Radiation therapy for chordomas of the base of skull and cervical spine: patterns of failure and outcome after relapse

Evolving Role of Proton Radiation Therapy in Clinical Practice

With the expansion of proton radiation therapy centers across the United States and a gradually expanding body of academic evidence supporting its use, more patients are receiving-and asking about-proton therapy than ever before. Here, we outline, for nonradiation oncologists, the theoretical benefits of proton therapy, the clinical evidence to date, the controversies affecting utilization, and the numerous randomized trials currently in progress. We also discuss the challenges of researching and delivering proton therapy, including the cost of constructing and maintaining centers, barriers with insurance approval, clinical situations in which proton therapy may be approached with caution, and the issue of equitable access for all patients. The purpose of this review is to assist practicing oncologists in understanding the evolving role of proton therapy and to help nonradiation oncologists guide patients regarding this technology.

A Prospective Phase I/II Clinical Trial of High-Dose Proton Therapy for Chordomas and Chondrosarcomas

Purpose

The purpose of this study was to evaluate the feasibility and safety of dose-escalated proton beam therapy for treating chordomas and chondrosarcomas of the skull base and spine. Methods: A prospective cohort of 54 patients (42 with chordomas and 12 with chondrosarcomas) was enrolled between 2010 and 2018. The primary endpoints were feasibility and <20% rate of acute grade ≥3 toxicity, and secondary endpoints included cancer-specific outcomes and toxicities. Patients were followed with magnetic resonance imaging or computed tomography at 3-month intervals. Proton beam therapy was delivered with doses up to 79.2 Gy using protons only, combination protons/intensity modulated radiation therapy (IMRT), or IMRT only.

Results

Feasibility endpoints were met, with only 2 out of 54 patient radiation therapy plans failing to meet dosimetric constraints with protons, and 4 out of 54 experiencing a delay or treatment break >5 days, none for toxicities related to treatment. There were no grade 4 acute toxicities and 1 grade 3 acute toxicity (sensory neuropathy). The only 2 grade 3 late toxicities recorded, osteoradionecrosis and intranasal carotid blowout (mild and not emergently treated), occurred in a single patient. We report overall survival as 83% at 5 years, with local failure-free survival and progression-free survival rates of 72% and 68%, respectively. Five patients developed distant disease, and among the 9/54 patients who died, 4 deaths were not attributed to treatment or recurrence.

Conclusions

Our findings suggest that high-dose proton therapy alone or in combination with IMRT is a safe and effective treatment option for chordomas and chondrosarcomas of the skull base and spine.

Proton beam therapy for clival chordoma: Optimising rare cancer treatments in Australia

With the anticipated launch of the Australian Bragg Centre for Proton Therapy and Research (ABCPTR) in Adelaide, Australia, proton therapy will become a significant addition to existing cancer treatment options for Australians. The anticipated benefits will be particularly evident in rare cancers such as clival chordomas, a challenging tumour entity due to the anatomical relationship with critical structures, and proven radio-resistance to conventional radiation therapy. The article synthesises key findings from major studies and evaluates the current evidence supporting various management strategies for clival chordomas. It also considers the influence of institutional volume and multidisciplinary team management on patient outcomes and outlines how high-quality care can be effectively delivered within the Australian healthcare system, emphasising the potential impact of proton therapy on the treatment paradigm of clival chordomas in Australia.

Mitigating Radiotoxicity in the Central Nervous System: Role of Proton Therapy

OPINION STATEMENT

Central nervous system (CNS) radiotoxicity remains a challenge in neuro-oncology. Dose distribution advantages of protons over photons have prompted increased use of brain-directed proton therapy. While well-recognized among pediatric populations, the benefit of proton therapy among adults with CNS malignancies remains controversial. We herein discuss the role of protons in mitigating late CNS radiotoxicities in adult patients. Despite limited clinical trials, evidence suggests toxicity profile advantages of protons over conventional radiotherapy, including retention of neurocognitive function and brain volume. Modelling studies predict superior dose conformality of protons versus state-of-the-art photon techniques reduces late radiogenic vasculopathies, endocrinopathies, and malignancies. Conversely, potentially higher brain tissue necrosis rates following proton therapy highlight a need to resolve uncertainties surrounding the impact of variable biological effectiveness of protons on dose distribution. Clinical trials comparing best photon and particle-based therapy are underway to establish whether protons substantially improve long-term treatment-related outcomes in adults with CNS malignancies.

Multifocal Ectopic Recurrence of a C2 Chordoma

Background  Chordomas are histologically benign but locally aggressive tumors with a high propensity to recur. Our case highlights the importance of long-term vigilance in patients who have undergone chordoma resection. Case Report  We report the case of a 47-year-old man with a cervical chordoma who developed multiple musculoskeletal ectopic recurrences in the left supraclavicular region, the proximal right bicep, and the left submandibular region without recurrence in the primary tumor site. Primary tumor resection was achieved via a combination of surgery, adjuvant radiation therapy, and imatinib. All recurrences were successfully resected and confirmed via pathology to be ectopic chordoma. Discussion  Ectopic recurrence of cervical chordoma is rare and lung is the most common site of distant spread. Chordoma recurrence in skeletal muscle is particularly rare, with only 10 cases described in the literature. A plausible mechanism of distant metastatic disease in chordoma patients suggests that tumor cells escape the surgical tract via a combination of cytokine release, vasodilation, and microtrauma induced during resection. Conclusion  Cervical chordoma with ectopic recurrence in skeletal muscle has not been previously described in the literature. Skull base surgeons should be aware of the phenomenon of chordoma ectopic recurrence in the absence of local recurrence.

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.

The prognostic significance of different degrees of resection of skull base chordoma

BACKGROUND

Complete resection combined with postoperative radiotherapy is ideal for skull base chordomas. The recent literature suggests that the degree of surgical resection is the most important prognostic factor.

METHODS

We retrospectively analyzed the clinical data of 16 patients with initial chordoma treated at our center between August 2015 and December 2021 and conducted a retrospective study on the prognosis of surgical treatment of skull base chordoma between 2013 and 2022.

RESULTS

According to the Kaplan-Meier method, there was a significant difference in PFS between patients aged > 50 years and < 50 years, and no significant difference was observed in PFS for tumor involvement of the internal carotid artery, dura, or superior or inferior clivus. However, there was still a correlation with prognosis. As observed in the included literature, the 5-year overall survival rate was significantly higher in patients undergoing total skull base chordoma resection than in those undergoing subtotal resection (STR), which in turn was significantly higher than in those undergoing partial resection (PR). Patients undergoing subtotal resection had significantly better 5-year PFS rates than those undergoing PR.

CONCLUSION

Our study shows that gross total resection and STR have better survival in patients with skull base chordomas compared to PR.

Long-term outcomes of high dose carbon-ion radiation therapy for unresectable upper cervical (C1-2) chordoma

Background

Chordoma is a rare, locally invasive neoplasm of the axial skeleton. Complete resection is often difficult, especially for the upper‐cervical (C1‐2) spine. We evaluated the efficacy and safety of carbon‐ion radiotherapy (CIRT) for unresectable C1‐2 chordoma.

Methods

Patients with C1‐2 chordoma treated with definitive CIRT (60.8 Gy [RBE] in 16 fractions) were retrospectively analyzed. We evaluated OS, LC, PFS, and toxicity.

Results

Nineteen eligible patients all completed the planned course of CIRT. With the median follow‐up 68 months (range: 29–144), median OS was 126 months (range: 36‐NA). Five‐year OS, LC, and PFS were 68.4% (95% CI, 42.8%–84.4%), 75.2% (46.1%–90.0%), and 64.1% (36.3%–82.3%), respectively. Regarding acute toxicity of grade ≥3, there was only one grade 3 mucositis. Late toxicity included radiation‐induced myelitis (grade 3 in 1 patient; 5.3%), and compression fractures (n = 5; 26.3%).

Conclusions

High‐dose CIRT is a promising treatment option for unresectable upper cervical chordoma.

Ectopic Recurrence of Skull Base Chordoma after Proton Therapy

Simple Summary

Chordoma are very rare tumors of the spine and skull base. Due to close proximity of crucial organs, like the brain stem, complete removal can often not be achieved, and tumor tissue, either macroscopic or microscopic, remains in situ. Local recurrence up to 88% occurs in 10 years. Ectopic recurrence as an early sign of treatment failure is considered rare. We retrospectively reviewed five patients with ectopic recurrence as a first sign of treatment failure after treatment with surgery and proton therapy, and studied the applied treatment strategies and imaging follow-up. We found 18 ectopic recurrences in these five patients, of which 17 (94%) could be related to prior surgical tracts. Our theory is that these relapses occur due to microscopic tumor spill during surgery. These cells did not receive a therapeutic radiation dose. Advances in surgical possibilities and adjusted radiotherapy target volumes might improve local control and survival.

Abstract

Background: Chordoma are rare tumors of the axial skeleton. The treatment gold standard is surgery, followed by particle radiotherapy. Total resection is usually not achievable in skull base chordoma (SBC) and high recurrence rates are reported. Ectopic recurrence as a first sign of treatment failure is considered rare. Favorable sites of these ectopic recurrences remain unknown. Methods: Five out of 16 SBC patients treated with proton therapy and surgical resection developed ectopic recurrence as a first sign of treatment failure were critically analyzed regarding prior surgery, radiotherapy, and recurrences at follow-up imaging. Results: Eighteen recurrences were defined in five patients. A total of 31 surgeries were performed for primary tumors and recurrences. Seventeen out of eighteen (94%) ectopic recurrences could be related to prior surgical tracts, outside the therapeutic radiation dose. Follow-up imaging showed that tumor recurrence was difficult to distinguish from radiation necrosis and anatomical changes due to surgery. Conclusions: In our cohort, we found uncommon ectopic recurrences in the surgical tract. Our theory is that these recurrences are due to microscopic tumor spill during surgery. These cells did not receive a therapeutic radiation dose. Advances in surgical possibilities and adjusted radiotherapy target volumes might improve local control and survival.

Linear Energy Transfer Incorporated Spot-Scanning Proton Arc Therapy Optimization: A Feasibility Study

Purpose

To integrate dose-averaged linear energy transfer (LET_d) into spot-scanning proton arc therapy (SPArc) optimization and to explore its feasibility and potential clinical benefits.

Methods

An open-source proton planning platform (OpenREGGUI) has been modified to incorporate LET_d into optimization for both SPArc and multi-beam intensity-modulated proton therapy (IMPT) treatment planning. SPArc and multi-beam IMPT plans with different beam configurations for a prostate patient were generated to investigate the feasibility of LET_d-based optimization using SPArc in terms of spatial LET_d distribution and plan delivery efficiency. One liver and one brain case were studied to further evaluate the advantages of SPArc over multi-beam IMPT.

Results

With similar dose distributions, the efficacy of spatially optimizing LET_d distributions improves with increasing number of beams. Compared with multi-beam IMPT plans, SPArc plans show substantial improvement in LET_d distributions while maintaining similar delivery efficiency. Specifically, for the liver case, the average LET_d in the GTV was increased by 124% for the SPArc plan, and only 9.6% for the 2-beam IMPT plan compared with the 2-beam non-LET_d optimized IMPT plan. In case of LET optimization for the brain case, the SPArc plan could effectively increase the average LET_d in the CTV and decrease the values in the critical structures while smaller improvement was observed in 3-beam IMPT plans.

Conclusion

This work demonstrates the feasibility and significant advantages of using SPArc for LET_d-based optimization, which could maximize the LET_d distribution wherever is desired inside the target and averts the high LET_d away from the adjacent critical organs-at-risk.

A Review of Particle Therapy for Skull Base Tumors: Modern Considerations and Future Directions

Skull base tumors constitute one of the established indications for particle therapy, specifically proton therapy. However, a number of prognostic factors, practical clinical management issues, and the emerging role of carbon ion therapy remain subjects of active clinical investigation. This review summarizes these topics, assesses the present status, and reflects on future research directions focusing on the management of chordomas, one of the most aggressive skull base tumors. In addition, the role of particle therapy for benign tumors of the skull base, including pituitary adenoma and acoustic neuroma, is reviewed.

Brain Necrosis in Adult Patients After Proton Therapy: Is There Evidence for Dependency on Linear Energy Transfer?

PURPOSE

To investigate if radiographic imaging changes defined as necrosis correlate with regions in the brain with elevated linear energy transfer (LET) for proton radiation therapy treatments with partial brain involvement in central nervous system and patients with head and neck cancer.

METHODS AND MATERIALS

Fifty patients with head and neck, skull base, or intracranial tumors who underwent proton therapy between 2004 to 2016 with a minimum prescription dose of 59.4 Gy (relative biological effectiveness) and with magnetic resonance imaging changes indicative of brain necrosis after radiation therapy were retrospectively reviewed. Each treatment plan was recalculated using Monte Carlo simulations to provide accurate dose distributions as well as 3-dimensional distributions of LET. To assess the effect of LET on radiographic imaging changes several voxel-based analyses were performed.

RESULTS

In this patient cohort, LET adjusted for dose was not found to be associated with risk of brain necrosis.

CONCLUSIONS

A voxel-based analysis of brain necrosis as an endpoint is difficult owing to uncertainties in the origin of necrosis, timing of imaging, variability in patient specific radiosensitivity, and the simultaneous effect of dose and LET. Even though it is expected that the LET and thus relative biological effectiveness increases at the end of range, effects in patients might be small compared with interpatient variability of radiosensitivity and might be obscured by other confounding factors.

Role of Proton Beam Therapy in Current Day Radiation Oncology Practice

Proton beam therapy (PBT), because of its unique physics of no–exit dose deposition in the tissue, is an exciting prospect. The phenomenon of Bragg peak allows protons to deposit their almost entire energy towards the end of the path of the proton and stops any further dose delivery. Braggs peak equips PBT with superior dosimetric advantage over photons or electrons because PBT doesn’t traverse the target/body but is stopped sharply at an energy dependent depth in the target/body. It also has no exit dose. Because of no exit dose and normal tissue sparing, PBT is hailed for its potential to bring superior outcomes. Pediatric malignancies is the most common malignancy where PBT have found utmost application. Nowadays, PBT is also being used in the treatment of other malignancies such as carcinoma prostate, carcinoma breast, head and neck malignancies, and gastrointestinal (GI) malignancies. Despite advantages of PBT, there is not only a high cost of setting up of PBT centers but also a lack of definitive phase-III data. Therefore, we review the role of PBT in current day practice of oncology to bring out the nuances that must guide the practice to choose suitable patients for PBT.

Outcomes, Prognostic Factors and Salvage Treatment for Recurrent Chordoma After Pencil Beam Scanning Proton Therapy at the Paul Scherrer Institute

AIMS

The outcome of chordoma patients with local or distant failure after proton therapy is not well established. We assessed the disease-specific (DSS) and overall survival of patients recurring after proton therapy and evaluated the prognostic factors affecting DSS.

MATERIALS AND METHODS

A retrospective analysis was carried out of 71 recurring skull base (n = 36) and extracranial (n = 35) chordoma patients who received adjuvant proton therapy at initial presentation (n = 42; 59%) or after post-surgical recurrence (n = 29; 41%). The median proton therapy dose delivered was 74 GyRBE (range 62-76). The mean age was 55 ± 14.2 years and the male/female ratio was about one.

RESULTS

The median time to first failure after proton therapy was 30.8 months (range 3-152). Most patients (n = 59; 83%) presented with locoregional failure only. There were only 12 (17%) distant failures, either with (n = 5) or without (n = 7) synchronous local failure. Eight patients (11%) received no salvage therapy for their treatment failure after proton therapy. Salvage treatments after proton therapy failure included surgery, systemic therapy and additional radiotherapy in 45 (63%), 20 (28%) and eight (11%) patients, respectively. Fifty-three patients (75%) died, most often from disease progression (47 of 53 patients; 89%). The median DSS and overall survival after failure was 3.9 (95% confidence interval 3.1-5.1) and 3.4 (95% confidence interval 2.5-4.4) years, respectively. On multivariate analysis, extracranial location and late failure (≥31 months after proton therapy) were independent favourable prognostic factors for DSS.

CONCLUSION

The survival of chordoma patients after a treatment failure following proton therapy is poor, particularly for patients who relapse early or recur in the skull base. Although salvage treatment is administered to most patients with uncontrolled disease, they will ultimately die as a result of disease progression in most cases.

Endoscopic Resection of Clival Chordoma: A Tertiary Care Experience

The primary management of the rare tumor chordoma is always surgical. This study indicates the advantage of endoscopic approach for clival chordoma resection. This is a Retrospective case series of 7 endoscopically operated clival chordoma patients between May 2015 and April 2018 in our tertiary care hospital. 5 patients presented with primary disease and 2 were recurrent disease cases. Endoscopic endonasal transphenoidal approach with wide clearance of margins of tumor were performed in all 7 cases. High energy photon radiotherapy were delivered to all. All patients with primary disease as well as recurrent disease had no evidence of disease 24-32 months post surgery. Endoscopic endonasal transphenoidal approach for clival chordoma provides a safe and reliable tumor resection. This less invasive surgery can be considered as an alternative to traditional surgical technique with reduced morbidity. This approach represents a combination of various endoscopic surgical techniques which are minimally invasive and can be applied to ventral skull base surgery.

Patient selection for proton therapy: a radiobiological fuzzy Markov model incorporating robust plan analysis

While proton therapy can offer increased sparing of healthy tissue compared with X-ray therapy, it can be difficult to predict whether a benefit can be expected for an individual patient. Predictive modelling may aid in this respect. However, the predictions of these models can be affected by uncertainties in radiobiological model parameters and in planned dose. The aim of this work is to present a Markov model that incorporates these uncertainties to compare clinical outcomes for individualised proton and X-ray therapy treatments. A time-inhomogeneous fuzzy Markov model was developed which estimates the response of a patient to a given treatment plan in terms of quality adjusted life years. These are calculated using the dose-dependent probabilities of tumour control and toxicities as transition probabilities in the model. Dose-volume data representing multiple isotropic patient set-up uncertainties and range uncertainties (for proton therapy) are included to model dose delivery uncertainties. The model was retrospectively applied to an example patient as a demonstration. When uncertainty in the radiobiological model parameter was considered, the model predicted that proton therapy would result in an improved clinical outcome compared with X-ray therapy. However, when dose delivery uncertainty was included, there was no difference between the two treatments. By incorporating uncertainties in the predictive modelling calculations, the fuzzy Markov concept was found to be well suited to providing a more holistic comparison of individualised treatment outcomes for proton and X-ray therapy. This may prove to be useful in model-based patient selection strategies.

Use of Salvage Surgery or Stereotactic Radiosurgery for Multiply Recurrent Skull Base Chordomas: A Single-Institution Experience and Review of the Literature

Introduction  Chordomas are locally destructive neoplasms characterized by appreciable recurrence rates after initial multimodality treatment. We examined the outcome of salvage treatment in recurrent/progressive skull base chordomas. Methods  This is a retrospective review of recurrent/progressive skull base chordomas at a tertiary urban academic medical center. The outcomes evaluated were overall survival, progression-free survival (PFS), and incidence of new toxicity. Results  Eighteen consecutive patients who underwent ≥1 course of treatment (35.3% salvage surgery, 23.5% salvage radiation, and 41.2% both) were included. The median follow-up was 98.6 months (range 16-215 months). After initial treatment, the median PFS was 17.7 months (95% confidence interval [CI]: 4.9-22.6 months). Following initial therapy, age ≥ 40 had improved PFS on univariate analysis ( p  = 0.03). All patients had local recurrence, with 15 undergoing salvage surgical resections and 16 undergoing salvage radiation treatments (mostly stereotactic radiosurgery [SRS]). The median PFS was 59.2 months (95% CI: 4.0-99.3 months) after salvage surgery, 58.4 months (95% CI: 25.9-195 months) after salvage radiation, and 58.4 months (95% CI: 25.9.0-98.4 months) combined. Overall survival for the total cohort was 98.7% ± 1.7% at 2 years and 92.8% ± 5.5% at 5 years. Salvage treatments were well-tolerated with two patients (11%) reporting tinnitus and one patient each (6%) reporting headaches, visual field deficits, hearing loss, anosmia, dysphagia, or memory loss. Conclusion  Refractory skull base chordomas present a challenging treatment dilemma. Repeat surgical resection or SRS seems to provide adequate salvage therapy that is well-tolerated when treated at a tertiary center offering multimodality care.

C3-C5 Chordoma Resection and Reconstruction with a Three-Dimensional Printed Titanium Patient-Specific Implant

BACKGROUND

With this case report, we aim to add to the clinical literature on the use of three-dimensional printed patient-specific implants in spinal surgery, show the current state of the art in patient-specific implant device design, present thorough clinical and radiographic outcomes, and discuss the suitability of titanium alloy as an implant material for patients with cancer.

CASE DESCRIPTION

A 45-year-old man presented with neck and left arm pain combined with shoulder weakness. Imaging revealed significant destruction of the C3-C5 vertebrae, and chordoma diagnosis was confirmed by biopsy. Gross total tumor resection including multilevel corpectomy was performed in combination with reconstruction using a three-dimensional printed titanium custom implant. Custom-designed features aimed to reduce reconstruction time and result in good clinical and radiographic outcomes. Clinical scores improved postoperatively and remained improved at 17-month postoperative follow-up: visual analog scale score 10/10 preoperatively improved to 2-6/10 at 17 months; Neck Disability Index 46% preoperatively improved to 32% at 17 months. Neither dysphagia nor dysphonia remained after surgical soft tissue swelling subsided. The patient was successfully treated with proton beam therapy after surgery, with no tumor recurrence at 17-month follow-up. Radiographic assessment showed incomplete fusion at 3 months, with clinically insignificant implant subsidence (2.7 mm) and no implant migration or failure at 14 months.

CONCLUSIONS

Computer-aided preoperative planning with three-dimensional printed biomodels and custom implant resulted in relatively quick and simple reconstruction after tumor resection, with good clinical and radiographic outcomes at 17 and 14 months, respectively. For patients with primary tumors who may require follow-up radiotherapy or postoperative magnetic resonance imaging, metals used in the devices cause significant imaging artifact.

The preliminary results of proton and carbon ion therapy for chordoma and chondrosarcoma of the skull base and cervical spine

Purpose

To evaluate the short-term outcomes in terms of tumor control and toxicity of patients with skull base or cervical spine chordoma and chondrosarcoma treated with intensity-modulated proton or carbon-ion radiation therapy.

Methods

Between 6/2014 and 7/2018, a total of 91 patients were treated in our Center. The median age was 38 (range, 4–70) years. Forty-six (50.5%) patients were treated definitively for their conditions as initial diagnosis, 45 (49.5%) patients had recurrent tumors including 14 had prior radiotherapy. The median gross tumor volume was 37.0 (range, 1.6–231.7) cc. Eight patients received proton therapy alone, 28 patients received combined proton and carbon ion therapy, 55 patients received carbon-ion therapy alone.

Results

With a median follow-up time of 28 (range, 8–59) months, the 2-year local control (LC), progression free (PFS) and overall survival (OS) rates was 86.2, 76.8, and 87.2%, respectively. Those rates for patients received definitive proton or carbon-ion therapy were 86.7, 82.8, and 93.8%, respectively. On multivariate analyses, tumor volume of > 60 cc was the only significant factor for predicting PFS (p = 0.045), while re-irradiation (p = 0.012) and tumor volume (> vs < 60 cc) (p = 0.005) were significant prognosticators for OS. Grade 1–2 late toxicities were observed in 11 patients, and one patient developed Grade 3 acute mucositis.

Conclusions

Larger tumor volume and re-irradiation were related to inferior survival for this group of patients. Further follow-up is needed for long-term efficacy and safety.

Dosimetric advantages of proton beam therapy compared to intensity-modulated radiation therapy for retroperitoneal chordoma

Retroperitoneal chordomas are exceedingly rare and account for less than 5% of all primary bone malignancies. Their etiology remains unknown. We report a rare case of an extravertebral chordoma of the retroperitoneum in a 71-year-old man treated with surgical resection and post-operative spot-scanning proton beam therapy. We describe how to safely treat a retroperitoneal target to a prescription dose over 70 Gy (relative biological effectiveness) with spot-scanning proton beam therapy and also report a dosimetric comparison of spot-scanning proton beam therapy versus intensity-modulated radiation therapy. This case not only highlights a rare diagnosis of an extravertebral retroperitoneal chordoma but it also draws attention to the dosimetric advantages of proton beam therapy and illustrates a promising radiotherapeutic option for retroperitoneal targets.

Volumetric and actuarial analysis of brain necrosis in proton therapy using a novel mixture cure model

BACKGROUND AND PURPOSE

High-dose fractionated radiotherapy is often necessary to achieve long-term tumor control in several types of tumors involving or within close proximity to the brain. There is limited data to guide on optimal constraints to the adjacent nontarget brain. This investigation explored the significance of the three-dimensional (3D) dose distribution of passive scattering proton therapy to the brain with other clinicopathological factors on the development of symptomatic radiation necrosis.

MATERIALS AND METHODS

All patients with head and neck, skull base, or intracranial tumors who underwent proton therapy (minimum prescription dose of 59.4 Gy(RBE)) with collateral moderate to high dose radiation exposure to the nontarget brain were retrospectively reviewed. A mixture cure model with respect to necrosis-free survival was used to derive estimates for the normal tissue complication probability (NTCP) model while adjusting for potential confounding factors.

RESULTS

Of 179 identified patients, 83 patients had intracranial tumors and 96 patients had primary extracranial tumors. The optimal dose measure obtained to describe the occurrence of radiation necrosis was the equivalent uniform dose (EUD) with parameter a = 9. The best-fit parameters of logistic NTCP models revealed D₅₀ = 57.7 Gy for intracranial tumors, D₅₀ = 39.5 Gy for extracranial tumors, and γ₅₀ = 2.5 for both tumor locations. Multivariable analysis revealed EUD and primary tumor location to be the strongest predictors of brain radiation necrosis.

CONCLUSION

In the current clinical volumetric data analyses with multivariable modelling, EUD was identified as an independent and strong predictor for brain radiation necrosis from proton therapy.

Skull base chordoma treated with proton therapy: A systematic review

Background:

Chordoma located in the skull base is usually a challenging surgical condition. It is often not possible to achieve gross total resection. Residual tumors have been treated with adjuvant focal radiation therapy employing high-energy particles most commonly through proton beam. In this review, we systematically analyzed indications and outcomes of this treatment with respect to local control rates of the lesion and factors determining recurrence of skull base chordomas. In addition, we collected data on treatment-associated radiation-induced side effects.

Methods:

In line with the PRISMA guidelines, the authors performed a literature search algorithm for relevant articles using three databases: PubMed, Embase, and Cochrane. Inclusion and exclusion criteria were applied to evaluate all identified studies published between 1980 and 2018.

Results:

Our review included 11 studies for analysis (n = 511 patients). The mean age of the study population was 47.3 ± 5.8 years. The mean dose of postsurgical irradiation at the time of initial treatment was 71.1 ± 3.1 Gy. The mean follow-up duration was 45.0 ± 17.5 months. Within this follow-up duration, recurrence occurred in 26.8% of the patients. The mean time to recurrence was 34.5 ± 15.2 months. A significant number of patients experienced side effects varying from Grade 1 (mild dermatitis) to Grade 4 (temporal lobe necrosis and visual disorders).

Conclusion:

Despite advances in proton therapy, recurrence rates in skull base chordoma remain high. The toxicity of proton therapy may be more prevalent than generally thought. Unfortunately, there is substantial variation in the methods of data reporting.

The clincoradiologic spectrum of notochordal derived masses

The notochord is an essential part of human development that regresses with age. Masses derived from notochordal tissue may be encountered during imaging of the neuroaxis. Fortunately, the majority of these are benign and can usually be differentiated by radiological and clinical findings. In this manuscript, we discuss the clinical and radiologic presentation of the four notochordal derived masses and present a brief overview of their management.

A step towards international prospective trials in carbon ion radiotherapy: investigation of factors influencing dose distribution in the facilities in operation based on a case of skull base chordoma

Background

Carbon ion radiotherapy (CIRT) has been delivered to more than 20,000 patients worldwide. International trials have been recommended in order to emphasize the actual benefits. The ULICE program (Union of Light Ion Centers in Europe) addressed the need for harmonization of CIRT practices. A comparative knowledge of the sources and magnitudes of uncertainties altering dose distribution and clinical effects during the whole CIRT procedure is required in that aim.

Methods

As part of ULICE WP2 task group, we sent a centrally reviewed questionnaire exploring candidate sources of uncertainties in dose deposition to the ten CIRT facilities in operation by February 2017. We aimed to explore native beam characterization, immobilization, anatomic data acquisition, target volumes and organs at risks delineation, treatment planning, dose delivery, quality assurance prior and during treatment. The responders had to consider the clinical case of a clival chordoma eligible for postoperative CIRT according to their clinical practice. With the results, our task group discussed ways to harmonize CIRT practices.

Results

We received 5 surveys from facilities that have treated 77% of the patients worldwide per November 2017. We pointed out the singularity of the facilities and beam delivery systems, a divergent definition of target volumes, the multiplicity of TPS and equieffective dose calculation approximations.

Conclusion

Multiple uncertainties affect equieffective dose definition, deposition and calculation in CIRT. Although it is not possible to harmonize all the steps of the CIRT planning between the centers, our working group proposed counter-measures addressing the improvable limitations.

Treatment outcomes of proton or carbon ion therapy for skull base chordoma: a retrospective study

BACKGROUND

The usefulness of particle therapy for skull base chordoma has not been established. The aim of this retrospective study was to analyse the treatment outcomes of proton therapy (PT) and carbon ion therapy (CIT) in patients with skull base chordoma at a single institution.

METHODS

All patients who underwent PT or CIT with curative intent between 2003 and 2014 at Hyogo Ion Beam Medical Center were included in this study. Twenty-four patients were enrolled. Eleven (46%) received PT and 13 (54%) received CIT. Overall survival (OS), progression-free survival (PFS) and local control (LC) were calculated using the Kaplan-Meier method. Late toxicities were evaluated according to the Common Terminology Criteria for Adverse Events version 4.0.

RESULTS

The median follow-up was 71.5 months (range, 14-175 months). The five-year LC, PFS and OS rates were 85, 81, and 86%, respectively. The LC (P = 0.048), PFS (P = 0.028) and OS (P = 0.012) were significantly improved in patients who had undergone surgery before particle therapy. No significant differences were observed in the LC rate and the incidence of grade 2 or higher late toxicities between patients who received PT and CIT.

CONCLUSIONS

Both PT and CIT appear to be effective and safe treatments and show potential to become the standard treatments for skull base chordoma. To increase the local control, surgery before particle therapy is preferable.

Feasibility of Intensity-Modulated Radiation Therapy in the Treatment of Advanced Cervical Chordoma

Aims and Background

Postoperative radiation is often given in cases of cervical chordoma because of the high incidence of local recurrence. The tumor mass usually surrounds the spinal cord and infiltrates vertebral bone. A combined technique using protons or electrons to boost the initial photon fields is generally applied. We evaluated the use of dynamic intensity-modulated radiation therapy as an alternative technique for treating advanced cervical chordoma.

Methods and Study Design

A female patient with incomplete resection of a vertebral chordoma surrounding C2-C3 was irradiated with a total dose of 58 Gy (ICRU point) in 2 Gy daily fractions for 29 days between December 2001 and January 2002. Beam arrangement consisted of seven 6 MV non-opposed coplanar fields. Pretreatment quality assurance included checking of the absolute dose at reference points and 2D dose map analysis. Treatment was delivered with a 120-leaf collimator in sliding window mode. To verify the daily setup, portal images at 0° and 90° were compared with the simulation images before treatment delivery (manual matching) and after treatment delivery (automatic anatomy matching).

Results and Conclusions

The mean dose to the planning target volume (PTV) was 57.6 ± 2.1 Gy covering 95% of the PTV per 95% isodose. The minimum dose to the PTV (D99) was 53.6 Gy in the overlapping area between the PTV and the spinal cord planning organ at risk volume (PRV). The maximum dose to the spinal cord was 42.2 Gy and to the spinal cord PRV (8 mm margin) 53.7 Gy. The mean dose to the parotid glands was 37.4 Gy (homolateral gland) and 19.5 Gy (contralateral gland). Average deviation in setup was -1.1 ± 2.5 mm (anterior-posterior), 2.4 ±1.3 mm (latero-lateral), 0.7 ± 0.9 mm (craniocaudal) and -0.43 ± 1° (rotation).

Conclusions

In the treatment of chordomas surrounding the spinal cord, intensity-modulated radiotherapy can provide high dose homogeneity and PTV coverage. Frequent digital portal image-based setup control is able to reduce random positioning errors for head and neck cancer patients immobilized with conventional thermoplastic masks.

Review of Current Protocols for Protontherapy in USA

The basis for interest in proton beams by clinical radiation oncologists lies in reduction in treatment volume. The yields from employing a smaller treatment volume are the increase of tumor control probability and the reduction of normal tissues complication probability. The clinical use of proton therapy began in 1954 at Uppsala University in Sweden and in 1961 at Harvard Cyclotron Laboratory in Boston, USA. So far, the total number of worldwide patients treated by protons is about 20,000. In this paper attention will be given to the treatment of patients at the Massachusetts General Hospital-Massachusetts Eye and Ear Infirmary-Harvard Cyclotron Laboratory, and at the Loma Linda University Medical Center. In particular, a review of the literature about the techniques and the results of treatment of skull base and cervical spine chordoma and low-grade chondrosarcoma, skull base meningioma, pituitary tumors, paranasal sinus carcinoma, glioblastoma multiforme, artero-venous malformations, uveal melanoma, macular degeneration, retinoblastoma, thoracic spine-sacrum tumors, and prostate carcinoma is presented. In order to verify and improve the clinical results, the conduct of prospective trials on an inter-institutional basis is essential. To facilitate the conduct of such studies the US National Cancer Institute and the American College of Radiology have established the Proton Therapy Oncology Group (PROG). Several phase III and some phase I-II trials are active at the Massachusetts General Hospital, Harvard Cyclotron Laboratory, and at the Loma Linda University Medical Center.

State-of-the-Art Imaging in Human Chordoma of the Skull Base

Purpose of Review

Chordoma are rare tumours of the axial skeleton which occur most often at the base of the skull and in the sacrum. Although chordoma are generally slow-growing lesions, the recurrence rate is high and the location makes it often difficult to treat. Both computed tomography (CT) and magnetic resonance imaging (MRI) are crucial in the initial diagnosis, treatment planning and post-treatment follow-up.

Recent Findings

Basic MRI and CT characteristics of chordoma were described in the late 1980s and early 1990s. Since then, imaging techniques have evolved with increased resolution and new molecular imaging tools are rapidly evolving. New imaging tools have been developed not only to study anatomy, but also physiologic changes and characterization of tissue and assessment of tumour biology. Recent studies show the uptake of multiple PET tracers in chordoma, which may become an important aspect in the diagnosis, follow-up and personalized therapy.

Summary

This review gives an overview of skull base chordoma histopathology, classic imaging characteristics, radiomics and state-of-the-art imaging techniques that are now emerging in diagnosis, treatment planning and disease monitoring of skull base chordoma.

A historical recount of chordoma

Chordoma, a rare bone tumor that occurs along the spine, has led scientists on a fascinating journey of discoveries. In this historical vignette, the authors track these discoveries in diagnosis and treatment, noting events and clinicians that played pivotal roles in our current understanding of chordoma. The study of chordoma begins in 1846 when Rudolf Virchow first observed its occurrence on a dorsum sellae; he coined the term “chordomata” 11 years later. The chordoma’s origin was greatly disputed by members of the scientific community. Eventually, Müller’s notochord hypothesis was accepted 36 years after its proposal. Chordomas were considered benign and slow growing until the early 1900s, when reported autopsy cases drew attention to their possible malignant nature. Between 1864 and 1919, the first-ever symptomatic descriptions of various forms of chordoma were reported, with the subsequent characterization of chordoma histology and the establishment of classification criteria shortly thereafter. The authors discuss the critical historical steps in diagnosis and treatment, as well as pioneering operations and treatment modalities, noting the physicians and cases responsible for advancing our understanding of chordoma.

Dural recurrence among esthesioneuroblastoma patients presenting with intracranial extension

OBJECTIVE

To quantify the rate of late intracranial recurrences among esthesioneuroblastoma patients treated with surgical resection and postoperative radiation.

STUDY DESIGN

Retrospective review.

METHODS

All patients receiving definitive-intent therapy for esthesioneuroblastoma between March 1995 and September 2015 were reviewed. Presenting disease extent was categorized based on radiologic, operative, and pathologic findings. Between-group survival differences were assessed using Kaplan-Meier method and log-rank test. Multivariate analyses were performed using Cox proportional hazards model.

RESULTS

Of 38 patients initially treated at our institution, 53% (20 of 38) presented with intracranial extension. At a median follow-up of 90 months (range, 6-199), 37% (14 of 38) recurred; 5- and 8-year disease-free survival rates were 69% and 54%; and overall survival rates were 81% and 72%, respectively. Among these patients, the dura was the most commonly involved site of relapse (8), followed by local (6), regional (5), and distant extracranial (3) sites; and five patients had ≥ two categories of failure. Eight-year dural disease-free survival was 57% versus 90% (P = 0.017) and 0% versus 87% (P < 0.0001), with and without intracranial extension and subtotal resection, respectively. Of six patients treated at recurrence, five (83%) experienced dural-based failure such that, among all 44 patients, 13 (65%) of 20 recurrences involved the dura. After dural recurrence, the median survival time was 42 months (range, 12-125); salvage treatments were effective in rare cases of isolated low-volume recurrence.

CONCLUSION

Esthesioneuroblastoma patients presenting with intracranial extension are at substantial and unique risk for long-term dural-based relapse.

LEVEL OF EVIDENCE

4. Laryngoscope, 128:2226-2233, 2018.

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.

Gamma Knife Management of Skull Base Chordomas: Is it a Choice?

Background:

Skull base chordomas are locally invasive tumors which able to extend in different directions with skull base invasion. Although they are histologically benign, they have invasive nature makes total resection virtually impossible to achieve in most cases and this lead to residual tumors after surgery. To decrease postoperative surgical resection morbidity of these tumors, gamma knife radiosurgery (GKRS) was performed as alternative management for these residual chordomas to evaluate its safety and efficacy.

Materials and Methods:

A retrospective study was made on eight residual skull base chordomas treated with GKRS between 2011 and 2015. The mean patient age was 49 years (range 30–73 years). Four patients harboring chordoma were male, and four patients were females with 1:1 ratio. All patients had undergone one prior surgery. Patients were treated with peripheral dose ranged between 12–15 gray (Gy) (mean 13.75 Gy) usually at 35% to 50% isodose curve (mean 38.8%). The maximum dose to the adjacent brain stem area ranged between 10 and 12 Gy. All patients were followed up from 8 to 39 months (mean 18 months).

Results:

The tumor control rate was 50% and 25% after 18 and 36 months, respectively, but we found that their wasdeclined in the tumor control rate with long follow-up time. Four tumors were stable in their size just for 18 months, and then there two of these tumors were progressed in their size, the other four patients showed progression in their tumors in their 1^st year of treatment without sign of central tumor necrosis.

Conclusion:

Skull base chordoma patients complained from symptoms due to tumor mass effect which were not prospected to respond to GKRS alone as the aim of this type of treatment was the local tumor control, the tumor control rate declined with long follow-up time and this correlated with radioresistant nature of skull base chordoma. We advise a gross total resection to decrease the tumor volume, and this making gamma knife a reasonable treatment modality.

Long-term follow-up after endoscopic trans-sphenoidal surgery or initial observation in clivus chordomas

BACKGROUND

Resection of clivus chordomas through extensive skull base approaches is associated with high mortality and morbidity even in experienced hands. We report our experience with endoscopic trans-sphenoidal surgery, or a "wait-and-scan" strategy in selected patients.

METHOD

Ten patients were diagnosed with clivus chordomas during an 8-year period. Six patients underwent primary treatment with endoscopic trans-sphenoidal surgery, followed by adjuvant proton-beam therapy in three of these patients. Four patients with minor symptoms were followed-up untreated. Mean follow-up was 91 months.

RESULTS

Of the six patients operated on, total or gross total resection was achieved in four, partial resection in one and biopsy was taken in one. Preoperative cranial neuropathies resolved in three out of five patients, and no new cranial nerve palsies were encountered. Postoperative cerebrospinal fluid leak occurred in one patient. Four patients were initially followed-up without any treatment, and three of these have remained stable without tumour progression for a mean of 94 months. Due to a slow, though progressive growth of tumour, one patient was operated on after 80 months of initial observation.

CONCLUSIONS

The natural course of clivus chordomas has yet to be defined. The endoscopic trans-sphenoidal approach is a valid, minimally invasive alternative for the treatment of clival chordomas, and in selected patients a "wait and scan" strategy can be considered. Our long-term results show low mortality and good functional outcome. An endonasal endoscopic trans-sphenoidal approach should be a principal part of the armamentarium of surgeons treating clivus chordomas.

Brachyury gene copy number gain and activation of the PI3K/Akt pathway: association with upregulation of oncogenic Brachyury expression in skull base chordoma

OBJECTIVE Chordoma is a slow-growing but clinically malignant tumor, and the prognosis remains poor in many cases. There is a strong impetus to develop more effective targeted molecular therapies. On this basis, the authors investigated the potential of Brachyury, a transcription factor involved in notochord development, as a candidate molecular target for the treatment of chordoma. METHODS Brachyury gene copy number and expression levels were evaluated by quantitative polymerase chain reaction in 27 chordoma samples, and the transcriptomes of Brachyury high-expression tumors (n = 4) and Brachyury low-expression tumors (n = 4) were analyzed. A chordoma cell line (U-CH2) was used to investigate the signaling pathways that regulate Brachyury expression. RESULTS All chordoma specimens expressed Brachyury, and expression levels varied widely. Patients with higher Brachyury expression had significantly shorter progression-free survival (5 months, n = 11) than those with lower expression (13 months, n = 16) (p = 0.03). Somatic copy number gain was confirmed in 12 of 27 (44%) cases, and copy number was positively correlated with Brachyury expression (R = 0.61, p < 0.001). Expression of PI3K/Akt pathway genes was upregulated in Brachyury high-expression tumors, and suppression of PI3K signaling led to reduced Brachyury expression and inhibition of cell growth in the U-CH2 chordoma cell line. CONCLUSIONS Activation of the PI3K/Akt pathway and Brachyury copy number gain are strongly associated with Brachyury overexpression, which appears to be a key event in chordoma growth regulation. These findings suggest that targeting Brachyury and PI3K/Akt signaling may be an effective new approach for treating chordoma.

Does Proton Therapy Have a Future in CNS Tumors?

OPINION STATEMENT

Proton therapy is characterized by certain physical properties leading to a reduction in integral dose. As proton therapy becomes more widely available, the ongoing discussion on the real indications for proton therapy becomes more important. In the present article, data on proton therapy for tumors of the central nervous system (CNS) is summarized and discussed in view of modern photon treatments. Still today, no randomized controlled trials are available confirming any clinical benefit of protons in CNS tumors. For certain skull base lesions, such as chordomas and chondrosarcomas, dose escalation is possible with protons thus patients should be referred to a proton center if readily available. For vestibular schwannoma, at present, proton data are inferior to advanced photons. For glioma patients, early data is present for low-grade gliomas, presenting comparable results to photons; dose escalation studies for high-grade gliomas have led to significant side effects, thus strategies of dose-escalation need to rethought. For skull base meningiomas, data from stereotactic series and IMRT present excellent local control with minimal side effects, thus any improvement with protons might only be marginal. The largest benefit is considered in pediatric CNS tumors, due to the intricate radiation sensitivity of children's normal tissue, as well as the potential of long-term survivorship. Long-term data is still lacking, and even recent analyses do not all lead to a clear reduction in side effects with improvement of outcome; furthermore, clinical data seem to be comparable. However, based on the preclinical evidence, proton therapy should be evaluated in every pediatric patient. Protons most likely have a benefit in terms of reduction of long-term side effects, such as neurocognitive sequelae or secondary malignancies; moreover, dose escalation can be performed in radio-resistant histologies. Clinical data with long-term follow-up is still warranted to prove any superiority to advanced photons in CNS tumors. If available, protons should be evaluated for chordoma or chondrosarcoma of the skull base and pediatric tumors. However, many factors are important for excellent oncology care, and no time delay or inferior oncological care should be accepted for the sake of protons only.

Proton therapy - Present and future

In principle, proton therapy offers a substantial clinical advantage over conventional photon therapy. This is because of the unique depth-dose characteristics of protons, which can be exploited to achieve significant reductions in normal tissue doses proximal and distal to the target volume. These may, in turn, allow escalation of tumor doses and greater sparing of normal tissues, thus potentially improving local control and survival while at the same time reducing toxicity and improving quality of life. Protons, accelerated to therapeutic energies ranging from 70 to 250MeV, typically with a cyclotron or a synchrotron, are transported to the treatment room where they enter the treatment head mounted on a rotating gantry. The initial thin beams of protons are spread laterally and longitudinally and shaped appropriately to deliver treatments. Spreading and shaping can be achieved by electro-mechanical means to treat the patients with "passively-scattered proton therapy" (PSPT) or using magnetic scanning of thin "beamlets" of protons of a sequence of initial energies. The latter technique can be used to treat patients with optimized intensity modulated proton therapy (IMPT), the most powerful proton modality. Despite the high potential of proton therapy, the clinical evidence supporting the broad use of protons is mixed. It is generally acknowledged that proton therapy is safe, effective and recommended for many types of pediatric cancers, ocular melanomas, chordomas and chondrosarcomas. Although promising results have been and continue to be reported for many other types of cancers, they are based on small studies. Considering the high cost of establishing and operating proton therapy centers, questions have been raised about their cost effectiveness. General consensus is that there is a need to conduct randomized trials and/or collect outcomes data in multi-institutional registries to unequivocally demonstrate the advantage of protons. Treatment planning and plan evaluation of PSPT and IMPT require special considerations compared to the processes used for photon treatment planning. The differences in techniques arise from the unique physical properties of protons but are also necessary because of the greater vulnerability of protons to uncertainties, especially from inter- and intra-fractional variations in anatomy. These factors must be considered in designing as well as evaluating treatment plans. In addition to anatomy variations, other sources of uncertainty in dose delivered to the patient include the approximations and assumptions of models used for computing dose distributions for planning of treatments. Furthermore, the relative biological effectiveness (RBE) of protons is simplistically assumed to have a constant value of 1.1. In reality, the RBE is variable and a complex function of the energy of protons, dose per fraction, tissue and cell type, end point, etc. These uncertainties, approximations and current technological limitations of proton therapy may limit the achievement of its true potential. Ongoing research is aimed at better understanding the consequences of the various uncertainties on proton therapy and reducing the uncertainties through image-guidance, adaptive radiotherapy, further study of biological properties of protons and the development of novel dose computation and optimization methods. However, residual uncertainties will remain in spite of the best efforts. To increase the resilience of dose distributions in the face of uncertainties and improve our confidence in dose distributions seen on treatment plans, robust optimization techniques are being developed and implemented. We assert that, with such research, proton therapy will be a commonly applied radiotherapy modality for most types of solid cancers in the near future.

[Indications and results for protontherapy in cancer treatments]

Purpose was to summarize results for proton therapy in cancer treatment. A systematic review has been done by selecting studies on the website www.pubmed.com (Medline) and using the following keywords: proton therapy, radiation therapy, cancer, chordoma, chondrosarcoma, uveal melanoma, retinoblastoma, meningioma, glioma, neurinoma, pituitary adenoma, medulloblastoma, ependymoma, craniopharyngioma and nasal cavity. There are several retrospective studies reporting results for proton therapy in cancer treatments in the following indications: ocular tumors, nasal tumors, skull-based tumors, pediatric tumors. There is no prospective study except one phase II trial in medulloblastoma. The use of proton therapy for these indications is due to dosimetric advantages offering better tumor coverage and organ at risk sparing in comparison with photon therapy. Clinical results are historically at least as efficient as photon therapy with a better toxicity profile in pediatric tumors (cognitive and endocrine functions, radiation-induced cancer) and a better tumoral control in tumors of the nasal cavity. Clinical advantages of proton therapy counterbalance its cost especially in pediatric tumors. Proton therapy could be used in other types of cancer. Proton therapy showed good outcome in ocular, nasal tumors, pediatric, skull-based and paraspinal tumors. Because of some dosimetric advantages, proton therapy could be proposed for other indications in cancer treatments.

Hyperfractionated high-dose proton beam radiotherapy for clival chordomas after surgical removal

OBJECTIVE

To evaluate the hyperfractionated high-dose proton beam therapy (PBT) for patients with clival chordomas.

METHODS

Records for 19 patients with pathologically verified clival chordomas treated with surgery followed by hyperfractionated PBT were retrospectively reviewed. The first 9 consecutive patients were treated with 77.44 cobalt gray equivalents (CGEs) in 64 fractions, and the latter 10 patients were treated with 78.4 CGE in 56 fractions.

RESULTS

The median follow-up period of all 19 cases was 61.7 months with a range from 31.5 to 115.4 months. At 5 years, the local control, cause-specific and overall survival rates for all 19 cases were 75%, 94% and 83.2%, respectively. Whereas the 5-year local control, cause-specific and over all survival rates of the latter 10 cases were 100%, 100% and 88.9%, respectively, with a median follow-up period of 59.5 months. One of the first nine patients demonstrated bilateral temporal lobe radiation necrosis, who were successfully treated conservatively. In the latter cohort, two cases showed transient neurological symptoms probably due to brain stem ischaemia, but both cases recovered completely with conservative treatment.

CONCLUSION

The hyperfractionated high-dose scheme combined with maximum surgical removal was shown to be efficient for patients with clival chordomas.

ADVANCES IN KNOWLEDGE

High-dose proton beam radiotherapy using a hyperfractionation scheme yielded a more favourable outcome than previous reports.

Long term outcomes of patients with skull-base low-grade chondrosarcoma and chordoma patients treated with pencil beam scanning proton therapy

PURPOSE

To evaluate the long term tumor control and toxicity of skull base tumors treated with pencil beam scanning proton therapy (PT).

MATERIALS AND METHODS

PT was delivered to 151 (68%) and 71 (32%) chordoma and chondrosarcoma (ChSa) patients, respectively. Mean age of patients was 40.8±18.4years and the male to female ratio was 0.53. The postoperative tumor was abutting the brainstem or optic apparatus in 71 (32.0%) patients. The postoperative mean gross tumor volume (GTV) was 35.7±29.1cm(3). The delivered mean PT dose was 72.5±2.2GyRBE.

RESULTS

After a mean follow-up of 50 (range, 4-176) months, 35 local (15.8%) failures were observed between 10.9 and 85.4months. The estimated 7-year LC rate for chordoma (70.9%; CI95% 61.5-81.8) was significantly lower compared to the LC rate for ChSa patients (93.6%; 95%CI 87.8-99.9; P=0.014). The estimated 7-year distant metastasis-free- and overall survival rate was 91.6% (95%CI 91.6-98.6) and 81.7% (95%CI 74.7-89.5), respectively. On multivariate analysis, optic apparatus and/or brainstem compression, histology and GTV were independent prognostic factors for LC and OS. The 7-year high grade toxicity-free survival was 87.2 (95%CI 82.4-92.3).

CONCLUSIONS

PBS PT is an effective treatment for skull base tumors with acceptable late toxicity. Optic apparatus and/or brainstem compression, histology and GTV allow independent prediction of the risk of local failure and death in skull base tumor patients.

Tumour seeding in the surgical pathway after resection of skull base chordoma

AIM

The aim of this study is to review the clinical series in which tumour seeding was reported after skull base surgery for chordomas.

BACKGROUND

The occurrence of implantation of cancer cells during surgical procedures for the removal of chordoma is a rare event described by a number of authors in a few patient series and case reports.

MATERIALS AND METHODS

Literature search was performed by PubMed and Scopus by using the words "surgical tumour seeding, tumour implantation, surgical pathway recurrence, skull base chordoma, and clivus chordoma".

RESULTS

Six retrospective series and 7 case reports were included in the analysis. In total, 34 patients are described with pathway recurrence, 30 at a single site and 4 at multiple sites. In the 5 largest chordoma series, the rate of occurrence of surgical seeding ranged from 1.3% to 7.3% (3.9%). In the 34 patients diagnosed with tumour seeding, the most frequent surgical approach was trans-nasal/trans-sphenoidal, that was used in 12 cases. The median time from primary treatment to surgical pathway tumour seeding ranged from 7 to 78 months. Data of the treatment of seeding are available in 26/34 patients. All of them underwent a new surgery, 6 received additional external beam radiotherapy, and 2 intraoperative radiotherapy.

CONCLUSIONS

The risk of surgical seeding should be taken into consideration when deciding on the surgical approach and the planning treatment volume for postoperative radiation therapy. The surgical pathway should be included in follow-up studies to diagnose this peculiar type of treatment failure possibly at an early phase.

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.

Gamma Knife surgery for intracranial chordoma and chondrosarcoma: radiosurgical perspectives and treatment outcomes

OBJECT

Intracranial chordomas and chondrosarcomas are histologically low-grade, locally invasive tumors that are reported to be similar in terms of anatomical location, clinical presentation, and radiological findings but different in terms of behavior and outcomes. The purpose of this study was to investigate and compare clinical outcomes after Gamma Knife surgery (GKS) for the treatment of intracranial chordoma and chondrosarcoma.

METHODS

The authors conducted a retrospective review of the results of radiosurgical treatment of intracranial chordomas and chondrosarcomas. They enrolled patients who had undergone GKS for intracranial chordoma or chondrosarcoma at the Yonsei Gamma Knife Center, Yonsei University College of Medicine, from October 2000 through June 2007. Analyses included only patients for whom the disease was pathologically diagnosed before GKS and for whom more than 5 years of follow-up data after GKS were available. Rates of progression-free survival and overall survival were analyzed and compared according to tumor pathology. Moreover, the association between tumor control and the margin radiation dose to the tumor was analyzed, and the rate of tumor volume change after GKS was quantified.

RESULTS

A total of 10 patients were enrolled in this study. Of these, 5 patients underwent a total of 8 sessions of GKS for chordoma, and the other 5 patients underwent a total of 7 sessions of GKS for chondrosarcoma. The 2- and 5-year progression-free survival rates for patients in the chordoma group were 70% and 35%, respectively, and rates for patients in the chondrosarcoma group were 100% and 80%, respectively (log-rank test, p = 0.04). The 2- and 5-year overall survival rates after GKS for patients in the chordoma group were 87.5% and 72.9%, respectively, and rates for patients in the chondrosarcoma group were 100% and 100%, respectively (log-rank test, p = 0.03). The mean rates of tumor volume change 2 years after radiosurgery were 79.64% and 39.91% for chordoma and chondrosarcoma, respectively (p = 0.05). No tumor progression was observed when margin doses greater than 16 Gy for chordoma and 14 Gy for chondrosarcoma were prescribed.

CONCLUSIONS

Outcomes after GKS were more favorable for patients with chondrosarcoma than for those with chordoma. The data also indicated that at 2 years after GKS, the rate of volume change is significantly higher for chordomas than for chondrosarcomas. The authors conclude that radiosurgery with a margin dose of more than 16 Gy for chordomas and more than 14 Gy for chondrosarcomas seems to enhance local tumor control with relatively few complications. Further studies are needed to determine the optimal dose of GKS for patients with intracranial chordoma or chondrosarcoma.

Image-guided, intensity-modulated radiation therapy (IG-IMRT) for skull base chordoma and chondrosarcoma: preliminary outcomes

BACKGROUND

We report our preliminary outcomes following high-dose image-guided intensity modulated radiotherapy (IG-IMRT) for skull base chordoma and chondrosarcoma.

METHODS

Forty-two consecutive IG-IMRT patients, with either skull base chordoma (n = 24) or chondrosarcoma (n = 18) treated between August 2001 and December 2012 were reviewed. The median follow-up was 36 months (range, 3-90 mo) in the chordoma cohort, and 67 months (range, 15-125) in the chondrosarcoma cohort. Initial surgery included biopsy (7% of patients), subtotal resection (57% of patients), and gross total resection (36% of patients). The median IG-IMRT total doses in the chondrosarcoma and chordoma cohorts were 70 Gy and 76 Gy, respectively, delivered with 2 Gy/fraction.

RESULTS

For the chordoma and chondrosarcoma cohorts, the 5-year overall survival and local control rates were 85.6% and 65.3%, and 87.8% and 88.1%, respectively. In total, 10 patients progressed locally: 8 were chordoma patients and 2 chondrosarcoma patients. Both chondrosarcoma failures were in higher-grade tumors (grades 2 and 3). None of the 8 patients with grade 1 chondrosarcoma failed, with a median follow-up of 77 months (range, 34-125). There were 8 radiation-induced late effects-the most significant was a radiation-induced secondary malignancy occurring 6.7 years following IG-IMRT. Gross total resection and age were predictors of local control in the chordoma and chondrosarcoma patients, respectively.

CONCLUSIONS

We report favorable survival, local control and adverse event rates following high dose IG-IMRT. Further follow-up is needed to confirm long-term efficacy.

Surgical pathway seeding of clivo-cervical chordomas

Objective Clival chordomas are slow-growing aggressive tumors that originate from the extra-axial remnants of the notochord. Current management of these tumors use surgical resection combined with radiation therapy. Given the location and invasive nature of these tumors, complete resection is difficult. A variety of both open and endoscopic therapeutic approaches have evolved and combined with the improvements in proton therapy, long-term control of these tumors appears to be improving. However, in recent literature the relatively rare complication of surgical seeding or surgical pathway recurrence has been reported. We report a case of surgical seeding following primary resection and review the world literature regarding surgical pathway recurrence.

Study Design Retrospective chart review and review of current literature.

Methods We report a case of a patient with a large chordoma that required treatment with a staged endoscopic endonasal and external transcervical approach. The patient subsequently developed recurrent disease along the cervical skin incision due to surgical seeding. Literature review and case reports were identified by a comprehensive search of Medline for the years 1950 to 2012.

Results The overall surgical pathway recurrence rate for clival chordoma resection based on analysis of the open nonendoscopic published case studies was 14 of 497 (2.8%).

Conclusion Tumor seeding can occur anywhere along the operative route and is often outside the field of radiotherapy. Increased awareness of this rare occurrence is necessary. The use of novel techniques to minimize exposure to tumor including primary endoscopic resection and so-called clean oncologic technique may help limit tumor seeding. Level of evidence: 4.