Faculty Bibliography

BACKGROUND:Diffuse Midline Glioma (DMG) with the H3K27M mutation is a lethal childhood brain cancer, with patients rarely surviving 2 years from diagnosis. METHODS:We conducted a multi-site Phase 1 trial of the imipridone ONC201 for children with H3K27M-mutant glioma (NCT03416530). Patients enrolled on Arm D of the trial (n=24) underwent serial lumbar puncture for cell-free tumor DNA (cf-tDNA) analysis and patients on all arms at the University of Michigan underwent serial plasma collection. We performed digital droplet polymerase chain reaction (ddPCR) analysis of cf-tDNA samples and compared variant allele fraction (VAF) to radiographic change (maximal 2D tumor area on MRI). RESULTS:Change in H3.3K27M VAF over time ("VAF delta") correlated with prolonged PFS in both CSF and plasma samples. Non-recurrent patients that had a decrease in CSF VAF displayed a longer progression free survival (p=0.049). Decrease in plasma VAF displayed a similar trend (p=0.085). VAF "spikes" (increase of at least 25%) preceded tumor progression in 8/16 cases (50%) in plasma and 5/11 cases (45.4%) in CSF. In individual cases, early reduction in H3K27M VAF predicted long-term clinical response (>1 year) to ONC201, and did not increase in cases of later-defined pseudo-progression. CONCLUSION/CONCLUSIONS:Our work demonstrates the feasibility and potential utility of serial cf-tDNA in both plasma and CSF of DMG patients to supplement radiographic monitoring. Patterns of change in H3K27M VAF over time demonstrate clinical utility in terms of predicting progression and sustained response and possible differentiation of pseudo-progression and pseudo-response.

Background/UNASSIGNED:The Head Start treatment protocols have focused on curing young children with brain tumors while avoiding or delaying radiotherapy through using a combination of high-dose, marrow-ablative chemotherapy and autologous hematopoietic cell transplantation (AuHCT). Late effects data from treatment on the Head Start II (HS II) protocol have previously been published for short-term follow-up (STF) at a mean of 39.7 months post-diagnosis. The current study examines long-term follow-up (LTF) outcomes from the same cohort. Methods/UNASSIGNED:Eighteen HS II patients diagnosed with malignant brain tumors <10 years of age at diagnosis completed a neurocognitive battery and parents completed psychological questionnaires at a mean of 104.7 months' post-diagnosis. Results/UNASSIGNED:There was no significant change in Full Scale IQ at LTF compared to baseline or STF. Similarly, most domains had no significant change from STF, including verbal IQ, performance IQ, academics, receptive language, learning/memory, visual-motor integration, and externalizing behaviors. Internalizing behaviors increased slightly at LTF. Clinically, most domains were within the average range, except for low average mathematics and receptive language. Additionally, performance did not significantly differ by age at diagnosis or time since diagnosis. Of note, children treated with high-dose methotrexate for disseminated disease or atypical teratoid/rhabdoid tumor displayed worse neurocognitive outcomes. Conclusions/UNASSIGNED:These results extend prior findings of relative stability in intellectual functioning for a LTF period. Ultimately, this study supports that treatment strategies for avoiding or delaying radiotherapy using high-dose, marrow-ablative chemotherapy and AuHCT may decrease the risk of neurocognitive and social-emotional declines in young pediatric brain tumor survivors.

Diffuse midline glioma (DMG) with the H3K27M mutation is a lethal childhood brain cancer, with patients rarely surviving 2 years from diagnosis. We conducted a multi-site Phase 1 trial of the imipridone ONC201 for children with H3K27M-mutant glioma (NCT03416530). Patients enrolled on Arm D of the trial (n=24) underwent serial lumbar puncture (baseline, 2, 6 months) for cell-free tumor DNA (cf-tDNA) analysis at time of MRI. Additionally, patients on all arms of the trial at the University of Michigan underwent serial plasma collection. CSF collection was feasible in this cohort, with no procedural complications. We collected 96 plasma samples and 53 CSF samples from 29 patients, including those with H3F3A (H3.3) (n=13), HIST13HB (H3.1) (n= 4), and unknown H3 status/not biopsied (n=12) [range of 0-8 CSF samples and 0-10 plasma samples]. We performed digital droplet polymerase chain reaction (ddPCR) analysis and/or ampliconbased electronic sequencing (Oxford Nanopore) of cf-tDNA samples and compared variant allele fraction (VAF) to radiographic change (maximal 2D tumor area on MRI). Preliminary analysis of samples demonstrates a correlation between changes in tumor size and H3K27M cf-tDNA VAF, when removing samples with concurrent bevacizumab. In multiple cases, early reduction in CSF cf-tDNA predicts long-term clinical response (>1 year) to ONC201, and does not increase in cases of later-defined pseudo-progression (radiation necrosis). For example, a now 9-year old patient with thalamic H3K27M-mutant DMG underwent treatment with ONC201 after initial radiation and developed increase in tumor size at 4 months post-radiation (124% baseline) of unclear etiology at the time. Meanwhile, her ddPCR declined from baseline 6.76% VAF to <1%, which has persisted, with now near complete response (15% tumor reduction) at 30 months on treatment from diagnosis. In summary, we present the feasibility and utility of serial CSF/plasma monitoring of a promising experimental therapy for DMG

PURPOSE/OBJECTIVE:Constitutional mismatch repair deficiency syndrome (CMMRD) is a lethal cancer predisposition syndrome characterized by early-onset synchronous and metachronous multiorgan tumors. We designed a surveillance protocol for early tumor detection in these individuals. PATIENTS AND METHODS/METHODS:Data were collected from patients with confirmed CMMRD who were registered in the International Replication Repair Deficiency Consortium. Tumor spectrum, efficacy of the surveillance protocol, and malignant transformation of low-grade lesions were examined for the entire cohort. Survival outcomes were analyzed for patients followed prospectively from the time of surveillance implementation. RESULTS:< .0001). Of the 64 low-grade tumors detected, the cumulative likelihood of transformation from low-to high-grade was 81% for GI cancers within 8 years and 100% for gliomas in 6 years. CONCLUSION/CONCLUSIONS:Surveillance and early cancer detection are associated with improved OS for individuals with CMMRD.

Early detection and serial therapeutic monitoring for pediatric brain tumors are essential for diagnosis and therapeutic intervention. Currently, neuropathological diagnosis relies on biopsy of tumor tissue and surgical intervention. There is a great clinical need for less invasive methods to molecularly characterize the tumor and allow for more reliable monitoring of patients during treatment and to identify patients that might potentially benefit from targeted therapies, particularly in the setting where diagnostic tissue cannot be safely obtained. In this literature review, we highlight recent studies that describe the use of circulating tumor DNA, circulating tumor cells, circulating RNA and microRNA, and extracellular vesicles as strategies to develop liquid biopsies in pediatric central nervous system tumors. Liquid biomarkers have been demonstrated using plasma, urine, and cerebrospinal fluid. The use of liquid biopsies to help guide diagnosis, determine treatment response, and analyze mechanisms of treatment resistance is foreseeable in the future. Continued efforts to improve signal detection and standardize liquid biopsy procedures are needed for clinical application.