Stereotactic Radiosurgery for Ependymoma in Pediatric and Adult Patients: A Single-Institution Experience

BACKGROUND AND OBJECTIVES

Ependymoma is commonly classified as World Health Organization grade 2 with the anaplastic variant categorized as grade 3. Incomplete resection or anaplastic features can result in unfavorable outcomes. Stereotactic radiosurgery (SRS) provides a minimally invasive approach for recurrent ependymomas. Our study investigates the efficacy and safety of SRS for grade 2 and 3 ependymomas in pediatric and adult populations.

METHODS

We conducted a retrospective analysis on 34 patients with 75 ependymomas after CyberKnife SRS between 1998 and 2023. Fourteen were pediatric (3-18 years), and 20 were adult (19-75 years) patients. The median age was 21 years, and the median tumor volume was 0.64 cc. The median single-fraction equivalent dose was 16.6 Gy, with SRS administered at 77% of the median isodose line.

RESULTS

After a median follow-up of 42.7 months (range: 3.8-438.3), 22.7% of ependymomas progressed. The 5-year local tumor control rate was 78.1%, varying between 59.6% and 90.2% for children and adults, with grade 2 at 85.9% compared with 58.5% for grade 3 tumors. The 5-year overall survival rate was 73.6%, notably higher in adults (94.7%) than in children (41%), and 100% for grade 2 but decreased to 35.9% for grade 3 patients. The 5-year progression-free survival rate was 68.5%, with 78.3% and 49.2% for adults and children, respectively, and a favorable 88.8% for grade 2, contrasting with 32.6% for grade 3 patients. Symptom improvement was observed in 85.3% of patients. Adverse radiation effects occurred in 21.4% of pediatric patients.

CONCLUSION

Our study supports SRS as a viable modality for pediatric and adult patients with grade 2 and 3 ependymomas. Despite lower local tumor control in pediatric and grade 3 cases, integrating SRS holds promise for improved outcomes. Emphasizing careful patient selection, personalized treatment planning, and long-term follow-up is crucial for optimal neurosurgical outcomes.

LETd Optimization Verification With an SOI Microdosimeter

PURPOSE

A first of its kind experimental verification of dose-averaged linear energy transfer (LETd) optimized treatment plans for proton therapy has been carried out using a silicon-on-insulator microdosimeter at the Massachusetts General Hospital (MGH), Boston, USA.

METHODS AND MATERIALS

Three clinical treatment plans of a typical ependymoma structure set were designed using the standard clinical approach, the proposed protocol approach, and a one-field approach. The plans were then reoptimized to reduce the LETd-weighted dose in the brain stem. All six plans were delivered in a solid water phantom and the experimental yD‾ measured.

RESULTS

After LETd optimization, a reduction in yD‾ was found within the brain stem by an average of 12%, 19%, and 4% for the clinical, protocol, and one-field plans, respectively, while maintaining adequate coverage of the tumor structure. The experimental LETd-weighted doses were in agreement with the treatment planning system calculations and Monte Carlo simulations and reinforced the improvement of the optimization.

CONCLUSIONS

This work demonstrates the first experimental verification of the clinical implementation of LETd optimization for patient treatment with proton therapy.

Brain and Brain Stem Necrosis After Reirradiation for Recurrent Childhood Primary Central Nervous System Tumors: A PENTEC Comprehensive Review

PURPOSE

Reirradiation is increasingly used in children and adolescents/young adults (AYA) with recurrent primary central nervous system tumors. The Pediatric Normal Tissue Effects in the Clinic (PENTEC) reirradiation task force aimed to quantify risks of brain and brain stem necrosis after reirradiation.

METHODS AND MATERIALS

A systematic literature search using the PubMed and Cochrane databases for peer-reviewed articles from 1975 to 2021 identified 92 studies on reirradiation for recurrent tumors in children/AYA. Seventeen studies representing 449 patients who reported brain and brain stem necrosis after reirradiation contained sufficient data for analysis. While all 17 studies described techniques and doses used for reirradiation, they lacked essential details on clinically significant dose-volume metrics necessary for dose-response modeling on late effects. We, therefore, estimated incidences of necrosis with an exact 95% CI and qualitatively described data. Results from multiple studies were pooled by taking the weighted average of the reported crude rates from individual studies.

RESULTS

Treated cancers included ependymoma (n = 279 patients; 7 studies), medulloblastoma (n = 98 patients; 6 studies), any CNS tumors (n = 62 patients; 3 studies), and supratentorial high-grade gliomas (n = 10 patients; 1 study). The median interval between initial and reirradiation was 2.3 years (range, 1.2-4.75 years). The median cumulative prescription dose in equivalent dose in 2-Gy fractions (EQD22; assuming α/β value = 2 Gy) was 103.8 Gy (range, 55.8-141.3 Gy). Among 449 reirradiated children/AYA, 22 (4.9%; 95% CI, 3.1%-7.3%) developed brain necrosis and 14 (3.1%; 95% CI, 1.7%-5.2%) developed brain stem necrosis with a weighted median follow-up of 1.6 years (range, 0.5-7.4 years). The median cumulative prescription EQD22 was 111.4 Gy (range, 55.8-141.3 Gy) for development of any necrosis, 107.7 Gy (range, 55.8-141.3 Gy) for brain necrosis, and 112.1 Gy (range, 100.2-117 Gy) for brain stem necrosis. The median latent period between reirradiation and the development of necrosis was 5.7 months (range, 4.3-24 months). Though there were more events among children/AYA undergoing hypofractionated versus conventionally fractionated reirradiation, the differences were not statistically significant (P = .46).

CONCLUSIONS

Existing reports suggest that in children/AYA with recurrent brain tumors, reirradiation with a total EQD22 of about 112 Gy is associated with an approximate 5% to 7% incidence of brain/brain stem necrosis after a median follow-up of 1.6 years (with the initial course of radiation therapy being given with conventional prescription doses of ≤2 Gy per fraction and the second course with variable fractionations). We recommend a uniform approach for reporting dosimetric endpoints to derive robust predictive models of late toxicities following reirradiation.

Brainstem toxicity after proton or photon therapy in children and young adults with localized intracranial ependymoma: A French retrospective study

BACKGROUND AND PURPOSE

Ependymoma is the third most frequent childhood braintumor. Standard treatment is surgery followed by radiation therapy including proton therapy (PBT). Retrospective studies have reported higher rates of brainstem injury after PBT than after photon therapy (XRT). We report a national multicenter study of the incidence of brainstem injury after XRT versus PBT, and their correlations with dosimetric data.

MATERIAL AND METHODS

We included all patients aged < 25 years who were treated with PBT or XRT for intracranial ependymoma at five French pediatric oncology reference centers between 2007 and 2020. We reviewed pre-irradiation MRI, follow-up MRIs over the 12 months post-treatment and clinical data.

RESULTS

Of the 83 patients, 42 were treated with PBT, 37 with XRT, and 4 with both (median dose: 59.4 Gy, range: 53‑60). No new or progressive symptomatic brainstem injury was found. Four patients presented asymptomatic radiographic changes (punctiform brainstem enhancement and FLAIR hypersignal), with median onset at 3.5 months (range: 3.0‑9.4) after radiation therapy, and median offset at 7.6 months (range: 3.7‑7.9). Two had been treated with PBT, one with XRT, and one with mixed XRT-PBT. Prescribed doses were 59.4, 55.8, 59.4 and 54 Gy.

CONCLUSION

Asymptomatic radiographic changes occurred in 4.8% of patients with ependymoma in a large national series. There was no correlation with dose or technique. No symptomatic brainstem injury was identified.

Adjuvant radiotherapy versus observation after gross total resection of WHO grade II ependymoma: a systematic review and individual-participant data meta-analysis

BACKGROUND

The role of adjuvant radiotherapy (RT) after gross total resection (GTR) of the World Health Organization (WHO) grade II ependymoma is controversial. Therefore, we aimed to compare the outcomes of adjuvant RT against observation after GTR of WHO grade II ependymoma. We also compared the outcomes of adjuvant RT against observation after subtotal resection (STR) of WHO grade II ependymoma and performed further subgroup analysis by age and tumor location.

METHODS

PubMed and Embase were systematically reviewed for studies published up till 25 November 2022. Studies that reported individual-participant data on patients who underwent surgery followed by adjuvant RT/observation for WHO grade II ependymoma were included. The exposure was whether adjuvant RT was administered, and the outcomes were recurrence and overall survival (OS). Subgroup analyses were performed by the extent of resection (GTR or STR), tumor location (supratentorial or infratentorial), and age at the first surgery (<18 or ≥18 years old).

RESULTS

Of the 4,647 studies screened, three studies reporting a total of 37 patients were included in the analysis. Of these 37 patients, 67.6% (25 patients) underwent GTR, and 51.4% (19 patients) underwent adjuvant RT. Adjuvant RT after GTR was not significantly associated with both recurrence (odds ratio =5.50; 95% confidence interval: 0.64-60.80; P=0.12) and OS (P=0.16). Adjuvant RT was also not significantly associated with both recurrence and OS when the cohort was analyzed as a whole and on subgroup analysis by age and tumor location. However, adjuvant RT was associated with significantly longer OS after STR (P=0.03) with the median OS being 6.33 years, as compared to 0.40 years for patients who underwent STR followed by observation.

CONCLUSIONS

Based on our meta-analysis of 37 patients, administration of adjuvant RT after GTR was not significantly associated with improvement in OS or recurrence in patients with WHO grade II ependymoma. However, due to the small number of patients included in the analysis, further prospective controlled studies are warranted.

Outcome after treatment of pediatric supratentorial ependymoma: long-term follow-up of a single consecutive institutional series of 26 patients

BACKGROUND

Long-term outcome after surgical treatment of supratentorial ependymoma (STE) in children has not been extensively reported.

FINDINGS

We identified 26 children who underwent primary tumor resection of STE between 1953 and 2011, with at least 8 years follow-up. Ten patients (38%) had anaplastic and 16 had low grade ependymoma. Four of 15 children (26%) treated in the years 1953-1976 survived more than 5 years, but the observed 10-year survival was only 7%. One patient lived for 37 years, and second surgery for a local recurrent lesion disclosed a glioblastoma, possibly secondary to radiotherapy. In contrast, the observed 5-year survival rate for 11 children treated in the years 1992-2011 was 8/11 (73%) and observed 10- and 25-year survival rates were 70% and 66%, respectively. Eight patients were alive and tumor-free with follow-up periods of 8-27 (median 18) years, all treated after 1992. Five of these long-term survivors were 23-39 years old with full-time (n = 3) or part-time (n = 2) work. The last three patients were still children (9-12 years old): one with good function and two with major neurological deficits. The majority of patients (n = 18) received adjuvant radiotherapy and eight children no adjuvant treatment. Repeated resections for residual or recurrent tumor were necessary in 11 patients (42%), mostly due to local disease with progressive clinical symptoms. Eight patients underwent only one repeat resection, whereas three patients had two or more repeat resections within 18 years after initial surgery. Four patients were tumor-free after repeated resections at the latest follow-up, 2-13 years after last surgery.

CONCLUSION

Pediatric STE has a marked risk for local recurrence even after gross total resection and postoperative radiotherapy, but survival has increased following the introduction of modern treatment in recent years. Repeated surgery is an important part of treatment and may lead to persistent tumor control.

Incorporating variable RBE in IMPT optimization for ependymoma

PURPOSE

To study the dosimetric impact of incorporating variable relative biological effectiveness (RBE) of protons in optimizing intensity-modulated proton therapy (IMPT) treatment plans and to compare it with conventional constant RBE optimization and linear energy transfer (LET)-based optimization.

METHODS

This study included 10 pediatric ependymoma patients with challenging anatomical features for treatment planning. Four plans were generated for each patient according to different optimization strategies: (1) constant RBE optimization (ConstRBEopt) considering standard-of-care dose requirements; (2) LET optimization (LETopt) using a composite cost function simultaneously optimizing dose-averaged LET (LETd ) and dose; (3) variable RBE optimization (VarRBEopt) using a recent phenomenological RBE model developed by McNamara et al.; and (4) hybrid RBE optimization (hRBEopt) assuming constant RBE for the target and variable RBE for organs at risk. By normalizing each plan to obtain the same target coverage in either constant or variable RBE, we compared dose, LETd , LET-weighted dose, and equivalent uniform dose between the different optimization approaches.

RESULTS

We found that the LETopt plans consistently achieved increased LET in tumor targets and similar or decreased LET in critical organs compared to other plans. On average, the VarRBEopt plans achieved lower mean and maximum doses with both constant and variable RBE in the brainstem and spinal cord for all 10 patients. To compensate for the underdosing of targets with 1.1 RBE for the VarRBEopt plans, the hRBEopt plans achieved higher physical dose in targets and reduced mean and especially maximum variable RBE doses compared to the ConstRBEopt and LETopt plans.

CONCLUSION

We demonstrated the feasibility of directly incorporating variable RBE models in IMPT optimization. A hybrid RBE optimization strategy showed potential for clinical implementation by maintaining all current dose limits and reducing the incidence of high RBE in critical normal tissues in ependymoma patients.

Challenges in Treating Childhood Infratentorial Ependymoma: A Low- and Middle-Income Country Experience

PURPOSE

Patients and physicians in low- and middle-income countries (LMICs) face challenges owing to limited expertise and suboptimal access to appropriate diagnostic and treatment modalities. We report our experience in treating posterior fossa ependymoma (PFE) at MAHAK, a charity organization in Iran whose radiation oncology department is the only one exclusively dedicated to childhood cancer in the whole country.

METHODS AND MATERIALS

Pediatric patients with PFE referred to MAHAK between November 2008 and January 2016 were identified. Details on investigations and management done before referral were collected. Management at MAHAK and patient outcomes were analyzed.

RESULTS

Of 80 patients diagnosed as having ependymoma, 54 with PFE were identified. Forty-three patients received adjuvant radiation therapy, and 11 were irradiated initially after recurrence. At a median follow-up of 5.1 years (range, 0.3-9.7 years), the latter group had the worst outcome, with a 5-year overall survival (OS) rate of 27% (95% CI, 7%-54%). Patients who started radiation therapy within 77 days after initial surgery had a better outcome compared with those who started later (5-year OS: 74% vs 32%; P = .05). Compliance with follow-up recommendations was poor. Only 22% of the patients had at least 2 IQ test assessments, and 50% showed some decline over time. Three cases of growth hormone deficiency were detected, but none of the patients received replacement therapy.

CONCLUSIONS

Access to pediatric neurosurgery, anesthesia, and timely radiation therapy are among the most challenging obstacles to be overcome in LMICs. Our series confirmed that chemotherapy is not an appropriate option for delaying radiation therapy, especially in young children. The importance of long-term follow-up should be acknowledged by the parents and medical team.

Conformal Radiation Therapy for Ependymoma at Age ≤3 Years: A 25-Year Experience

PURPOSE

Adjuvant radiation therapy (RT) affects survival after surgery for young children (age <3 years) diagnosed with intracranial ependymoma. Conformal photon RT promised to spare normal tissue and was introduced more than 25 years ago to improve outcomes for these vulnerable patients. Long-term results for those first treated with conformal methods provide valuable information and serve as a comparison against newer methods.

METHODS AND MATERIALS

Between 1997 and 2018, 101 patients <3.1-years-old were treated with conformal and intensity modulated photon therapy after definitive surgery for intracranial ependymoma. The median age at RT was 2.1 years and the time from diagnosis to the start of RT was 10 weeks. The extent of resection was gross-total in 82%, and 38% underwent more than 1 attempt at resection. The total prescribed dose was 54 to 59.4 Gy at 1.8 Gy per fraction.

RESULTS

The 10-year event-free and overall survivals were 58.5% ± 5.0% and 72.6% ± 4.5%, respectively, with a median follow-up of 18.4 years (range, 4.2-23.3 years). Tumor progression occurred in 34 patients with a median time of 1.6 years. Death occurred in 34 patients from ependymoma (n = 24), secondary malignancy (n = 6), necrosis (n = 2), shunt failure (n = 1), and anaphylactic reaction (n = 1). Twenty-three patients developed a secondary tumor including 6 cases of fatal high-grade glioma. Of the surviving cohort and those ≥18 years old, 98% obtained a high school diploma, 64% had a current driver's license, 89% were students or employed full or part time, 32% were living independently, and 70% received higher education or training.

CONCLUSIONS

Long-term results of children treated using photon conformal RT after surgery demonstrate that adjuvant RT resulted in long-term disease control and functional independence. These results point to the need for new treatment strategies to improve tumor control and provide investigators hope that newer RT methods will further reduce complications.

Outcomes following limited-volume proton therapy for multifocal spinal myxopapillary ependymoma

PURPOSE

Spinal myxopapillary ependymoma (MPE) often presents with a multifocal distribution, complicating attempts at resection. There remains no standard approach to irradiating these patients. We report disease control and toxicity in pediatric patients with multifocal spinal MPE treated with limited-volume proton therapy.

MATERIALS/METHODS

Twelve patients (≤21 years old) with multifocal spinal MPE were treated between 2009 and 2018 with limited-volume brain-sparing proton therapy. Median age was 13.5 years (range, 7-21). Radiotherapy was given as adjuvant therapy after primary surgery in five patients (42%) and for recurrence in seven (58%). No patient received prior radiation. Eleven patients (92%) had evidence of gross disease at radiotherapy. Eleven patients received 54 GyRBE; one received 50.4 GyRBE. Treatment toxicity was graded per the CTCAEv4.0. We estimated disease control and survival using the Kaplan-Meier product-limit method.

RESULTS

The median follow-up was 3.6 years (range, 1.8-10.6). The five-year actuarial rates of local control, progression-free survival, and overall survival were 100%, 92%, and 100%, respectively. One patient experienced an out-of-field recurrence in the spine superior to the irradiated region. No patients developed in-field recurrences. Following surgery and irradiation, one patient developed grade three spinal kyphosis and one patient developed grade 2 unilateral L5 neuropathy.

CONCLUSION

54 GyRBE to a limited volume appears effective for disseminated spinal MPE in both the primary and salvage settings, sparing children the toxicity of full craniospinal irradiation. Compared with historical reports, this approach using proton therapy improves the therapeutic ratio, resulting in minimal side effects and high rates of disease control.

A DNA damage multiscale model for NTCP in proton and hadron therapy

PURPOSE

To develop a first principle and multiscale model for normal tissue complication probability (NTCP) as a function of dose and LET for proton and in general for particle therapy with a goal of incorporating nanoscale radio-chemical to macroscale cell biological pathways, spanning from initial DNA damage to tissue late effects.

METHODS

The method is a combination of analytical and multiscale computational steps including (a) derivation of functional dependencies of NTCP on DNA-driven cell lethality in nanometer and mapping to dose and LET in millimeter, and (b) three-dimensional-surface fitting to Monte Carlo data set generated based on postradiation image change and gathered for a cohort of 14 pediatric patients treated by scanning beam of protons for ependymoma. We categorize voxel-based dose and LET associated with development of necrosis in NTCP.

RESULT

Our model fits well the clinical data, generated for postradiation tissue toxicity and necrosis. The fitting procedure results in extraction of in vivo radio-biological α-β indices and their numerical values.

DISCUSSION AND CONCLUSION

The NTCP model, explored in this work, allows to correlate the tissue toxicities to DNA initial damage, cell lethality and the properties and qualities of radiation, dose, and LET.

Radiotherapy in addition to surgical resection may not improve overall survival in WHO grade II spinal ependymomas

OBJECTIVES

Spinal ependymomas are rare intramedullary neoplasms. The paucity of cases limits the ability to conduct large prospective studies. Current guidelines recommend maximal safe resection followed by adjuvant radiotherapy (RT) in cases of grade II spinal ependymomas with subtotal resections (STR) and all grade III spinal ependymomas. Herein we assess the impact of RT on survival in grades II and III spinal ependymomas.

PATIENTS AND METHODS

The National Cancer Database was queried for adult patients with WHO grades II or III spinal ependymomas diagnosed between 2004 and 2014 who underwent resection or biopsy. Kaplan-Meier and multivariable Cox regression models were used to determine the impact of radiotherapy on survival.

RESULTS

A total of 1058 patients met inclusion criteria. Most patients (85.9 %) received a biopsy/STR versus gross total resection (GTR, 14.1 %). Radiotherapy was preferentially performed in those with residual tumor (p = 0.001). We found a 10-fold increased hazard of death in grade III versus grade II tumors (HR: 10.33; 95 % CI: 5.01-21.3; p < 0.001). Age positively correlated with worsened survival (HR: 1.04; 95 % CI: 1.02-1.10; p < 0.001). Adjuvant RT did not reduce the hazard of death for the cohort overall (HR: 1.08; 95 % CI: 0.55-2.10; p = 0.810) or among those with grade II tumors (HR: 0.90; 95 % CI: 0.38-2.10; p = 0.810). We found no additional survival benefit of GTR compared to biopsy/STR (HR: 0.52; 95 % CI: 0.19-1.50; p = 0.217).

CONCLUSION

While RT may improve progression-free survival, it may not impact overall survival in surgically resected grade II and III spinal ependymomas. Future studies should evaluate the impact of RT on local recurrence and symptomatic improvement.

Clinical Importance of Free Thyroxine Concentration Decline After Radiotherapy for Pediatric and Adolescent Brain Tumors

CONTEXT

Clinical significance of a decline in free T4 (FT4) concentrations across the reference range in children with brain tumors treated with radiation therapy (RT) is uncertain.

OBJECTIVES

To study trends in FT4 in children after RT and risk factors and health outcomes associated with plasma FT4 concentrations.

DESIGN AND SETTING

Longitudinal, single-center retrospective cohort study.

PATIENTS

Low-grade glioma or ependymoma patients (n = 267; age ≤25 years) who received RT (50.4 to 59.4 Gy) at a single institution (1996 to 2016) and followed with serial FT4 measurements.

MAIN OUTCOME MEASURE

A linear mixed-effects model with a random intercept was used to investigate risk factors for longitudinal changes in FT4 concentrations. A two-stage mixed-effects model examined associations between clinical outcomes and plasma FT4 concentrations.

RESULTS

FT4 concentrations declined over time after RT (P < 0.001). Females (P < 0.001) and younger patients (P < 0.001) demonstrated greater declines in FT4 concentrations over time. The rate of weight gain, but not of height loss, increased with a higher FT4 decline rate (P < 0.001). At last follow-up, patients with lower baseline FT4 concentrations had increased risk of glucose disorder (OR, 19.73; P = 0.002) or dyslipidemia (OR, 19.40; P = 0.003) but not high fat mass (P = 0.18). Lower baseline FT4 concentrations were not associated with impaired scores for intelligence, attention, memory, or psychosocial functioning.

CONCLUSIONS

FT4 concentrations significantly decline in children with brain tumor after RT. Variation and trends in FT4 concentration are associated with physical health outcomes. Future studies should assess whether continuous FT4 concentrations and trends, rather than population-based cut-off values, can distinguish between euthyroid and hypothyroid states.

The European Society of Paediatric Oncology Ependymoma-II program Core-Plus model: Development and initial implementation of a cognitive test protocol for an international brain tumour trial

It is increasingly accepted that survival alone is an inadequate measure of the success of childhood brain tumour treatments. Consequently, there is growing emphasis on capturing quality of survival. Ependymomas are the third most frequently occurring brain tumours in childhood and present significant clinical challenges. European Society of Paediatric Oncology Ependymoma II is a comprehensive international program aiming to evaluate outcomes under different treatment regimens and improve diagnostic accuracy. Importantly, there has been agreement to lower the age at which children with posterior fossa ependymoma undergo focal irradiation from three years to either eighteen months or one year of age. Hitherto radiotherapy in Europe had been reserved for children over three years due to concerns over adverse cognitive outcomes following irradiation of the developing brain. There is therefore a duty of care to include longitudinal cognitive follow-up and this has been agreed as an essential trial outcome. Discussions between representatives of 18 participating European countries over 10 years have yielded European consensus for an internationally accepted test battery for follow-up of childhood ependymoma survivors. The 'Core-Plus' model incorporates a two-tier approach to assessment by specifying core tests to establish a minimum dataset where resources are limited, whilst maintaining scope for comprehensive assessment where feasible. The challenges leading to the development of the Core-Plus model are presented alongside learning from the initial stages of the trial. We propose that this model could provide a solution for future international trials addressing both childhood brain tumours and other conditions associated with cognitive morbidity.

The value of high-dose radiotherapy in intracranial ependymoma

BACKGROUND

We sought to evaluate the impact of adjuvant radiotherapy dose on overall survival (OS) after surgical resection for localized intracranial ependymoma.

PROCEDURE

The National Cancer Database (NCDB) was queried from 2004 to 2015 for patients of all ages with intracranial WHO grade II to III ependymoma treated with surgery and 4500 to 7000 cGy of adjuvant radiotherapy. Pearson χ² test and multivariate logistic regression analyses were used to assess clinicodemographic factors and patterns of care. After propensity-score matching, OS was assessed with Kaplan-Meier analyses and doubly robust estimation with multivariate Cox proportional hazards modeling.

RESULTS

Of the 1153 patients meeting criteria, 529 (46%) received ≤ 5400 cGy and 624 (54%) received > 5400 cGy. At a median follow-up of 54.5 months, an OS benefit was observed for > 5400 cGy in pediatric patients aged 2-18 years (hazard ratio [HR] 0.53; 95% confidence interval [CI] 0.28-0.99, P = 0.047). No OS difference was found between ≤ 5400 cGy and > 5400 cGy in pediatric patients aged < 2 years (P = 0.819) or in adults (P = 0.180). Increasing age, WHO grade III, subtotal resection, and receipt of chemotherapy portended worse OS. Age 2 to 18 years, WHO III grade, supratentorial location, and receipt of chemotherapy were associated with receiving > 5400 cGy.

CONCLUSION

Adjuvant radiotherapy dose > 5400 cGy was associated with improved OS for children aged 2-18 years with WHO grade II-III intracranial ependymoma. No OS benefit was found with > 5400 cGy in adults or children less than two years of age.

Clinical outcomes following proton therapy for children with central nervous system tumors referred overseas

BACKGROUND

International, multidisciplinary care of children with central nervous system (CNS) tumors presents unique challenges. The aim of this study is to report patient outcomes of U.K. children referred for proton therapy to a North American facility.

METHODS

From 2008 to 2016, 166 U.K. children with approved CNS tumors were treated with proton therapy at a single academic medical center in the United States. Median age was 7 years (range, 1-19). Median follow-up was 2.6 years.

RESULTS

The 3-year actuarial overall survival (OS) and local control (LC) rates were 96% and 91%, respectively, for the overall group, 92% and 85% for the ependymoma subgroup (n = 57), 95% and 88% for the low-grade glioma subgroup (n = 54), and 100% and 100%, respectively, for the craniopharyngioma subgroup (n = 45). Cyst expansion was observed in 13 patients, including one case resulting in visual impairment. Serious side effects included new-onset seizures in three patients (1.8%), symptomatic vasculopathy in three patients (1.8%), and symptomatic brainstem necrosis in one patient (0.6%).

CONCLUSIONS

In this cohort of British children referred overseas for proton therapy, disease control does not appear compromised, toxicity is acceptable, and improvement in long-term function is anticipated in survivors owing to the reduced brain exposure afforded by proton therapy.

Outcomes After Reirradiation for Recurrent Pediatric Intracranial Ependymoma

PURPOSE

To determine the long-term outcomes and the optimal dose and volume for reirradiation of recurrent pediatric ependymoma.

METHODS AND MATERIALS

Patients with recurrent ependymoma treated with a second course of fractionated radiation therapy (RT2) were reviewed retrospectively. Eligible patients had localized, intracranial ependymoma at initial diagnosis that was treated with focal radiation (RT1) without craniospinal irradiation (CSI) and were aged ≤21 years at the time of RT2. The median doses of RT1, focal RT2, and CSI-RT2 were 59.4, 54, and 39.6 Gy, respectively. The primary endpoint, overall survival (OS), was measured from the first day of RT2.

RESULTS

We included 101 patients in the study. The median interval between RT1 and RT2 was 26.8 months (interquartile range, 18.0-43.1). The median durations of OS and freedom from progression (FFP) were 75.1 and 27.3 months, respectively. Male sex and anaplastic histology at recurrence were associated with decreased OS and FFP on multivariate analysis. Distant-only failure treated with CSI-RT2 was independently associated with improved OS compared with individuals with local failure treated with focal RT2 (hazard ratio 0.37; 95% confidence interval 0.16-0.87). Among individuals experiencing any distant failure after RT1, gain of chromosome 1q was adversely associated with poorer OS (hazard ratio 3.5; 95% confidence interval 1.1-10.6). No distant-only failures were observed in individuals with RT1 local failure who received CSI-RT2 (n=10). The 10-year cumulative incidence of grade ≥3 radiation necrosis after RT2 was 7.9%.

CONCLUSIONS

Reirradiation for relapsed pediatric ependymoma was well tolerated by most patients and resulted in long-term survival in a subset of patients. The best results were observed in patients who experienced distant-only failure after RT1 and were treated with CSI as part of RT2, without anaplasia at recurrence. The option of reirradiation should be discussed with patients who develop recurrent ependymoma.

[Radiation Necrosis in the Upper Cervical Spinal Cord in a Patient Treated with Proton Therapy after Radical Resection of the Fourth Ventricle Ependymoma]

BACKGROUND

Radiation necrosis in eloquent areas of the central nervous system (CNS) is one of the most serious forms of toxicity from radiation therapy. The occurrence of radiation necrosis in the CNS is described in a wide range of 3 months to 13 years after radiation therapy. The incidence of this complication covers a wide range of 3-47%. The potential advantage of proton therapy is the ability to reduce dose to normal tissue and escalate tumor dose. Proton beams enter and pass through the tissue with minimal dose deposition until they reach the end of their paths, where the peak of dose, known as the Bragg peak, occurs. Thereafter, a steep dose fall-off is evident. Such a precisely-distributed dose should reduce the toxicity of the treatment.

PATIENT

A 23 year-old female patient underwent radical microsurgical resection of anaplastic ependymoma that originated from the floor of the fourth ventricle. The tumor was growing into the foramen magnum dorsally from the medulla oblongata. Taking into account the age of the patient, the localization of the tumor and the required dose of 60 Gy, proton therapy was chosen due to the lower risk of damage to the brain stem. Radiation therapy was performed using pencil beam scanning and one dorsal field. Following this course of treatment, radiation necrosis of the medulla oblongata and the upper cervical spinal cord occurred with fatal clinical impact on the patient. The article analyses possible causes of this complication and a review of the current literature is given.

CONCLUSION

Despite the theoretical advantages of proton therapy, no clinical benefit in CNS tumors has yet been proven in comparison with modern methods of photon therapy. Proton therapy is accompanied by many uncertainties which can cause unpredictable complications, such as radiation necrosis at the edges of the target volume. Following proton therapy, there is not only a higher incidence of radiation necrosis but it occurs both sooner and to a higher degree. In cases of high anatomical complexity, the neurosurgeon should cooperate in the creation of the radiation treatment planning to ensure its optimization.Key words: brain tumors - ependymoma - radiation therapy - proton therapy - necrosis - radiation necrosis This work was partially supported by research project MH CZ - DRO (Faculty Hospital in Pilsen - FNPl, 00669806). The authors declare they have no potential conflicts of interest concerning drugs, products, or services used in the study. The Editorial Board declares that the manuscript met the ICMJE recommendation for biomedical papers.Submitted: 29. 6. 2017Accepted: 25. 7. 2017.

Silencing of DNA repair sensitizes pediatric brain tumor cells to γ-irradiation using gold nanoparticles

We present a nanoparticle (NP)-mediated delivery vehicle that effectively carries and protects siRNA in pediatric ependymoma (EP) and medulloblastoma (MB) cells. The delivery vehicle consists of gold NPs coated with a polymeric shell comprising polyethylene glycol (PG), chitosan and polyethyleneimine (Au-CP-PEI). NPs loaded with siRNA knocked down Ape1 expression by over 75% in both MB and EP cells. Further, this reduction in Ape1 expression is associated with an increase in DNA damage after irradiation. The results indicate that NP-associated delivery of siApe1 is a feasible approach to circumventing pediatric brain tumor resistance to radiation therapy.

Reoptimization of Intensity Modulated Proton Therapy Plans Based on Linear Energy Transfer

PURPOSE

We describe a treatment plan optimization method for intensity modulated proton therapy (IMPT) that avoids high values of linear energy transfer (LET) in critical structures located within or near the target volume while limiting degradation of the best possible physical dose distribution.

METHODS AND MATERIALS

To allow fast optimization based on dose and LET, a GPU-based Monte Carlo code was extended to provide dose-averaged LET in addition to dose for all pencil beams. After optimizing an initial IMPT plan based on physical dose, a prioritized optimization scheme is used to modify the LET distribution while constraining the physical dose objectives to values close to the initial plan. The LET optimization step is performed based on objective functions evaluated for the product of LET and physical dose (LET×D). To first approximation, LET×D represents a measure of the additional biological dose that is caused by high LET.

RESULTS

The method is effective for treatments where serial critical structures with maximum dose constraints are located within or near the target. We report on 5 patients with intracranial tumors (high-grade meningiomas, base-of-skull chordomas, ependymomas) in whom the target volume overlaps with the brainstem and optic structures. In all cases, high LET×D in critical structures could be avoided while minimally compromising physical dose planning objectives.

CONCLUSION

LET-based reoptimization of IMPT plans represents a pragmatic approach to bridge the gap between purely physical dose-based and relative biological effectiveness (RBE)-based planning. The method makes IMPT treatments safer by mitigating a potentially increased risk of side effects resulting from elevated RBE of proton beams near the end of range.

Clinical evidence of variable proton biological effectiveness in pediatric patients treated for ependymoma

BACKGROUND AND PURPOSE

A constant relative biological effectiveness (RBE) is used for clinical proton therapy; however, experimental evidence indicates that RBE can vary. We analyzed pediatric ependymoma patients who received proton therapy to determine if areas of normal tissue damage indicated by post-treatment image changes were associated with increased biological dose effectiveness.

MATERIAL AND METHODS

Fourteen of 34 children showed T2-FLAIR hyperintensity on post-treatment magnetic resonance (MR) images. We delineated regions of treatment-related change and calculated dose and linear energy transfer (LET) distributions with Monte Carlo. Voxel-level image change data were fit to a generalized linear model incorporating dose and LET. Cross-validation was used to determine model parameters and for receiver operating characteristic curve analysis. Tolerance dose (TD50; dose at which 50% of patients would experience toxicity) was interpolated from the model.

RESULTS

Image changes showed dependence on increasing LET and dose. TD50 decreased with increasing LET, indicating an increase in biological dose effectiveness. The cross-validated area under the curve for the model was 0.91 (95% confidence interval 0.88-0.94).

CONCLUSIONS

Our correlation of changes on MR images after proton therapy with increased LET constitutes the first clinical evidence of variable proton biological effectiveness.

Evaluation of Integral Dose in Cranio-spinal Axis (CSA) Irradiation with Conventional and Helical Delivery

In cranio-spinal axis (CSA) irradiation, patients are usually treated in the prone position with junctions between cranial and spinal fields. Collimator angle and pedestal rotations are introduced to obtain coplanar alignment of the matched junction. Furthermore, daily moving junctions are commonly used to feather out the junctional dose as additional safe-guards to avoid radiation myelopathy.

Helical tomotherapy integrates linear accelerator and CT technology capable of delivering CSA treatment without geometric matches or feathering of junctions. The patient is treated with helical beams in the supine position. Since CSA is used mainly in the pediatric population, the potential increase in integral dose to structures or the whole body from linac- or tomotherapy-based IMRT raises concerns of increased rates of secondary malignancies.

In this study, we will present an integral dose comparison between conventional CSA (3D) and helical delivery to the CSA (TOMO) utilizing the Tomotherapy Hi-ART system for three pediatric patients. Integral dose was calculated for organ at risk (OAR), two targets (PTV-BRAIN and PTV-SPINE), entire planning CT data set and to the healthy tissue (entire CT-DATA SET minus the PTV).

Overall integral dose was 8% higher in the TOMO plans for Patients #1 and #3, but 2% lower in Patient #2. DVH analysis shows that TOMO plans give lower doses to larger volumes and higher doses to smaller volumes of tissue in all three cases. The advantages of the TOMO plans are minimization of matched junctions and better sparing of most OARs. With increased computational and memory power in the tomotherapy planning station, the excess integral dose to the healthy tissue can be re-distributed within the patient and in turn the total integral dose can be same or lower than in conventional delivery. The impact of a small increase in overall integral dose and the associated risks of secondary malignancies are unknown. Long-term follow-up is needed to answer this question.

Tumor pseudoprogression and true progression following gamma knife radiosurgery for recurrent ependymoma

BACKGROUND

Gamma knife radiosurgery (GKRS) has become an effective salvage therapeutic option for recurrent ependymomas. However, its effectiveness can be assessed only by neuroimaging before clinical deterioration occurs. We analyzed the evolution of post-GKRS magnetic resonance imaging (MRI) features and sought to establish the feasibility of timely appropriate clinical management of the recurrent tumors.

METHODS

We retrospectively investigated 19 recurrent ependymomas of 11 patients treated with GKRS in our hospital from 1994 to 2013. All included tumors had sequential MRI at 3-6-month intervals, and tumor response was volumetrically calculated on consecutive MRI.

RESULTS

Post-GKRS tumors might show an increased enhancement or loss of enhancement associated with tumor enlargement or straight shrinkage. Seven of 19 tumors (37%) had continuously regressed or remained stable up to the last follow-up. Twelve of 19 tumors (63%) showed enlargement of enhancing lesions through examination of the post-GKRS follow-up MRI within the first 18 months. Five of 12 tumors (42%) showed continuous enlargement, which was interpreted as true progression; seven of 12 (58%) exhibited transient increasing enhanced volume that resolved within 6 months, and which was interpreted as pseudoprogression. There was no significant association between the presence of pseudoprogression and the pathological grades or locations of the tumors, and the concomitant chemotherapy or previous radiotherapy. Statistically significant differences were found for mean apparent diffusion coefficient (ADC) values and ADC ratio (prior to and after GKRS) of enhancing lesions between pseudoprogression and true progression.

CONCLUSION

The MRI patterns of post-GKRS recurrent ependymomas are heterogeneous. Transient increased tumor volume may represent pseudoprogression, whose final tumor control rate was not significantly different from those cases with straight tumor shrinkage. ADC values, ADC ratio, and sequential follow-up MRI scans are beneficial to differentiate between pseudoprogression and true progression, and help guide clinical management.

Anaplastic extramedullary cervical ependymoma with leptomeningeal metastasis

We present a rare extramedullary ependymoma with diffuse spinal metastatic disease, and review the previous reports of extramedullary spinal ependymomas. Ependymomas are the most common intramedullary spinal cord tumor in adults. These tumors rarely present as extramedullary masses. We treated a 23-year-old man with a history of progressive neck, shoulder and arm pain, with sensory and motor symptoms in the C7 dermatome. MRI of the cervical spine demonstrated a ventral contrast-enhancing lesion with evidence of enhancement along the dura and spinal cord of the upper cervical spine, thoracic spine, and cauda equina. He underwent a tumor debulking procedure without complications. Following surgery, he received craniospinal radiation to treat the remaining tumor and diffuse leptomeningeal disease. The final pathology of the tumor revealed that is was a World Health Organization Grade III anaplastic ependymoma. At the 1 year follow-up, the patient had stable imaging and had returned to his preoperative functional status. Of the 19 reported patients with primary intradural, extramedullary spinal ependymomas, two had extradural components and seven had anaplastic grades. Only one tumor with an anaplastic grade resulted in metastatic disease, but without spinal recurrence. To our knowledge, this is the first report of an intradural, extramedullary spinal ependymoma with an anaplastic grade, presenting with concomitant diffuse, nodular leptomeningeal metastasis involving the upper cervical spine, thoracic spine, conus medullaris, and cauda equina. Similar to the treatment of intramedullary ependymomas with metastasis, this patient underwent an aggressive debulking procedure followed by radiation therapy to the entire neuroaxis.