Proton therapy for pediatric malignancies: Fact, figures and costs. A joint consensus statement from the pediatric subcommittee of PTCOG, PROS and EPTN

Radiation Therapy Technology Advances and Mitigation of Subsequent Neoplasms in Childhood Cancer Survivors

PURPOSE

In this Pediatric Normal Tissue Effects in the Clinic (PENTEC) vision paper, challenges and opportunities in the assessment of subsequent neoplasms (SNs) from radiation therapy (RT) are presented and discussed in the context of technology advancement.

METHODS AND MATERIALS

The paper discusses the current knowledge of SN risks associated with historic, contemporary, and future RT technologies. Opportunities for research and SN mitigation strategies in pediatric patients with cancer are reviewed.

RESULTS

Present experience with radiation carcinogenesis is from populations exposed during widely different scenarios. Knowledge gaps exist within clinical cohorts and follow-up; dose-response and volume effects; dose-rate and fractionation effects; radiation quality and proton/particle therapy; age considerations; susceptibility of specific tissues; and risks related to genetic predisposition. The biological mechanisms associated with local and patient-level risks are largely unknown.

CONCLUSIONS

Future cancer care is expected to involve several available RT technologies, necessitating evidence and strategies to assess the performance of competing treatments. It is essential to maximize the utilization of existing follow-up while planning for prospective data collection, including standardized registration of individual treatment information with linkage across patient databases.

Preoperative three-dimensional modelling and virtual reality planning aids nephron sparing surgery in a child with bilateral Wilms tumour

Bilateral Wilms tumour (BWT) is a surgically challenging condition. Virtual reality (VR) reconstruction aids surgeons to foresee the anatomy ahead of Nephron Sparing Surgery (NSS). Three-dimensional (3D) visualisation improves the anatomical orientation of surgeons performing NSS. We herewith report a case of BWT where VR planning and 3D printing were used to aid NSS. Conventional imaging is often found to be inadequate while assessing the tumour-organ-vascular anatomy. Advances like VR and 3D printing help surgeons plan better for complex surgeries like bilateral NSS. Next-generation extended reality tools will likely aid robotic-assisted precision NSS and improve patient outcomes.

Proton PBS Planning Techniques, Robustness Evaluation, and OAR Sparing for the Whole-Brain Part of Craniospinal Axis Irradiation

Proton therapy is a promising modality for craniospinal irradiation (CSI), offering dosimetric advantages over conventional treatments. While significant attention has been paid to spine fields, for the brain fields, only dose reduction to the lens of the eye has been reported. Hence, the objective of this study is to assess the potential gains and feasibility of adopting different treatment planning techniques for the entire brain within the CSI target. To this end, eight previously treated CSI patients underwent retrospective replanning using various techniques: (1) intensity modulated proton therapy (IMPT) optimization, (2) the modification/addition of field directions, and (3) the pre-optimization removal of superficially placed spots. The target coverage robustness was evaluated and dose comparisons for lenses, cochleae, and scalp were conducted, considering potential biological dose increases. The target coverage robustness was maintained across all plans, with minor reductions when superficial spot removal was utilized. Single- and multifield optimization showed comparable target coverage robustness and organ-at-risk sparing. A significant scalp sparing was achieved in adults but only limited in pediatric cases. Superficial spot removal contributed to scalp V30 Gy reduction at the expense of lower coverage robustness in specific cases. Lens sparing benefits from multiple field directions, while cochlear sparing remains impractical. Based on the results, all investigated plan types are deemed clinically adoptable.

Complete patient exposure during paediatric brain cancer treatment for photon and proton therapy techniques including imaging procedures

Background

In radiotherapy, especially when treating children, minimising exposure of healthy tissue can prevent the development of adverse outcomes, including second cancers. In this study we propose a validated Monte Carlo framework to evaluate the complete patient exposure during paediatric brain cancer treatment.

Materials and methods

Organ doses were calculated for treatment of a diffuse midline glioma (50.4 Gy with 1.8 Gy per fraction) on a 5-year-old anthropomorphic phantom with 3D-conformal radiotherapy, intensity modulated radiotherapy (IMRT), volumetric modulated arc therapy (VMAT) and intensity modulated pencil beam scanning (PBS) proton therapy. Doses from computed tomography (CT) for planning and on-board imaging for positioning (kV-cone beam CT and X-ray imaging) accounted for the estimate of the exposure of the patient including imaging therapeutic dose. For dose calculations we used validated Monte Carlo-based tools (PRIMO, TOPAS, PENELOPE), while lifetime attributable risk (LAR) was estimated from dose-response relationships for cancer induction, proposed by Schneider et al.

Results

Out-of-field organ dose equivalent data of proton therapy are lower, with doses between 0.6 mSv (testes) and 120 mSv (thyroid), when compared to photon therapy revealing the highest out-of-field doses for IMRT ranging between 43 mSv (testes) and 575 mSv (thyroid). Dose delivered by CT ranged between 0.01 mSv (testes) and 72 mSv (scapula) while a single imaging positioning ranged between 2 μSv (testes) and 1.3 mSv (thyroid) for CBCT and 0.03 μSv (testes) and 48 μSv (scapula) for X-ray. Adding imaging dose from CT and daily CBCT to the therapeutic demonstrated an important contribution of imaging to the overall radiation burden in the course of treatment, which is subsequently used to predict the LAR, for selected organs.

Conclusion

The complete patient exposure during paediatric brain cancer treatment was estimated by combining the results from different Monte Carlo-based dosimetry tools, showing that proton therapy allows significant reduction of the out-of-field doses and secondary cancer risk in selected organs.

Early in vivo Radiation Damage Quantification for Pediatric Craniospinal Irradiation Using Longitudinal MRI for Intensity Modulated Proton Therapy

Purpose

Proton vertebral body sparing craniospinal irradiation (CSI) treats the thecal sac while avoiding the anterior vertebral bodies in an effort to reduce myelosuppression and growth inhibition. However, robust treatment planning needs to compensate for proton range uncertainty, which contributes unwanted doses within the vertebral bodies. This work aimed to develop an early in vivo radiation damage quantification method using longitudinal magnetic resonance (MR) scans to quantify the dose effect during fractionated CSI.

Methods and Materials

Ten pediatric patients were enrolled in a prospective clinical trial of proton vertebral body sparing CSI, in which they received 23.4 to 36 Gy. Monte Carlo robust planning was used, with spinal clinical target volumes defined as the thecal sac and neural foramina. T1/T2-weighted MR scans were acquired before, during, and after treatments to detect a transition from hematopoietic to less metabolically active fatty marrow. MR signal intensity histograms at each time point were analyzed and fitted by multi-Gaussian models to quantify radiation damage.

Results

Fatty marrow filtration was observed in MR images as early as the fifth fraction of treatment. Maximum radiation-induced marrow damage occurred 40 to 50 days from the treatment start, followed by marrow regeneration. The mean damage ratios were 0.23, 0.41, 0.59, and 0.54, corresponding to 10, 20, 40, and 60 days from the treatment start.

Conclusions

We demonstrated a noninvasive method for identifying early vertebral marrow damage based on radiation-induced fatty marrow replacement. The proposed method can be potentially used to quantify the quality of CSI vertebral sparing and preserve metabolically active hematopoietic bone marrow.

Proton Therapy in the Adolescent and Young Adult Population

BACKGROUND

Adolescent and young adult cancer patients are at high risk of developing radiation-associated side effects after treatment. Proton beam radiation therapy might reduce the risk of these side effects for this population without compromising treatment efficacy.

METHODS

We review the current literature describing the utility of proton beam radiation therapy in the treatment of central nervous system tumors, sarcomas, breast cancer and Hodgkin lymphoma for the adolescent and young adult cancer population.

RESULTS

Proton beam radiation therapy has utility for the treatment of certain cancers in the young adult population. Preliminary data suggest reduced radiation dose to normal tissues, which might reduce radiation-associated toxicities. Research is ongoing to further establish the role of proton therapy in this population.

CONCLUSION

This report highlights the potential utility of proton beam radiation for certain adolescent young adult cancers, especially with reducing radiation doses to organs at risk and thereby potentially lowering risks of certain treatment-associated toxicities.

Development of a smartphone virtual reality game to support the radiation therapy of children and adolescents in proton centers

Introduction

For most patients, cancer therapy with radiation is a new experience coming with many unknown challenges. This can be stressful, particularly for children and adolescents. With the aim of reducing this stress and anxiety, a virtual-reality (VR) game, which can be used by patients prior to treatment, was developed and evaluated in a proton therapy center.

Methods

The specifications were derived from literature and from interviews with medical staff and patients. The gantry including the sound of its moving components and the sound of the interlock and safety system were identified as the main features relevant for preparation of a radiation course. Potential implementation difficulties were identified in a literature study and regarded in the design. Within the VR game, patients could interact with modeled equipment of the treatment room and hear the reportedly stress-inducing sounds in a stress-free environment prior to the treatment. The VR game was evaluated in a second series of interviews with patients.

Results and Discussion

This exploratory study demonstrated the specification, implementation and safe application of a VR game dedicated to young proton therapy patients. Initial anecdotal evidence suggested that the VR gaming experience was well received and found to be helpful when preparing young patients for radiation therapy.

Global democratisation of proton radiotherapy

Proton radiotherapy is an advanced treatment option compared with conventional x-ray treatment, delivering much lower doses of radiation to healthy tissues surrounding the tumour. However, proton therapy is currently not widely available. In this Review, we summarise the evolution of proton therapy to date, together with the benefits to patients and society. These developments have led to an exponential growth in the number of hospitals using proton radiotherapy worldwide. However, the gap between the number of patients who should be treated with proton radiotherapy and those who have access to it remains large. We summarise the ongoing research and development that is contributing to closing this gap, including the improvement of treatment efficiency and efficacy, and advances in fixed-beam treatments that do not require an enormously large, heavy, and costly gantry. The ultimate goal of decreasing the size of proton therapy machines to fit into standard treatment rooms appears to be within reach, and we discuss future research and development opportunities to achieve this goal.

Early outcome after craniospinal irradiation with pencil beam scanning proton therapy for children, adolescents and young adults with brain tumors

Central nervous system (CNS) tumors are the most common solid malignancies in children and adolescents and young adults (C-AYAs). Craniospinal irradiation (CSI) is an essential treatment component for some malignancies, but it can also lead to important toxicity. Pencil beam scanning proton therapy (PBSPT) allows for a minimization of dose delivered to organs at risk and, thus, potentially reduced acute and late toxicity. This study aims to report the clinical outcomes and toxicity rates after CSI for C-AYAs treated with PBSPT. Seventy-one C-AYAs (median age: 7.4 years) with CNS tumors were treated with CSI between 2004 and 2021. Medulloblastoma (n = 42: 59%) and ependymoma (n = 8; 11%) were the most common histologies. Median prescribed total PBSPT dose was 54 Gy_RBE (range: 18-60.4), and median prescribed craniospinal dose was 24 Gy_RBE (range: 18-36.8). Acute and late toxicities were coded according to Common Terminology Criteria for Adverse Events. After a median follow-up of 24.5 months, the estimated 2-year local control, distant control, and overall survival were 86.3%, 80.5%, and 84.7%, respectively. Late grade ≥3 toxicity-free rate was 92.6% at 2 years. Recurrent and metastatic tumors were associated with worse outcome. In conclusion, excellent tumor control with low toxicity rates was observed in C-AYAs with brain tumors treated with CSI using PBSPT.

Health Care Resource Utilization for Esophageal Cancer Using Proton versus Photon Radiation Therapy

Purpose

In patients treated with chemoradiation for esophageal cancer (EC), randomized trial data demonstrate that proton beam therapy (PBT) reduces toxicities and postoperative complications (POCs) compared with intensity-modulated radiation therapy (IMRT). However, whether radiation therapy modality affects postoperative health care resource utilization remains unknown.

Materials and Methods

We examined 287 patients with EC who received chemoradiation (prescribed 50.4 Gy/GyE) followed by esophagectomy, including a real-world observational cohort of 237 consecutive patients treated from 2007 to 2013 with PBT (n = 81) versus IMRT (n = 156); and an independent, contemporary comparison cohort of 50 patients from a randomized trial treated from 2012 to 2019 with PBT (n = 21) versus IMRT (n = 29). Postoperative complications were abstracted from medical records. Health care charges were obtained from institutional claims and adjusted for inflation (2021 dollars). Charge differences (Δ = $PBT - $IMRT) were compared by treatment using adjusted generalized linear models with the gamma distribution.

Results

Baseline PBT versus IMRT characteristics were not significantly different. In the observational cohort, during the neoadjuvant chemoradiation phase, health care charges were higher for PBT versus IMRT (Δ = +$71,959; 95% confidence interval [CI], $62,274-$82,138; P < .001). There was no difference in surgical charges (Δ = -$2234; 95% CI, -$6003 to $1695; P = .26). However, during postoperative hospitalization following esophagectomy, health care charges were lower for PBT versus IMRT (Δ = -$25,115; 95% CI, -$37,625 to -$9776; P = .003). In the comparison cohort, findings were analogous: Charges were higher for PBT versus IMRT during chemoradiation (Δ = +$61,818; 95% CI, $49,435-$75,069; P < .001), not different for surgery (Δ = -$4784; 95% CI, -$6439 to $3487; P = .25), and lower for PBT postoperatively (Δ = -$27,048; 95% CI, -$41,974 to -$5300; P = .02). Lower postoperative charges for PBT were especially seen among patients with any POCs in the contemporary comparison (Δ = -$176,448; 95% CI, -$209,782 to -$78,813; P = .02).

Conclusion

Higher up-front chemoradiation resource utilization for PBT in patients with EC was partially offset postoperatively, moderated by reduction in POC risks. Results extend existing clinical evidence of toxicity reduction with PBT.

A scoping review of patient selection methods for proton therapy

The aim was to explore various national and international clinical decision-making tools and dose comparison methods used for selecting cancer patients for proton versus X-ray radiation therapy. To address this aim, a literature search using defined scoping review methods was performed in Medline and Embase databases as well as grey literature. Articles published between 1 January 2015 and 4 August 2020 and those that clearly stated methods of proton versus X-ray therapy patient selection and those published in English were eligible for inclusion. In total, 321 studies were identified of which 49 articles met the study's inclusion criteria representing 13 countries. Six different clinical decision-making tools and 14 dose comparison methods were identified, demonstrating variability within countries and internationally. Proton therapy was indicated for all paediatric patients except those with lymphoma and re-irradiation where individualised model-based selection was required. The most commonly reported patient selection tools included the Normal Tissue Complication Probability model, followed by cost-effectiveness modelling and dosimetry comparison. Model-based selection methods were most commonly applied for head and neck clinical indications in adult cohorts (48% of studies). While no 'Gold Standard' currently exists for proton therapy patient selection with variations evidenced globally, some of the patient selection methods identified in this review can be used to inform future practice in Australia. As literature was not identified from all countries where proton therapy centres are available, further research is needed to evaluate patient selection methods in these jurisdictions for a comprehensive overview.

Cellular plasticity upon proton irradiation determines tumor cell radiosensitivity

Proton radiotherapy has been implemented into the standard-of-care for cancer patients within recent years. However, experimental studies investigating cellular and molecular mechanisms are lacking, and prognostic biomarkers are needed. Cancer stem cell (CSC)-related biomarkers, such as aldehyde dehydrogenase (ALDH), are known to influence cellular radiosensitivity through inactivation of reactive oxygen species, DNA damage repair, and cell death. In a previous study, we found that ionizing radiation itself enriches for ALDH-positive CSCs. In this study, we analyze CSC marker dynamics in prostate cancer, head and neck cancer, and glioblastoma cells upon proton beam irradiation. We find that proton irradiation has a higher potential to target CSCs through induction of complex DNA damages, lower rates of cellular senescence, and minor alteration in histone methylation pattern compared with conventional photon irradiation. Mathematical modeling indicates differences in plasticity rates among ALDH-positive CSCs and ALDH-negative cancer cells between the two irradiation types.

How can we consider variable RBE and LETd prediction during clinical practice? A pediatric case report at the Normandy Proton Therapy Centre using an independent dose engine

BACKGROUND

To develop an auxiliary GPU-accelerated proton therapy (PT) dose and LETd engine for the IBA Proteus®ONE PT system. A pediatric low-grade glioma case study is reported using FRoG during clinical practice, highlighting potential treatment planning insights using variable RBE dose (DvRBE) and LETd as indicators for clinical decision making in PT.

METHODS

The physics engine for FRoG has been modified for compatibility with Proteus®ONE PT centers. Subsequently, FRoG was installed and commissioned at NPTC. Dosimetric validation was performed against measurements and the clinical TPS, RayStation (RS-MC). A head patient cohort previously treated at NPTC was collected and FRoG forward calculations were compared against RS-MC for evaluation of 3D-Γ analysis and dose volume histogram (DVH) results. Currently, treatment design at NPTC is supported with fast variable RBE and LETd calculation and is reported in a representative case for pediatric low-grade glioma.

RESULTS

Simple dosimetric tests against measurements of iso-energy layers and spread-out Bragg Peaks in water verified accuracy of FRoG and RS-MC. Among the patient cohort, average 3D-Γ applying 2%/2 mm, 3%/1.5 mm and 5%/1 mm were > 97%. DVH metrics for targets and OARs between FRoG and RayStation were in good agreement, with ∆D50,CTV and ∆D2,OAR both ⪅1%. The pediatric case report demonstrated implications of different beam arrangements on DvRBE and LETd distributions. From initial planning in RayStation sharing identical optimization constraints, FRoG analysis led to plan selection of the most conservative approach, i.e., minimized DvRBE,max and LETd,max in OARs, to avoid optical system toxicity effects (i.e., vision loss).

CONCLUSION

An auxiliary dose calculation system was successfully integrated into the clinical workflow at a Proteus®ONE IBA facility, in excellent agreement with measurements and RS-MC. FRoG may lead to further insight on DvRBE and LETd implications to help clinical decision making, better understand unexpected toxicities and establish novel clinical procedures with metrics currently absent from the standard clinical TPS.

Young Adult Populations Face Yet Another Barrier to Care With Insurers: Limited Access to Proton Therapy

PURPOSE

Young patients, including pediatric, adolescent, and young adult (YA) patients, are most likely to benefit from the reduced integral dose of proton beam radiation therapy (PBT) resulting in fewer late toxicities and secondary malignancies. This study sought to examine insurance approval and appeal outcomes for PBT among YA patients compared with pediatric patients at a large-volume proton therapy center.

METHODS AND MATERIALS

We performed a cross-sectional cohort study of 284 consecutive patients aged 0 to 39 years for whom PBT was recommended in 2018 through 2019. Pediatric patients were defined as aged 0 to 18 years and YA patients 19 to 39 years. Rates of approval, denials, and decision timelines were calculated. Tumor type and location were also evaluated as factors that may influence insurance decisions.

RESULTS

A total of 207 patients (73%) were approved for PBT at initial request. YA patients (n = 68/143, 48%) were significantly less likely to receive initial approval compared with pediatric patients (n = 139/141; 99%) (P < .001). Even after 47% (n = 35 of 75) of the PBT denials for YA patients were overturned, YAs had a significantly lower final PBT approval (72% vs pediatric 99%; P < .001). The median wait time was also significantly longer for YA patients (median, 8 days; interquartile range [IQR] 3-17 vs median, 2 days; IQR, 0-6; P < .001). In those patients requiring an appeal, the median wait time was 16 days (IQR, 9-25).

CONCLUSION

Given the decades of survivorship of YA patients, PBT is an important tool to reduce late toxicities and secondary malignancies. Compared with pediatric patients, YA patients are significantly less likely to receive insurance approval for PBT. Insurance denials and subsequent appeal requests result in significant delays for YA patients. Insurers need to re-examine their policies to include expedited decisions and appeals and removal of arbitrary age cutoffs so that YA patients can gain easier access to PBT. Furthermore, consensus guidelines encouraging greater PBT access for YA may be warranted from both medical societies and/or AYA experts.

New aspects and innovations in the local treatment of renal and urogenital pediatric tumors

Local treatment plays a key role for patients' outcome in tumors of the urogenital tract in children. Despite a great variety of different etiologies, the specific localization of pediatric urogenital tumors renders several characteristic demands to the treating personnel. Surgery and radiotherapy are the main elements of local treatment in this group of neoplasms. Numerous new guidelines and innovative technical developments of surgery and radiotherapy have recently been integrated into treatment concepts for pediatric urogenital tumors. Due to the broadness of the field it is not possible to give a full overview over all aspects. Therefore, this article highlights the most important innovations and new guidelines of surgery and radiotherapy of pediatric urogenital tumors.

Inhibition of ATM Induces Hypersensitivity to Proton Irradiation by Upregulating Toxic End Joining

Proton Bragg peak irradiation has a higher ionizing density than conventional photon irradiation or the entrance of the proton beam profile. Whether targeting the DNA damage response (DDR) could enhance vulnerability to the distinct pattern of damage induced by proton Bragg peak irradiation is currently unknown. Here, we performed genetic or pharmacologic manipulation of key DDR elements and evaluated DNA damage signaling, DNA repair, and tumor control in cell lines and xenografts treated with the same physical dose across a radiotherapy linear energy transfer spectrum. Radiotherapy consisted of 6 MV photons and the entrance beam or Bragg peak of a 76.8 MeV spot scanning proton beam. More complex DNA double-strand breaks (DSB) induced by Bragg peak proton irradiation preferentially underwent resection and engaged homologous recombination (HR) machinery. Unexpectedly, the ataxia-telangiectasia mutated (ATM) inhibitor, AZD0156, but not an inhibitor of ATM and Rad3-related, rendered cells hypersensitive to more densely ionizing proton Bragg peak irradiation. ATM inhibition blocked resection and shunted more DSBs to processing by toxic ligation through nonhomologous end-joining, whereas loss of DNA ligation via XRCC4 or Lig4 knockdown rescued resection and abolished the enhanced Bragg peak cell killing. Proton Bragg peak monotherapy selectively sensitized cell lines and tumor xenografts with inherent HR defects, and the repair defect induced by ATM inhibitor coadministration showed enhanced efficacy in HR-proficient models. In summary, inherent defects in HR or administration of an ATM inhibitor in HR-proficient tumors selectively enhances the relative biological effectiveness of proton Bragg peak irradiation. SIGNIFICANCE: Coadministration of an ATM inhibitor rewires DNA repair machinery to render cancer cells uniquely hypersensitive to DNA damage induced by the proton Bragg peak, which is characterized by higher density ionization.See related commentary by Nickoloff, p. 3156.

Ethical Allocation of Proton Therapy and the Insurance Review Process

PURPOSE

The purpose of this study was to delineate a scoring system to maximize the ethical allocation of proton beam therapy (PBT) and determine what factors are associated with receipt of PBT, including the role of specific insurance providers.

METHODS AND MATERIALS

Our scoring system was developed in collaboration with a multidisciplinary panel of experts. Patients submitted for PBT consideration were assigned a score by committee at a weekly peer-reviewed session at a time when our center was operating at capacity. Univariate analysis and multivariable analysis of initial and final insurance response were performed.

RESULTS

One hundred ninety-seven patients were prospectively reviewed. Ninety-three percent of patients with Medicaid coverage, 88% of patients with Medicare, and 78% of patients with private insurance were ultimately approved for PBT. Median time to final insurance response was 12 days (interquartile range, 9-18 days) for patients who were ultimately denied PBT coverage. Having primary provider C (odds ratio [OR], 14; 95% confidence interval [CI], 1.20-1.96; P = .033) or third party providers A (OR, 4.22; 95% CI, 1.71-10.9; P = .002) or B (OR, 5.28; 95% CI, 1.56-17.2; P = .006) was significantly associated with final insurance denial for PBT on univariate analysis. Total score (OR, 0.79; 95% CI, 0.67-0.90; P = .002) and having coverage through third party provider A (OR, 24.2; 95% CI, 9.51-68.9; P < .001) were associated with final insurance response on multivariable analysis.

CONCLUSIONS

Our scoring system was significantly associated with receipt of proton beam therapy. Certain insurance providers are less likely to approve PBT for patients, all else being equal. Such a scoring system could be implemented effectively at other PBT facilities, and additional work is needed in ensuring patients with the most to gain from PBT will be approved by their insurance providers.

A New Proton Therapy Solution Provides Superior Cardiac Sparing Compared With Photon Therapy in Whole Lung Irradiation for Pediatric Tumor Patients

Objective

Whole lung irradiation (WLI) plays a crucial role in local control in pediatric patients with lung metastases and improves patient survival. The intention of this research was to explore the advantage of cardiac sparing between photons and protons during WLI. We also propose a new solution for cardiac sparing with proton techniques.

Methods

Eleven patients with pediatric tumors and pulmonary metastasis treated with 12 Gy WLI (all received volumetric-modulated arc therapy (VMAT)) in our institute between 2010 and 2019 were retrospectively selected. Each patient was replanned with intensity-modulated radiation therapy (IMRT), helical tomotherapy (HT), and two intensity-modulated proton radiotherapy (IMPT) plans (IMPT-1 and IMPT-2). IMPT-1 considered the whole lung as the planning target volume (PTV), utilizing the anteroposterior technique (0/180°). IMPT-2 was a new proton solution that we proposed in this research. This approach considered the unilateral lung as the PTV, and 3 ipsilateral fields were designed for each lung. Then, IMPT-2 was generated by summing two unilateral lung plans. The primary objective was to obtain adequate coverage (95% of the prescription dose to the PTV) while maximally sparing the dose to the heart. The PTV coverage, conformity index (CI), homogeneity index (HI), and dose–volume statistics of the heart and substructures were assessed by means of the averages of each comparison parameter.

Results

All treatment techniques achieved the target volume coverage required by clinical practice. HT yielded the best coverage and homogeneity for the target structure compared with other techniques. The CI from IMRT was excellent. For photon radiation therapy, the HT plan afforded superior dose sparing for the V₅, V₆, V₇, V₈, and D_mean of the heart and D_mean of the right ventricle (RV). IMRT displayed the most notable dose reductions in the V₉, V₁₀, V₁₁, and V₁₂ of the heart and D_mean of the right atrium (RA). The VMAT plan was the least effective on the heart and substructures. However, compared with photon radiation therapy, IMPT-1 did not show an advantage for heart protection. Interestingly, IMPT-2 provided significant superiority in cardiac sparing, including maximum dose sparing for the V₅, V₆, V₇, V₈, V₉ and D_mean of the heart and D_mean of the RA, RV, left atrium (LA) and left ventricle (LV) compared to all other techniques.

Conclusions

Considering the complex anatomical relation between target volumes and organs at risk (OARs), IMPT can provide a dose advantage for organs located outside of the target area rather than within or surrounding the area. It is hoped that advances in proton therapy (PT) plan design will lead to further improvements in radiotherapy approaches and provide the best treatment choice for individual patients.

Diffusion Tensor Imaging-Based Analysis of Baseline Neurocognitive Function and Posttreatment White Matter Changes in Pediatric Patients With Craniopharyngioma Treated With Surgery and Proton Therapy

PURPOSE

To determine the preirradiation baseline association of white matter integrity with neurocognitive function and to assess posttreatment changes in pediatric patients with craniopharyngioma treated with proton therapy.

METHODS AND MATERIALS

Ninety children and adolescents (2-20 years old) with craniopharyngioma were treated with proton therapy (54 Gy[RBE]) in a prospective therapeutic trial. Neurocognitive performance at the postoperative baseline before proton therapy and diffusion tensor imaging (DTI) data acquired at baseline and at annual follow-up were analyzed. Tract-based spatial statistics and structural connectomics were used to derive global and local white matter features from DTI. Baseline DTI features were compared for patients with average and below-average neurocognitive performance. Longitudinal DTI data were analyzed to determine the proton dose effect on white matter structures in relation to the irradiated brain volume and baseline age.

RESULTS

Before proton therapy, patients with below-average working memory, processing speed, verbal fluency, verbal learning, or fine motor dexterity exhibited more globally degraded white matter structures compared with their counterparts with average performance, as indicated by lower mean fractional anisotropy, decreased global efficiency, or higher modularity. Surgery, obstructive hydrocephalus, and preoperative hypothalamic involvement appeared to be related to this degradation. In local analyses, tract-based spatial statistics revealed left-lateralized associations with verbal and motor functions, which supported surgical approaches to midline tumors via the right hemisphere. The mean fractional anisotropy of the brain and the global efficiency derived from DTI increased over the 5 years after proton therapy. The rate of increase was lower with larger irradiated brain volumes and in older children.

CONCLUSIONS

Below-average baseline neurocognitive performance in patients with craniopharyngioma before proton therapy appeared to be related to structural degradation of white matter tracts. Posttherapy longitudinal DTI showed improving trends in global integrity and efficiency measures, particularly in children in whom a smaller brain volume was irradiated.

Preliminary Experience of Treating Children and Young Adults With Image-Guided Proton Beam Therapy in India

PURPOSE

Proton beam therapy (PBT) has been a preferred modality in pediatric malignancies requiring radiotherapy. We report our preliminary experience of treating consecutive patients younger than 25 years with image-guided pencil beam scanning PBT from the first and only center on the Indian subcontinent.

METHODS

Patients were selected for PBT on the basis of a multidisciplinary tumor board decision. Patient demographic data, as well as tumor and treatment-related characteristics of the cohort, were captured. Patient and treatment-related factors and their association with acute toxicities were analyzed using univariable and multivariable analyses.

RESULTS

Forty-seven patients (27 with CNS and 20 with non-CNS tumors) with a median age of 9 years (range, 2-25 years) were evaluated. Most common diagnoses were ependymoma, rhabdomyosarcoma, and glioma. Seventy-seven percent of patients traveled more than 500 km, and 70% of them lived in metropolitan cities. Forty-nine percent of patients had recurrent disease at presentation, and 15% had received a previous course of radiation. The median dose delivered was 54.8 cobalt gray equivalents (range, 40.0-70.4 cobalt gray equivalents) to a median clinical target volume of 175 mL (range, 18.7-3,083.0 mL), with 34% of patients requiring concurrent chemotherapy (CCT). Acute grade 2 and grade 3 dermatitis, mucositis, and hematologic toxicity was noted in 45% and 2%, 34% and 0%, and 38% and 30% of patients, respectively. Grade 2 fatigue was noted in 26% of patients. On multivariable analysis, for CNS tumors, both CCT and craniospinal irradiation were independently associated with ≥ 2 grade hematologic toxicity, whereas among non-CNS tumors, a clinical target volume > 150 mL was associated with ≥ 2 grade fatigue, head and neck irradiation was associated with ≥ 2 grade mucositis, and CCT was associated with grade ≥ 2 hematologic toxicity.

CONCLUSION

This study demonstrates safe implementation of a PBT program for children and young adults on the Indian subcontinent. Image-guided pencil beam scanning PBT in judiciously selected patients is feasible and can be delivered with acceptable acute toxicities.

Neurocognitive impairment following proton therapy for paediatric brain tumour: a systematic review of post-therapy assessments

BACKGROUND

Proton therapy (PT), frequently utilised to treat paediatric brain tumour (PBT) patients, eliminates exit dose and minimises dose to healthy tissues that theoretically can mitigate treatment-related effects including cognitive deficits. As clinical outcome data are emerging, we aimed to systematically review current evidence of cognitive changes following PT of PBT.

MATERIALS AND METHODS

We searched PubMed and Scopus electronic databases to identify eligible reports on cognitive changes following PT of PBT according to PRISMA guidelines. Reports were extracted for information on demographics and cognitive outcomes. Then, they were systematically reviewed based on three themes: (1) comparison with photon therapy, (2) comparison with baseline cognitive measures, to population normative mean or radiotherapy-naïve PBT patients and (3) effects of dose distribution to cognition.

RESULTS

Thirteen reports (median size (range): 70 (12-144)) were included. Four reports compared the cognitive outcome between PBT patients treated with proton to photon therapy and nine compared with baseline/normative mean/radiotherapy naïve from which two reported the effects of dose distribution. Reports found significantly poorer cognitive outcome among patients treated with photon therapy compared with proton therapy especially in general cognition and working memory. Craniospinal irradiation (CSI) was consistently associated with poorer cognitive outcome while focal therapy was associated with minor cognitive change/difference. In limited reports available, higher doses to the hippocampus and temporal lobes were implicated to larger cognitive change.

CONCLUSION

Available evidence suggests that PT causes less cognitive deficits compared with photon therapy. Children who underwent focal therapy with proton were consistently shown to have low risk of cognitive deficit suggesting the need for future studies to separate them from CSI. Evidence on the effect of dose distribution to cognition in PT is yet to mature.

Training and education of pediatric radiation oncologists: A survey from the 2019 Pediatric Radiation Oncology Society meeting

To examine the educational background, clinical practice, and preferences regarding continuing medical education (CME) among radiation oncologists who attended the 2019 meeting of the Pediatric Radiation Oncology Society (PROS), a survey consisting of 20 questions was distributed asking for demographic and educational background, clinical practice, and preferences regarding pediatric radiation oncology CME. Of 188 participants, 130 (69.2%) returned the questionnaire. More than 80% reported access to CT simulation, three-dimensional radiotherapy, and general anesthesia while <30% had access to intraoperative radiotherapy, proton, and heavy particle therapy. After residency, 12.1% did further training in pediatric radiation oncology. When asked about further training in pediatrics after residency, 88.8% answered that there should be a formal training program beyond residency in order to treat children. More than 75% acquired knowledge in pediatric radiation oncology through journals, books, live meetings, and tumor boards. The results of this survey may help Pediatric Radiation Oncology Society (PROS) in creating guidelines and recommendations for improvement in pediatric radiation oncology training and practice support as well as the development of CME activities most likely to benefit practitioners.

Survey of clinician opinions on the role of proton beam therapy in Australia and New Zealand

INTRODUCTION

We surveyed the Australian and New Zealand (ANZ) radiation oncology community to assess their perceptions, understanding and experience of the current role of proton beam therapy (PBT) and the existing referral process to access PBT overseas, ahead of the development of the first PBT centre in Australia.

METHODS

The survey was conducted between September and October 2019 using a 17-question instrument, which was distributed by email to all 632 radiation oncology fellows and trainees listed in the Royal Australian and New Zealand College of Radiologists database.

RESULTS

One hundred and one respondents completed the survey, with an overall response rate of 16%. Most respondents were based in Australia (93%), with the majority working in public centres only (59%); 51% were > 10 years post fellowship and 17% were trainees. Most respondents (76%) reported moderate or high levels of confidence in the role of PBT. Only 28% had previously referred a patient for PBT overseas, with the most common referral indication being chordoma. Of those who had not previously referred a patient, 48% were not convinced about the rationale of PBT over current therapies available locally, 33% were not aware of the referral process, and 24% had concerns about the timeliness of a decision for government-funded PBT abroad.

CONCLUSION

This survey has demonstrated that, although there is reasonable confidence in the role of PBT among ANZ radiation oncologists, there are a number of important aspects of PBT awareness, education and access that need to be developed prior to commencement of PBT in Australia.

Proton therapy and the European Particle Therapy Network: The past, present and future

Proton therapy is delivered to selected cancer patients presenting with rare tumours, for which a dose escalation paradigm and/or a reduced dose-bath to the organs at risk is pursued. It is a costly treatment with an additional cost factor of 2–3 when compared to photon radiotherapy. Notwithstanding the 180′000 patients treated with protons, scars robust clinical evidence is available to justify the administration of this treatment modality. The European Particle Therapy Network (EPTN) was created in 2015 to answer the critical European needs for cooperation among protons and carbon ions centres in the framework of clinical research networks. EPTN with other European groups will launch a number of prospective clinical trials that could be practice changing if positive. Alternative way to generate clinical data could be provided by alternative methodologies, such as the Dutch model-based approach, or could be provided by European infrastructure projects.

Particle therapy in Europe

Particle therapy using protons or heavier ions is currently the most advanced form of radiotherapy and offers new opportunities for improving cancer care and research. Ions deposit the dose with a sharp maximum – the Bragg peak – and normal tissue receives a much lower dose than what is delivered by X‐ray therapy. Particle therapy has also biological advantages due to the high linear energy transfer of the charged particles around the Bragg peak. The introduction of particle therapy has been slow in Europe, but within the last decade, more than 20 clinical facilities have opened and facilitated access to this frontline therapy. In this review article, the basic concepts of particle therapy are reviewed along with a presentation of the current clinical indications, the European clinical research, and the established networks.

Comparative proton versus photon treatment planning for the Medicare Medical Treatment Overseas Program: The Royal Adelaide Hospital experience

INTRODUCTION

Australia's first proton beam therapy (PBT) service, The Australian Bragg Centre for Proton Therapy and Research, is scheduled to open in the near future providing PBT for patients closer to home. Patients currently access Commonwealth funding for PBT via the Medicare Medical Treatment Overseas Program (MTOP). Proton versus photon treatment planning is a pre-requisite for the MTOP application. The Royal Adelaide Hospital (RAH) Department of Radiation Oncology has been providing this since 2016. We aim to provide a descriptive overview of our proton versus photon treatment planning process, presenting a summary of the comparative planning results and the treatment pathways selected for the patients referred.

METHODS

All patients referred to the RAH for comparative planning between January 2016 and December 2018 were included in the analysis. Comparative plans were generated for each case using Pinnacle or Eclipse treatment planning systems. The planning techniques used and plan quality metrics were reported.

RESULTS

Forty three patients were referred for comparative planning. The age range was 1-63 years, with the majority (72%) being paediatric patients (age ≤18 years). Of the 19 cases that have been submitted to MTOP, 16 have been accepted and 3 denied. Two of the accepted cases chose not to travel abroad for PBT. The other 14 cases have received PBT overseas.

CONCLUSIONS

The RAH has provided an important service to demonstrate the dosimetric difference between PBT and photon therapy for Australian patients, an important step in supporting the funding of patients for treatment overseas.

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

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

Is there any benefit to particles over photon radiotherapy?

Particle, essentially, proton radiotherapy (RT) could provide some benefits over photon RT, especially in reducing the side effects of RT. We performed a systematic review to identify the performed randomised clinical trials (RCTs) and ongoing RCTs comparing particle RT with photon therapy. So far, there are no results available from phase 3 RCTs comparing particle RT with photon therapy. Furthermore, the results on side effects comparing proton and carbon ion beam RT with photon RT do vary. The introduction of new techniques in photon RT, such as image-guided RT (IGRT), intensity-modulated RT (IMRT), volumetric arc therapy (VMAT) and stereotactic body RT (SBRT) was already effective in reducing side effects. At present, the lack of evidence limits the indications for proton and carbon ion beam RTs and makes the particle RT still experimental.

Proton versus Photon Radiotherapy for Pediatric Central Nervous System Malignancies: A Systematic Review and Meta-Analysis of Dosimetric Comparison Studies

BACKGROUND

Radiotherapy (RT) plays a fundamental role in the treatment of pediatric central nervous system (CNS) malignancies, but its late sequelae are still a challenging question. Despite developments in modern high-conformal photon techniques and proton beam therapy (PBT) are improving the normal tissues dose-sparing while maintaining satisfactory target coverage, clinical advantages supporting the optimal treatment strategy have to be better evaluated in long-term clinical studies and assessed in further radiobiological analyses. Our analysis aimed to systematically review current knowledge on the dosimetric advantages of PBT in the considered setting, which should be the basis for future specific studies.

MATERIALS AND METHODS

A PubMed and Google Scholar search was conducted in June 2019 to select dosimetric studies comparing photon versus proton RT for pediatric patients affected by CNS tumors. Then, a systematic review and meta-analysis according to the PRISMA statement was performed. Average and standard deviation values of Conformity Index, Homogeneity Index, and mean and maximum doses to intracranial and extracranial organs at risk (OARs) were specifically evaluated for secondary dosimetric comparisons. The standardized mean differences (SMDs) for target parameters and the mean differences (MDs) for OARs were summarized in forest plots (P < 0.05 was considered statistically significant). Publication bias was also assessed by the funnel plot and Egger's regression test.

RESULTS

Among the 88 identified papers, a total of twelve studies were included in the meta-analysis. PBT showed dosimetric advantages in target homogeneity (significant especially in the subgroup comparing PBT and 3D conformal RT), as well as in the dose sparing of almost all analyzed OARs (significantly superior results for brainstem, normal brain, and hippocampal dose constraints and for extracranial OARs parameters, excluding the kidneys). Publication bias was observed for Conformity Index.

CONCLUSION

Our analysis supports the evidence of dosimetric advantages of PBT over photon RT, especially in the dose sparing of normal growing tissues. Confirmations from wider well-designed studies are required.

Normal tissue complication probability models in plan evaluation of children with brain tumors referred to proton therapy

Background: Children with brain tumors undergoing radiotherapy are at particular risk of radiation-induced morbidity and are therefore routinely considered for proton therapy (PT) to reduce the dose to healthy tissues. The aim of this study was to apply pediatric constraints and normal tissue complication probability (NTCP) models when evaluating the differences between PT and contemporary photon-based radiotherapy, volumetric modulated arc therapy (VMAT). Methods: Forty patients (aged 1-17 years) referred from Norwegian institutions to cranial PT abroad during 2014-2016 were selected for VMAT re-planning using the original CT sets and target volumes. The VMAT and delivered PT plans were compared by dose/volume metrics and NTCP models related to growth hormone deficiency, auditory toxicity, visual impairment, xerostomia, neurocognitive outcome and secondary brain and parotid gland cancers. Results: The supratentorial brain, temporal lobes, hippocampi, hypothalamus, pituitary glands, cochleas, salivary glands, optic nerves and chiasm received lower mean doses from PT. Reductions in population median NTCP were significant for auditory toxicity (VMAT: 3.8%; PT: 0.3%), neurocognitive outcome (VMAT: 3.0 IQ points decline at 5 years post RT; PT: 2.5 IQ points), xerostomia (VMAT: 2.0%; PT: 0.6%), excess absolute risk of secondary cancer of the brain (VMAT: 9.2%; PT: 6.7%) and salivary glands (VMAT: 2.8%; PT:0.5%). Across all patients, 23/38 PT plans had better or comparable estimated risks for all endpoints (within ±10% of the risk relative to VMAT), whereas for 1/38 patients all estimates were better or comparable with VMAT. Conclusions: PT reduced the volumes of normal tissues exposed to radiation, particularly low-to-intermediate dose levels, and this was reflected in lower NTCP. Of the included endpoints, substantial reductions in population medians were seen from the delivered PT plans for auditory complications, xerostomia, and risk of secondary cancers of the brain and salivary glands.

45 GyRBE for group III orbital embryonal rhabdomyosarcoma

Purpose: Despite widespread concerns of radiotherapy toxicity in children with head and neck tumors, recent Children's Oncology Group (COG) findings suggest that the use of 45 Gy results in an unacceptably high rate of local recurrences in patients with low-risk orbital rhabdomyosarcoma. We therefore evaluated outcomes in our pediatric patients who received 45 GyRBE using proton therapy. Material and methods: To assess disease control and toxicity, we reviewed the medical records of 30 children (≤21 years old) with COG stage 1, group III embryonal orbital rhabdomyosarcoma enrolled on a prospective outcome study and treated with proton therapy between 2007 and 2018. Results: Median age at the time of radiation was 4.8 years old. Twenty-one and nine patients received ifosfamide- and cyclophosphamide-based chemotherapy according to their respective cooperative group regimens. Median duration between the start of induction chemotherapy and radiation was 12 weeks. Two patients had a complete response to induction chemotherapy and two had stable disease. Twenty-six patients had a partial response to induction chemotherapy, with a median volume reduction of 66%. With a median follow-up of 4.0 years (range, 0.5-9.5 years), we observed 1 local failure 6 months following treatment in a patient who had a partial response to cyclosphophomide-based induction chemotherapy. The 5-year local control, progression-free survival, and overall survival rates were 97%, 97%, and 100%, respectively. Serious late toxicities included 18 patients with cataracts, 4 with exposure keratoconjunctivitis resulting in permanently reduced visual acuity, and 1 with chronic sinusitis. Conclusion: 45 GyRBE offers effective local control for most patients with group III orbital rhabdomyosarcoma. The delivery of proton therapy to the postinduction tumor volume plus a small margin can mitigate early- and intermediate-term toxicity, but side effects still occur and long-term data are needed to demonstrate the dosimetric advantage of proton therapy.

Treatment planning for proton therapy: what is needed in the next 10 years?

Treatment planning is the process where the prescription of the radiation oncologist is translated into a deliverable treatment. With the complexity of contemporary radiotherapy, treatment planning cannot be performed without a computerized treatment planning system. Proton therapy (PT) enables highly conformal treatment plans with a minimum of dose to tissues outside the target volume, but to obtain the most optimal plan for the treatment, there are a multitude of parameters that need to be addressed. In this review areas of ongoing improvements and research in the field of PT treatment planning are identified and discussed. The main focus is on issues of immediate clinical and practical relevance to the PT community highlighting the needs for the near future but also in a longer perspective. We anticipate that the manual tasks performed by treatment planners in the future will involve a high degree of computational thinking, as many issues can be solved much better by e.g. scripting. More accurate and faster dose calculation algorithms are needed, automation for contouring and planning is required and practical tools to handle the variable biological efficiency in PT is urgently demanded just to mention a few of the expected improvements over the coming 10 years.

First-In-Human Phase 1 Study of a Nonwoven Fabric Bioabsorbable Spacer for Particle Therapy: Space-Making Particle Therapy (SMPT)

Purpose

Surgical spacer placement (SSP) is useful in particle therapy (PT) for patients with abdominal or pelvic tumors located adjacent to normal organs. We developed a nonwoven fabric bioabsorbable spacer made of polyglycolic acid (PGA) sutures that degrades via hydrolysis. We then conducted this first-in-human phase 1 study of the combination of SSP and PT using the PGA spacer, which we termed space-making PT (SMPT). This study aimed to evaluate the safety and efficacy of SMPT in patients with unresectable malignant tumor located adjacent to normal organs.

Methods and Materials

The eligibility criteria included histologically proven malignant abdominal or pelvic tumor adjacent to the intestines, no metastasis, and no previous radiation therapy. Periodic computed tomography (CT) images were obtained before SSP and before, during, and after PT until the spacer disappeared. Treatment planning was performed for each CT image set until the end of PT, and doses for the planning target volume and organs at risk were analyzed. The thickness and volume of the PGA spacer were measured in each CT image set. Adverse events were evaluated according to the Common Terminology Criteria for Adverse Events version 4.0.

Results

Five patients were enrolled in this study. All patients received 70.4 Gy (relative biological effectiveness) of irradiation. V_95% of the planning target volume before SSP, at the beginning of PT, and at the end of PT was 82.1% ± 11.3%, 98.1% ± 1.1%, and 97.1% ± 0.8%, respectively. The PGA spacers maintained enough thickness (≥1 cm) until the end of PT and disappeared within 8 months after SSP in all patients. No grade ≥3 acute adverse events were observed.

Conclusions

The SMPT is feasible and useful for abdominal or pelvic tumors adjacent to the intestines. This method may be applicable to unresectable tumors located adjacent to normal organs and may expand the indications of PT.

Timing of Local Therapy Affects Survival in Ewing Sarcoma

PURPOSE

We aimed to investigate the relationship between survival and time to local therapy after initiation of up-front chemotherapy in the treatment of patients with localized Ewing sarcoma.

METHODS AND MATERIALS

The National Cancer Database was queried for patients with localized Ewing sarcoma treated with primary chemotherapy and subsequent local therapy. Kaplan-Meier survival curves were generated for patients initiating local therapy 6 to 15 weeks and ≥16 weeks after chemotherapy initiation. Multivariable binomial logistic regression was used to identify factors associated with prolonged time to local therapy. A multivariable Cox proportional hazards model was used to identify factors associated with overall survival (OS).

RESULTS

The final cohort included 1318 patients. A higher proportion of patients initiating local therapy 6 to 15 weeks after chemotherapy initiation versus ≥16 weeks after chemotherapy initiation were ≤21 years old (79.5% vs 72.0%; P = .004). Age >21 years (P < .001; hazard ratio, 1.65; 95% confidence interval, 1.28-2.12), tumor size >8 cm (P = .016), and time to local therapy ≥16 weeks (P = .005; hazard ratio, 1.41; 95% confidence interval, 1.11-1.80) were associated with reduced OS; after review of margin status, negative margins were associated with improved OS compared with gross disease (P = .029). Patients initiating local therapy at 6 to 15 weeks versus ≥16 weeks had a 5-year OS of 78.7% versus 70.4% and a 10-year OS of 70.3% versus 57.1%, respectively (P < .001). The difference in OS according to time to local therapy was particularly more important in patients receiving radiation therapy alone. Age >21 years and treatment by radiation therapy alone were associated with delayed time (>16 weeks) to local therapy, whereas private insurance and income >$48,000 were less likely to be associated with delayed local therapy.

CONCLUSIONS

Delayed time to local therapy ≥16 weeks after chemotherapy initiation was independently associated with worse survival in patients with localized Ewing sarcoma.