Recurrence Patterns and Surveillance Imaging in Pediatric Brain Tumor Survivors.

Surveillance magnetic resonance imaging (MRI) is routinely used to detect recurrence in pediatric central nervous system (CNS) tumors. The frequency of neuroimaging surveillance varies without a standardized approach. A single-institutional retrospective cohort study evaluated the frequency of recurrences. This study included 476 patients with the majority diagnosed with low-grade glioma (LGG) (n=138, 29%), high-grade glioma (HGG) (n=77, 16%), ependymoma (n=70, 15%), or medulloblastoma (n=61, 13%). LGG, HGG, and ependymoma patients more commonly had multiply recurrent disease ( P =0.08), with ependymoma patients demonstrating ≥2 relapses in 47% of cases. Recurrent disease was identified by imaging more often than clinical symptoms (65% vs. 32%; P =<0.01). Patients diagnosed with meningioma demonstrated the longest mean time to first relapse (74.7 mo) whereas those with atypical teratoid rhabdoid tumor and choroid plexus carcinoma tended to have the shortest time to relapse (8.9 and 9 mo, respectively). Overall, 22 patients sustained first relapse >10 years from initial diagnosis. With a higher tendency toward detection of tumor recurrence/progression on MRI surveillance in comparison to clinical progression, surveillance imaging is necessary in routine follow up of pediatric CNS tumor survivors. With some relapses >10 years from initial diagnosis, imaging beyond this time point may be useful in particular tumor types. While the study is limited in outcome analysis, earlier detection of recurrence would lead to earlier initiation of treatment and implementation of salvage treatment regimens which can impact survival and quality of life.

Performance of the eHealth decision support tool, MIPOGG, for recognising children with Li-Fraumeni, DICER1, Constitutional mismatch repair deficiency and Gorlin syndromes.

BACKGROUND: Cancer predisposition syndromes (CPSs) are responsible for at least 10% of cancer diagnoses in children and adolescents, most of which are not clinically recognised prior to cancer diagnosis. A variety of clinical screening guidelines are used in healthcare settings to help clinicians detect patients who have a higher likelihood of having a CPS. The McGill Interactive Pediatric OncoGenetic Guidelines (MIPOGG) is an electronic health decision support tool that uses algorithms to help clinicians determine if a child/adolescent diagnosed with cancer should be referred to genetics for a CPS evaluation. METHODS: This study assessed MIPOGG's performance in identifying Li-Fraumeni, DICER1, Constitutional mismatch repair deficiency and Gorlin (nevoid basal cell carcinoma) syndromes in a retrospective series of 84 children diagnosed with cancer and one of these four CPSs in Canadian hospitals over an 18-year period. RESULTS: MIPOGG detected 82 of 83 (98.8%) evaluable patients with any one of these four genetic conditions and demonstrated an appropriate rationale for suggesting CPS evaluation. When compared with syndrome-specific clinical screening criteria, MIPOGG's ability to correctly identify children with any of the four CPSs was equivalent to, or outperformed, existing clinical criteria respective to each CPS. CONCLUSION: This study adds evidence that MIPOGG is an appropriate tool for CPS screening in clinical practice. MIPOGG's strength is that it starts with a specific cancer diagnosis and incorporates criteria relevant for associated CPSs, making MIPOGG a more universally accessible diagnostic adjunct that does not require in-depth knowledge of each CPS.

Pediatric central nervous system tumor survivor and caregiver experiences with multidisciplinary telehealth.

PURPOSE: Telehealth use to facilitate cancer survivorship care is accelerating; however, patient satisfaction and barriers to facilitation have not been studied amongst pediatric central nervous system (CNS) tumor survivors. We assessed the telehealth experiences of survivors and caregivers in the Pediatric Neuro-Oncology Outcomes Clinic at Dana-Farber/ Boston Children's Hospital. METHODS: Cross-sectional study of completed surveys among patients and caregivers with ≥ 1 telehealth multidisciplinary survivorship appointment from January 2021 through March 2022. RESULTS: Thirty-three adult survivors and 41 caregivers participated. The majority agreed or strongly agreed that telehealth visits started on time [65/67 (97%)], scheduling was convenient [59/61 (97%)], clinician's explanations were easy-to-understand [59/61 (97%)], listened carefully/addressed concerns [56/60 (93%)], and spent enough time with them [56/59 (95%)]. However, only 58% (n = 35/60) of respondents agreed or strongly agreed they would like to continue with telehealth and 48% (n = 32/67) agreed telehealth was as effective as in person office visits. Adult survivors were more likely than caregivers to prefer office visits for personal connection [23/32 (72%) vs. 18/39 (46%), p = 0.027]. CONCLUSION: Offering telehealth multi-disciplinary services may provide more efficient and accessible care for a subset of pediatric CNS tumor survivors. Despite some advantages, patients and caregivers were divided on whether they would like to continue with telehealth and whether telehealth was as effective as office visits. To improve survivor and caregiver satisfaction, initiatives to refine patient selection as well as enhance personal communication through telehealth systems should be undertaken.

Advances in Treatment of Diffuse Midline Gliomas.

PURPOSE OF REVIEW: Diffuse midline gliomas (DMGs) generally carry a poor prognosis, occur during childhood, and involve midline structures of the central nervous system, including the thalamus, pons, and spinal cord. RECENT FINDINGS: To date, irradiation has been shown to be the only beneficial treatment for DMG. Various genetic modifications have been shown to play a role in the pathogenesis of this disease. Current treatment strategies span targeting epigenetic dysregulation, cell cycle, specific genetic alterations, and the immune microenvironment. Herein, we review the complex features of this disease as it relates to current and past therapeutic approaches.

DICER1 mutations in primary central nervous system tumors: new insights into histologies, mutations, and prognosis.

PURPOSE: We sought to characterize clinical outcomes for adult and pediatric patients with primary CNS tumors harboring DICER1 mutations or loss of DICER1. METHODS: We conducted a retrospective cohort study of 98 patients who were treated between 1995 and 2020 for primary CNS tumors containing DICER1 mutations or loss of DICER1 on chromosome 14q, identified by targeted next generation sequencing. Kaplan-Meier plots and log rank tests were used to analyze survival. Cox proportional-hazards model was used for univariate and multivariable analyses for all-cause mortality (ACM). RESULTS: Within our cohort, the most common malignancies were grade 3/4 glioma (61%), grade 1/2 glioma (17%), and CNS sarcoma (6%). Sarcoma and non-glioma histologies, and tumors with biallelic DICER1 mutations or deletions were common in the pediatric population. Mutations occurred throughout DICER1, including missense mutations in the DexD/H-box helicase, DUF283, RNaseIIIa, and RNaseIIIb domains. For patients with grade 3/4 glioma, MGMT methylation (Hazard ratio [HR] 0.35, 95% Confidence Interval [CI] 0.16-0.73, p = 0.005), IDH1 R132 mutation (HR 0.11, 95% CI 0.03-0.41, p = 0.001), and missense mutation in the DexD/H-box helicase domain (HR 0.06, 95% CI 0.01-0.38, p = 0.003) were independently associated with longer time to ACM on multivariable analyses. CONCLUSION: DICER1 mutations or loss of DICER1 occur in diverse primary CNS tumors, including previously unrecognized grade 3/4 gliomas as the most common histology. While prior studies have described RNaseIIIb hotspot mutations, we document novel mutations in additional DICER1 functional domains. Within the grade 3/4 glioma cohort, missense mutation in the DexD/H-box helicase domain was associated with prolonged survival.

Frosted Branch Angiitis Associated With Cytomegalovirus in a Pediatric Autologous Stem Cell Transplant Patient: Case Report and Review of the Literature.

BACKGROUND: Frosted branch angiitis (FBA) is a rare phenomenon of panuveitis which may occur secondary to cytomegalovirus (CMV) causing acute visual disturbances. CMV infection is a known complication in allogenic stem cell transplant (SCT) patients but is uncommon following autologous SCT. OBSERVATION: We describe a 17-month-old medulloblastoma patient with sudden onset visual impairment following second autologous SCT. The patient was CMV seropositive, polymerase chain reaction negative before second SCT. At the time of presentation with visual complaints, the patient was diagnosed with FBA associated with CMV reactivation. Treatment included antivirals and immunosuppressive medication with visual recovery. CONCLUSION: FBA induced by CMV should be considered as a differential diagnosis in pediatric patients undergoing autologous bone marrow transplant with rapidly progressive visual impairment.

Desmoplastic Small Round Cell Tumor With Ascending Intraspinal Metastasis at Recurrence: Case Report and Review of the Literature.

BACKGROUND: Desmoplastic small round cell tumor (DSRCT) is a rare and aggressive malignancy commonly involving the abdomen and/or pelvic peritoneum. Despite aggressive therapy, the prognosis remains poor. Central nervous system relapse is rare in abdominal/pelvic primary DSRCT. OBSERVATION: We report a case of a 10-year-old female with a large pelvic DSRCT and involvement of the rectosigmoid colon and liver. Following treatment with chemotherapy, and cytoreductive surgery with hyperthermic intraperitoneal chemotherapy an initial response was noted. With progressive lower limb weakness, recurrence with perineural invasion in the lumbosacral nerve root involving the conus was noted 2.5 years from diagnosis. Cerebrospinal fluid showed tumor cells with a molecular confirmation. CONCLUSIONS: Perineural invasion and ascending paralysis secondary to primary abdominal DSRCT has not been previously reported to our knowledge. We recommend a high index of suspicion for early and accurate diagnosis of this rare presentation.

Late effects care for childhood brain Tumor Survivors: A Quality-Improvement Initiative.

Childhood and adolescent brain tumor survivors are at risk for long-term consequences of therapy. We reviewed adherence to long-term follow-up (LTFU) guidelines, assessed provider perspectives, and studied the needs, experience and quality of life (QOL) of pediatric malignant brain tumor survivors in the McMaster Children's Hospital Neuro-Oncology clinic. LTFU areas for improvement were evaluated using an anonymous health provider needs assessment questionnaire. The Cancer Care Experience Questionnaire (CCEQ), Cancer Worry Scale (CWS), Self-Management Skills Scale (SMSS), and PedsQL measured parents/patients' needs and QOL. Individual care plans were based on the Children's Oncology Group (COG) LTFU guidelines. Based on 17 responses, staff perceived areas for improvement included: increased multi-disciplinary participation, improved patient education and increased surveillance for therapy-related late effects. Thirty-two families participated, most felt they received high-quality care. Mean cancer worry scores were low (71.8 (± 28.4)). Survivors reported limited self-management skills (58.5 (±18.2)), requiring support with medical needs and activities of daily living. Overall median QOL scores were 'good' (parental report 72.3 (±17.7), survivor 68.2 (±16.6)). Utilizing survivorship guidelines and assessments from patients, caregivers and health providers, we implemented improvements in our provision of neuro-oncology survivorship care. Lessons learned may assist other LTFU programs.

Advances in the molecular classification of pediatric brain tumors: a guide to the galaxy.

Central nervous system (CNS) tumors are the most common solid tumor in pediatrics, accounting for approximately 25% of all childhood cancers, and the second most common pediatric malignancy after leukemia. CNS tumors can be associated with significant morbidity, even those classified as low grade. Mortality from CNS tumors is disproportionately high compared to other childhood malignancies, although surgery, radiation, and chemotherapy have improved outcomes in these patients over the last few decades. Current therapeutic strategies lead to a high risk of side effects, especially in young children. Pediatric brain tumor survivors have unique sequelae compared to age-matched patients who survived other malignancies. They are at greater risk of significant impairment in cognitive, neurological, endocrine, social, and emotional domains, depending on the location and type of the CNS tumor. Next-generation genomics have shed light on the broad molecular heterogeneity of pediatric brain tumors and have identified important genes and signaling pathways that serve to drive tumor proliferation. This insight has impacted the research field by providing potential therapeutic targets for these diseases. In this review, we highlight recent progress in understanding the molecular basis of common pediatric brain tumors, specifically low-grade glioma, high-grade glioma, ependymoma, embryonal tumors, and atypical teratoid/rhabdoid tumor (ATRT). © 2020 Pathological Society of Great Britain and Ireland. Published by John Wiley & Sons, Ltd.

Transfusion-related Iron Overload in Children With Leukemia.

BACKGROUND: Children with leukemia commonly receive red blood cell (RBC) transfusions and transfusion-related iron overload (TRIO) is a major complication. However, few studies have evaluated TRIO in children with leukemia and no guidelines for screening exist. This retrospective, observational cohort study in children with acute leukemia evaluates the prevalence of TRIO and its impact on end-organ function. RESULTS: The study included 139 patients; 60% standard-risk acute lymphoblastic leukemia (ALL), 32% high-risk (HR) ALL, and 9% acute myeloid leukemia (AML). The mean age at diagnosis was 6 years (range: 5 mo to 18 y). Patients with HR-ALL and AML were more likely to be transfused with ≥10 RBC units (59% and 92%, respectively) compared with those with standard-risk ALL (18%) (P<0.0001). Ferritin levels were measured in 68% patients and elevated (>1000 mcg/L) in 23%. Endocrinopathies were the most common end-organ abnormality. Hepatic dysfunction was significantly higher in patients with ≥10 RBC units transfused compared with those with <10 units (P=0.008). CONCLUSIONS: Although the RBC transfusion burden is highest in patients with AML and HR-ALL, TRIO screening was not commonly performed. Patients who receive ≥10 RBC units are at risk for hepatic and endocrine dysfunction. We recommend routine screening for TRIO in children with leukemia, who are at risk for a higher transfusion burden.

Oral Corticosteroid Therapy as an Adjuvant Treatment for Acute Bleeding in Hemophilia Patients With High Titer Inhibitors.

Treatment options exist for patients with severe hemophilia and high titer factor VIII inhibitors but is often inadequate. Few studies have been conducted to evaluate the utility of short-term corticosteroid therapy for improvement in bleeding complications and temporary or sustained resolution of inhibitors in these patients. We describe 2 patients with acute muscular hematomas successfully treated with 4 to 5 days of oral adjuvant corticosteroid therapy resulting in improvement in their acute bleeds and temporary reduction of inhibitors. Thus, the addition of corticosteroids to traditional therapy of hemophilia with inhibitors may be beneficial in some patients. In those with impending compartment syndrome steroids may improve edema and bleeding symptoms preventing the need for surgical interventions.

Early signs of metabolic syndrome in pediatric central nervous system tumor survivors after high-dose chemotherapy and autologous stem-cell transplantation and radiation.

PURPOSE: Cancer survivors treated with stem-cell transplant (SCT) and radiation therapy are at a high risk for late effects including the metabolic syndrome. This study reviewed the prevalence of the metabolic syndrome in pediatric central nervous system (CNS) tumor survivors treated with autologous SCT and craniospinal radiation. METHODS: A prospective, cross-sectional study in pediatric CNS tumor patients, who underwent a one-time evaluation at least 18 months post-autologous SCT for the presence of components of metabolic syndrome: obesity, hypertension, hyperlipidemia, and abnormal glucose levels. RESULTS: Twelve patients were evaluated, and two (16%) met full criteria for the metabolic syndrome. Seven patients (58%) had at least one component of metabolic syndrome: elevated glucose levels in 8% (1/12), obesity 17% (2/12), hypertriglyceridemia 17% (2/12), and reduced HDL cholesterol in 25% (3/12). None had hypertension. Nine patients (75%) demonstrated abnormal fasting lipid profiles with elevated total cholesterol levels, although only 25% (3/12) fulfilled criteria for a diagnosis of dyslipidemia. CONCLUSION: Pediatric CNS tumor survivors treated with autologous SCT and craniospinal radiation are at risk for early signs of metabolic syndrome, most commonly hyperlipidemia. Further studies evaluating the progression of these early signs to full criteria for the metabolic syndrome diagnosis are required.

Immune checkpoint inhibition for pediatric patients with recurrent/refractory CNS tumors: a single institution experience.

INTRODUCTION: Immune checkpoint inhibition through PD-1 and CTLA-4 blockade has shown efficacy in some adult malignancies and generated interest in pediatrics, including central nervous system (CNS) tumors. We describe our experience with immune checkpoint inhibition in recurrent/refractory pediatric CNS tumors. METHODS: We performed a retrospective chart review of pediatric patients with recurrent or refractory CNS tumors treated with ipilimumab, nivolumab and/or pembrolizumab at Dana-Farber/Boston Children's Hospital between 2018 and 2019. RESULTS: Eleven patients were identified. Diagnoses included diffuse intrinsic pontine glioma (DIPG) (n = 2), high-grade glioma (HGG) (n = 5), ependymoma (n = 1), craniopharyngioma (n = 1), high-grade neuroepithelial tumor (n = 1) and non-germinomatous germ cell tumor (NGGCT) (n = 1). Eight patients had recurrent disease, while three had refractory disease. Nine patients received combination therapy (ipilimumab/nivolumab); two patients received either nivolumab or pembrolizumab. Median time from diagnosis-to-treatment was 8 months (range 0.8-156). All patients received prior radiation therapy (RT), with median time from RT-to-immunotherapy was 3.8 years. One patient received concurrent then adjuvant immunotherapy with RT. Median duration of treatment was 6.1 months (range 1-25). Therapy was discontinued in nine patients: seven due to disease progression and two due to toxicity (colitis; transaminitis). Other pertinent toxicities included Type 1 diabetes mellitus, hypothyroidism and skin toxicity. Based on iRANO criteria, best responses included partial response (n = 3), stable disease (n = 7) and progressive disease (n = 1). Durable response was noted in two patients. CONCLUSION: Immune checkpoint inhibition was relatively well tolerated in a cohort of pediatric patients spanning several CNS tumor diagnoses. Results from prospective clinical trials will be critical to inform clinical decisions.

Hand Mirror Cells and Hypercalcemia: A Rare Presentation of Pediatric Acute Lymphoblastic Leukemia.

Hand mirror cell (HMC) leukemia is a variant of acute lymphoblastic leukemia previously described in the adult population where lymphoblasts manifest distinctive hand mirror morphologic features. HMC has been previously identified in 23% of childhood acute lymphoblastic leukemia patients, but its prognostic significance in children is not well understood. Hypercalcemia is also uncommon in childhood leukemias. Hypercalcemia associated with HMC leukemia has not been previously reported. We report a 5-year-old boy with HMC B-lymphoblastic leukemia who presented with hypercalcemia.

Case report: Pediatric low-grade gliomas: a fine balance between treatment options, timing of therapy, symptom management and quality of life.

Introduction: Pediatric low-grade gliomas (pLGG) are the most common brain tumor in children and encompass a wide range of histologies. Treatment may pose challenges, especially in those incompletely resected or those with multiple recurrence or progression. Case description: We report the clinical course of a girl diagnosed with pilocytic astrocytoma and profound hydrocephalus at age 12 years treated with subtotal resection, vinblastine chemotherapy, and focal proton radiotherapy. After radiotherapy the tumor increased in enhancement temporarily with subsequent resolution consistent with pseudoprogression. Despite improvement in imaging and radiographic local control, the patient continues to have challenges with headaches, visual and auditory concerns, stroke-like symptoms, and poor quality of life. Conclusion: pLGG have excellent long-term survival; thus, treatments should focus on maintaining disease control and limiting long-term toxicities. Various treatment options exist including surgery, chemotherapy, targeted agents, and radiation therapy. Given the morbidity associated with pLGG, individualized treatment approaches are necessary, with a multi-disciplinary approach to care focused on minimizing treatment side effects, and promoting optimal quality of life for patients.

Canadian Consensus for Treatment of BRAF V600E Mutated Pediatric and AYA Gliomas.

Background: The treatment of BRAF V600E gliomas with BRAF inhibitors (BRAFis) and MEK inhibitors (MEKis) has been increasingly integrated into clinical practice for pediatric low-grade gliomas (PLGGs) and pediatric high-grade gliomas (HGGs). However, some questions remain unanswered, such as the best time to start targeted therapy, duration of treatment, and discontinuation of therapy. Given that no clinical trial has been able to address these critical questions, we developed a Canadian Consensus statement for the treatment of BRAF V600E mutated pediatric as well as adolescent and young adult (AYA) gliomas. Methods: Canadian neuro-oncologists were invited to participate in the development of this consensus. The consensus was discussed during monthly web-based national meetings, and the algorithms were revised until a consensus was achieved. Results: A total of 26 participants were involved in the development of the algorithms. Two treatment algorithms are proposed, one for the initiation of treatment and one for the discontinuation of treatment. We suggest that most patients with BRAF V600E gliomas should be treated with BRAFis ± MEKis upfront. Discontinuation of treatment can be considered in certain circumstances, and we suggest a slow wean. Conclusions: Based on expert consensus in Canada, we developed algorithms for treatment initiation of children and AYA with BRAF V600E gliomas as well as a discontinuation algorithm.

The effect of pediatric central nervous system tumors on identity in young adult survivors: a project REACH study.

PURPOSE: Of all childhood cancers, adult survivors of pediatric central nervous system (CNS) tumors are at the highest risk for late mortality as well as neurocognitive, physical, and psychosocial late effects. Their identity with cancer survivorship, the relationship of their identity to health outcomes, and how their identity differs from other childhood cancer survivors is poorly understood. METHODS: A total of 127 young adults previously treated for pediatric CNS tumors enrolled in Project REACH, a locally-treated childhood cancer survivor cohort. Participants completed self-report measures on the effects of cancer on identity, someone who had cancer, victim and survivor identity, frequency of thoughts of diagnosis, and health outcomes. RESULTS: The majority of participants identified as a survivor (83%). Survivor identity was linked to diagnosis and treatment but not health outcomes. A minority (9%) endorsed a victim identity, and they were more likely to have poorer mental health (p = 0.03) and depression (p = 0.04) than non-victims. Participants who reported a stronger effect of cancer on their identity also had poorer mental health (p = 0.005). A higher frequency of diagnosis-related thoughts was associated with significantly poorer mental health (p < 0.001), more severe anxiety (p = 0.008), depression (p < 0.001), and neurocognitive impairments (p < 0.01). Those who experienced relapse, radiation, and/or chemotherapy were more likely to identify as someone who had cancer, independent of diagnosis. IMPLICATIONS FOR CANCER SURVIVORS: Our findings suggest the relationships previously reported between identity and sociodemographic, treatment, and health outcomes after adult and pediatric non-CNS cancers cannot be generalized to pediatric CNS tumors. Understanding the unique features of how this population identifies is important for patient-centered care.

Thiopurine Methyltransferase Intermediate Metabolizer Status and Thiopurine-Associated Toxicity During Maintenance Therapy in Childhood Acute Lymphoblastic Leukemia.

Mercaptopurine is a cornerstone of maintenance chemotherapy in childhood acute lymphoblastic leukemia (ALL). Its cytotoxic effects are mediated by 6-thioguanine nucleotides (TGNs) incorporation into lymphocyte DNA. Thiopurine methyltransferase (TPMT) inactivates mercaptopurine, and deficiency resulting from genetic variants increases TGN exposure and hematopoietic toxicity. Although mercaptopurine-dose reduction reduces toxicity risk without compromising relapse rate in patients with TPMT deficiency, dosing recommendations for those with moderately reduced activity (intermediate metabolizer (IM)) are less clear and their clinical impacts have yet to be established. This cohort study assessed the effect of TPMT IM status on mercaptopurine-associated toxicity and TGN blood exposure in pediatric patients with ALL initiated on standard dose mercaptopurine. Of 88 patients studied (mean age 4.8 years), 10 (11.4%) were TPMT IM, and all had undergone ≥ 3 cycles of maintenance therapy (80% completed). A larger proportion of TPMT IM than normal metabolizers (NM) had febrile neutropenia (FN) during the first two cycles of maintenance, reaching significance in the second cycle (57% vs. 15%, respectively; odds ratio = 7.33, P < 0.05). Compared to NM, FN events occurred more frequently and with prolonged duration in IM in cycles 1 and 2 (adjusted P < 0.05). IM had a 2.46-fold increased hazard ratio for FN, and about twofold higher TGN level than NM (P < 0.05). Myelotoxicity was more common in IM than NM (86% vs. 42%, respectively) during cycle 2 (odds ratio = 8.2, P < 0.05). TPMT IM initiated at a standard mercaptopurine dose are at greater risk for FN during early cycles of maintenance therapy, thus our findings support genotype-guided dose adjustment to reduce toxicity.

Outcomes of Infants and Young Children With Relapsed Medulloblastoma After Initial Craniospinal Irradiation-Sparing Approaches: An International Cohort Study.

PURPOSE: Infant and young childhood medulloblastoma (iMB) is usually treated without craniospinal irradiation (CSI) to avoid neurocognitive late effects. Unfortunately, many children relapse. The purpose of this study was to assess salvage strategies and prognostic features of patients with iMB who relapse after CSI-sparing therapy. METHODS: We assembled a large international cohort of 380 patients with relapsed iMB, age younger than 6 years, and initially treated without CSI. Univariable and multivariable Cox models of postrelapse survival (PRS) were conducted for those treated with curative intent using propensity score analyses to account for confounding factors. RESULTS: The 3-year PRS, for 294 patients treated with curative intent, was 52.4% (95% CI, 46.4 to 58.3) with a median time to relapse from diagnosis of 11 months. Molecular subgrouping was available for 150 patients treated with curative intent, and 3-year PRS for sonic hedgehog (SHH), group 4, and group 3 were 60%, 84%, and 18% (P = .0187), respectively. In multivariable analysis, localized relapse (P = .0073), SHH molecular subgroup (P = .0103), CSI use after relapse (P = .0161), and age ≥ 36 months at initial diagnosis (P = .0494) were associated with improved survival. Most patients (73%) received salvage CSI, and although salvage chemotherapy was not significant in multivariable analysis, its use might be beneficial for a subset of children receiving salvage CSI < 35 Gy (P = .007). CONCLUSION: A substantial proportion of patients with relapsed iMB are salvaged after initial CSI-sparing approaches. Patients with SHH subgroup, localized relapse, older age at initial diagnosis, and those receiving salvage CSI show improved PRS. Future prospective studies should investigate optimal CSI doses and the role of salvage chemotherapy in this population.