Frontline and Relapsed Rhabdomyosarcoma (FAR-RMS) Clinical Trial: A Report from the European Paediatric Soft Tissue Sarcoma Study Group (EpSSG)

The Frontline and Relapsed Rhabdomyosarcoma (FaR-RMS) clinical trial is an overarching, multinational study for children and adults with rhabdomyosarcoma (RMS). The trial, developed by the European Soft Tissue Sarcoma Study Group (EpSSG), incorporates multiple different research questions within a multistage design with a focus on (i) novel regimens for poor prognostic subgroups, (ii) optimal duration of maintenance chemotherapy, and (iii) optimal use of radiotherapy for local control and widespread metastatic disease. Additional sub-studies focusing on biological risk stratification, use of imaging modalities, including [18F]FDG PET-CT and diffusion-weighted MRI imaging (DWI) as prognostic markers, and impact of therapy on quality of life are described. This paper forms part of a Special Issue on rhabdomyosarcoma and outlines the study background, rationale for randomisations and sub-studies, design, and plans for utilisation and dissemination of results.

The organization of care in pediatric radiotherapy across SIOP Europe affiliated centers: A multicenter survey in the framework of the 'Joint Action on Rare Cancers' project

BACKGROUND/PURPOSE

To reduce inequalities among SIOPE-affiliated countries, standard and optional levels to deliver 'Good Clinical Practice' compliant treatment in pediatric radiation oncology have been published. The aim of this project was to map the availability of pediatric radiotherapy resources across SIOPE-affiliated radiotherapy departments.

MATERIALS/METHODS

An online survey with 34 questions was distributed to 246 radiotherapy departments across 35 SIOPE-affiliated countries. In addition to demographic data, 15 general items related to the organization of the radiotherapy process, and 10 radiotherapy-specific items were defined. For each of the 25 items, sum scores were calculated per center and country. Mann-Whitney U tests were used to analyze associations.

RESULTS

Between March-June 2019, 121 departments (49 %) out of 31 countries (89 %) completed the survey. At center level, involvement of core disciplines in tumor boards (28 %), and integration of dedicated pediatric radiation therapy technologists (24 %) are limited, while rare & complex brachytherapy procedures are performed in many centers (23 %). For general and radiotherapy-specific items respectively, a relevant variation of sum scores was observed across countries (Δgeneral: ≤10 points; ΔRT_specific: ≤5 points) and among centers within a country (Δgeneral: ≤9 points; ΔRT_specific: ≤6 points). Sum scores for general and radiotherapy-specific items were higher in countries with a high-income (p < 0.01) and higher health development index (p < 0.01). A larger annual number of irradiated pediatric patients was associated with higher sum scores for general items (p < 0.01).

CONCLUSION

This survey demonstrates the disparities in organization of pediatric radiotherapy departments between SIOPE-affiliated countries and centers within the same country. Investment is needed to reduce inequalities in pediatric radiotherapy care.

The need for consensus on delineation and dose constraints of dentofacial structures in paediatric radiotherapy: Outcomes of a SIOP Europe survey

Background and purpose

Children receiving radiotherapy for head-and-neck tumours often experience severe dentofacial side effects. Despite this, recommendations for contouring and dose constraints to dentofacial structures are lacking in clinical practice. We report on a survey aiming to understand current practice in contouring and dose assessment to dentofacial structures.

Methods

A digital survey was distributed to European Society for Paediatric Oncology members of the Radiation Oncology Working Group, and member-affiliated centres in Europe, Australia, and New Zealand. The questions focused on clinical practice and aimed to establish areas for future development.

Results

Results from 52 paediatric radiotherapy centres across 27 countries are reported. Only 29/52 centres routinely delineated some dentofacial structures, with the most common being the mandible (25 centres), temporo-mandibular joint (22), dentition (13), orbit (10) and maxillary bone (eight). For most bones contoured, an 'As Low As Reasonably Achievable' dose objective was implemented. Only four centres reported age-adapted dose constraints.The largest barrier to clinical implementation of dose constraints was firstly, the lack of contouring guidance (49/52, 94%) and secondly, that delineation is time-consuming (33/52, 63%). Most respondents who routinely contour dentofacial structures (25/27, 90%) agreed a contouring atlas would aid delineation.

Conclusion

Routine delineation of dentofacial structures is infrequent in paediatric radiotherapy. Based on survey findings, we aim to 1) define a consensus-contouring atlas for dentofacial structures, 2) develop auto-contouring solutions for dentofacial structures to aid clinical implementation, and 3) carry out treatment planning studies to investigate the importance of delineation of these structures for planning optimisation.

Facial deformation following treatment for pediatric head and neck rhabdomyosarcoma; the difference between treatment modalities. Results of a trans-Atlantic, multicenter cross-sectional cohort study

BACKGROUND

The four different local therapy strategies used for head and neck rhabdomyosarcoma (HNRMS) include proton therapy (PT), photon therapy (RT), surgery with radiotherapy (Paris-method), and surgery with brachytherapy (AMORE). Local control and survival is comparable; however, the impact of these different treatments on facial deformation is still poorly understood. This study aims to quantify facial deformation and investigates the differences in facial deformation between treatment modalities.

METHODS

Across four European and North American institutions, HNRMS survivors treated between 1990 and 2017, more than 2 years post treatment, had a 3D photograph taken. Using dense surface modeling, we computed facial signatures for each survivor to show facial deformation relative to 35 age-sex-ethnicity-matched controls. Additionally, we computed individual facial asymmetry.

FINDINGS

A total of 173 HNRMS survivors were included, survivors showed significantly reduced facial growth (p < .001) compared to healthy controls. Partitioned by tumor site, there was reduced facial growth in survivors with nonparameningeal primaries (p = .002), and parameningeal primaries (p ≤.001), but not for orbital primaries (p = .080) All patients were significantly more asymmetric than healthy controls, independent of treatment modality (p ≤ .001). There was significantly more facial deformation in orbital patients when comparing RT to AMORE (p = .046). In survivors with a parameningeal tumor, there was significantly less facial deformation in PT when compared to RT (p = .009) and Paris-method (p = .007).

INTERPRETATION

When selecting optimal treatment, musculoskeletal facial outcomes are an expected difference between treatment options. These anticipated differences are currently based on clinicians' bias, expertise, and experience. These data supplement clinician judgment with an objective analysis highlighting the impact of patient age and tumor site between existing treatment options.

Radiotherapy quality assurance in paediatric clinical trials: first report from six QUARTET-affiliated trials

BACKGROUND AND PURPOSE

SIOP Europe's QUARTET project launched in 2016; aiming to improve access to high-quality radiotherapy for children and adolescents treated within clinical trials across Europe. The aim of this report is to present the profile of institutions participating in six QUARTET-affiliated trials and a description of the initial individual case review (ICR) outcomes.

METHODS

This is a two-part analysis. Firstly, using facility questionnaires, beam output audit certificates, and advanced technique credentialing records to create a profile of approved institutions, and secondly, collating trial records for ICRs submitted prior to 31/10/2022. Trials included are: SIOPEN HR-NBL1, SIOPEN-LINES, SIOPEN- VERITAS, SIOP-BTG HRMB, EpSSG-FaR-RMS, and SIOPEN HR-NBL2.

RESULTS

By 31/10/2022, a total of 103 institutions had commenced QUARTET site approval procedures to participate in QUARTET-affiliated trials; 66 sites across 20 countries were approved. These participating institutions were often paediatric referral sites with intensity modulated radiotherapy or proton beam therapy, designated paediatric radiation oncologists, and paediatric adapted facilities and imaging protocols available. In total, 263 patient plans were submitted for ICR, 254 ICRs from 15 countries were completed. ICRs had a rejection rate of 39.8%, taking an average of 1.4 submissions until approval was achieved. Target delineation was the most frequent reason for rejection.

CONCLUSION

The QUARTET facility questionnaire is a valuable tool for mapping resources, personnel, and technology available to children and adolescents receiving radiotherapy. Prospective ICR is essential for paediatric oncology clinical trials and should be prioritised to reduce protocol violations.

Nonmetastatic Rhabdomyosarcoma in Children and Adolescents: Overall Results of the European Pediatric Soft Tissue Sarcoma Study Group RMS2005 Study

Clinical trials frequently include multiple end points that mature at different times. The initial report, typically based on the primary end point, may be published when key planned co-primary or secondary analyses are not yet available. Clinical Trial Updates provide an opportunity to disseminate additional results from studies, published in JCO or elsewhere, for which the primary end point has already been reported.The RMS2005 study included two phase III randomized trials for high-risk (HR) and observational trials for low (LR), standard (SR), and very high-risk (VHR) patients who have been partially reported. Herein, we present a comprehensive report of results achieved for the complete unselected nonmetastatic cohort and analyze the evolution of treatment in comparison with previous European protocols. After a median follow-up of 73.1 months, the 5-year event-free survival (EFS) and overall survival (OS) of the 1,733 patients enrolled were 70.7% (95% CI, 68.5 to 72.8) and 80.4% (95% CI, 78.4 to 82.3), respectively. The results by subgroup: LR (80 patients) EFS 93.7% (95% CI, 85.5 to 97.3), OS 96.7% (95% CI, 87.2 to 99.2); SR (652 patients) EFS 77.4% (95% CI, 73.9 to 80.5), OS 90.6% (95% CI, 87.9 to 92.7); HR (851 patients) EFS 67.3% (95% CI, 64.0 to 70.4), OS 76.7% (95% CI, 73.6 to 79.4); and VHR (150 patients) EFS 48.8% (95% CI, 40.4 to 56.7), OS 49.7% (95% CI, 40.8 to 57.9). The RMS2005 study demonstrated that 80% of children with localized rhabdomyosarcoma could be long-term survivors. The study has established the standard of care across the European pediatric Soft tissue sarcoma Study Group countries with the confirmation of a 22-week vincristine/actinomycin D regimen for LR patients, the reduction of the cumulative ifosfamide dose in the SR group, and for HR disease, the omission of doxorubicin and the addition of maintenance chemotherapy.

Institutional experience of using active breathing control for paediatric and teenage patients receiving thoraco-abdominal radiotherapy

Introduction

Active Breathing Control (ABC) is a motion management strategy that facilitates reproducible breath-hold for thoracic radiotherapy (RT), which may reduce radiation dose to organs at risk (OARs). Reduction of radiation-induced toxicity is of high importance in younger patients. However, there is little published literature on the feasibility of ABC in this group. The purpose of this study was to report our experience of using ABC for paediatric and teenage patients.

Methods

Patients ≤18 years referred for thoracic RT using ABC at our centre from 2013-2021 were identified. Electronic records were retrospectively reviewed to obtain information on diagnosis, RT dose and technique, OAR dosimetry, tolerability of ABC, post-treatment imaging and early toxicity rates.

Results

12 patients completed RT and were able to comply with ABC during planning and for the duration of RT. Median age was 15.5 years (10-18 years). Diagnoses were: Hodgkin lymphoma (n = 5), mediastinal B-cell lymphoma (n = 1), Ewing sarcoma (n = 5) and rhabdomyosarcoma (n = 1). For mediastinal RT cases (n = 6), median dose delivered was 30.6Gy(19.8-40Gy), median mean heart dose was 11.4Gy(4.8-19.4Gy), median mean lung dose was 9.9Gy(5.7-14.5Gy) and mean lung V20 was 10.9%. For ipsilateral RT cases, (n = 6), median hemithorax and total doses to primary tumour were 18Gy(15-20Gy) and 52.2Gy(36-60Gy) respectively. Median mean heart dose was 19.5Gy(10.6-33.2Gy) and median mean lung dose was 17.7Gy(16.3-30.5Gy). Mean bilateral lung V20 was 39.6%. Median mean contralateral lung dose was 5.2Gy(3.5-11.6Gy) and mean contralateral lung V20 was 1.5%. At a median follow-up of 36 months, only 1 patient had symptomatic radiation pneumonitis having received further thoracic RT following relapse.

Conclusions

ABC is feasible and well tolerated in younger patients receiving RT. Children as young as 10 years are able to comply. Use of ABC results in OAR dosimetry which is comparable to similar data in adults and can facilitate RT for extensive thoracic sarcoma.

Perianal/perineal rhabdomyosarcoma: Results of the SIOP MMT 95, Italian RMS 96, and EpSSG RMS 2005 studies

BACKGROUND/OBJECTIVES

Rhabdomyosarcoma of the perianal/perineal region (PRMS) is rare, with poor survival and limited understanding of the functional consequences of treatment.

DESIGN/METHODS

International Society of Pediatric Oncology (SIOP) malignant mesenchymal tumor (MMT) 95, Italian RMS 96, and European paediatric Soft tissue sarcoma Study Group (EpSSG) RMS 2005 studies were interrogated to identify factors that impact survival; in RMS 2005, functional outcomes were analyzed.

RESULTS

Fifty patients (nonmetastatic) were identified, median age 6.4 years (range: 0.1-19.6): 29 male, 21 female. Tumors were >5 cm in 33 patients. Histopathological subtype was alveolar in 35. Lymph nodes were involved in 23 patients. In RMS 2005, 16/21 (76%) tested alveolar tumors had positive FOXO1 fusion status. Diagnostic biopsy was performed in 37. Primary resection (13) was complete (R0) in one. Delayed primary excision (16) was complete in three. Radiotherapy (RT) in 34/50 patients included external beam (28), brachytherapy (3), and both (3). Nodal RT was given in 16/23 N1 patients (70%). Median follow-up of alive patients (29) was 84.1 months (range: 3.6-221.1). Relapse or progression occurred in 24 patients (48%), 87% were fatal and most events (63%) were locoregional. Five-year event-free survival (EFS) was 47.8 (95% CI: 32.8-61.3), and 5-year overall survival (OS) was 52.6 (95% CI: 36.7-66.2), with age ≥10 years and tumor size >5 cm impacting 5-year EFS and OS (p < .05). Functional outcome data showed bowel, genito-urinary, and psychological issues; fecal incontinence in four of 21 survivors, and urinary symptoms in two of 21.

CONCLUSIONS

About 60% of patients with nonmetastatic PRMS survive; older patients and those with large tumors have the worst outcomes. Biopsy should be the initial procedure, and definitive local therapy individualized. Quality-of-life and functional studies are needed to better understand the consequences of treatment.

Local control of parameningeal rhabdomyosarcoma: An expert consensus guideline from the International Soft Tissue Sarcoma Consortium (INSTRuCT)

The International Soft Tissue Sarcoma Database Consortium (INSTRuCT) consists of a collaboration between the Children's Oncology Group (COG) Soft Tissue Sarcoma Committee, the European pediatric Soft Tissue Sarcoma Study Group (EpSSG), and the Cooperative Weichteilsarkom Studiengruppe (CWS). As part of the larger initiative of INSTRuCT to provide consensus expert opinions for clinical treatment of pediatric soft tissue sarcoma, we sought to provide updated, evidenced-based consensus guidelines for local treatment of parameningeal rhabdomyosarcoma using both existing literature as well as recommendations from the relevant cooperative group clinical trials. Overall, parameningeal rhabdomyosarcoma represents a distinctly challenging disease to treat, given its location near many critical structures in the head and neck, frequently advanced local presentation, and predilection for local failure. Definitive chemoradiation remains the standard treatment approach for parameningeal rhabdomyosarcoma, with surgery often limited to biopsy or salvage therapy for recurrent disease. In this consensus paper, we specifically discuss consensus guidelines and evidence for definitive local management with radiotherapy, with a focus on imaging for radiotherapy planning, dose and timing of radiation, approach for nodal irradiation, various radiation techniques, including proton therapy, and the limited role of surgical resection.

Neurological Symptom Improvement After Re-Irradiation in Patients With Diffuse Intrinsic Pontine Glioma: A Retrospective Analysis of the SIOP-E-HGG/DIPG Project

Purpose

The aim of this study is to investigate the spectrum of neurological triad improvement in patients with diffuse intrinsic pontine glioma (DIPG) treated by re-irradiation (re-RT) at first progression.

Methods

We carried out a re-analysis of the SIOP-E retrospective DIPG cohort by investigating the clinical benefits after re-RT with a focus on the neurological triad (cranial nerve deficits, ataxia, and long tract signs). Patients were categorized as “responding” or “non-responding” to re-RT. To assess the interdependence between patients’ characteristics and clinical benefits, we used a chi-square or Fisher’s exact test. Survival according to clinical response to re-RT was calculated by the Kaplan–Meier method.

Results

As earlier reported, 77% (n = 24/31) of patients had any clinical benefit after re-RT. Among 25/31 well-documented patients, 44% (n = 11/25) had improvement in cranial nerve palsies, 40% (n = 10/25) had improvement in long-tract signs, and 44% (11/25) had improvement in cerebellar signs. Clinical benefits were observed in at least 1, 2, or 3 out of 3 symptoms of the DIPG triad, in 64%, 40%, and 24%, respectively. Patients irradiated with a dose ≥20 Gy versus <20 Gy may improve slightly better with regard to ataxia (67% versus 23%; p-value = 0.028). The survival from the start of re-RT to death was not different between responding and non-responding DIPG patients (p-value = 0.871).

Conclusion

A median re-irradiation dose of 20 Gy provides a neurological benefit in two-thirds of patients with an improvement of at least one symptom of the triad. DIPG patients receiving ≥20 Gy appear to improve slightly better with regard to ataxia; however, we need more data to determine whether dose escalation up to 30 Gy provides additional benefits.

DIPG-24. Neurological symptom improvement after re-irradiation in patients with diffuse intrinsic pontine glioma (DIPG): A retrospective analysis of the SIOP-E-HGG/DIPG project

PURPOSE: To investigate the spectrum of neurological triad improvement in patients with diffuse intrinsic pontine glioma (DIPG) treated by re-irradiation (re-RT) at first progression. METHODS: Re-analysis of the SIOP-E retrospective DIPG cohort by investigating clinical benefits after re-RT with focus on the neurological triad. Patients were divided as "responding" or "non-responding" to re-RT. To assess the interdependence between patients’ characteristics and clinical benefits we used a Chi-Square or Fisher’s Exact test. Survival according to clinical response to re-RT was calculated by the Kaplan-Meier method. RESULTS: As earlier reported, 77% (n = 24/31) of patients had any clinical benefit after re-RT. Among 25/31 well documented patients, 44% (n=11/25) had improvement in cranial nerve palsies, 40% (n=10/25) in long-tract signs, 44% (11/25) in cerebellar signs. Clinical benefits were observed in at least 1, 2 or 3 out of 3 symptoms of the DIPG triad, in 64%, 40% and 24% respectively. Patients irradiated with a dose ≥ 20 Gy versus &lt; 20 Gy may improve slightly better with regards of ataxia (67% versus 23%; P-value = 0.028). The survival from the start of re-RT to death was not different between responding and non-responding DIPG patients (P-value = 0.871). CONCLUSION: A median re-irradiation dose of 20 Gy provides a neurological benefit in two-third of patients with an improvement of at least one symptom of the triad. DIPG patients receiving ≥20 Gy appear to improve slightly better with regards of ataxia, however we need more data to determine whether dose escalation up to 30 Gy provides additional benefit.

Circulating tumour DNA sequencing to determine therapeutic response and identify tumour heterogeneity in patients with paediatric solid tumours

OBJECTIVE

Clinical diagnostic sequencing of circulating tumour DNA (ctDNA) is well advanced for adult patients, but application to paediatric cancer patients lags behind.

METHODS

To address this, we have developed a clinically relevant (67 gene) NGS capture panel and accompanying workflow that enables sensitive and reliable detection of low-frequency genetic variants in cell-free DNA (cfDNA) from children with solid tumours. We combined gene panel sequencing with low pass whole-genome sequencing of the same library to inform on genome-wide copy number changes in the blood.

RESULTS

Analytical validity was evaluated using control materials, and the method was found to be highly sensitive (0.96 for SNVs and 0.97 for INDEL), specific (0.82 for SNVs and 0.978 for INDEL), repeatable (>0.93 [95% CI: 0.89-0.95]) and reproducible (>0.87 [95% CI: 0.87-0.95]). Potential for clinical application was demonstrated in 39 childhood cancer patients with a spectrum of solid tumours in which the single nucleotide variants expected from tumour sequencing were detected in cfDNA in 94.4% (17/18) of cases with active extracranial disease. In 13 patients, where serial samples were available, we show a close correlation between events detected in cfDNA and treatment response, demonstrate that cfDNA analysis could be a useful tool to monitor disease progression, and show cfDNA sequencing has the potential to identify targetable variants that were not detected in tumour samples.

CONCLUSIONS

This is the first pan-cancer DNA sequencing panel that we know to be optimised for cfDNA in children for blood-based molecular diagnostics in paediatric solid tumours.

Non-rhabdomyosarcoma soft-tissue sarcoma

Non-rhabdomyosarcoma soft-tissue sarcomas (NRSTS) comprise 4% of childhood cancers and consist of numerous histologic subtypes. Prognostic factors associated with poor outcome include high histologic grade, large tumor size, presence of metastases, and unresectability. Complete surgical resection is critical for the best oncologic outcomes and is prioritized in treatment algorithms. The use of radiation therapy (RT) and chemotherapy is based upon factors such as resectability, histologic grade, tumor size, and stage. North American and European trials are defining a risk-based approach to NRSTS to limit treatment-related toxicity and to maximize therapeutic efficacy. In this paper, we summarize the current roles of surgery, RT, and chemotherapy in NRSTS and describe ongoing research that is advancing the care of NRSTS patients.

Inter-clinician delineation variation for a new highly-conformal flank target volume in children with renal tumors: A SIOP-Renal Tumor Study Group international multicenter exercise

BACKGROUND AND PURPOSE

Recently, the SIOP-RTSG developed a highly-conformal flank target volume definition for children with renal tumors. The aims of this study were to evaluate the inter-clinician delineation variation of this new target volume definition in an international multicenter setting and to explore the necessity of quality assurance.

MATERIALS AND METHODS

Six pediatric renal cancer cases were transferred to ten radiation oncologists from seven European countries ('participants'). These participants delineated the pre- and postoperative Gross Tumor Volume (GTVpre/post), and Clinical Target Volume (CTV) during two test phases (case 1-2 and 3-4), followed by guideline refinement and a quality assurance phase (case 5-6). Reference target volumes (TVref) were established by three experienced radiation oncologists. The Dice Similarity Coefficient between the reference and participants (DSCref/part) was calculated per case. Delineations of case 5-6 were graded by four independent reviewers as 'per protocol' (0-4 mm), 'minor deviation' (5-9 mm) or 'major deviation' (≥10 mm) from the delineation guideline using 18 standardized criteria. Also, a major deviation resulting in underestimation of the CTVref was regarded as an unacceptable variation.

RESULTS

A total of 57/60 delineation sets were completed. The median DSCref/part for the CTV was 0.55 without improvement after sequential cases (case 3-4 vs. case 5-6: p = 0.15). For case 5-6, a major deviation was found for 5/18, 12/17, 18/18 and 4/9 collected delineations of the GTVpre, GTVpost, CTV-T and CTV-N, respectively. An unacceptable variation from the CTVref was found for 7/9 participants for case 5 and 6/9 participants for case 6.

CONCLUSION

This international multicenter delineation exercise demonstrates that the new consensus for highly-conformal postoperative flank target volume delineation leads to geometrical variation among participants. Moreover, standardized review showed an unacceptable delineation variation in the majority of the participants. These findings strongly suggest the need for additional training and centralized pre-treatment review when this target volume delineation approach is implemented on a larger scale.

Alveolar rhabdomyosarcoma with regional nodal involvement: Results of a combined analysis from two cooperative groups

BACKGROUND

Treatment of children and adolescents with alveolar rhabdomyosarcoma (ARMS) and regional nodal involvement (N1) have been approached differently by North American and European cooperative groups. In order to define a better therapeutic strategy, we analyzed two studies conducted between 2005 and 2016 by the European paediatric Soft tissue sarcoma Study Group (EpSSG) and Children's Oncology Group (COG).

METHODS

We retrospectively identified patients with ARMS N1 enrolled in either EpSSG RMS2005 or in COG ARST0531. Chemotherapy in RMS2005 comprised ifosfamide + vincristine + dactinomycin + doxorubicin (IVADo), IVA and maintenance (vinorelbine, cyclophosphamide); in ARST0531, it consisted of either vincristine + dactinomycin + cyclophosphamide (VAC) or VAC alternating with vincristine + irinotecan (VI). Local treatment was similar in both protocols.

RESULTS

The analysis of the clinical characteristics of 239 patients showed some differences between study groups: in RMS2005, advanced Intergroup Rhabdomyosarcoma Study Group (IRS) and large tumors predominated. There were no differences in outcomes between the two groups: 5-year event-free survival (EFS), 49% (95% confidence interval [CI]: 39-59) and 44% (95% CI: 30-58), and overall survival (OS), 51% (95% CI: 41-61) and 53.6% (95% CI: 40-68) in RMS2005 and ARST0531, respectively. In RMS2005, EFS of patients with FOXO1-positive tumors was significantly inferior to those with FOXO1-negative (49.3% vs 73%, P = .034). In contrast, in ARST0531, EFS of patients with FOXO1-positive tumors was 45% compared with 43.8% for those with FOXO1-negative.

CONCLUSIONS

The outcome of patients with ARMS N1 was similar in both protocols. However, patients with FOXO1 fusion-negative tumors enrolled in RMS2005 showed a significantly better outcome, suggesting that different strategies of chemotherapy may have an impact in the outcome of this subgroup of patients.

Radical radiotherapy for paediatric solid tumour metastases: An overview of current European protocols and outcomes of a SIOPE multicenter survey

PURPOSE/OBJECTIVE

About 20% of children with solid tumours (ST) present with distant metastases (DM). Evidence regarding the use of radical radiotherapy of these DM is sparse and open for personal interpretation. The aim of this survey was to review European protocols and to map current practice regarding the irradiation of DM across SIOPE-affiliated countries.

MATERIALS/METHODS

Radiotherapy guidelines for metastatic sites (bone, brain, distant lymph nodes, lung and liver) in eight European protocols for rhabdomyosarcoma, non-rhabdomyosarcoma soft-tissue sarcoma, Ewing sarcoma, neuroblastoma and renal tumours were reviewed. SIOPE centres irradiating ≥50 children annually were invited to participate in an online survey.

RESULTS

Radiotherapy to at least one metastatic site was recommended in all protocols, except for high-risk neuroblastoma. Per protocol, dose prescription varied per site, and information on delineation and treatment planning/delivery was generally missing. Between July and September 2019, 20/27 centres completed the survey. Around 14% of patients were deemed to have DM from ST at diagnosis, of which half were treated with curative intent. A clear cut-off for a maximum number of DM was not used in half of the centres. Regardless of the tumour type and site, conventional radiotherapy regimens were most commonly used to treat DM. When stereotactic radiotherapy was used, a wide range of fractionation regimens were applied.

CONCLUSION

Current radiotherapy guidelines for DM do not allow a consistent approach in a multicentre setting. Prospective (randomised) trials are needed to define the role of radical irradiation of DM from paediatric ST.

GCT-61. CORRELATION OF PATTERNS OF DISEASE RECURRENCE WITH RADIOTHERAPY TECHNIQUES AND DOSE IN INTRACRANIAL GERM CELL TUMOURS (icGCT): LESSONS FROM THE UK COHORT OF SIOP GCT96 STUDY

BACKGROUND

There are global variations in radiotherapy approaches for icGCT. An understanding of patterns of disease recurrence correlated with radiation techniques and doses is important in standardising and improving the quality of radiotherapy using high-precision techniques.

METHODS AND RESULTS

Data from 20 patients with tumour recurrence after treatment within the SIOP GCT96 study in the UK were analysed. Seven (35%) patients had germinoma and 13 (65%) had non-germinoma. Twelve patients had local recurrence, 5 had metastatic and 3 had local and metastatic disease. Radiotherapy details were retrieved in only 8 patients (40%). Six patients had received focal radiotherapy and two craniospinal radiotherapy. Of the patients who received focal radiotherapy, 4 had recurrence within the radiation portal, one had periventricular recurrence and one had marker-positive recurrence with no radiological lesions. Both patients who received CSI recurred within the CSF space. The main reasons for poor retrieval of treatment details were difficulty in retrieving archived information and that the study was conducted during a period before PACS or electronic radiotherapy records.

CONCLUSION

This study highlights the importance prospective data collection and analysis to understand the patterns of recurrence in icGCT. Even within a prospective study, radiotherapy techniques varied between centres. There is therefore an urgent need for centralised radiological review and prospective radiotherapy quality assurance measures in future clinical trials.

MBRS-33. TEMPORARY RESTORATION OF p53 ACTIVITY DURING FRACTIONATED RADIOTHERAPY IN A GROUP3 MEDULLOBLASTOMA GEMM REPRESENTS A POWERFUL TOOL FOR RADIOBIOLOGY STUDIES

TP53 pathway alterations are well-described events in medulloblastoma (MB) and are predictive of poor clinical outcome. Alterations are rare at diagnosis in Group3 (Gr3) and Group4, but enriched in Sonic Hedgehog and WNT subgroups. However, TP53 mutations are observed in all subgroups at relapse. Radiation therapy, along with surgery and chemotherapy, represents the standard of care treatment for MB. Loss of p53 function correlates with increased resistance to radiation in several cancers conferring poor survival for patients. In this study, we exposed the MYCN-driven/Trp53^kiki (with tamoxifen-inducible p53 activation) Gr3 MB GEMM to a clinically relevant fractionated radiation therapy (RT) regime, to assess the role of p53 in Gr3 radio-resistance and relapse. Mice exhibiting tumour progression (bioluminescence (BLI) signal >10⁹ photons/second) were randomized to treatment groups. A small animal radiation research platform was used to deliver CT-guided cranio-spinal irradiation (CSI) and a cranial boost (CB). Mice were followed for survival and tumour burden tracked using BLI. Bodyweight was monitored to evaluate treatment tolerability. Full dose radiation therapy (54Gy CB, 36Gy CSI, α/β=10) or dose modulation (12Gy CB, 8Gy CSI) was performed. The results showed comparable primary tumour regression in response to RT in p53 inactive and active backgrounds, followed by imminent relapse or prolonged remission respectively. No significant acute toxicity was observed. Temporary activation of p53 during RT improved tumour-free survival and decreased the incidence of relapse. In conclusion, we developed a new model which will help improve understanding of the radiobiology of high-risk MB and future preclinical trials.

Local staging and treatment in extremity rhabdomyosarcoma. A report from the EpSSG-RMS2005 study

Rhabdomyosarcoma of the extremities present with two main challenges: correct evaluation of initial regional nodal involvement and define adequate local treatment.

METHODS

Pediatric patients with localized rhabdomyosarcoma of the extremity included in the EpSSG-RMS2005 study between 2005 and 2014 were evaluated for staging, treatment, and survival. The outcome was compared to the preceding European SIOP-MMT studies.

RESULTS

Of the 162 patients included, histology was unfavorable in 113 (70%), 124 (77%) were younger than 10 years, 128 (79%) were IRS III, and 47 (29%) were node-positive. A regional node biopsy was performed in 97 patients (60%) and modified the lymph node stage in 15/97 (16%). Primary and delayed surgery was performed in 155 (96%) and radiotherapy delivered in 118 (73%) patients. Relapse occurred in 61 cases (38%), local in 14 (23%), regional in 13 (21%), distant in 22 (36%), and combined relapse in 12 (20%) with five progressive diseases (8%) and four secondary tumors (7%). Five-year event free (EFS) and overall survival (OS) were 58.4% (95%CI, 50.3-65.7) and 71.7% (63.6-78.4), respectively. In the previous studies MMT89 and MMT95, tumor surgery was performed in 32/53 (60%) and 74/82(90%), respectively, and radiotherapy delivered in 13/53 (25%) and 26/82 (30%), respectively. Five-year EFS and OS were 35.6%, and 50.3% in MMT89 and 54.3% and 68.2% in the MMT95 study.

CONCLUSIONS

Even if the lymph node staging was not always complete according to the RMS2005 protocol, node sampling changed lymph node status in a significant number of patients. Despite the higher rate of patients treated with locoregional radiotherapy, survival in RMS2005 did not improve compared to the previous European SIOP-MMT95 study.

Radiological pseudoprogression post-radiotherapy in a child with pineal germ cell tumour

Little is known about pseudoprogression in brain tumours other than gliomas. A 9-year-old male child with a pineal teratoma/germinoma underwent surgical resection followed by adjuvant chemo-radiotherapy. The magnetic resonance imaging scan 4 months post-radiotherapy showed a contrast-enhancing lesion within the surgical cavity suspicious of recurrence. These radiological findings subsequently resolved without any specific intervention. The child continues in remission 2 years post-treatment. This case illustrates the occurrence of pseudoprogression post-radiotherapy in intracranial GCT and highlights an unmet need for greater implementation of functional imaging techniques in paediatric neuro-oncology to avoid undue discontinuation of effective treatments or inappropriate enrolment in clinical trials.

Estimating brain volume loss after radiation therapy in children treated for posterior fossa tumors (Corpus callosum and whole brain volume changes following radiotherapy in children)

BACKGROUND

More than half of pediatric tumors of central nervous system (CNS) primarily originate in the posterior fossa and are conventionally treated with radiation therapy (RT).

OBJECTIVES

The objective of this study was to establish whether corpus callosum volumes (CCV) and whole brain volumes (WBV) are correlated and to determine the impact of whole-brain lowvs high-dose RT on brain parenchymal volume loss as assessed using each technique.

MATERIAL AND METHODS

Of the 30 identified children (6-12 years) with newly diagnosed posterior fossa tumors treated with cranial RT, including focal and whole-brain RT, suitable imaging was obtained for 23. Radiotherapy regimens were the following: no whole-brain RT (Group 1, n = 7), low-dose whole-brain RT (<30 Gy, Group 2, n = 9) and high-dose whole-brain RT (>30 Gy, Group 3, n = 7) in addition to focal boost. Magnetic resonance images (MRIs) were analyzed at baseline and follow-up (median 14 months). The CCVs were manually segmented on midline sagittal slice (n = 23), while WBVs were segmented semi-automatically using Freesurfer (n = 15). This was done twice (6-month interval) for all baseline CCV measurements and 5 randomly selected WBV measurements to establish measurement reproducibility. Correlations between CCV and WBV were investigated and percentage of children demonstrating reduction in CCV or WBV noted.

RESULTS

Correlation between baseline CCV and WBV was not significant (p = 0.37). Measurement reproducibility was from 6% to -9% for CCV and from 4.8% to -1.2% for WBV. Among the children studied, 30.4% (7/23) had >9% reduction in CCV at follow-up, while 33.3% (5/15) had >1.2% reduction in WBV. Five of 7 patients with CCV loss were not picked up by WBV measurements. Similarly, 3 of 5 patients with WBV loss were not picked up by CCV measurements.

CONCLUSIONS

The CCV and the WBV are unrelated and may indicate different brain parenchymal losses following RT. Up to a third of posterior fossa tumors treated with RT have measurable CCV or WBV loss; incidence was equivalent in lowvs high-dose whole-brain RT.

A tailored molecular profiling programme for children with cancer to identify clinically actionable genetic alterations

BACKGROUND

For children with cancer, the clinical integration of precision medicine to enable predictive biomarker-based therapeutic stratification is urgently needed.

METHODS

We have developed a hybrid-capture next-generation sequencing (NGS) panel, specifically designed to detect genetic alterations in paediatric solid tumours, which gives reliable results from as little as 50 ng of DNA extracted from formalin-fixed paraffin-embedded (FFPE) tissue. In this study, we offered an NGS panel, with clinical reporting via a molecular tumour board for children with solid tumours. Furthermore, for a cohort of 12 patients, we used a circulating tumour DNA (ctDNA)-specific panel to sequence ctDNA from matched plasma samples and compared plasma and tumour findings.

RESULTS

A total of 255 samples were submitted from 223 patients for the NGS panel. Using FFPE tissue, 82% of all submitted samples passed quality control for clinical reporting. At least one genetic alteration was detected in 70% of sequenced samples. The overall detection rate of clinically actionable alterations, defined by modified OncoKB criteria, for all sequenced samples was 51%. A total of 8 patients were sequenced at different stages of treatment. In 6 of these, there were differences in the genetic alterations detected between time points. Sequencing of matched ctDNA in a cohort of extracranial paediatric solid tumours also identified a high detection rate of somatic alterations in plasma.

CONCLUSION

We demonstrate that tailored clinical molecular profiling of both tumour DNA and plasma-derived ctDNA is feasible for children with solid tumours. Furthermore, we show that a targeted NGS panel-based approach can identify actionable genetic alterations in a high proportion of patients.

Managing peritoneal involvement in children and young people with rhabdomyosarcoma: A single-center experience from the United Kingdom

We describe our experience in managing nine children and adolescents with rhabdomyosarcoma (RMS) and peritoneal involvement. The radiological pattern of peritoneal involvement was diverse from only ascites to solid peritoneal mass/omental caking. Treatment included systemic chemotherapy in all, surgery in three, and radiotherapy in eight. Two patients with presumed nonmalignant ascites, no solid peritoneal metastasis, nonalveolar histology, near-complete resection of residual disease, and radiotherapy survived long term. One patient has just completed treatment, and the remaining six relapsed/progressed at the time of reporting. Five of six patients died after a median of 5 (3-7) months from relapse despite second-line chemotherapy.

Embryonal and Alveolar Rhabdomyosarcoma in Adults: Real-Life Data From a Tertiary Sarcoma Centre

AIMS

Embryonal and alveolar rhabdomyosarcoma (ERMS, ARMS) are subtypes of RMS that mainly occur in children, with relatively good outcomes. The incidence in adults is extremely low and survival is significantly worse compared with children. Data are scarce and literature generally combines all RMS subtypes, including pleomorphic RMS, which primarily occurs in adults and behaves more like undifferentiated pleomorphic sarcoma. The aim of this study was to evaluate patient and tumour characteristics, outcome and prognostic factors in adult patients with ERMS and ARMS.

MATERIALS AND METHODS

All adult (18 years or older) ERMS and ARMS patients (presenting 1990-2016) were identified from a prospectively maintained database and were included in this analysis.

RESULTS

Overall, 66 patients were included (42 men, 24 women). The median age at presentation was 28 years (range 18-71). The median overall survival for all ARMS (n = 42) and ERMS (n = 24) patients was 18 months, with a 5-year overall survival rate of 27%. Patients presenting with localised disease (n = 38, 58%) and metastatic disease (n = 25, 42%), had a 5-year overall survival rate of 36% and 11%, respectively. In univariate analysis we found alveolar subtype, fusion gene positivity, infiltrative tumour and metastatic presentation to be negative prognostic factors.

CONCLUSION

Survival in adult ERMS and ARMS patients is poor and the current data may be useful in the design of trials with novel agents. Ideally, paediatric and adult oncologists should set up trials together to get a better understanding of biological, genetic and clinically relevant factors in this disease.

A step and shoot intensity modulated technique for total body irradiation

Introduction

Total body irradiation (TBI) is a part of the conditioning regimen for bone marrow transplant.At the Royal Marsden (Sutton, UK) and Rigshospitalet (Copenhagen, Denmark), we introduced a step and shoot IMRT (SS IMRT) technique for TBI. This technique requires no equipment other than that used to deliver other external beam radiation. In this paper, we describe this technique and report on data from the two clinics.

Materials and methods

The patients were positioned supine, supported by vacuum bag(s). The entire body of the patients were CT scanned with 5 mm slices. Multiple multi-leaf collimator (MLC) defined fields were used.In-vivo dosimetry was performed at the Royal Marsden for 113 patients.Calculated doses for 18 adult and 4 paediatric patients from Rigshospitalet were extracted.

Results

The in-vivo data from the Royal Marsden showed that the mean TLD measured dose difference was -1.9% with a standard deviation of 4.5%.SS IMRT plans for 22 patients from Rigshospitalet resulted in mean doses to the brain, lungs and kidneys all within the range of 11.1-11.8 Gy, while the V(12 Gy) was below 5% for the brain, 2% for the lungs and 0% for the kidneys.

Discussion

SS IMRT is feasible for TBI and can deliver targeted doses to the organs at risk.

Recommendations for the organisation of care in paediatric radiation oncology across Europe: a SIOPE-ESTRO-PROS-CCI-Europe collaborative project in the framework of the JARC

Disparities in survival and long-term side-effects from paediatric cancer are observed across European Society for Paediatric Oncology (SIOPE)-affiliated countries. The Joint Action on Rare Cancers (JARC) is a project supported by the European Union and member states aiming to formulate recommendations on rare cancers, including paediatric malignancies, to reduce inequalities and to improve health outcomes. Most paediatric cancers are treated by a combination of systemic agents, surgery and/or radiotherapy. Radiotherapy for children is becoming increasingly complex because of the growing availability of new modalities and techniques and the evolution in molecular biology. These added challenges have the potential to enhance disparities in survival and side-effects between countries, but also among centres in the same country. To tackle radiotherapy-related inequalities, representatives of SIOPE, European SocieTy for Radiotherapy and Oncology, Paediatric Radiation Oncology Society and Childhood Cancer International-Europe defined 'standard' and 'optional' levels to deliver Good Clinical Practice-compliant treatment in paediatric radiation oncology with a focus on patient-related care, education and training. In addition, more than 250 paediatric radiotherapy centres across the SIOPE-affiliated countries have been mapped. For a better understanding of resources in paediatric radiotherapy, JARC representatives are working on an online survey for paediatric radiation oncologists of each centre in SIOPE-affiliated countries. The outcome of this survey will give an insight into the strengths and weaknesses of paediatric radiotherapy across SIOPE-affiliated countries and can be relevant for European Reference Networks in terms of collaboration pathways and referrals in paediatric radiotherapy.

Post-radiotherapy apparent diffusion coefficient (ADC) in children and young adults with high-grade gliomas and diffuse intrinsic pontine gliomas

Objectives: Diffusion-weighted magnetic resonance imaging (DW-MRI) offers potential to monitor response and predict survival in high-grade gliomas (HGG) and diffuse intrinsic pontine gliomas (DIPG). We hypothesized that post-radiotherapy DW-MRI may provide prognostic imaging biomarkers in children and young adults with these tumors. Methods: Patients aged ≤21 years diagnosed between 2005 and 2012 were eligible. The tumor median apparent diffusion coefficient (ADC) and its 5th percentile (C5-ADC) were determined at the first post-radiotherapy scan and at the time of radiological progression. DW-MRI parameters were correlated with survival endpoints, temozolomide use and pseudoprogression, when it occurred. Results: Out of 40 patients (20 HGG, 20 DIPG), 23 had evaluable DW-MRI post-radiotherapy and 25 at radiological progression. There were 6 episodes of pseudoprogression. Hazard ratios (95%CI) for progression-free survival were 0.998 (0.993-1.003) for median ADC and 1.003 (0.996-1.010) for C5-ADC. Hazard ratios (95%CI) for overall survival were 1.0009 (0.996-1.006) for median ADC and 0.998 (0.992-1.004) for C5-ADC. Post-radiotherapy median and C5-ADC values were not significantly different between patients treated with radiotherapy alone versus radiotherapy/temozolomide. The median and C5-ADC values were not significantly different at the time of pseudoprogression compared to those at tumor progression. Conclusions: Post-radiotherapy median ADC and C5-ADC were not prognostic, nor able to differentiate radiosensitization with temozolomide or occurrence of pseudoprogression in this cohort of HGG and DIPG patients. Further exploration of alternative DW parameters, study timepoints or data modeling may contribute to the development of prognostic/predictive imaging biomarkers for children and young adults with HGG or DIPG.

Survival benefit for patients with diffuse intrinsic pontine glioma (DIPG) undergoing re-irradiation at first progression: A matched-cohort analysis on behalf of the SIOP-E-HGG/DIPG working group

BACKGROUND

Overall survival (OS) of patients with diffuse intrinsic pontine glioma (DIPG) is poor. The purpose of this study is to analyse benefit and toxicity of re-irradiation at first progression.

METHODS

At first progression, 31 children with DIPG, aged 2-16 years, underwent re-irradiation (dose 19.8-30.0 Gy) alone (n = 16) or combined with systemic therapy (n = 15). At initial presentation, all patients had typical symptoms and characteristic MRI features of DIPG, or biopsy-proven high-grade glioma. An interval of ≥3 months after upfront radiotherapy was required before re-irradiation. Thirty-nine patients fulfilling the same criteria receiving radiotherapy at diagnosis, followed by best supportive care (n = 20) or systemic therapy (n = 19) at progression but no re-irradiation, were eligible for a matched-cohort analysis.

RESULTS

Median OS for patients undergoing re-irradiation was 13.7 months. For a similar median progression-free survival after upfront radiotherapy (8.2 versus 7.7 months; P = .58), a significant benefit in median OS (13.7 versus 10.3 months; P = .04) was observed in favour of patients undergoing re-irradiation. Survival benefit of re-irradiation increased with a longer interval between end-of-radiotherapy and first progression (3-6 months: 4.0 versus 2.7; P < .01; 6-12 months: 6.4 versus 3.3; P = .04). Clinical improvement with re-irradiation was observed in 24/31 (77%) patients. No grade 4-5 toxicity was recorded. On multivariable analysis, interval to progression (corrected hazard ratio = .27-.54; P < .01) and re-irradiation (corrected hazard ratio = .18-.22; P < .01) remained prognostic for survival. A risk score (RS), comprising 5 categories, was developed to predict survival from first progression (ROC: .79). Median survival ranges from 1.0 month (RS-1) to 6.7 months (RS-5).

CONCLUSIONS

The majority of patients with DIPG, responding to upfront radiotherapy, do benefit of re-irradiation with acceptable tolerability.

Pseudoprogression in children, adolescents and young adults with non-brainstem high grade glioma and diffuse intrinsic pontine glioma

Pseudoprogression (PsP) is a treatment-related phenomenon which hinders response interpretation. Its prevalence and clinical impact have not been evaluated in children/adolescents. We assessed the characteristics, risk factors and prognosis of PsP in children/adolescents and young-adults diagnosed with non-brainstem high grade gliomas (HGG) and diffuse intrinsic pontine gliomas (DIPG). Patients aged 1-21 years diagnosed with HGG or DIPG between 1995 and 2012 who had completed radiotherapy were eligible. PsP was assessed according to study-specific criteria and correlated with first-line treatment, molecular biomarkers and survival. Ninety-one patients (47 HGG, 44 DIPG) were evaluable. Median age: 10 years (range, 2-20). Eleven episodes of PsP were observed in 10 patients (4 HGG, 6 DIPG). Rates of PsP: 8.5 % (HGG); 13.6 % (DIPG). Two episodes of PsP were based on clinical findings alone; nine episodes had concurrent radiological changes: increased size of lesions (n = 5), new focal enhancement (n = 4). Temozolomide, MGMT methylation or H3F3A mutations were not found to be associated with increased occurrence of PsP. For HGG, 1-year progression-free survival (PFS) was 41.9 % no-PsP versus 100 % PsP (p = 0.041); differences in 1-year overall survival (OS) were not significant. For DIPG, differences in 1-year PFS and OS were not statistically significant. Hazard ratio (95 %CI) of PsP for OS was 0.551 (0.168-1.803; p = 0.325) in HGG; and 0.308 (0.107-0.882; p = 0.028) in DIPG. PsP occurred in both pediatric HGG and DIPG patients at a comparable rate to adult HGG. PsP was associated with improved 1-yr PFS in HGG patients. PsP had a protective effect upon OS in DIPG patients.