The impact of radiotherapy in metastatic rhabdomyosarcoma: Results from the XXXX study: Running title: Radiotherapy in metastatic rhabdomyosarcoma.

PURPOSE: Radiation oncologists utilize radiation variably for children with metastatic rhabdomyosarcoma (RMS). Data from the XXXX study was retrospectively analyzed to validate the prior observation that the use of radiation is associated with improved outcomes, and guide future recommendations on radiation use in this patient group. METHODS AND MATERIALS: The radiation delivered to 216 patients aged 0-21 years with metastatic RMS was retrospectively reviewed and classified as radical (all sites of disease irradiated within the protocol parameters), partial (some sites irradiated within the protocol parameters) and none (no radiation or delivered outside the protocol parameters). Landmark analysis excluded those with an event prior to day 221. Overall survival (OS) and progression free survival (PFS) were modelled using the Kaplan-Meier method to investigate the impact of radiation. The joint effect of treatment and known prognostic factors was examined using the Cox regression model. RESULTS: Overall 56 patients received radical, 104 partial and 56 no radiation per protocol. Due to non-randomised data, the groups were heterogeneous, particularly fewer sites of metatatic disease and less with bone metatases in those receiving radical radiation. 3-year PFS was 62.0% (95%CI 47.9-73.4) v 39.5% (29.8-49.1) v 30.1% (18.7-42.3)(p=0.002) for radical v partial v no radiotherapy respectively; 3-year OS was 70.1 % (55.8-80.6) v 53.1% (42.6-62.5) v 52.3% (38.3-64.5)(p=0.019) respectively. Multivariable analysis confirmed incremental improvement in OS with additional radiation with hazard ratio (HR) 1 v 1.8 v 2.4 (p=0.022) for radical v partial v no per protocol radiation. CONCLUSIONS: Radiation to all sites of disease seems to improve outcomes for children with metastatic RMS and should be considered when feasible. If not feasible, radiation is still recommended to the primary site and involved regional lymphadenopathy. Randomized clinical trials are required to confirm these findings, given the heterogeneity between the groups and potential confounding factors in this analysis.

Localized incompletely resected standard risk rhabdomyosarcoma in children and adolescents: Results from the European Paediatric Soft Tissue Sarcoma Study Group RMS 2005 trial.

BACKGROUND: The authors report the prospective evaluation of reduced dose alkylator chemotherapy combined with radiotherapy for European Pediatric Soft Tissue Sarcoma Study Group (EpSSG) standard risk nonalveolar rhabdomyosarcoma (NA-RMS). PATIENTS AND METHODS: Localized node negative Intergroup Rhabdomyosarcoma Study (IRS) II/III NA-RMS at favorable sites (subgroup C), <25 years old, received five cycles of ifosfamide, vincristine, and dactinomycin (IVA) chemotherapy (30 g/m2 ifosfamide) and four cycles of vincristine and dactinomycin (if receiving radiotherapy), or nine cycles of IVA (54 g/m2 ifosfamide) ± radiotherapy. Delayed primary tumor excision was considered for IRS III tumors. The primary end points were event-free survival (EFS) and overall survival (OS). RESULTS: From October 2005 to December 2016, 359 evaluable patients were recruited: orbit, 164 (45.7%); head and neck nonparameningeal, 77 (21.4%); and genitourinary non-bladder/prostate, 118 (32.9%). EFS and OS were 77.4% (95% confidence interval [CI], 72.5-81.6) and 93.5% (95% CI, 90.1-95.8), respectively. Lower dose alkylator chemotherapy and radiotherapy achieved 5-year OS of 93.7% but the difference with higher dose alkylator chemotherapy +/- radiotherapy was not significant (p = 0.8003). Adjuvant radiotherapy improved EFS with 5-year estimates of 84.7% versus 65.2% for nonirradiated (p < .0001), but not OS (p = .9298). Omitting radiotherapy for orbital tumors reduced OS (5-year was 87.1% vs. 97.3% for irradiated, p = .0257). Following R0 resection (n = 60), radiotherapy did not significantly improve EFS or OS. CONCLUSIONS: Radiotherapy for local tumor control allows for reduction of cumulative dose of alkylators in EpSSG standard risk subgroup C RMS patients. The omission of radiotherapy did not affect OS in all patients except those with orbital RMS and was associated with inferior EFS.

Brachytherapy for rhabdomyosarcoma: Survey of international clinical practice and development of guidelines.

BACKGROUND AND PURPOSE: The purpose of this study was to address the lack of published data on the use of brachytherapy in pediatric rhabdomyosarcoma by describing current practice as starting point to develop consensus guidelines. MATERIALS AND METHODS: An international expert panel on the treatment of pediatric rhabdomyosarcoma comprising 24 (pediatric) radiation oncologists, brachytherapists and pediatric surgeons met for a Brachytherapy Workshop hosted by the European paediatric Soft tissue Sarcoma Study Group (EpSSG). The panel's clinical experience, the results of a previously distributed questionnaire, and a review of the literature were presented. RESULTS: The survey indicated the most common use of brachytherapy to be in combination with tumor resection, followed by brachytherapy as sole local therapy modality. HDR was increasingly deployed in pediatric practice, especially for genitourinary sites. Brachytherapy planning was mostly by 3D imaging based on CT. Recommendations for patient selection, treatment requirements, implant technique, delineation, dose prescription, dose reporting and clinical management were defined. CONCLUSIONS: Consensus guidelines for the use of brachytherapy in pediatric rhabdomyosarcoma have been developed through multicenter collaboration establishing the basis for future work. These have been adopted for the open EpSSG overarching study for children and adults with Frontline and Relapsed RhabdoMyoSarcoma (FaR-RMS).

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.

Novel therapeutic approaches for pediatric diencephalic tumors: improving functional outcomes.

Pediatric diencephalic tumors represent a histopathologically and molecularly diverse group of neoplasms arising in the central part of the brain and involving eloquent structures, including the hypothalamic-pituitary axis (HPA), optic pathway, thalamus, and pineal gland. Presenting symptoms can include significant neurological, endocrine, or visual manifestations which may be exacerbated by injudicious intervention. Upfront multidisciplinary assessment and coordinated management is crucial from the outset to ensure best short- and long-term functional outcomes. In this review we discuss the clinical and pathological features of the neoplastic entities arising in this location, and their management. We emphasize a clear move towards 'function preserving' diagnostic and therapeutic approaches with novel toxicity-sparing strategies, including targeted therapies.

Quantitative diffusion-weighted MRI response assessment in rhabdomyosarcoma: an international retrospective study on behalf of the European paediatric Soft tissue sarcoma Study Group Imaging Committee.

OBJECTIVE: To investigate the feasibility of diffusion-weighted magnetic resonance imaging (DW-MRI) as a predictive imaging marker after neoadjuvant chemotherapy in patients with rhabdomyosarcoma. MATERIAL AND METHODS: We performed a multicenter retrospective study including pediatric, adolescent and young adult patients with rhabdomyosarcoma, Intergroup Rhabdomyosarcoma Study group III/IV, treated according to the European paediatric Soft tissue sarcoma Study Group (EpSSG) RMS2005 or MTS2008 studies. DW-MRI was performed according to institutional protocols. We performed two-dimensional single-slice tumor delineation. Areas of necrosis or hemorrhage were delineated to be excluded in the primary analysis. Mean, median and 5th and 95th apparent diffusion coefficient (ADC) were extracted. RESULTS: Of 134 included patients, 82 had measurable tumor at diagnosis and response and DW-MRI scans of adequate quality and were included in the analysis. Technical heterogeneity in scan acquisition protocols and scanners was observed. Mean ADC at diagnosis was 1.1 (95% confidence interval [CI]: 1.1-1.2) (all ADC expressed in * 10-3 mm2/s), versus 1.6 (1.5-1.6) at response assessment. The 5th percentile ADC was 0.8 (0.7-0.9) at diagnosis and 1.1 (1.0-1.2) at response. Absolute change in mean ADC after neoadjuvant chemotherapy was 0.4 (0.3-0.5). Exploratory analyses for association between ADC and clinical parameters showed a significant difference in mean ADC at diagnosis for alveolar versus embryonal histology. Landmark analysis at nine weeks after the date of diagnosis showed no significant association (hazard ratio 1.3 [0.6-3.2]) between the mean ADC change and event-free survival. CONCLUSION: A significant change in the 5th percentile and the mean ADC after chemotherapy was observed. Strong heterogeneity was identified in DW-MRI acquisition protocols between centers and in individual patients.

Management of the vertebrae as an organ at risk in paediatric radiotherapy clinical trials: Initial QUARTET experience.

Irradiation of the vertebrae in prepubertal patients, if non-homogenous, can result in future growth deformities including kyphoscoliosis. Vertebral delineation and dosimetry were assessed for 101 paediatric cases reviewed within QUARTET-affiliated trials. Despite the availability of published consensus guidelines, a high variability in vertebral delineation was observed, with impact on dosimetry.

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.

Shedding a Light on the Challenges of Adolescents and Young Adults with Rhabdomyosarcoma.

Rhabdomyosarcoma (RMS) is a typical tumour of childhood but can occur at any age. Several studies have reported that adolescent and young adult (AYA) patients with RMS have poorer survival than do younger patients. This review discusses the specific challenges in AYA patients with pediatric-type RMS, exploring possible underlying factors which may influence different outcomes. Reasons for AYA survival gap are likely multifactorial, and might be related to differences in tumor biology and intrinsic aggressiveness, or differences in clinical management (that could include patient referral patterns, time to diagnosis, enrolment into clinical trials, the adequacy and intensity of treatment), as well as patient factors (including physiology and comorbidity that may influence treatment tolerability, drug pharmacokinetics and efficacy). However, improved survival has been reported in the most recent studies for AYA patients treated on pediatric RMS protocols. Different strategies may help to further improve outcome, such as supporting trans-age academic societies and national/international collaborations; developing specific clinical trials without upper age limit; defining integrated and comprehensive approach to AYA patients, including the genomic aspects; establishing multidisciplinary tumor boards with involvement of both pediatric and adult oncologists to discuss all pediatric-type RMS patients; developing dedicated projects with specific treatment recommendations and registry/database.

QUARTET: A SIOP Europe project for quality and excellence in radiotherapy and imaging for children and adolescents with cancer.

The European Society for Paediatric Oncology (SIOPE) Radiation Oncology Working Group presents the QUARTET Project: a centralised quality assurance programme designed to standardise care and improve the quality of radiotherapy and imaging for international clinical trials recruiting children and adolescents with cancer throughout Europe. QUARTET combines the paediatric radiation oncology expertise of SIOPE with the infrastructure and experience of the European Organisation for Research and Treatment of Cancer to deliver radiotherapy quality assurance programmes for large, prospective, international clinical trials. QUARTET-affiliated trials include children and adolescents with brain tumours, neuroblastoma, sarcomas including rhabdomyosarcoma, and renal tumours including Wilms' tumour. With nine prospective clinical trials and two retrospective studies within the active portfolio in March 2022, QUARTET will collect one of the largest repositories of paediatric radiotherapy and imaging data, support the clinical assessment of radiotherapy, and evaluate the role and benefit of radiotherapy quality assurance for this cohort of patients within the context of clinical trials.

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.

Adolescents and young adults with rhabdomyosarcoma treated in the European paediatric Soft tissue sarcoma Study Group (EpSSG) protocols: a cohort study.

BACKGROUND: Adolescent and young adult patients with rhabdomyosarcoma often have poorer outcomes than do children. We aimed to compare the findings of adolescent and young adult patients with children enrolled in two prospective clinical protocols. METHODS: This retrospective observational analysis was based on data from the European paediatric Soft tissue sarcoma Study Group (EpSSG) rhabdomyosarcoma 2005 trial (phase 3 randomised trial for localised rhabdomyosarcoma, open from April, 2006, to December, 2016) and the EpSSG MTS 2008 protocol (prospective, observational, single-arm study for metastatic rhabdomyosarcoma, open from June, 2010, to December, 2016), which involved 108 centres from 14 different countries in total. For this analysis, patients were categorised according to their age into children (age 0-14 years) and adolescents and young adults (age 15-21 years). For the analysis of adherence to treatment and toxicity, only patients with high-risk localised rhabdomyosarcoma included in the randomised part of the rhabdomyosarcoma 2005 study were considered. The primary outcome of event-free survival (assessed in all participants) was defined as the time from diagnosis to the first event (eg, tumour progression, relapse) or to the latest follow-up. Secondary outcomes were overall survival, response to chemotherapy, and toxicity. FINDINGS: Our analysis included 1977 patients, 1720 children (median age 4·7 years; IQR 2·6-8·4) and 257 adolescents and young adults (16·6 years; 15·8-18·0). 1719 patients were from the EpSSG rhabdomyosarcoma 2005 study (1523 aged <15 years and 196 aged 15-21 years) and 258 patients were from the EPSSG MTS 2008 study (197 aged <15 years and 61 aged 15-21 years). Adolescent and young adult patients were more likely than were children to have metastatic tumours (61 [23·7%] of 257 vs 197 [11·5%] of 1720; p<0·0001), unfavourable histological subtypes (119 [46·3%] vs 451 [26·2%]; p<0·0001), tumours larger than 5 cm (177 [68·9%] vs 891 [51·8%]; p<0·0001), and regional lymph node involvement (109 [42·4%] vs 339 [19·7%]; p<0·0001). Adolescent and young adult patients had lower 5-year event-free survival (52·6% [95% CI 46·3-58·6] vs 67·8% [65·5-70·0]; p<0·0001) and lower 5-year overall survival (57·1% [50·4-63·1] vs 77·9% [75·8-79·8]; p<0·0001) than did children. The multivariable analysis confirmed the inferior prognosis of patients aged 15-21 years (hazard ratios 1·48 [95% CI 1·20-1·83; p=0·0002] for poorer event-free survival and 1·73 [1·37-2·19; p<0·0001] for poorer overall survival). Modifications of administered chemotherapy occurred in 13 (15·3%) of 85 adolescents and young adults, and in 161 (21·4%) of 754 children. Grade 3-4 haematological toxicity and infection were observed more frequently in children than in adolescent and young adult patients. INTERPRETATION: This study found better outcomes for adolescent and young adult patients than those reported in epidemiological studies (eg, the EUROCARE-5 study reported 5-year overall survival of 39·6% for patients aged 15-19 years in the 2000-07 study period), suggesting that adolescent and young adult patients, at least up to age 21 years, can be treated with intensive paediatric therapies with no major tolerability issues and should be included in paediatric rhabdomyosarcoma trials. However, the inferior outcomes in adolescent and young adult patients compared with those in children, despite receiving similar therapy, suggest that a tailored and intensive treatment strategy might be warranted for these patients. FUNDING: Fondazione Città della Speranza.