Craniospinal irradiation and/or intraventricular radioimmunotherapy after high-dose chemotherapy and autologous stem cell rescue in patients with CNS retinoblastoma-Safety and outcomes.

BACKGROUND: The prognosis for patients with central nervous system (CNS) retinoblastoma (RB) (trilateral or stage 4b metastatic RB) treated with high-dose chemotherapy and autologous stem cell transplant (HDC-ASCT) remains poor. The impact of irradiation when administered as part of upfront therapy post HDC-ASCT on treatment outcomes and survival is unknown. METHODS: We performed a retrospective review of all patients with CNS RB (seven stage 4b, eight trilateral, one pineal lesion belonging to methylation group RB) who underwent induction chemotherapy with an intent to proceed to HDC-ASCT at two institutions. RESULTS: Twelve of 16 patients (n = 75%) achieved an objective response to induction chemotherapy, while four patients had progressive/refractory disease; two patients responded to subsequent therapy and proceeded to ASCT, and two patients did not. Seven of 14 patients who underwent HDC-ASCT, received radiotherapy as part of upfront therapy post HDC-ASCT in the form of craniospinal irradiation (CSI) (n = 3), intraventricular radioimmunotherapy (n = 3), or both CSI and intraventricular radioimmunotherapy (n = 1). The Kaplan-Meier estimate of overall survival for these patients was 62.5% at 5 years; no patients developed second malignant neoplasms within the radiation fields. For the seven patients who did not receive radiotherapy, the overall survival was 28.6% at 5 years. CONCLUSIONS: CSI (23.4 Gy) alone or in conjunction with intraventricular RIT may have clinical utility in eliminating persistent MRD post HDC-ASCT, contributing to improved disease-free survival in patients with CNS RB. This treatment strategy merits evaluation in a prospective, multicenter clinical trial for patients with CNS metastatic RB.

Theranostic Intratumoral Convection-Enhanced Delivery of 124I-Omburtamab in Patients with Diffuse Intrinsic Pontine Glioma: Pharmacokinetics and Lesion Dosimetry.

Diffuse intrinsic pontine glioma (DIPG) is a rare childhood malignancy with poor prognosis. There are no effective treatment options other than external beam therapy. We conducted a pilot, first-in-human study using 124I-omburtamab imaging and theranostics as a therapeutic approach using a localized convection-enhanced delivery (CED) technique for administering radiolabeled antibody. We report the detailed pharmacokinetics and dosimetry results of intratumoral delivery of 124I-omburtamab. Methods: Forty-five DIPG patients who received 9.0-370.7 MBq of 124I-omburtamab intratumorally via CED underwent serial brain and whole-body PET/CT imaging at 3-5 time points after injection within 4, 24-48, 72-96, 120-144, and 168-240 h from the end of infusion. Serial blood samples were obtained for kinetic analysis. Whole-body, blood, lesion, and normal-tissue activities were measured, kinetic parameters (uptake and clearance half-life times) estimated, and radiation-absorbed doses calculated using the OLINDA software program. Results: All patients showed prominent activity within the lesion that was retained over several days and was detectable up to the last time point of imaging, with a mean 124I residence time in the lesion of 24.9 h and dose equivalent of 353 ± 181 mSv/MBq. Whole-body doses were low, with a dose equivalent of 0.69 ± 0.28 mSv/MBq. Systemic distribution and activities in normal organs and blood were low. Radiation dose to blood was very low, with a mean value of 0.27 ± 0.21 mGy/MBq. Whole-body clearance was monoexponential with a mean biologic half-life of 62.7 h and an effective half-life of 37.9 h. Blood clearance was biexponential, with a mean biologic half-life of 22.2 h for the rapid α phase and 155 h for the slower ß phase. Conclusion: Intratumoral CED of 124I-omburtamab is a novel theranostics approach in DIPG. It allows for delivery of high radiation doses to the DIPG lesions, with high lesion activities and low systemic activities and high tumor-to-normal-tissue ratios and achieving a wide safety margin. Imaging of the actual therapeutic administration of 124I-omburtamab allows for direct estimation of the therapeutic lesion and normal-tissue-absorbed doses.

RB1 circulating-tumor DNA in the blood of Retinoblastoma patients increases in untreated patients.

PURPOSE: Circulating tumor DNA (ctDNA) in plasma has been identified in many cancers, including retinoblastoma at diagnosis. We have previously shown that with treatment (enucleation or ophthalmic artery chemosurgery (OAC)) all ctDNA disappears; and if there is persistent plasma ctDNA after treatment metastases develop. The purpose of this study was to determine how the ctDNA RB1 variant allele frequency (VAF) changes in patients with retinoblastoma who have delayed treatment. METHODS: Circulating tumor DNA RB1 was detected and VAF was measured at diagnosis and again prior to any intervention at some time later ranging from 2 to 28 days. RESULTS: Four patients with five ctDNA RB1 mutations were detected at diagnosis and VAF was increased on re-evaluation of the same RB1 mutations in ctDNA. CONCLUSION: In this small cohort, every patient (4) and every RB1 mutation (5) plasma level VAF% increased when measured at two time periods before treatment was instituted suggesting that growing tumors demonstrate increasing plasma ctDNA.

Hypofractionated re-irradiation for diffuse intrinsic pontine glioma.

BACKGROUND: Re-irradiation (reRT) increases survival in locally recurrent diffuse intrinsic pontine glioma (DIPG). There is no standard dose and fractionation for reRT, but conventional fractionation (CF) is typically used. We report our institutional experience of reRT for DIPG, which includes hypofractionation (HF). METHODS: We reviewed pediatric patients treated with brainstem reRT for DIPG at our institution from 2012 to 2022. Patients were grouped by HF or CF. Outcomes included steroid use, and overall survival (OS) was measured from both diagnosis and start of reRT. RESULTS: Of 22 patients who received reRT for DIPG, two did not complete their course due to clinical decline. Of the 20 who completed reRT, the dose was 20-30 Gy in 2-Gy fractions (n = 6) and 30-36 Gy in 3-Gy fractions (n = 14). Median age was 5 years (range: 3-14), median interval since initial RT was 8 months (range: 3-20), and 12 received concurrent bevacizumab. Median OS from diagnosis was 18 months [95% confidence interval: 17-24]. Median OS from start of reRT for HF versus CF was 8.2 and 7.5 months, respectively (p = .20). Thirteen (93%) in the HF group and three (75%) in the CF group tapered pre-treatment steroid dose down or off within 2 months after reRT due to clinical improvement. There was no significant difference in steroid taper between HF and CF (p = .4). No patients developed radionecrosis. CONCLUSION: reRT with HF achieved survival duration comparable to published outcomes and effectively palliated symptoms. Future investigation of this regimen in the context of new systemic therapies and upfront HF is warranted.

Circulating Tumor DNA Posttreatment Measurements and Clinical Correlates in Retinoblastoma.

Importance: Plasma measurements of RB1 circulating tumor DNA (ctDNA) after completion of treatment may be associated with the development of metastases in patients with retinoblastoma. Objective: To determine if the absence of previously detectable plasma ctDNA is associated with metastasis-free survival in patients with a minimum of 1 year follow-up after treatment of retinoblastoma. Design, Setting, and Participants: This cohort study was conducted from June 2019 to September 2023. Patients with retinoblastoma who had measurable ctDNA levels at diagnosis and had repeated ctDNA measurements after ocular treatment (enucleation or intra-arterial chemotherapy) with a minimum of 1 year of follow-up (mean [SD], 28.2 [10.3] months) were included in the study. Patients were recruited from a single-center, tertiary cancer hospital. Exposure: Memorial Sloan Kettering's New York State-approved gene test, which interrogates 129 known cancer genes (called ACCESS), was performed on plasma samples before and after ocular treatments. All exons of the RB1 gene are included in the test and listed as ctDNA in this article. Main Outcomes and Measures: Plasma ctDNA level before treatment, after completion of ocular treatment, and development or absence of metastases. Results: A total of 24 patients (mean [SD] age, 20.7 [17.1] months; 15 female [62.5%]) were included in the study. None of the 23 patients who had a measurable ctDNA level and then no detectable ctDNA level after completion of ocular treatment developed metastases with a minimum of 1 year of follow-up. One patient had persistent measurable ctDNA after initial treatment and developed metastases. Conclusion and Relevance: Patients with retinoblastoma who had a measurable ctDNA level at diagnosis did not develop metastases if the plasma ctDNA level became unrecordable after ocular treatment; 1 patient who had persistent measurable ctDNA after treatment did develop metastasis.

A multi-institutional feasibility study of intra-arterial chemotherapy in children with retinoblastoma. A Children's Oncology Group study (COG ARET12P1).

BACKGROUND: Intra-arterial chemotherapy (IA) as a treatment to salvage the eye with advanced retinoblastoma is increasingly utilized based on successes reported by institutions around the world mainly through retrospective studies. OBJECTIVE: To study the feasibility of delivering melphalan directly into the ophthalmic artery in a multi-institutional prospective study in children with newly diagnosed unilateral group D retinoblastoma. METHODS: The Children's Oncology Group (COG) initiated study ARET12P1 in 2014 and was open to nine institutions. Eligible patients older than six months of age were enrolled. The feasibility of delivering three injections of melphalan into the ophthalmic artery every 28 days was assessed. RESULTS: Nine institutions participated in this trial. Fourteen patients were enrolled, two of whom were unevaluable for feasibility. Four patients experienced a feasibility failure. In two patients, the ophthalmic artery could not be accessed for the second IA injection, in one the artery could not be accessed for the first injection, and one patient experienced grade 4 hypotension during the procedure. CONCLUSION: Delivery of prescribed therapy within the context of this study did not meet the feasibility goals of the study with only a 67% feasibility success rate. These results should caution centers that plan to initiate this treatment and suggest investment in training to achieve technical expertise or referral to centers with expertise.

Phase I trial of panobinostat in children with diffuse intrinsic pontine glioma: A report from the Pediatric Brain Tumor Consortium (PBTC-047).

BACKGROUND: Diffuse intrinsic pontine glioma (DIPG) is a lethal childhood cancer with median survival of less than 1 year. Panobinostat is an oral multihistone deacetylase inhibitor with preclinical activity in DIPG models. Study objectives were to determine safety, tolerability, maximum tolerated dose (MTD), toxicity profile, and pharmacokinetics of panobinostat in children with DIPG. PATIENTS AND METHODS: In stratum 1, panobinostat was administered 3 days per week for 3 weeks on, 1 week off to children with progressive DIPG, with dose escalation following a two-stage continual reassessment method. After this MTD was determined, the study was amended to evaluate the MTD in children with nonprogressive DIPG/Diffuse midline glioma (DMG) (stratum 2) on an alternate schedule, 3 days a week every other week in an effort to escalate the dose. RESULTS: For stratum 1, 19 subjects enrolled with 17/19 evaluable for dose-finding. The MTD was 10 mg/m2/dose. Dose-limiting toxicities included thrombocytopenia and neutropenia. Posterior reversible encephalopathy syndrome was reported in 1 patient. For stratum 2, 34 eligible subjects enrolled with 29/34 evaluable for dose finding. The MTD on this schedule was 22 mg/m2/dose. DLTs included thrombocytopenia, neutropenia, neutropenia with grade 4 thrombocytopenia, prolonged intolerable nausea, and increased ALT. CONCLUSIONS: The MTD of panobinostat is 10 mg/m2/dose administered 3 times per week for 3 weeks on/1 week off in children with progressive DIPG/DMG and 22 mg/m2/dose administered 3 times per week for 1 week on/1 week off when administered in a similar population preprogression. The most common toxicity for both schedules was myelosuppression.

Slipped capital femoral epiphyses: A major on-target adverse event associated with FGFR tyrosine kinase inhibitors in pediatric patients.

Fibroblast growth factor receptor (FGFR) tyrosine kinase inhibitors (TKIs) are increasingly being used off label in pediatrics. Long-term safety data are limited, and serious toxicities unique to pediatrics may emerge. In a retrospective analysis of patients less than 18 years of age with recurrent/refractory FGFR altered gliomas treated with FGFR TKIs at MSKCC (n = 7), we observed slipped capital femoral epiphyses in three of seven patients along with increased linear growth velocity. Clinicians should closely monitor bone health and have a low index of suspicion for serious orthopedic complications including slipped capital femoral epiphyses and inform patients of related risks as part of consent when treating with FGFR TKIs.

Dabrafenib, alone or in combination with trametinib, in BRAF V600-mutated pediatric Langerhans cell histiocytosis.

Langerhans cell histiocytosis (LCH) is a rare, heterogenous, neoplastic disorder primarily affecting children. BRAF mutations have been reported in >50% of patients with LCH. The selective BRAF inhibitor, dabrafenib, in combination with the MEK1/2 inhibitor, trametinib, has been approved in select BRAF V600-mutant solid tumors. Two open-label phase 1/2 studies were conducted in pediatric patients with BRAF V600-mutant, recurrent/refractory malignancies treated with dabrafenib monotherapy (CDRB436A2102; NCT01677741) or dabrafenib plus trametinib (CTMT212X2101; NCT02124772). The primary objectives of both studies were to determine safe and tolerable doses that achieve similar exposure to the approved doses for adults. Secondary objectives included safety, tolerability, and preliminary antitumor activity. Thirteen and 12 patients with BRAF V600-mutant LCH received dabrafenib monotherapy and in combination with trametinib, respectively. Investigator-assessed objective response rates per Histiocyte Society criteria were 76.9% (95% confidence interval [CI], 46.2-95.0) and 58.3% (95% CI, 27.7-84.8) in the monotherapy and combination studies, respectively. More than 90% of responses were ongoing at study completion. The most common treatment-related adverse events (AEs) were vomiting and increased blood creatinine with monotherapy and pyrexia, diarrhea, dry skin, decreased neutrophil count, and vomiting with combination therapy. Two patients each discontinued treatment with monotherapy and combination therapy because of AEs. Overall, dabrafenib monotherapy or in combination with trametinib demonstrated clinical efficacy and manageable toxicity in relapsed/refractory BRAF V600-mutant pediatric LCH, with most responses ongoing. Safety was consistent with that reported in other pediatric and adult conditions treated with dabrafenib plus trametinib.

Mutant-RB1 circulating tumor DNA in the blood of unilateral retinoblastoma patients: What happens during enucleation surgery: A pilot study.

Cell free DNA (cfDNA) and circulating tumor cell free DNA (ctDNA) from blood (plasma) are increasingly being used in oncology for diagnosis, monitoring response, identifying cancer causing mutations and detecting recurrences. Circulating tumor RB1 DNA (ctDNA) is found in the blood (plasma) of retinoblastoma patients at diagnosis before instituting treatment (naïve). We investigated ctDNA in naïve unilateral patients before enucleation and during enucleation (6 patients/ 8 mutations with specimens collected 5-40 minutes from severing the optic nerve) In our cohort, following transection the optic nerve, ctDNA RB1 VAF was measurably lower than pre-enucleation levels within five minutes, 50% less within 15 minutes and 90% less by 40 minutes.

Nivolumab with or without ipilimumab in pediatric patients with high-grade CNS malignancies: Safety, efficacy, biomarker, and pharmacokinetics-CheckMate 908.

BACKGROUND: Therapeutic options are limited in pediatric CNS malignancies. CheckMate 908 (NCT03130959) is an open-label, sequential-arm, phase 1b/2 study investigating nivolumab (NIVO) and NIVO + ipilimumab (IPI) in pediatric patients with high-grade CNS malignancies. METHODS: Patients (N = 166) in 5 cohorts received NIVO 3 mg/kg every 2 weeks (Q2W) or NIVO 3 mg/kg + IPI 1 mg/kg every 3 weeks (4 doses) followed by NIVO 3 mg/kg Q2W. Primary endpoints included overall survival (OS; newly diagnosed diffuse intrinsic pontine glioma [DIPG]) and progression-free survival (PFS; other recurrent/progressive or relapsed/resistant CNS cohorts). Secondary endpoints included other efficacy metrics and safety. Exploratory endpoints included pharmacokinetics and biomarker analyses. RESULTS: As of January 13, 2021, median OS (80% CI) was 11.7 (10.3-16.5) and 10.8 (9.1-15.8) months with NIVO and NIVO + IPI, respectively, in newly diagnosed DIPG. Median PFS (80% CI) with NIVO and NIVO + IPI was 1.7 (1.4-2.7) and 1.3 (1.2-1.5) months, respectively, in recurrent/progressive high-grade glioma; 1.4 (1.2-1.4) and 2.8 (1.5-4.5) months in relapsed/resistant medulloblastoma; and 1.4 (1.4-2.6) and 4.6 (1.4-5.4) months in relapsed/resistant ependymoma. In patients with other recurrent/progressive CNS tumors, median PFS (95% CI) was 1.2 (1.1-1.3) and 1.6 (1.3-3.5) months, respectively. Grade 3/4 treatment-related adverse-event rates were 14.1% (NIVO) and 27.2% (NIVO + IPI). NIVO and IPI first-dose trough concentrations were lower in youngest and lowest-weight patients. Baseline tumor programmed death ligand 1 expression was not associated with survival. CONCLUSIONS: NIVO ± IPI did not demonstrate clinical benefit relative to historical data. The overall safety profiles were manageable with no new safety signals.

Lack of complete response pretransplant is not associated with inferior overall survival for stage 4a metastatic retinoblastoma.

BACKGROUND: Stage 4a metastatic retinoblastoma (RB) is curable with intensive multimodality therapy including myeloablative chemotherapy with autologous stem cell transplant (HDC-ASCT) and involved field radiation therapy (IFRT). To our knowledge, no data exist on the impact of (a) pre-ASCT disease status, and (b) IFRT to sites of metastatic disease post ASCT on survival. PROCEDURE: We retrospectively reviewed patients with stage 4a metastatic RB who underwent induction chemotherapy followed by HDC-ASCT, with or without IFRT, to residual tumor sites at Memorial Sloan Kettering Cancer Center (MSKCC) (n = 24). RESULTS: The degree of postinduction response prior to ASCT did not affect outcome, with 5-year overall survival (OS) of 68% and 86% in patients who achieved complete response (CR) and very good partial response (VGPR)/partial response (PR) prior to ASCT, respectively. IFRT administered post ASCT in patients with possible residual bony metastatic disease increases the likelihood of developing osteosarcoma in the radiation field. CONCLUSION: OS for patients with stage 4a metastatic RB treated with ASCT with VGPR or PR to pretransplant chemotherapy was not significantly different from patients with CR. In addition, IFRT does not seem to be required for bony disease control and increased the likelihood of developing osteosarcoma.

Intensive Multimodality Therapy for Extraocular Retinoblastoma: A Children's Oncology Group Trial (ARET0321).

PURPOSE: Metastatic retinoblastoma has a poor prognosis when treated with conventional chemotherapy and radiation therapy (RT). Intensified therapy may improve the outcome. METHODS: A prospective, international trial enrolled patients with extraocular retinoblastoma. Patients with stage II or III (locoregional) retinoblastoma received four cycles of chemotherapy, followed by involved field RT (45 Gy). Patients with stage IVa or IVb (metastatic or trilateral) retinoblastoma also received four cycles of chemotherapy and those with ≥ partial response then received one cycle of high-dose carboplatin, thiotepa, and etoposide with autologous hematopoietic stem-cell support. Patients with stage IVa or IVb with residual tumor postchemotherapy received RT. The proportion of patients who achieved event-free survival would be reported and compared with historical controls separately for each of the three groups of patients. RESULTS: Fifty-seven eligible patients were included in the analyses. Event-free survival at 1 year was 88.1% (90% CI, 66.6 to 96.2) for stage II-III, 82.6% (90% CI, 61.0 to 92.9) for stage IVa, and 28.3% (90% CI, 12.7 to 46.2) for stage IVb/trilateral. Toxicity was significant as expected and included two therapy-related deaths. CONCLUSION: Intensive multimodality therapy is highly effective for patients with regional extraocular retinoblastoma and stage IVa metastatic retinoblastoma. Although the study met its aim for stage IVb, more effective therapy is still required for patients with CNS involvement (ClinicalTrials.gov identifier: NCT00554788).

Chemotherapy-induced thrombocytopenia in pediatric oncology: Scope of the problem and opportunities for intervention.

BACKGROUND: Chemotherapy-induced thrombocytopenia (CIT) is a known hematologic complication of oncology treatment. This single-institution study examines the degree with which CIT impacts specific pediatric solid tumor cohorts reflected by platelet transfusion burden and treatment modifications. PROCEDURE: Data regarding clinically relevant CIT were obtained via a retrospective chart review of pediatric solid tumor patients treated at Memorial Sloan Kettering Cancer Center from 2013 to 2020. Patients were stratified based on histologic diagnoses as well as chemotherapy regimen. CIT impact was assessed through platelet transfusion means, chemotherapy dose reductions, and treatment delays. RESULTS: A total of 150 patients were included with mean age 10.3 [0.2-21.0]. Patients receiving therapy for high-risk neuroblastoma and localized Ewing sarcoma, both of which included high-dose cyclophosphamide and doxorubicin, required the most platelet transfusions over the treatment course, with a mean of 13 and 9, respectively. Reduced relative dose intensity (RDI), due in part to CIT, was greatest for the patients receiving therapy for high-risk and intermediate-risk rhabdomyosarcoma. Fifty-six percent of high-risk patients experienced a reduced RDI during the final two cycles of treatment and 69% of intermediate-risk patients experienced one during the final four cycles of treatment. CONCLUSIONS: The impact of CIT varied by the administered chemotherapy regimens and dose intensity of chemotherapy agents. This study demonstrated that CIT causes both marked platelet transfusion burden as well as treatment reduction and delay within certain solid tumor cohorts. This can lend to future studies aimed at reducing the burden of CIT and targeting the most at-risk populations.

Next-generation sequencing of cerebrospinal fluid for clinical molecular diagnostics in pediatric, adolescent and young adult brain tumor patients.

BACKGROUND: Safe sampling of central nervous system tumor tissue for diagnostic purposes may be difficult if not impossible, especially in pediatric patients, and an unmet need exists to develop less invasive diagnostic tests. METHODS: We report our clinical experience with minimally invasive molecular diagnostics using a clinically validated assay for sequencing of cerebrospinal fluid (CSF) cell-free DNA (cfDNA). All CSF samples were collected as part of clinical care, and results reported to both clinicians and patients/families. RESULTS: We analyzed 64 CSF samples from 45 pediatric, adolescent and young adult (AYA) patients (pediatric = 25; AYA = 20) with primary and recurrent brain tumors across 12 histopathological subtypes including high-grade glioma (n = 10), medulloblastoma (n = 10), pineoblastoma (n = 5), low-grade glioma (n = 4), diffuse leptomeningeal glioneuronal tumor (DLGNT) (n = 4), retinoblastoma (n = 4), ependymoma (n = 3), and other (n = 5). Somatic alterations were detected in 30/64 samples (46.9%) and in at least one sample per unique patient in 21/45 patients (46.6%). CSF cfDNA positivity was strongly associated with the presence of disseminated disease at the time of collection (81.5% of samples from patients with disseminated disease were positive). No association was seen between CSF cfDNA positivity and the timing of CSF collection during the patient's disease course. CONCLUSIONS: We identified three general categories where CSF cfDNA testing provided additional relevant diagnostic, prognostic, and/or therapeutic information, impacting clinical assessment and decision making: (1) diagnosis and/or identification of actionable alterations; (2) monitor response to therapy; and (3) tracking tumor evolution. Our findings support broader implementation of clinical CSF cfDNA testing in this population to improve care.

Biochemical measures of ovarian function in female survivors of retinoblastoma treated with intra-arterial melphalan: an initial report.

Since 2006, ophthalmic artery chemosurgery (OAC) has been used for ocular-sparing treatment of retinoblastoma. Systemic exposure to melphalan is known to cause ovarian dysfunction, but the effect of melphalan-based OAC has not yet been determined. Here, we assess biochemical and symptomatic measures of ovarian function in a cohort of pubertal female survivors of retinoblastoma treated with melphalan-based OAC. These 13 patients all had normal gonadotropins at a median age of 11.1 years, 9.6 years from the completion of therapy. None had symptoms of ovarian dysfunction. This study provides initial evidence that ovarian function remains intact after melphalan-based OAC.

Vorinostat and isotretinoin with chemotherapy in young children with embryonal brain tumors: A report from the Pediatric Brain Tumor Consortium (PBTC-026).

BACKGROUND: Embryonal tumors of the CNS are the most common malignant tumors occurring in the first years of life. This study evaluated the feasibility and safety of incorporating novel non-cytotoxic therapy with vorinostat and isotretinoin to an intensive cytotoxic chemotherapy backbone. METHODS: PBTC-026 was a prospective multi-institutional clinical trial for children <48 months of age with newly diagnosed embryonal tumors of the CNS. Treatment included three 21-day cycles of induction therapy with vorinostat and isotretinoin, cisplatin, vincristine, cyclophosphamide, and etoposide; three 28-day cycles of consolidation therapy with carboplatin and thiotepa followed by stem cell rescue; and twelve 28-day cycles of maintenance therapy with vorinostat and isotretinoin. Patients with M0 medulloblastoma (MB) received focal radiation following consolidation therapy. Molecular classification was by DNA methylation array. RESULTS: Thirty-one patients with median age of 26 months (range 6-46) received treatment on study; 19 (61%) were male. Diagnosis was MB in 20 and supratentorial CNS embryonal tumor in 11. 24/31 patients completed induction therapy within a pre-specified feasibility window of 98 days. Five-year progression-free survival (PFS) and overall survival (OS) for all 31 patients were 55 ± 15 and 61 ± 13, respectively. Five-year PFS was 42 ± 13 for group 3 MB (n = 12); 80 ± 25 for SHH MB (n = 5); 33 ± 19 for embryonal tumor with multilayered rosettes (ETMR, n = 6). CONCLUSION: It was safe and feasible to incorporate vorinostat and isotretinoin into an intensive chemotherapy regimen. Further study to define efficacy in this high-risk group of patients is warranted.