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Background Cross-sectional tumor measures are traditional clinical trial endpoints; however volumetric measures may better assess tumor growth. We determined the correlation and compared the prognostic impact of cross-sectional and volumetric measures of progressive disease (PD) among patients with DIPG. Methods Imaging and clinical data were abstracted from the International DIPG Registry. Tumor volume and cross-sectional product (CP) were measured with mint Lesion™ software using manual contouring. Correlation between CP and volume (segmented and mathematical [ellipsoid] model) thresholds of PD were assessed by linear regression. Landmark analyses determined differences in survival (via log-rank) between patients classified as PD versus non-PD by CP and volumetric measurements at 1, 3, 5, 7, and 9 months postradiotherapy (RT). Hazard ratios (HR) for survival after these time points were calculated by Cox regression. Results A total of 312 MRIs (46 patients) were analyzed. Comparing change from the previous smallest measure, CP increase of 25% (PD) correlated with a segmented volume increase of 30% (R2 = 0.710), rather than 40% (spherical model extrapolation). CP-determined PD predicted survival at 1 month post-RT (HR = 2.77), but not other time points. Segmented volumetric-determined PD (40% threshold) predicted survival at all imaging timepoints (HRs = 2.57, 2.62, 3.35, 2.71, 16.29), and 30% volumetric PD threshold predicted survival at 1, 3, 5, and 9 month timepoints (HRs = 2.57, 2.62, 4.65, 5.54). Compared to ellipsoid volume, segmented volume demonstrated superior survival associations. Conclusions Segmented volumetric assessments of PD correlated better with survival than CP or ellipsoid volume at most time points. Semiautomated tumor volume likely represents a more accurate, prognostically-relevant measure of disease burden in DIPG.

While autopsy-repository programs with a variety of pediatric central nervous system (CNS) tumor types are a critical resource for preclinical neuro-oncology research, few exist and there is no published guidance on how to develop one. The goal of this prospective Pediatric Brain Tumor Repository (PBTR) study was to develop such a program at Cincinnati Children’s Hospital Medical Center (CCHMC) and then publish the quantitative and experiential data as a guide to support the development of similar programs. Protocols and infrastructure were established—to educate oncologists and families, establish eligibility, obtain consent, address pre- and post-autopsy logistics (e.g., patient and tissue transportation), process and authenticate tissue samples, and collect and analyze data. Of the 129 pediatric CNS tumor patients at CCHMC who died between 2013 and 2018, 109 were eligible for our study. Of these, 74% (81 of 109) were approached for PBTR donation, and 68% (55 of 81) consented. In the final year of the study, approach and consent rates were 93% and 85%, respectively. Median time from death to autopsy (postmortem interval, PMI) was 10 h (range, 1.5–30). In the outpatient setting, PMI increased with distance (from the hospice/home where the patient died to CCHMC). In all patients, PMI appeared to be lower, when consent was obtained more than 24 h before death. Procurement of autopsy specimens need not be a barrier in neuro-oncology research. Regional centers, strict timing-of-consent, patient education, and dedicated staff are all needed to minimize PMI and, thereby, increase the value of the procured tissue for an array of basic and translational research applications.

Cyclin-dependent kinase-retinoblastoma (CDK-RB) pathway is dysregulated in some diffuse intrinsic pontine gliomas (DIPG). We evaluated safety, feasibility, and early efficacy of the CDK4/6-inhibitor ribociclib, administered following radiotherapy in newly-diagnosed DIPG patients. Following radiotherapy, eligible patients received ribociclib in 28-day cycles (350 mg/m2; 21 days on/7 days off). Feasibility endpoints included tolerability for at least 6 courses, and a less than 2-week delay in restarting therapy after 1 dose reduction. Early efficacy was measured by 1-year and median overall survival (OS). Patient/parent-by-proxy reported outcomes measurement information system (PROMIS) assessments were completed prospectively. The study included 10 evaluable patients, 9 DIPG and 1 diffuse midline glioma (DMG)—all 3.7 to 19.8 years of age. The median number of courses was 8 (range 3–14). Three patients required dose reduction for grade-4 neutropenia, and 1 discontinued therapy for hematological toxicity following course 4. The most common grade-3/4 toxicity was myelosuppression. After 2 courses, MRI evaluations in 4 patients revealed increased necrotic volume, associated with new neurological symptoms in 3 patients. The 1-year and median OS for DIPG was 89% and 16.1 months (range 10–30), respectively; the DMG patient died at 6 months post-diagnosis. Five patients donated brain tissue and tumor; 3 were RB+ . Ribociclib administered following radiotherapy is feasible in DIPG and DMG. Increased tumor necrosis may represent a treatment effect. These data warrant further prospective volumetric analyses of tumors with necrosis. Feasibility and stabilization findings support further investigation of ribociclib in combination therapies. NCT02607124.

Molecularly targeted therapy with MEK inhibitors has been increasingly incorporated into the treatment of pediatric low-grade gliomas, but this promising therapy is associated with distinctive and specific toxicities. Understanding life-threatening MEK inhibitor toxicities and their management is critical to MEK inhibitor safety, especially among young children. This report describes severe hyponatremia associated with trametinib in an infant with progressive low-grade glioma without underlying endocrine dysfunction, which recurred despite significant dose reduction. Therapy with an alternative MEK inhibitor, binimetinib, provided excellent tumor response without hyponatremia, suggesting that some toxicities may be avoided by changing MEK inhibitor agents within the same class.

Purpose: The 2-part, phase I/IIa, open-label study (NCT01677741) sought to determine the safety, tolerability, pharmacokinetics, and preliminary activity of dabrafenib in pediatric patients with advanced BRAF V600–mutated cancers. Patients and Methods: This phase I dose-finding part treated patients ages 1 to Results: Between May 2013 and November 2014, 27 patients [12 male; median age, 9 years (range, 1–17 years)] with BRAF V600–mutant solid tumors recurrent/refractory to treatment (low- or high-grade glioma, Langerhans cell histiocytosis, neuroblastoma, or thyroid cancer) were enrolled. The median treatment duration was 75.6 weeks (range, 5.6–148.7 weeks), with 63% treated for >52 weeks and 52% undergoing treatment at data cutoff date. The most common grade 3/4 adverse events suspected to be related to study drug were maculopapular rash and arthralgia (2 patients each). No dose-limiting toxicities were observed. Pharmacokinetic analyses showed a dose-dependent increase in AUC0–12 and achievement of adult exposure levels at the recommended phase II doses of 5.25 mg/kg/day (age Conclusions: In this first clinical trial in pediatric patients with pretreated BRAF V600–mutant tumors, dabrafenib was well tolerated while achieving target exposure levels; the average treatment duration was >1 year with many patients still on treatment. The phase II component is also closed and will be reported separately.

BACKGROUND: Dual inhibition of CDK4/6 and mTOR in DIPG and pediatric HGG has strong biologic rationale, given prevalent genetic alterations resulting in upregulated cell cycle and PI3K/mTOR pathways in these diseases, as well as non-overlapping agent toxicities. This study sought to evaluate safety/tolerability and determine the recommended phase 2 dose (RP2D) of ribociclib and everolimus among children with newly diagnosed DIPG and HGG post-radiotherapy. METHODS: Patients were enrolled according to a Rolling-6 design and received oral ribociclib and everolimus once daily for 21 and 28 days, respectively, starting 2-4 weeks post-completion of radiotherapy. All HGG and biopsied DIPG patients were screened for RB protein presence by immunohistochemistry. Pharmacokinetics and survival data were analyzed. RESULTS: Nineteen patients enrolled (median age: 8 years [range: 2-18]). Three patients enrolled at each of dose levels 1 and 2 without dose-limiting toxicities (DLTs). Thirteen patients enrolled at dose level 3, with one patient experiencing a DLT (grade 3 infection). One patient came off therapy prior to cycle 9 due to cardiac toxicity. The most common grade 3/4 toxicities were neutropenia (33%), leucopenia (17%), and lymphopenia (11%). Steady-state everolimus exposures in combination were 1.9±0.9-fold higher than single-agent administration. Median overall survival (OS) for 15 patients with DIPG was 13.9 months, with 12-, 24-, and 36-month OS of 53.3%, 38.9%, and 38.9%. Median event-free survival for four patients with HGG was 10.5 months. Among patients with tumor molecular profiling, two longer survivors (OS: 20, >37 months) had evidence of cell cycle upregulation with CDKN2A/B deletion and CDK4 overexpression identified. CONCLUSIONS: The combination of ribociclib and everolimus was well-tolerated post-radiotherapy in children with newly diagnosed DIPG and HGG, with a RP2D of ribociclib 170 mg/m2 days 1-21 and everolimus 1.5 mg/m2 days 1-28. Results will inform a molecularly-guided phase II study currently underway to evaluate efficacy.

INTRODUCTION Cross-sectional tumor measures are used as endpoints in clinical trials of DIPG, but may not capture meaningful changes in disease burden. Volumetric measures may provide a more accurate assessment of tumor growth. We measured the correlation between cross-sectional and volumetric measures and compared their prognostic impact to better understand response evaluation in DIPG. METHODS Patients from the International DIPG Registry with diagnostic and post-radiation MRIs were included. Utilizing mint LesionTM software, tumors were manually contoured by an experienced pediatric neuro-radiologist to extrapolate cross-sectional product (CP) and volume measures. Correlation between CP and volume was assessed by linear regression. Landmark analyses were performed to determine differences in overall survival (OS) (via log-rank) between patients classified as progressive disease (PD) versus non-PD according to CP and volumetric measurements at one-, three-, and five-months post-radiation. Imaging consistent with pseudoprogression was designated non-PD. Hazard ratios (HR) for survival after these timepoints were calculated by Cox regression. RESULTS A total of 317 MRIs from 46 patients were analyzed. When comparing change from smallest previous tumor size, CP increase of 25% (PD by RAPNO) correlated with volume increase of 28% (R2=0.685). There was no difference in OS between patients classified as PD versus non-PD by CP at one-month, three-months, or five-months post-radiation (p >0.05). However, significant differences in OS were observed between patients classified as PD versus non-PD by volume (28% increase) at one-month (2.7 vs. 12.8 months, p=0.005), three-months (1.9 vs. 10.7 months, p=0.036), and five-months post-radiation (3.7 vs. 9.1 months, p=0.023). PD by volume, but not by CP, was predictive of survival at all timepoints (HR: 5.0, 2.4, 2.4). CONCLUSIONS Volumetric assessments of PD correlated better with survival than CP at all post-radiation timepoints. Tumor volume likely represents a more accurate, prognostically-relevant measure of disease burden that deserves investigation in future DIPG trials.

BACKGROUND Recent discoveries have provided valuable insight into the genomic landscape of pediatric low-grade gliomas (LGGs) at diagnosis, facilitating molecularly targeted treatment. However, little is known about their temporal and therapy-related genomic heterogeneity. An adequate understanding of the evolution of pediatric LGGs’ genomic profiles over time is critically important in guiding decisions about targeted therapeutics and diagnostic biopsy at recurrence. METHODS Fluorescence in situ hybridization, mutation-specific immunohistochemistry, exome analyses, and/or targeted sequencing were performed on paired tumor samples from diagnostic and subsequent surgeries. RESULTS Ninety-four tumor samples from 45 patients (41 with two specimens, four with three specimens) from three institutions underwent testing. Conservation of BRAF fusion, BRAFV600E mutation, and FGFR1 rearrangement status was observed in 100%, 98%, and 96% of paired specimens, respectively. No loss or gain of IDH1 mutations or NTRK2, MYB, or MYBL1 rearrangements were detected over time. Histologic diagnosis remained the same in all tumors, with no acquired H3K27M mutations or malignant transformation. Changes in CDKN2A deletion status occurred in 10 patients (40%), with acquisition of CDKN2A deletion in seven (including three who received chemotherapy [two with temozolomide] and one who received radiation) and loss in three (including one who received targeted therapy and radiation). A trend toward shorter time to progression was observed among patients with acquired CDKN2A deletions compared to patients without acquisition of this alteration (median: 5.5 versus 14.0 months [p=0.078]). CONCLUSIONS Most targetable genetic aberrations in pediatric LGGs, including BRAF alterations, are conserved at recurrence and following chemotherapy or radiation. However, changes in CDKN2A deletion status over time were demonstrated. Acquisition of CDKN2A deletion may define a higher risk subgroup of pediatric LGGs with a poorer prognosis. Given the potential for targeted therapies for tumors harboring CDKN2A deletions, biopsy at recurrence may be indicated in certain patients, especially those with rapid progression.

BACKGROUND: Molecular profiling is commonly performed in pediatric CNS tumors, however the clinical utilization of genomic data in pediatric neuro-oncology is not fully characterized. We describe a single institution experience adopting a personalized therapeutic approach based on tumor genetic alterations. METHODS: We retrospectively analyzed genomic data, generated using fluorescent in situ hybridization, single gene, or panel sequencing, of pediatric CNS tumors in patients diagnosed between 2010 and 2018 at Cincinnati Children’s Hospital Medical Center. We aimed to identify common genetic aberrations, characterize targeted therapies used, and disease response. RESULTS: One hundred and sixty patients (median age: 7 years, range: 0–27 years) had tumor sequencing performed yielding 147 evaluable results. Low-grade lesions (LGL) (N=94, 63.9%), were mostly low-grade gliomas and glioneuronal tumors; high-grade lesions (HGL) (N=53, 36.0%) included high-grade gliomas (N=35), embryonal neoplasms (N=12), and choroid plexus carcinomas (N=3). Specific BRAF aberrations were more interrogated in LGL while larger panel sequencing was performed in HGL. Targetable aberrations were found in 99 patients (67.3%), most commonly BRAF alterations in LGL as expected, and aberrations in the RTK-PI3K pathway in HGL. Among 99 patients, 56.5% received therapy informed by sequencing data. Thirty three patients with LGL (35.1%) received targeted therapy after a median of 3 prior therapies and remained on treatment for a median of 7 months (range: 1–24 months). Twenty three patients with HGL (43.4%) received targeted therapy after a median of 2 therapies and remained on treatment for a median of 3 months (range: 1–23 months). Targeted therapy was most frequently stopped due to disease progression, only 5 patients developed toxicity that led to cessation of targeted agents. CONCLUSION: Targetable alterations are frequent in pediatric CNS tumors; when identified they guided therapy in a majority of patients commonly at progression and were used earlier and more often in HGL. GERM CELL TUMORS

INTRODUCTION Recent discoveries have provided valuable insight into the genomic landscape of pediatric low grade gliomas (LGGs) at diagnosis, facilitating molecularly targeted treatment. However, little is known about their temporal and therapy-related genomic heterogeneity. An adequate understanding of the evolution of pediatric LGGs’ genomic profiles over time is critically important in guiding decisions about targeted therapeutics and diagnostic biopsy at recurrence. METHODS Fluorescence in situ hybridization, mutation-specific immunohistochemistry, and exome analyses were performed on paired tumor samples from primary diagnostic and subsequent surgeries. RESULTS 101 tumor samples from 48 patients (43 with 2 specimens, 5 with 3 specimens) from 3 institutions underwent testing. BRAF fusion and BRAFV600E status were conserved in 100% and 97% of paired specimens, respectively. No loss or gain of IDH1 mutations or FGFR1, NTRK2, MYB, or MYBL1 rearrangements were detected over time. Histologic diagnosis remained the same in all tumors, with no acquired H3K27M mutations or malignant transformation. CDKN2A deletions were acquired in 7 patients (including 3 who received chemotherapy [2 with temozolomide] and 1 who received radiation), and were associated with a trend toward shorter time to progression (median: 5.5 vs. 13.0 months [p=0.08]). CONCLUSIONS Most targetable genetic alterations in pediatric LGGs, including BRAF alterations, are conserved at recurrence and following chemotherapy or radiation. However, CDKN2A deletion acquisition was demonstrated and may define a higher risk group. Given potential for targeted therapies for tumors acquiring CDKN2A deletions, performing a biopsy at recurrence may be indicated in certain patients, especially those with rapid progression.

Molecularly targeted therapy with MEK inhibitors is increasingly being incorporated into the treatment of pediatric low-grade gliomas (LGGs). Trametinib is an orally available MEK1/2 inhibitor that has demonstrated tumor control in LGGs with BRAF alterations. Safe expansion of MEK inhibitor therapy within the pediatric patient population demands adequate understanding of and surveillance for potential MEK-inhibitor specific toxicities, especially among young children. Hyponatremia has been reported in adult patients receiving BRAF/MEK inhibitor combination treatment as well as in two pediatric patients with known diabetes insipidus treated with trametinib monotherapy. To our knowledge, single-agent trametinib has not previously been reported to be associated with hyponatremia in children in the absence of an underlying endocrinopathy. We present a case of hyponatremia associated with trametinib use in an infant with progressive LGG without known endocrine dysfunction, which recurred after significant dose reduction. Therapy with an alternative MEK1/2 inhibitor, binimetinib, provided excellent tumor response without hyponatremia. Hyponatremia is a rare but serious side effect of trametinib, even without underlying pituitary dysfunction. Infants and patients lacking the ability to quickly regulate fluid intake in response to osmolality changes are at particular risk of suffering severe consequences from hyponatremia and should be monitored closely with initiation of trametinib. Switching to a different drug within the same class may offer an alternative to significant dose reduction or discontinuation due to this toxicity.

INTRODUCTION Because treatment and clinical management decisions for children with NF1-OPG remain challenging, we sought to establish evidence-based guidelines. We prospectively enrolled children with newly-diagnosed NF1-OPGs, and gathered standardized clinical neuro-oncology and ophthalmology assessments. METHODS Only children with NF1 and newly diagnosed OPGs, confirmed by central review, were eligible. Indications for obtaining the initial MRI, as well as factors associated with the decision to treat with chemotherapy or observe without treatment, were obtained. Quantitative visual acuity (VA), other ophthalmic features, and imaging were captured at standard time points. Goal enrollment is 250 subjects. RESULTS One-hundred thirty-three children (52% female) from 20 institutions met inclusion criteria, and were included in this preliminary analysis. Eighty-six percent of subjects were able to perform quantitative VA testing at enrollment. The most common reasons for the diagnostic MRI included screening related to NF1 diagnosis (36.8%), ophthalmologic concerns (29.3%), and non-ophthalmologic concerns (24.8%), such as headache. To date, twenty subjects have initiated treatment with chemotherapy, twelve (9%) at the time of the initial OPG diagnosis. Median age at OPG diagnosis was 3.1 years. Age and sex distribution were similar in subjects immediately entering the observation and treatment arms (median age 3.0 versus 3.5 years, respectively). CONCLUSION Most children with NF1-OPGs are observed at time of their initial OPG diagnosis, rather than treated. Importantly, a large proportion of children are able to complete quantitative VA testing at enrollment. Once enrollment is complete, these data will help to establish evidence-based guidelines for clinical management of NF1-OPGs.

Genomic aberrations in the cell cycle and mTOR pathways have been reported in diffuse pontine gliomas (DIPG) and high-grade gliomas (HGG). Dual inhibition of CDK4/6 (ribociclib) and mTOR (everolimus) has strong biologic rationale, non-overlapping single-agent toxicities, and adult clinical experience. The maximum tolerated dose (MTD) and/or recommended phase two dose (RP2D) of ribociclib and everolimus administered during maintenance therapy following radiotherapy was determined in the phase I study as a rolling 6 design. Ribociclib and everolimus were administered once daily for 21 days and 28 days, respectively starting two-four weeks post completion of radiotherapy. All HGG patients and any DIPG patient who had undergone biopsy were screened for RB protein by immunohistochemistry. Eighteen eligible patients enrolled (median age 8 years; range: 2–18). Six patients enrolled at dose levels 1,2, and 3 without dose limiting toxicities (DLT). Currently, five patients are enrolled at dose level 3 expansion cohort. The median number of cycles are 4.5 (range: 1–20+). Among the expansion cohort, one dose limiting toxicity included a grade 3 infection and one patient required a dose reduction in course 3 due to grade 3 ALT and grade 4 hypokalemia. The most common grade 3/4 adverse events included neutropenia. Preliminary pharmacokinetic studies on 12 patients suggest an impact of ribociclib on everolimus pharmacokinetics. The MTD/RP2D of ribociclib and everolimus following radiotherapy in newly diagnosed DIPG and HGG is anticipated to be 170 mg/m2/day x 21 days and 1.5 mg/ m2/day every 28 days which is equivalent to the adult RP2D.

Telomerase activation is critical in many cancers including central nervous system (CNS) tumors. Imetelstat is an oligonucleotide that binds to the template region of the RNA component of telomerase, inhibiting its enzymatic activity. We conducted an investigator-sponsored molecular biology (MB) and phase II study to estimate inhibition of tumor telomerase activity and sustained responses by imetelstat in children with recurrent CNS malignancies. In the MB study, patients with recurrent medulloblastoma, high-grade glioma (HGG) or ependymoma undergoing resection received one dose of imetelstat as a 2-h intravenous infusion at 285 mg/m(2), 12-24 h before surgery. Telomerase activity was evaluated in fresh tumor from surgery. Post-surgery and in the phase II study, patients received imetelstat IV (days 1 and 8 q21-days) at 285 mg/m(2). Imetelstat pharmacokinetic and pharmacodynamic studies were performed. Of two evaluable patients on the MB trial, intratumoral telomerase activity was inhibited by 95 % compared to baseline archival tissue in one patient and was inevaluable in one patient. Forty-two patients (40 evaluable for toxicity) were enrolled: 9 medulloblastomas, 18 HGG, 4 ependymomas, 9 diffuse intrinsic pontine gliomas. Most common grade 3/4 toxicities included thrombocytopenia (32.5 %), lymphopenia (17.5 %), neutropenia (12.5 %), ALT (7.5 %) and AST (5 %) elevation. Two patients died of intratumoral hemorrhage secondary to thrombocytopenia leading to premature study closure. No objective responses were observed. Telomerase inhibition was observed in peripheral blood mononuclear cells (PBMCs) for at least 8 days. Imetelstat demonstrated intratumoral and PBMC target inhibition; the regimen proved too toxic in children with recurrent CNS tumors.

Genomic sequencing studies have uncovered alterations of checkpoint cell cycle regulators (CDK4/6, CDK2NA) in diffuse intrinsic pontine gliomas (DIPG) and high-grade gliomas (HGG). Ribociclib (LEE011) is an orally bioavailable, small molecule inhibitor of CDK4/CyclinD1 and CDK6/CyclinD3 complexes resulting in hypophosphorylation of RB and cell cycle arrest. In a feasibility, phase II study, patients with newly-diagnosed DIPG or HGG received radiation therapy prior to enrollment. All HGG patients and any DIPG patient who had undergone biopsy were screened for total RB protein by immunohistochemistry. Ribociclib was administered daily for 21 of 28 days at 350 mg/m/day. Feasibilty endpoints included toxic death, Grade 3/4 toxicities possibly related to ribociclib resulting in drug discontinuation, > 2 weeks delay in the start of any course or discontinuation of the protocol therapy even after appropriate dose modification. Efficacy was measured by the overall survival distribution for DIPG and HGG. Of the 10 patients enrolled (median 6.5 years; range:4–20), 9 received treatment (8 DIPG, 1 HGG) and one developed leptomeningeal disease prior to therapy. To date, the median number of courses are 4.5 (range: 1–10). Ribociclib was well-tolerated; three patients required dose reduction for grade 4 neutropenia; no patients have come off therapy for toxicity. The most common adverse events were leukopenia, neutropenia, lymphopenia, nausea, vomiting, and fatigue. MRI evaluations in 2 patients revealed increased T2 FLAIR signal with new neurological symptoms within the first 2 cycles of therapy. These patients were responsive to steroids and remain on study. Six patients remain on active therapy at a median of 9 months post diagnosis (range: 3–12). The preliminary analysis demonstrates that ribociclib, administered post radiation therapy is well-tolerated in children and young adults with DIPG and RB+ HGG. Analyses for efficacy and correlative studies will be presented at the meeting.

Pediatric high-grade gliomas (pHGG) are aggressive malignant neoplasms representing approximately 20% of all pediatric central nervous system tumors. Current therapies offer limited disease control, and patients with recurrent disease have a particularly poor prognosis. While the empiric use of targeted therapy, especially at progression, is being increasingly practiced, there is a paucity of data regarding temporal and therapy-driven genomic evolution in pHGGs. To better understand the genetic landscape of pHGGs at recurrence, we performed whole exome, transcriptome and methylation analyses on pHGG matched primary and recurrent tumors from 16 patients, median age of 15 years (range: 4–29). Matched normal tissue, where available, was evaluated to determine mutation somatic status. Genetic mutational results suggested that our cohort could be segregated into 3 groups. Group 1 tumor pairs (n=6) carry driver mutations in histone 3 (H3F3A, HIST1H3B) or IDH1 that were retained between the primary tumor and recurrence. In tumors with H3F3A and IDH1 mutations, their obligate partner TP53 or ATRX mutations were also conserved. Group 2 tumor pairs (n=8) were histone 3 or IDH1 wild-type, but most harbored mutations in genes that are modifiers of histone or chromatin (KMT2D, ZMYND11, EP300, BCOR). TP53 and ATRX driver mutations were present in 50% (n=4) of tumors, and 25% (n=2) had a BRAF V600E mutation. Mutations in other putative drug targets (EGFR, ERBB2, PI3-kinase mutations) were not always shared between primary and recurrent tumors, indicating evolution during tumor progression. Group 3 samples (n=2) carried germline mutations in NF1. Mutational burden, gene ontology analysis and correlation with treatment exposure are ongoing. The finding that key driver mutations, some of which are targetable (e.g. IDH1, BRAF V600E) are conserved at recurrence, while other targetable mutations are acquired, indicates that re-biopsy at recurrence may provide better guidance for effective treatment of pHGG with targeted therapy.

There is a paucity of data regarding patterns of progression in children with high-grade glioma (HGG) or diffuse intrinsic pontine glioma (DIPG) treated with bevacizumab (BVZ) at diagnosis. We performed a retrospective study of 20 children with HGG or DIPG who received BVZ-based therapy at diagnosis on, or according to, a bi-institutional study. Magnetic resonance imaging (MRI) characteristics of first and most recent progressions were reviewed. Comparison was made to a control group of 19 patients who never received BVZ. Imaging definitions of progressive disease (PD) were local: at primary site or within 2 cm, contiguous; diffuse: >2 cm away but contiguous with primary site, ill-defined and infiltrative; distant: new, non-contiguous disease. In the BVZ-treated group, 14 patients had DIPG, six patients had HGG. Median age was 7 years (range: 3-21). Median time to PD and follow-up were 8.8 months (range 4-21) and 11 months (range: 6-25), respectively. Among 14 patients with PD, 8 (57.1 %) had local PD, 6 (42.9 %) had local and diffuse/distant PD, at initial progression. At most recent progression, a median of 10.8 months (range 6-25) from diagnosis, 10 of 14 (71.4 %) had at least diffuse (n = 8), or distant (n = 6) PD. In the comparable control group, 15 patients had PD: 11(73.3 %) local, 4 (26.7 %) local and diffuse/distant PD at first and most recent progressions. Based on these data, we postulate that BVZ may lead to a higher incidence of distant and diffuse disease in newly-diagnosed children with HGG or DIPG who received BVZ-based therapy.

Purpose We conducted a pediatric phase I study to estimate the maximum tolerated dose (MTD), dose-limiting toxicities (DLT), and pharmacokinetic properties of vorinostat, a histone deacetylase (HDAC) inhibitor, when given in combination with temozolomide in children with refractory or recurrent CNS malignancies. Patients and Methods Vorinostat, followed by temozolomide approximately 1 hour later, was orally administered, once daily, for 5 consecutive days every 28 days at three dose levels using the rolling six design. Studies of histone accumulation in peripheral blood mononuclear cells were performed on Day 1 at 0, 6, and 24 hours after vorinostat dosing. Vorinostat pharmacokinetics (PK) and serum MGMT promoter status were also assessed. Results Nineteen eligible patients were enrolled and 18 patients were evaluable for toxicity. There were no DLTs observed at dose level 1 or 2. DLTs occurred in four patients at dose level 3: thrombocytopenia (4), neutropenia (3), and leucopenia (1). Non-dose limiting grade 3 or 4 toxicities related to protocol therapy were also hematologic and included neutropenia, lymphopenia, thrombocytopenia, anemia, and leucopenia. Three patients exhibited stable disease and one patient had a partial response. There was no clear relationship between vorinostat dosage and drug exposure over the dose range studied. Accumulation of acetylated H3 histone in PBMC was observed after administration of vorinostat. Conclusion Five-day cycles of vorinostat in combination with temozolomide are well tolerated in children with recurrent CNS malignancies with myelosuppression as the DLT. The recommended phase II combination doses are vorinostat, 300 mg/m2/day and temozolomide, 150 mg/m2/day. Pediatr Blood Cancer 2013;160:1452–1457. © 2013 Wiley Periodicals, Inc.

Primary glial brain tumors account for the majority of primary brain tumors in children. They are classified as low-grade gliomas (LGG) or high-grade gliomas (HGG), based on specific pathologic characteristics of the tumor, resulting in disparate clinical prognoses. Surgery is a mainstay of treatment for HGG, although it is not curative, and adjuvant therapy is required. Temozolomide, an oral imidazotetrazine prodrug, while considered standard of care for adult HGG, has not shown the same degree of benefit in the treatment of pediatric HGG. There are significant biologic differences that exist between adult and pediatric HGG, and targets specifically aimed at the biology in the pediatric population are required. Novel and specific therapies currently being investigated for pediatric HGG include small molecule inhibitors of epidermal growth factor receptor, platelet-derived growth factor receptor, histone deacetylase, the RAS/AKT pathway, telomerase, integrin, insulin-like growth factor receptor, and γ-secretase. Surgery is also the mainstay for LGG. There are defined front-line, multiagent chemotherapy regimens, but there are few proven second-line chemotherapy options for refractory patients. Approaches such as the inhibition of the mammalian target of rapamycin pathway, inhibition of MEK1 and 2, as well as BRAF, are discussed. Further research is required to understand the biology of pediatric gliomas as well as the use of molecularly targeted agents, especially in patients with surgically unresectable tumors.

Desmoplastic infantile gangliogliomas (DIG) are intracranial tumors described in 1987 as benign lesions of infancy. A literature review and the clinical course of 3 patients reported herein suggest that the initial description should be amended. Nearly 23% of DIG cases occur in children older than 24 months. Approximately 40% of DIG cases require additional medical, radiation, and/or further surgical intervention, and 15% of infants and children develop leptomeningeal spread or die from DIG. Such adverse outcomes, combined with the recognition that DIG represents a heterogeneous disease, underscore the need for an expanded biological and molecular investigation.

Malignant peripheral nerve sheath tumor (MPNST) is a rare soft-tissue sarcoma with an unfavorable prognosis and limited therapeutic options. MPNSTs can be sporadic, but are often associated with neurofibromatosis (NF) 1 and usually arise from preexisting neurofibromas. MPNSTs in patients with NF2 have been reported in only exceedingly rare cases, and the mechanisms underlying transformation into an MPNST have not been fully elucidated. Here, we describe the clinicopathological and genomic features of a peripheral nerve sheath tumor (PNST), with a primary diagnosis of a neurofibroma, as it transforms into a high-grade MPNST in the context of NF2.

INTRODUCTION: Pediatric low-grade gliomas (pLGG) represent the most common brain tumors in children. Though malignant transformation is rare, these tumors pose a formidable therapeutic challenge due to anatomy-limiting surgical options and local recurrence. The temporal and therapy-driven genomic evolution in pLGG is largely unknown. METHODS: To characterize the temporal genomic heterogeneity of pLGG, we performed fluorescence in situ hybridization, mutation-specific immunohistochemistry, and exome analyses on paired tumor samples from primary diagnostic and subsequent surgeries of 27 pLGG patients. RESULTS: 59 tumor samples were available for review and included pilocytic / pilomyxoid astrocytoma (PA) (67%), low grade astrocytoma (19%), ganglioglioma (11%), and pleomorphic xanthoastrocytoma (3%). BRAF duplication/rearrangement was detected in 56% of tested samples, limited to PA in all but one patient (ganglioglioma). 58% of samples harbored CDKN2A deletion, which was demonstrable across various histologies. BRAF duplication/rearrangement was found consistently conserved across primary and subsequent surgical samples, whereas CDKN2A status changed in 60% of tested temporal pairs, with deletion acquisition the most frequent finding (40%) at second surgery. Likewise, BRAF V600E mutation in one PA was lost at second surgery. Although CDKN2A status changes were seen following surgery alone, the addition of chemo-and/or radiation therapy was associated with a higher rate of temporal CDKN2A deletion acquisition (50%, versus 33% with surgery alone). CONCLUSION: Temporal genomic heterogeneity may be encountered in a significant proportion of pLGG, with some alterations potentially facilitated by therapy. Recurrence biopsy may provide improved guidance, particularly if targeted therapeutics are being considered.

10506Background: The primary treatment for many pediatric patients (pts) with low-grade glioma (LGG) remains surgical resection with curative intent. However, pts whose tumors cannot be completely ...

Juvenile pilocytic astrocytoma, the most common pediatric central nervous system (CNS) neoplasm, characteristically displays an indolent growth pattern and rarely demonstrates metastatic dissemination. Reports of infections mimicking CNS metastatic disease are also rare and can impact treatment. We report the youngest known case of a child with a CNS Nocardia farcinica infection who had a known cerebellar pilocytic astrocytoma, review other infections that may masquerade as CNS neoplasms, and discuss N. farcinica CNS infections.

Although bevacizumab has not proven effective in adults with newly diagnosed high-grade gliomas (HGG), feasibility in newly diagnosed children with diffuse intrinsic pontine gliomas (DIPG) or HGG has not been reported in a prospective study. In a safety and feasibility study, children and young adults with newly diagnosed HGG received radiotherapy (RT) with bevacizumab (10 mg/kg: days 22, 36) and temozolomide (75-90 mg/m(2)/day for 42 days) followed by bevacizumab (10 mg/kg, days 1, 15), irinotecan (125 mg/m(2), days 1, 15) and temozolomide (150 mg/m(2)/day days 1-5). DIPG patients did not receive temozolomide. Telomerase activity, quality of life (QOL), and functional outcomes were assessed. Among 27 eligible patients (15 DIPG, 12 HGG), median age 10 years (range 3-29 years), 6 discontinued therapy for toxicity: 2 during RT (grade 4 thrombocytopenia, grade 3 hepatotoxicity) and 4 during maintenance therapy (grade 3: thrombosis, hypertension, skin ulceration, and wound dehiscence). Commonest ≥grade 3 toxicities included lymphopenia, neutropenia and leukopenia. Grade 3 hypertension occurred in 2 patients. No intracranial hemorrhages occurred. For DIPG patients, median overall survival (OS) was 10.4 months. For HGG patients, 3-year progression free survival and OS were 33 % (SE ± 14 %) and 50 % (SE ± 14 %), respectively. All 3 tested tumor samples, demonstrated histone H3.3K27M (n = 2 DIPG) or G34R (n = 1 HGG) mutations. QOL scores improved over the course of therapy. A bevacizumab-based regimen is feasible and tolerable in newly diagnosed children and young adults with HGG and DIPG.

INTRODUCTION: Telomerase activation is critical in many cancers including CNS tumors making telomerase inhibition a potential therapeutic target. Imetelstat is an oligonucleotide that binds to the template region of the RNA component of human telomerase and inhibits its enzymatic activity. METHODS: We conducted a molecular biology (MB) and phase II study to estimate inhibition of tumor telomerase activity and sustained responses by imetelstat in children with recurrent CNS malignancies. In the MB study, patients with recurrent medulloblastoma, high-grade glioma (HGG) or ependymoma undergoing resection received one dose of imetelstat as a 2-hour intravenous infusion at 285 mg/m2, 12-24 hours before surgery. Telomerase activity was evaluated by TRAP assay in fresh tumor from surgery. Post-surgery and in the phase II study, patients received imetelstat IV (days 1 and 8 q 21-days) at 285mg/m2. Imetelstat pharmacokinetic and pharmacodynamics studies were performed during cycle 1. RESULTS: Of 2 evaluable patients on the MB trial, intratumoral telomerase activity was inhibited by 95% compared to baseline archival tissue in one patient (HGG) and was inevaluable in one patient (medulloblastoma) due to tumor hemorrhage. Forty-two patients (40 evaluable for toxicity) were enrolled: 9 medulloblastomas, 18 HGG, 4 ependymomas, 9 diffuse intrinsic pontine gliomas. The most common grade 3/4 toxicities included thrombocytopenia (32.5%), lymphopenia (17.5%), neutropenia (12.5%), ALT (7.5%) and AST (5%) elevation. Two patients died of intratumoral hemorrhage secondary to thrombocytopenia leading to premature study closure. The median number of courses in the phase II trial was 1 (range 1-3). No objective responses were observed. Telomerase inhibition was observed in peripheral blood mononuclear cells (PBMCs) for at least 8 days. CONCLUSION: Imetelstat demonstrated intratumoral and PBMC target inhibition; however, the regimen proved too toxic in children with recurrent CNS tumors.

BACKGROUND: Primary pediatric central nervous system (CNS) malignancies often have poor outcomes despite intensive treatment. Clinical immunotherapeutic trials targeting the programmed cell death receptor (PD-1) and its ligand (PD-L1) have been successful in some cancers. One of the most promising biomarkers for response has been the expression of PD-L1, although this has been not universally predictive and its presence in pediatric CNS tumors remains unknown. METHODS: One hundred formalin-fixed, paraffin embedded samples from children with various pediatric CNS malignancies were collected, including twenty-five of each of the following: ependymoma, high-grade glioma (HGG), supratentorial primitive neuroectodermal tumor (sPNET), and medulloblastoma. Patient characteristics and disease outcomes were also obtained. Chromogenic immunohistochemical staining of PD-L1 and PD1 was completed with prevalence of stained cells scored on a 0–5 scale. ‘Positive’ expression was assigned to scores of three or greater. Gene expression was analyzed using an nCounter Nanostring immunologic gene expression codeset. RESULTS: IHC was successful except in one patient with sPNET and two with HGG. PDL1 expression was robust in a subset of tumors, with ‘positive’ staining in 8 (33%) ependymomas, 4 (17%) high-grade gliomas, 2 (8%) sPNETs, and 0 medulloblastomas; PD1 staining was similarly heterogeneous. RNA extraction and expression analysis was successful in all but one sPNET and one HGG. Hierarchical clustering with respect to genes involved in inflammatory pathways identified distinct subgroups within each tumor type; in particular, medulloblastoma was noted to demonstrate activation of inflammatory genes. PD1/PD-L1 expression data did not correlate with histologic staining. Further analysis of the relationship between clinical information and gene expression is ongoing. CONCLUSIONS: This study demonstrates the tumor-specific PDL1/PD1 expression across tumor types and also provides immunologic phenotypic information that may be useful for future rational immunotherapy development in children with CNS malignancy.

Pediatric tectal plate gliomas are indolent slow-growing gliomas that often present with increased intracranial pressure or incidentally on routine brain imaging. We investigated clinical outcomes, endocrinopathies, and neuropsychological sequelae associated with tectal plate gliomas. Twenty-six patients with tectal plate glioma were identified in a 20-year retrospective review. Clinical outcomes, treatments, endocrine function, neuropsychological testing outcomes and radiographic imaging were reviewed for possible signs correlating with tumor progression. Among 26 patients, 19 presented with signs or symptoms of increased intracranial pressure (73 %) versus an incidental finding in 7 (27 %). Median follow-up was 46 months (range 8-143 months). Six of 26 (23 %) experienced progressive disease after diagnosis. Five of 26 (19 %) required more than one surgical procedure due to failure of initial endoscopic third ventriculostomy. Seven of 26 had history of endocrine dysfunction, of which, five presented with endocrine dysfunction (precocious puberty or short stature), 1 developed menstrual irregularities after surgical intervention and 1 had preexisting pan hypopituitarism. Of 12 patients with available neuropsychological testing, eleven had at least one indicator of executive functioning in the low-average to impaired range. While tectal plate gliomas have been considered indolent tumors that are rarely progressive, 23 % of patients in our cohort experienced disease progression and required further therapy. Neurocognitive deficits may occur, while endocrine deficiency is uncommon. Regular multidisciplinary oncology follow-up, routine monitoring with MRI and formal neurocognitive evaluation are imperative to provide early recognition of disease progression or recurrent hydrocephalus and to improve school functioning in this population.

BK virus (BKV) is an increasingly identified cause of pathology in immunocompromised transplant recipients. BKV is a well-known cause of graft dysfunction following renal transplantation and has also been reported in the native kidneys of other solid organ recipients. Less commonly, BKV nephropathy occurs in allogeneic stem-cell transplant (SCT) recipients. We now describe the first reported case of BKV nephropathy after pediatric autologous SCT. Pediatr Blood Cancer 2011;56:495–497. © 2010 Wiley-Liss, Inc.

Plexiform neurofibromas (PN) are a hallmark of neurofibromatosis type 1 (NF1). These large nerve tumors can be disfiguring and surgery is the only known standard therapy. Surgical intervention may be suboptimal due to the diffuse nature of PN. Here, we present a case in which we describe the use of high-dose carboplatin to treat the patient's testicular seminoma which resulted in the decrease in size of a PN in a patient with NF1.

Embryonal renal sarcomas were first identified in 1995 among banked tumor samples originally classified as adult Wilms tumor. Few long-term remissions were observed when these rare tumors were treated with chemotherapy usually used for childhood Wilms. Data were collected from the medical record of an adolescent female with embryonal renal sarcoma and treated with sarcoma-directed chemotherapy and radiation. At 66 months following diagnosis, the patient has no evidence of tumor but has experienced severe renal dysfunction and ovarian failure. We believe there is a subset of patients with disseminated embryonal renal sarcoma that respond to intense sarcoma-directed therapy.

Background Prior reviews of phase I pediatric oncology trials involving primarily cytotoxic agents have reported objective response rates (ORRs) and toxic death rates of 7.9–9.6% and 0.5%, respectively. These data may not reflect safety and efficacy in phase I trials of molecularly targeted (targeted) drugs. Methods A systematic review of pediatric phase I solid tumor trials published in 1990–2013 was performed. The published reports were evaluated for patient characteristics, toxicity information, and response numbers. Results A total of 143 phase I pediatric clinical trials enrolling 3,896 children involving 53 targeted and 48 cytotoxic drugs were identified. A meta-analysis demonstrated that the ORR is 2.1-fold higher with cytotoxic drugs (0.066 vs. 0.031 per subject; P = 0.007). By contrast, the pooled estimate of the stable disease rate (SDR) is similar for cytotoxic and targeted drugs (0.2 vs. 0.23 per subject; P = 0.27). The pooled estimate of the dose-limiting toxicity rate is 1.8-fold larger with cytotoxic drugs (0.24 vs. 0.13 per subject; P = 0.0003). The hematologic grade 3–4 (G3/4) toxicity rate is 3.6-fold larger with cytotoxic drugs (0.43 vs. 0.12 per treatment course; P = 0.0001); however, the nonhematologic G3/4 toxicities and toxic deaths occur at similar rates for cytotoxic and targeted drugs. Conclusions In phase I pediatric solid tumor trials, ORRs were significantly higher for cytotoxic versus targeted agents. SDRs were similar in targeted and cytotoxic drug trials. Patients treated with cytotoxic agents were more likely to experience hematologic G3/4 toxicities than those patients receiving targeted drugs.

Optic pathway gliomas (OPGs) occur in 15%-20% of children with neurofibromatosis type 1 (NF1); up to half become symptomatic. There is little information regarding ophthalmologic outcomes after chemotherapy. A retrospective multicenter study was undertaken to evaluate visual outcomes following chemotherapy for NF1-associated OPG, to identify risks for visual loss, and to ascertain indications for treatment. Subjects included children undergoing initial treatment for OPGs with chemotherapy between January 1997 and December 2007. Of 115 subjects, visual acuity (VA) decline and tumor progression were the primary reasons to initiate treatment, although there were significant differences in the pattern of indications cited among the institutions. Eighty-eight subjects and 168 eyes were evaluable for VA outcome. At completion of chemotherapy, VA improved (32% of subjects), remained stable (40%), or declined (28%). Tumor location was the most consistent prognostic factor for poor VA outcome. There was poor correlation between radiographic and VA outcomes. Although visual outcomes for NF1-associated OPG are not optimal, approximately one-third of children regain some vision with treatment. Since radiographic outcomes do not predict visual outcomes, their use as the primary measure of treatment success is in question. The lack of consensus regarding the indications for treatment underlines the need for better standardization of care. Future clinical trials for OPG require standardized visual assessment methods and clear definitions of visual outcomes.

Purpose: Plexiform neurofibromas (pNF) are Schwann cell tumors found in a third of individuals with neurofibromatosis type 1 (NF1). pNF can undergo transformation to malignant peripheral nerve sheath tumors (MPNST). There are no identified serum biomarkers of pNF tumor burden or transformation to MPNST. Serum biomarkers would be useful to verify NF1 diagnosis, monitor tumor burden, and/or detect transformation. Experimental Design: We used microarray gene expression analysis to define 92 genes that encode putative secreted proteins in neurofibroma Schwann cells, neurofibromas, and MPNST. We validated differential expression by quantitative reverse transcription-PCR, Western blotting, and ELISA assays in cell conditioned medium and control and NF1 patient sera. Results: Of 13 candidate genes evaluated, only adrenomedullin (ADM) was confirmed as differentially expressed and elevated in serum of NF1 patients. ADM protein concentrati on was further elevated in serum of a small sampling of NF1 patients with MPNST. MPNST cell conditioned medium, containing ADM and hepatocyte growth factor, stimulated MPNST migration and endothelial cell proliferation. Conclusions: Thus, microarray analysis identifies potential serum biomarkers for disease, and ADM is a serum biomarker of NF1. ADM serum levels do not seem to correlate with the presence of pNFs but may be a biomarker of transformation to MPNST. Clin Cancer Res; 16(20); 5048–57. ©2010 AACR.

10004 Background: Dabrafenib is an orally available, selective ATP-competitive inhibitor of BRAF V600E kinase, approved in unresectable or metastatic melanoma pts with the V600E mutation. This international study was designed to determine the recommended phase 2 dose (RP2D) in pts 12yrs and [≤] 12yrs. Doses of 3.0, 3.75, 4.5, and 5.25mg/kg/day were assessed by a rolling six design. When a dose level was filled and under assessment, additional pts could join the previous dose level deemed tolerable. Results: Enrollment for phase 1 completed at 27 pts, 15 male, median age 9yrs (range 1-17), with HGG n = 8, LGG n = 15, LCH n = 2, and OST n = 2. One pt had a dose-limiting toxicity (DLT) of grade 3 maculopapular rash (MR) at 4.5mg/kg/day, but is on study {approx}9mths after restarting dabrafenib at 3.75mg/kg/day. Serious adverse events judged related to dabrafenib included MR (1 pt); hypotension, disseminated intravascular coagulation, fever (1 pt, outside DLT period); and arthralgia (1 pt). Duration on study ranged from 9wks to 19mo (ongoing); 20 pts remain on treatment. The RP2D for pts > 12yrs is 4.5mg/kg/day (median AUC 5285) and 5.25mg/kg/day (median AUC 4384) for [≤] 12yrs. Investigator-assessed best radiographic responses included 3 complete response (CR), 3 partial response (PR) and 2 progressive disease (PD) in HGG; 8 PR, 6 stable disease (SD) and 1 PD in LGG; 2 CR in LCH; 1 SD and 1 PD in OST (source data verification ongoing). Conclusions: The RP2D of dabrafenib for children > 12yrs and for those [≤] 12 was determined based on the target AUC when taken twice daily. The drug was well-tolerated with manageable toxicity. A high proportion of pts demonstrated radiographic responses in this phase 1 trial in different BRAF V600E-positive tumors. The disease stratified phase 2 component of the study is underway (NCT01677741). Clinical trial information: NCT01677741.

11011 Background: NGS has been rapidly introduced into routine clinical care for select adult malignancies, and the National Cancer Institute genomic precision medicine initiatives (e.g. M-PACT, NC...

10056 Background: Dabrafenib is a selective inhibitor of V600 mutant BRAF kinase activity with a mechanism of action consistent with adenosine triphosphate-competitive inhibition. Dabrafenib has de...

9579 Background: The looser chromatin structure seen following treatment with histone deacetylase (HDAC) inhibitors is hypothesized to render cells more sensitive to drugs targeting DNA. A phase I trial of vorinostat (VOR), an HDAC inhibitor, combined with temozolomide (TEM) was conducted to investigate the maximum tolerated dose (MTD) and dose limiting toxicity (DLT) of this combination. VOR pharmacokinetics (PK), serum MGMT promoter status, and histone acetylation in peripheral blood mononuclear cells were also assessed. Methods: VOR followed by TEM were orally administered, once daily, for 5 consecutive days every 28 days at 3 dose levels using the rolling 6 design. The respective dose levels for VOR and TEM were: (1) 230 mg/m2/day; 150 mg/m2/day, (2) 300 mg/m2/day; 150 mg/m2/day and (3) 300 mg/m2/day; 200 mg/m2/day. Studies of histone accumulation in peripheral blood mononuclear cells were performed on day 1 at 0, 6, and 24 h after vorinostat dosing. Vorinistat pharmacokinetics (PK) and serum MGMT pro...

9543 Background: Prior reviews of phase I pediatric oncology trials involving primarily cytotoxic agents have reported objective response rates (ORR) and toxic death rates (TDR) of 7.9-9.6% and 0.5%, respectively. These data may not reflect safety and efficacy in phase I trials of often cytostatic, molecularly targeted drugs. Methods: A systematic review of pediatric phase I oncology trials in patients with refractory solid tumors published from 1990 to 2010 was performed. Publications were identified through a PubMed query for “phase I,” “pediatric” and “cancer” search terms. The published reports were evaluated for patient characteristics, toxicity information and response numbers. Additional data regarding disease response and stability, time to progression, and toxicity will be obtained from a subgroup of 18 published Children’s Oncology Group phase I trials for further analyses. Results: Eighty-nine phase I pediatric solid tumor clinical trials enrolling 2505 children were identified. Thirty trials i...