reflecting the building momentum of PT use worldwide, construction has recently commenced for The Australian Bragg Centre for Proton Therapy and Research in Adelaide - the first PT centre in Australia. This systematic review aims to update the clinical evidence base for PT, both proton beam and carbon ion therapy. The purpose is to inform clinical decision-making for referral of patients to PT centres in Australia as they become operational and overseas in the interim. Three major databases were searched by two independent researchers, and evidence quality was classified according to the National Health and Medical Research Council evidence hierarchy. One hundred and thirty-six studies were included, two-thirds related to proton beam therapy alone. PT at the very least provides equivalent tumour outcomes compared to photon controls with the possibility of improved control in the case of carbon ion therapy. There is suggestion of reduced morbidities in a range of tumour sites, supporting the predictions from dosimetric modelling and the wide international acceptance of PT for specific indications based on this. Though promising, this needs to be counterbalanced by the overall low quality of evidence found, with 90% of studies of level IV (case series) evidence. Prospective comparative clinical trials, supplemented by database-derived outcome information, preferably conducted within international and national networks, are strongly recommended as PT is introduced into Australasia.

Performance of a 6D Treatment Chair for Patient Positioning in an Upright Posture for Fixed Ion Beam Lines

Purpose: To evaluate the mechanical accuracy and the robustness of position alignment under x-ray-based image guidance of a treatment chair with six degrees of freedom (6DTC) which was developed for patient treatment in an upright posture at fixed horizontal beam lines in particle (proton, carbon ion, or others) radiotherapy facilities. Method and Material: The positional accuracy including translational and axial rotational accuracy of the 6DTC was evaluated by using a Vicon Motion Capture System (VMCS). Stability of the chair rotation isocenter was determined by a CCD camera with an in-house developed software. The tests were carried out to examine two key motion components of the 6DTC: a floor/rail-mount 360°-rotating platform and a 6-degree-of-freedom (6DOF) platform. The measurement results were compared to that of a commercial clinical robot couch. The accuracy of position alignment, simulating the actual clinical protocol, through an Image-guided Radiation Therapy (IGRT) system was studied at the pre-treatment position and beam specific treatment position. Results: The translational accuracy was 0.12 mm (SD 0.07 mm) for the 6DOF platform. The rotational accuracy was 0.04° (SD 0.03°) and 0.02° (SD 0.02°) for the 6DOF platform and the 360° -rotating platform, respectively. The displacement between the chair rotation center and the room isocenter center was no more than 0.18 mm in all three rotational axes. Combined with an x-ray-based IGRT system, the treatment alignment test with a rigid phantom yielded a total positional accuracy of 0.23 mm (SD 0.17 mm) and 0.14° (SD 0.14°) at treatment position. Conclusions: On the basis of the rigid phantom study, the 6DTC showed comparable accuracy to the robot treatment couch. Combining with the IGRT, the 6DTC can provide position alignment with submillimeter accuracy for rigid phantom in upright posture.

Accurate proton treatment planning for pencil beam crossing titanium fixation implants

PURPOSE

To present a planning strategy for proton pencil-beam scanning when titanium implants need to be crossed by the beam.

METHODS

We addressed three issues: the implementation of a CT calibration curve to assign to titanium the correct stopping power; the effect of artefacts on CT images and their reduction by a dedicated algorithm; the differences in dose computation depending on the dose engine, pencil-beam vs Monte-Carlo algorithms. We performed measurement tests on a simple cylinder phantom and on a real implant. These phantoms were irradiated with three geometries (single spots, uniform mono-energetic layer and uniform box), measuring the exit dose either by radio-chromic film or multi-layer ionization chamber. The procedure was then applied on two patients treated for chordoma.

RESULTS

We had to set in the calibration curve a mass density equal to 4.37 g/cm³ to saturated Hounsfield Units, in order to have the correct stopping power assigned to titanium in TPS. CT artefact reduction algorithm allowed a better reconstruction of the shape and size of the implant. Monte-Carlo resulted accurate in computing the dose distribution whereas the pencil-beam algorithm failed due to sharp density interfaces between titanium and the surrounding material. Finally, the treatment plans obtained on two patients showed the impact of the dose engine algorithm, with 10-20% differences between pencil-beam and Monte-Carlo in small regions distally to the titanium screws.

CONCLUSION

The described combination of CT calibration, artefacts reduction and Monte-Carlo computation provides a reliable methodology to compute dose in patients with titanium implants.

Long-term outcomes of high-dose single-fraction radiosurgery for chordomas of the spine and sacrum

OBJECTIVE

The current treatment of chordomas is associated with significant morbidity, high rates of local recurrence, and the potential for metastases. Stereotactic radiosurgery (SRS) as a primary treatment could reduce the need for en bloc resection to achieve wide or marginal margins. Spinal SRS outcomes support the exploration of SRS's role in the durable control of these conventionally radioresistant tumors. The goal of the study was to evaluate outcomes of patients with primary chordomas treated with spinal SRS alone or in combination with surgery.

METHODS

Clinical records were reviewed for outcomes of patients with primary chordomas of the mobile spine and sacrum who underwent single-fraction SRS between 2006 and 2017. Radiographic local recurrence-free survival (LRFS), overall survival (OS), symptom response, and toxicity were assessed in relation to the extent of surgery.

RESULTS

In total, 35 patients with de novo chordomas of the mobile spine (n = 17) and sacrum (n = 18) received SRS and had a median post-SRS follow-up duration of 38.8 months (range 2.0-122.9 months). The median planning target volume dose was a 24-Gy single fraction (range 18-24 Gy). Overall, 12 patients (34%) underwent definitive SRS and 23 patients (66%) underwent surgery and either neoadjuvant or postoperative adjuvant SRS. Definitive SRS was selectively used to treat both sacral (n = 7) and mobile spine (n = 5) chordomas. Surgical strategies for the mobile spine were either intralesional, gross-total resection (n = 5) or separation surgery (n = 7) and for the sacrum en bloc sacrectomy (n = 11). The 3- and 5-year LRFS rates were 86.2% and 80.5%, respectively. Among 32 patients (91%) receiving 24-Gy radiation doses, the 3- and 5-year LRFS rates were 96.3% and 89.9%, respectively. The 3- and 5-year OS rates were 90.0% and 84.3%, respectively. The symptom response rate to treatment was 88% for pain and radiculopathy. The extent or type of surgery was not associated with LRFS, OS, or symptom response rates (p > 0.05), but en bloc resection was associated with higher surgical toxicity, as measured using the Common Terminology Criteria for Adverse Events (version 5.0) classification tool, than epidural decompression and curettage/intralesional resection (p = 0.03). The long-term rate of toxicity ≥ grade 2 was 31%, including 20% grade 3 tissue necrosis, recurrent laryngeal nerve palsy, myelopathy, fracture, and secondary malignancy.

CONCLUSIONS

High-dose spinal SRS offers the chance for durable radiological control and effective symptom relief with acceptable toxicity in patients with primary chordomas as either a definitive or adjuvant therapy.

Proton therapy in the most common pediatric non-central nervous system malignancies: an overview of clinical and dosimetric outcomes

Radiation therapy represents an important approach in the therapeutic management of children and adolescents with malignant tumors and its application with modern techniques – including Proton Beam Therapy (PBT) – is of great interest. In particular, potential radiation-induced injuries and secondary malignancies – also associated to the prolonged life expectancy of patients – are still questions of concern that increase the debate on the usefulness of PBT in pediatric treatments. This paper presents a literary review of current applications of PBT in non-Central Nervous System pediatric tumors (such as retinoblastoma, Hodgkin Lymphoma, Wilms tumor, bone and soft tissues sarcomas). We specifically reported clinical results achieved with PBT and dosimetric comparisons between PBT and the most common photon-therapy techniques. The analysis emphasizes that PBT minimizes radiation doses to healthy growing organs, suggesting for reduced risks of late side-effects and radiation-induced secondary malignancies. Extended follow up and confirms by prospective clinical trials should support the effectiveness and long-term tolerance of PBT in the considered setting.

Stereotactic body radiation therapy and minimally invasive surgery in the management of spinal metastases: a change in the paradigm

The main goal of treatment in spinal metastatic patients is local control of the disease, pain relief and the maintenance of ambulation. Traditionally, wide surgical resection of the tumour followed by adjuvant radiation and/or chemotherapy has been recommended. Currently, single-fraction or hypofractionated stereotactic body radiation therapy (SBRT) yields a one-year local control rate of over 95% with minimum morbidity, even for tumours previously considered radioresistant. In addition, by posterolateral and circumferential decompression and stabilisation of the spinal cord, it is feasible to create a 2 to 3 mm epidural margin between the dura mater and the tumour (separation surgery), enough to deliver safe and ablative doses of SBRT to the vertebrae. As these patients tend to be frail, such interventions should ideally be minimally invasive, thereby reducing surgical aggressiveness and helping to minimise the delay of any systemic therapies.

Advances in the treatment of metastatic spine tumors: the future is not what it used to be

An improved understanding of tumor biology, the ability to target tumor drivers, and the ability to harness the immune system have dramatically improved the expected survival of patients diagnosed with cancer. However, many patients continue to develop spine metastases that require local treatment with radiotherapy and surgery. Fortunately, the evolution of radiation delivery and operative techniques permits durable tumor control with a decreased risk of treatment-related toxicity and a greater emphasis on restoration of quality of life and daily function. Stereotactic body radiotherapy allows delivery of ablative radiation doses to the majority of spine tumors, reducing the need for surgery. Among patients who still require surgery for decompression of the spinal cord or spinal column stabilization, minimal access approaches and targeted tumor excision and ablation techniques minimize the surgical risk and facilitate postoperative recovery. Growing interdisciplinary collaboration among scientists and clinicians will further elucidate the synergistic possibilities among systemic, radiation, and surgical interventions for patients with spinal tumors and will bring many closer to curative therapies.

Clinical outcome of proton therapy for patients with chordomas

Purpose

To investigate the clinical outcome of proton therapy (PT) in patients with chordoma.

Materials and Methods

Fifty-eight patients with chordoma treated with PT between June 2007 and December 2015 at the National Cancer Center, Korea, were retrospectively analyzed. The median total dose was 69.6 cobalt gray equivalent (CGE; range, 64.8 to 79.2 CGE). Local progression-free survival (LPFS), distant metastasis-free survival (DMFS), overall survival (OS), and diseasespecific survival (DSS) rates were calculated by the Kaplan–Meier method.

Results

With the median follow-up of 42.8 months (range, 4 to 174 months), the 5-year LPFS, DMFS, OS, and DSS rates were 87.9%, 86.7%, 88.3%, and 92.9%, respectively. The tumor location was associated with the patterns of failure: the LPFS rates were lower for cervical tumors (57.1%) than for non-cervical tumors (93.1%) (p = 0.02), and the DMFS rates were lower for sacral tumors (53.5%) than for non-sacral tumors (100%) (p = 0.001). The total dose was associated with both the LPFS rate and DMFS rate. The initial tumor size was associated with the DMFS rate, but was not associated with the LPFS rate. Three patients had grade 3 late toxicity with none ≥grade 4.

Conclusion

PT is an effective and safe treatment in patients with chordomas. The tumor location was associated with the patterns of failure: local failure was common in cervical tumors, and distant failure was common in sacral tumors. Further refinement of PT, such as the utilization of intensity modulated PT for cervical tumors, is warranted to improve the outcome.

Survival analysis of patients with spinal chordomas

This study was aimed to analyze the survival of patients with spinal chordomas. Patients' data in the Surveillance, Epidemiology, and End Results (SEER) database were retrieved and analyzed statistically. There were 765 patients with spinal chordomas between 1974 and 2013. The overall survival did not improve significantly over decades for patients receiving surgery and radiotherapy (SR) (P = 0.221). There were significant differences in overall survival among subgroups of patients receiving surgery (S), radiotherapy (R), and neither S nor R (NSR) (P = 0.031, 0.037, and 0.031, respectively). Cancer-specific survival did not change significantly among subgroups of patients receiving R (P = 0.411), while it increased steadily among subgroups of patients receiving S, SR, and NSR (P < 0.001, 0.001, and 0.049, respectively). In the multivariate Cox regression model, younger onset age (hazard ratio [HR] 1.052, P < 0.001), surgery (HR 0.291, P = 0.001), and tumor location of the sacrum (HR 0.401, P = 0.002) were associated with a better overall survival. Similarly, younger onset age (HR 1.036, P = 0.029), surgery (HR 0.221, P = 0.009), and tumor location of the sacrum (HR 0.287, P = 0.002) were also associated with a higher cancer-specific survival. The changes in overall and cancer-specific survival over time differ among different treatment groups. Younger onset age, surgical strategy, and tumor location of the sacrum may be correlated with a higher overall and cancer-specific survival.

Best practices for the management of local-regional recurrent chordoma: a position paper by the Chordoma Global Consensus Group

Chordomas are rare, malignant bone tumors of the skull-base and axial skeleton. Until recently, there was no consensus among experts regarding appropriate clinical management of chordoma, resulting in inconsistent care and suboptimal outcomes for many patients. To address this shortcoming, the European Society of Medical Oncology (ESMO) and the Chordoma Foundation, the global chordoma patient advocacy group, convened a multi-disciplinary group of chordoma specialists to define by consensus evidence-based best practices for the optimal approach to chordoma. In January 2015, the first recommendations of this group were published, covering the management of primary and metastatic chordomas. Additional evidence and further discussion were needed to develop recommendations about the management of local-regional failures. Thus, ESMO and CF convened a second consensus group meeting in November 2015 to address the treatment of locally relapsed chordoma. This meeting involved over 60 specialists from Europe, the United States and Japan with expertise in treatment of patients with chordoma. The consensus achieved during that meeting is the subject of the present publication and complements the recommendations of the first position paper.

Outcomes of Patients With Primary Sacral Chordoma Treated With Definitive Proton Beam Therapy

PURPOSE

To evaluate the efficacy and safety of definitive proton beam therapy (PBT) for primary sacral chordoma.

METHODS AND MATERIALS

We conducted a retrospective analysis of the clinical outcomes of eligible patients with primary sacral chordoma who had undergone definitive PBT with 70.4 Gy (relative biological effectiveness) in 32 fractions at our institution from September 2009 to October 2015. Local progression-free survival, distant metastasis-free survival, disease-free survival, cause-specific survival, and overall survival were evaluated. To explore the factors that influenced local progression, the following parameters were analyzed: sex, the presence of a spacer (Gore-Tex sheets), gross tumor volume, and extent of cranial tumor extension. Adverse events were evaluated using the Common Terminology Criteria for Adverse Events, version 4.0. To assess the impact of PBT on pain relief, the change in pain grades was investigated between the initiation of PBT and the last follow-up visit.

RESULTS

Thirty-three eligible patients were analyzed. The median follow-up period was 37 months. The 3-year estimated local progression-free survival, distant metastasis-free survival, disease-free survival, cause-specific survival, and overall survival rates were 89.6%, 88.2%, 81.9%, 95.7%, and 92.7%, respectively. No significant association was between the patients' clinicopathologic characteristics and local progression-free survival. Four patients developed grade 3 adverse events, including acute dermatitis (n = 1), ileus (n = 1), and pain due to sacral insufficiency fractures (n = 2). The pain grades had improved, were unchanged, or had deteriorated in 15, 7, and 11 patients, respectively.

CONCLUSIONS

Definitive PBT with 70.4 Gy (relative biological effectiveness) in 32 fractions is an effective treatment with acceptable toxicity for primary sacral chordoma and has the potential to reduce pain.

Proton beam therapy for bone sarcomas of the skull base and spine: A retrospective nationwide multicenter study in Japan

We conducted a retrospective, nationwide multicenter study to evaluate the clinical outcomes of proton beam therapy for bone sarcomas of the skull base and spine in Japan. Eligibility criteria included: (i) histologically proven bone sarcomas of the skull base or spine; (ii) no metastases; (iii) ≥20 years of age; and (iv) no prior treatment with radiotherapy. Of the 103 patients treated between January 2004 and January 2012, we retrospectively analyzed data from 96 patients who were followed-up for >6 months or had died within 6 months. Seventy-two patients (75.0%) had chordoma, 20 patients (20.8%) had chondrosarcoma, and four patients (7.2%) had osteosarcoma. The most frequent tumor locations included the skull base in 68 patients (70.8%) and the sacral spine in 13 patients (13.5%). Patients received a median total dose of 70.0 Gy (relative biological effectiveness). The median follow-up was 52.6 (range, 6.3-131.9) months. The 5-year overall survival, progression-free survival, and local control rates were 75.3%, 49.6%, and 71.1%, respectively. Performance status was a significant factor for overall survival and progression-free survival, whilst sex was a significant factor for local control. Acute Grade 3 and late toxicities of ≥Grade 3 were observed in nine patients (9.4%) each (late Grade 4 toxicities [n = 3 patients; 3.1%]). No treatment-related deaths occurred. Proton beam therapy is safe and effective for the treatment of bone sarcomas of the skull base and spine in Japan. However, larger prospective studies with a longer follow-up are warranted.

Surgery Combined with Radiotherapy to Treat Spinal Tumors: A Review of Published Reports

Spinal tumors result in high morbidity and a high rate of lower limb paralysis. Both surgical therapy and radiation therapy (RT) are used to treat spinal tumors; however, how best to combine these two therapies to maximize the benefits and minimize the risks is still being debated. It is also difficult to decide the optimal timing, course and dose of RT, especially in pregnant women and children. The aim of this review is to assist surgeons who are dealing with spinal tumors by providing comprehensive information about advanced techniques for administering RT with greater precision and safety, and about the impact of various ways of combining surgery and RT on therapeutic outcomes. We here review published reports about treating spinal tumors with a combination of these two forms of therapy and attempt to draw appropriate conclusions concerning selection of optimal treatment protocols. Our conclusion is that postoperative radiotherapy, especially with high-precision, low-dose and multiple fractions, and brachytherapy are promising therapies to combined with surgery.

Helical tomotherapy of spinal chordomas: French Multicentric, retrospective study of a cohort of 30 cases

PURPOSE

To evaluate the efficacy and toxicity of helical tomotherapy (HT) in the management of spine chordomas when proton therapy is unavailable or non-feasible.

METHODS AND MATERIALS

Between 2007 and 2013, 30 patients with biopsy-proven chordomas were treated by HT in five French institutions. Information regarding local control (LC), overall survival (OS), progression-free survival (PFS) and metastasis-free survival (MFS) was collected. Clinical efficacy, toxicity and treatment quality were evaluated.

RESULTS

Two-year actuarial LC, OS, PFS and MFS were 69.9%, 96.7%, 61.2% and 76.4%, respectively. HT treatments were well tolerated and no Grade 4-5 toxicities were observed. HT permitted the delivery of a mean dose of 68 Gy while respecting organ at risk (OAR) dose constraints, in particular in the spinal cord and cauda equina.

CONCLUSIONS

This multicentric, retrospective study demonstrated the feasibility of HT in the treatment of spine chordomas, in the absence of hadron therapy.

Safety and Local Control of Radiation Therapy for Chordoma of the Spine and Sacrum: A Systematic Review

STUDY DESIGN

Systematic literature review.

OBJECTIVE

To assess the toxicity, common radiation doses, and local control (LC) rates of radiation therapy for chordoma of the spine and sacrum and identify the difference in LC and toxicity between adjuvant, salvage, and primary therapy using radiation.

SUMMARY OF BACKGROUND DATA

Chordoma of the spine is typically a low-grade malignant tumor thought to be relatively radioresistant with a high rate of local recurrence and the potential for metastases. Improved results of modern radiation therapy in the treatment of chordoma support exploration of its role in the management of primary/de novo chordoma or recurrent chordoma.

METHODS

We conducted a systematic literature review using PubMed and Embase databases to assess information available regarding the toxicity, LC rates, and overall survival (OS) rates for adjuvant, salvage, and primary radiation therapy for spinal and sacral chordoma.

RESULTS

A total of 40 articles were reviewed. Evidence quality was low or very low. The highest rates of LC and OS were with early adjuvant RT for primary/de novo disease. Salvage RT for recurrent disease has very small cohorts and thus strong conclusions were not able be made.

CONCLUSION

The use of pre- and/or post-operative photon image-guided radiotherapy (IGRT), proton or carbon ion therapy should be considered for patients undergoing surgery for the treatment of primary and recurrent chordomas in the mobile spine and sacrum, since these RT modalities may improve local control. Preoperative evaluation by the surgeon and radiation oncologist should be used to formulate a cohesive treatment plan.The use of photon IGRT or carbon ion therapy as the primary treatment of chordoma, when currently in its developmental stage, shows promise and requires clear delineation of toxicity profile and long-term local control.

LEVEL OF EVIDENCE

2.

A Prospective Outcomes Study of Proton Therapy for Chordomas and Chondrosarcomas of the Spine

PURPOSE

To evaluate the effectiveness of definitive or adjuvant external beam proton therapy on survival in patients with chordomas and chondrosarcomas of the spine.

METHODS AND MATERIALS

Between March 2007 and May 2013, 51 patients with a median age of 58 years (range, 22-83 years) with chordoma (n=34) or chondrosarcomas (n=17) of the sacrum (n=21), the cervical spine (n=20), and the thoracolumbar spine (n=10) were treated with external beam proton therapy to a median dose of 70.2 Gy(RBE) [range, 64.2-75.6 Gy(RBE)] at our institution. Distant metastases, overall survival, cause-specific survival, local control, and disease-free survival were calculated.

RESULTS

The mean follow-up time was 3.7 years (range, 0.3-7.7 years). Across all time points, 25 patients experienced disease recurrence: 18 local recurrences, 6 local and distant recurrences, and 1 distant metastasis. The 4-year rates of overall survival and cause-specific survival were 72%; disease-free survival was 57%, local control was 58%, and freedom from distant metastases was 86%. The median time to local progression was 1.7 years (range, 0.2-6.0 years), and the median time to distant progression was 1.6 years (range, 0.2-6.0 years). The risk factors for local recurrence were age ≤58 years (62% vs 26%; P=.04) and recurrence after prior surgery (29% vs 81%; P=.01). Secondary cancers developed in 2 patients: B-cell lymphoma 5.5 years after treatment and bladder cancer 2 years after treatment. We observed the following toxicities: sacral soft tissue necrosis requiring surgery (n=2), T1 vertebral fracture requiring fusion surgery (n=1), chronic urinary tract infections (n=1), surgery for necrotic bone cyst (n=1), and grade 2 bilateral radiation nephritis (n=1).

CONCLUSION

High-dose proton therapy controls more than half of spinal chordomas and chondrosarcomas and compares favorably with historic photon data. Local progression is the dominant mode of treatment failure and may be reduced by treating patients at the time of initial diagnosis. The impact of age is a novel finding of this study.

Primary osseous tumors of the pediatric spinal column: review of pathology and surgical decision making

Spinal column tumors are rare in children and young adults, accounting for only 1% of all spine and spinal cord tumors combined. They often present diagnostic and therapeutic challenges. In this article, the authors review the current management of primary osseous tumors of the pediatric spinal column and highlight diagnosis, management, and surgical decision making.

Single-Fraction Spine Stereotactic Body Radiation Therapy for the Treatment of Chordoma

PURPOSE

Chordoma is a radioresistant tumor that presents a therapeutic challenge with spine involvement, as high doses of radiation are needed for local control while limiting dose to the spinal cord. The purpose of this study is to determine the efficacy and safety of single-fraction spine stereotactic body radiation therapy for the treatment of spine chordoma.

METHODS

A retrospective review of our institutional database from 2006 to 2013 identified 8 patients (12 cases) with chordoma of the spine who were treated with spine stereotactic body radiation therapy. Surgical resection was performed in 7 of the 12 cases. The treatment volume was defined by the bony vertebral level of the tumor along with soft tissue extension appreciated on magnetic resonance imaging fusion. Medical records and imaging were assessed for pain relief and local control. Treatment toxicity was evaluated using Common Terminology Criteria for Adverse Events version 4.0.

RESULTS

Median age was 59 years (range, 17-91). Median target volume was 48 cm³ (1-304), and median prescription dose was 16 Gy (11-16). Median conformality index was 1.44 (1.14-3.21), and homogeneity index was 1.12 (1.05-1.19). With a median follow-up time of 9.7 months (.5-84), local control was achieved in 75% of the cases treated. One patient developed limited grade 2 spinal cord myelopathy that resolved with steroids. There were no other treatment toxicities from spine stereotactic body radiation therapy.

CONCLUSION

Single-fraction spine stereotactic body radiation therapy can be safely delivered to treat chordoma of the spine with the potential to improve pain symptoms. Although the early data are suggestive, long-term follow-up with more patients is necessary to determine the efficacy of spine stereotactic body radiation therapy in the treatment of chordoma of the spine.

UK guidelines for the management of bone sarcomas

This document is an update of the British Sarcoma Group guidelines published in 2010. The aim is to provide a reference standard for the clinical care of patients in the UK with bone sarcomas. Recent recommendations by the European Society of Medical Oncology, The National Comprehensive Cancer Network and The National Institute for Health and Care Excellence have been incorporated, and the literature since 2010 reviewed. The standards represent a consensus amongst British Sarcoma Group members in 2015. It is acknowledged that these guidelines will need further updates as care evolves. The key recommendations are that bone pain or a palpable mass should always lead to further investigation and that patients with clinico-radiological findings suggestive of a primary bone tumour at any site in the skeleton should be referred to a specialist centre and managed by a fully accredited bone sarcoma multidisciplinary team. Treatment recommendations are provided for the major tumour types and for localised, metastatic and recurrent disease. Follow up schedules are suggested.

Carbon Ion Radiation Therapy for Unresectable Sacral Chordoma: An Analysis of 188 Cases

PURPOSE

To evaluate the results of carbon ion radiation therapy administered to 188 patients with unresectable primary sacral chordomas.

PATIENTS AND METHODS

One hundred eighty-eight patients were treated with carbon ion radiation therapy at a single institute between 1996 and 2013 and retrospectively analyzed. The median age was 66 years. The highest proximal invasion reached past S2 level in 137 patients. The median clinical target volume was 345 cm(3). One hundred six patients received 67.2 gray equivalents (GyE)/16 fractions (fr), 74 patients received 70.4 GyE/16 fr, 7 patients received 73.6 GyE/16 fr, and 1 patient received 64.0 GyE/16 fr.

RESULTS

The median follow-up period was 62 months (range, 6.8-147.5 months). Seventy percent of patients were followed for 5 years or until death. The 5-year local control, overall survival, and disease-free survival rates were 77.2%, 81.1%, and 50.3%, respectively. Forty-one patients had a local recurrence. Sex, tumor volume, level of proximal invasion, and irradiated dose were unrelated to local control. There was grade 3 toxicity of the peripheral nerves in 6 patients and grade 4 toxicity of the skin in 2 patients. Ambulation remained in 97% of patients.

CONCLUSIONS

Carbon ion radiation therapy was safe and effective for unresectable chordoma and provided good local control and survival while preserving ambulation.

Dose perturbation effect of metallic spinal implants in proton beam therapy

The purpose of this study was to investigate the effect of dose perturbations for two metallic spinal screw implants in proton beam therapy in the perpendicular and parallel beam geometry. A 5.5 mm (diameter) by 45 mm (length) stainless steel (SS) screw and a 5.5 mm by 35 mm titanium (Ti) screw commonly used for spinal fixation were CT‐scanned in a hybrid phantom of water and solid water. The CT data were processed with an orthopedic metal artifact reduction (O‐MAR) algorithm. Treatment plans were generated for each metal screw with a proton beam oriented, first parallel and then perpendicular, to the longitudinal axis of the screw. The calculated dose profiles were compared with measured results from a plane‐parallel ion chamber and Gafchromic EBT2 films. For the perpendicular setup, the measured dose immediately downstream from the screw exhibited dose enhancement up to 12% for SS and 8% for Ti, respectively, but such dose perturbation was not observed outside the lateral edges of the screws. The TPS showed 5% and 2% dose reductions immediately at the interface for the SS and Ti screws, respectively, and up to 9% dose enhancements within 1 cm outside of the lateral edges of the screws. The measured dose enhancement was only observed within 5 mm from the interface along the beam path. At deeper depths, the lateral dose profiles appeared to be similar between the measurement and TPS, with dose reduction in the screw shadow region and dose enhancement within 1–2 cm outside of the lateral edges of the metals. For the parallel setup, no significant dose perturbation was detected at lateral distance beyond 3 mm away from both screws. Significant dose discrepancies exist between TPS calculations and ion chamber and film measurements in close proximity of high‐Z inhomogeneities. The observed dose enhancement effect with proton therapy is not correctly modeled by TPS. An extra measure of caution should be taken when evaluating dosimetry with spinal metallic implants.

PACS number: 87.50.sj

Building a global consensus approach to chordoma: a position paper from the medical and patient community

Chordomas are very rare bone malignant tumours that have had a shortage of effective treatments for a long time. New treatments are now available for both the local and the metastatic phase of the disease, but the degree of uncertainty in selecting the most appropriate treatment remains high and their adoption remains inconsistent across the world, resulting in suboptimum outcomes for many patients. In December, 2013, the European Society for Medical Oncology (ESMO) convened a consensus meeting to update its clinical practice guidelines on sarcomas. ESMO also hosted a parallel consensus meeting on chordoma that included more than 40 chordoma experts from several disciplines and from both sides of the Atlantic, with the contribution and sponsorship of the Chordoma Foundation, a global patient advocacy group. The consensus reached at that meeting is shown in this position paper.

Update on management of vertebral column tumors

Treatment options for metastatic and primary spinal tumors have expanded in recent years, in part due to the advances made in stereotactic radiosurgery. For metastatic spinal tumors, our institution utilizes the neurologic, oncologic, mechanical, and systemic (NOMS) decision framework, which provides a treatment paradigm based on the neurologic, oncologic, mechanical and systemic status of the patient. Radiosurgery as a supplement to surgical decompression has allowed for less-invasive surgical procedures carrying minimal morbidity while still providing effective local tumor control. Although wide en bloc excision has traditionally been the goal for the treatment of high-grade primary spine tumors, recent studies have shown promise for radiosurgery in providing control in tumors such as chordomas and high-grade sarcomas. Despite advances in radiosurgery, there continues to be limitations in providing effective conformational doses with minimal toxicity to critical structures. One of the ways to circumvent this and supplement external beam radiation is through the use of brachytherapy delivered by radioactive plaque or seeds.

Carbon ion beam treatment in patients with primary and recurrent sacrococcygeal chordoma

PURPOSE

The purpose of this work was to evaluate the results of high-dose radiation treatment using carbon ion therapy, alone or combined with intensity-modulated radiation treatment (IMRT), in patients with sacral chordoma.

MATERIALS AND METHODS

Between 2009 and 2012, 56 patients with sacral chordoma were treated in our center. The tumor was located above S3 in 33 patients and in S3 or below in 23 patients. In all, 41 patients received radiation therapy for the primary tumor, while 15 patients were treated for the recurrent tumor. Toxicity was measured using NCI CTCAE v.4.03. Local control (LC) and overall survival (OS) were evaluated with the Kaplan-Meier method.

RESULTS

A total of 23 patients were irradiated with carbon ions in combination with photon IMRT, while 33 received carbon ion therapy only. Forty-three patients had a macroscopic tumor at treatment start with a median tumor size (GTV) of 244 ml (range 5-1188 ml). The median total dose was 66 Gy (range 60-74 Gy; RBE). After a median follow-up time of 25 months, the 2- and 3-year local control probability was 76 % and 53 %, respectively. The overall survival rate was 100 %. Treatment for primary tumor and male patients resulted in significant better local control. No higher toxicity occurred within the follow-up time.

CONCLUSION

High-dose photon/carbon ion beam radiation therapy is safe and, especially for primary sacral chordomas, highly effective. A randomized trial is required to evaluate the role of primary definitive hypofractionated particle therapy compared with surgery with or without adjuvant radiotherapy.

Factors Predicting Recurrence After Resection of Clival Chordoma Using Variable Surgical Approaches and Radiation Modalities

BACKGROUND:

Clival chordomas frequently recur because of their location and invasiveness.

OBJECTIVE:

To investigate clinical, operative, and anatomic factors associated with clival chordoma recurrence.

METHODS:

Retrospective review of clival chordomas treated at our center from 1993 to 2013.

RESULTS:

Fifty patients (56% male) with median age of 59 years (range, 8–76) were newly diagnosed with clival chordoma of mean diameter 3.3 cm (range, 1.5-6.7). Symptoms included headaches (38%), diplopia (36%), and dysphagia (14%). Procedures included transsphenoidal (n = 34), transoral (n = 4), craniotomy (n = 5), and staged approaches (n = 7). Gross total resection (GTR) rate was 52%, with 83% mean volumetric reduction, values that improved over time. While the lower third of the clivus was the least likely superoinferior zone to contain tumor (upper third = 72%/middle third = 82%/lower third = 42%), it most frequently contained residual tumor (upper third = 33%/middle third = 38%/lower third = 63%; P &lt; .05). Symptom improvement rates were 61% (diplopia) and 53% (headache). Postoperative radiation included proton beam (n = 19), cyberknife (n = 7), intensity-modulated radiation therapy (n = 6), external beam (n = 10), and none (n = 4). At last follow-up of 47 patients, 23 (49%) remain disease-free or have stable residual tumor. Lower third of clivus progressed most after GTR (upper/mid/lower third = 32%/41%/75%). In a multivariate Cox proportional hazards model, male gender (hazard ratio [HR] = 1.2/P = .03), subtotal resection (HR = 5.0/P = .02), and the preoperative presence of tumor in the middle third (HR = 1.2/P = .02) and lower third (HR = 1.8/P = .02) of the clivus increased further growth or regrowth, while radiation modality did not.

CONCLUSION:

Our findings underscore long-standing support for GTR as reducing chordoma recurrence. The lower third of the clivus frequently harbored residual or recurrent tumor, despite staged approaches providing mediolateral (transcranial + endonasal) or superoinferior (endonasal + transoral) breadth. There was no benefit of proton-based over photon-based radiation, contradicting conventional presumptions.