ONC201 (Dordaviprone) in Recurrent H3 K27M-Mutant Diffuse Midline Glioma

PURPOSE

Histone 3 (H3) K27M-mutant diffuse midline glioma (DMG) has a dismal prognosis with no established effective therapy beyond radiation. This integrated analysis evaluated single-agent ONC201 (dordaviprone), a first-in-class imipridone, in recurrent H3 K27M-mutant DMG.

METHODS

Fifty patients (pediatric, n = 4; adult, n = 46) with recurrent H3 K27M-mutant DMG who received oral ONC201 monotherapy in four clinical trials or one expanded access protocol were included. Eligible patients had measurable disease by Response Assessment in Neuro-Oncology (RANO) high-grade glioma (HGG) criteria and performance score (PS) ≥60 and were ≥90 days from radiation; pontine and spinal tumors were ineligible. The primary end point was overall response rate (ORR) by RANO-HGG criteria. Secondary end points included duration of response (DOR), time to response (TTR), corticosteroid response, PS response, and ORR by RANO low-grade glioma (LGG) criteria. Radiographic end points were assessed by dual-reader, blinded independent central review.

RESULTS

The ORR (RANO-HGG) was 20.0% (95% CI, 10.0 to 33.7). The median TTR was 8.3 months (range, 1.9-15.9); the median DOR was 11.2 months (95% CI, 3.8 to not reached). The ORR by combined RANO-HGG/LGG criteria was 30.0% (95% CI, 17.9 to 44.6). A ≥50% corticosteroid dose reduction occurred in 7 of 15 evaluable patients (46.7% [95% CI, 21.3 to 73.4]); PS improvement occurred in 6 of 34 evaluable patients (20.6% [95% CI, 8.7 to 37.9]). Grade 3 treatment-related treatment-emergent adverse events (TR-TEAEs) occurred in 20.0% of patients; the most common was fatigue (n = 5; 10%); no grade 4 TR-TEAEs, deaths, or discontinuations occurred.

CONCLUSION

ONC201 monotherapy was well tolerated and exhibited durable and clinically meaningful efficacy in recurrent H3 K27M-mutant DMG.

Clinical Efficacy of ONC201 in H3K27M-Mutant Diffuse Midline Gliomas Is Driven by Disruption of Integrated Metabolic and Epigenetic Pathways

Patients with H3K27M-mutant diffuse midline glioma (DMG) have no proven effective therapies. ONC201 has recently demonstrated efficacy in these patients, but the mechanism behind this finding remains unknown. We assessed clinical outcomes, tumor sequencing, and tissue/cerebrospinal fluid (CSF) correlate samples from patients treated in two completed multisite clinical studies. Patients treated with ONC201 following initial radiation but prior to recurrence demonstrated a median overall survival of 21.7 months, whereas those treated after recurrence had a median overall survival of 9.3 months. Radiographic response was associated with increased expression of key tricarboxylic acid cycle-related genes in baseline tumor sequencing. ONC201 treatment increased 2-hydroxyglutarate levels in cultured H3K27M-DMG cells and patient CSF samples. This corresponded with increases in repressive H3K27me3 in vitro and in human tumors accompanied by epigenetic downregulation of cell cycle regulation and neuroglial differentiation genes. Overall, ONC201 demonstrates efficacy in H3K27M-DMG by disrupting integrated metabolic and epigenetic pathways and reversing pathognomonic H3K27me3 reduction.

SIGNIFICANCE

The clinical, radiographic, and molecular analyses included in this study demonstrate the efficacy of ONC201 in H3K27M-mutant DMG and support ONC201 as the first monotherapy to improve outcomes in H3K27M-mutant DMG beyond radiation. Mechanistically, ONC201 disrupts integrated metabolic and epigenetic pathways and reverses pathognomonic H3K27me3 reduction. This article is featured in Selected Articles from This Issue, p. 2293.

Capicua (CIC) mutations in gliomas in association with MAPK activation for exposing a potential therapeutic target

Gliomas are the most prevalent neurological cancer in the USA and care modalities are not able to effectively combat these aggressive malignancies. Identifying new, more effective treatments require a deep understanding of the complex genetic variations and relevant pathway associations behind these cancers. Drawing connections between gene mutations with a responsive genetic target can help drive therapy selections to enhance patient survival. We have performed extensive molecular profiling of the Capicua gene (CIC), a tumor and transcriptional suppressor gene, and its mutation prevalence in reference to MAPK activation within clinical glioma tissue. CIC mutations occur far more frequently in oligodendroglioma (52.1%) than in low-grade astrocytoma or glioblastoma. CIC-associated mutations were observed across all glioma subtypes, and MAPK-associated mutations were most prevalent in CIC wild-type tissue regardless of the glioma subtype. MAPK activation, however, was enhanced in CIC-mutated oligodendroglioma. The totality of our observations reported supports the use of CIC as a relevant genetic marker for MAPK activation. Identification of CIC mutations, or lack thereof, can assist in selecting, implementing, and developing MEK/MAPK-inhibitory trials to improve patient outcomes potentially.

Radiotherapy combined with nivolumab or temozolomide for newly diagnosed glioblastoma with unmethylated MGMT promoter: An international randomized phase III trial

BACKGROUND

Addition of temozolomide (TMZ) to radiotherapy (RT) improves overall survival (OS) in patients with glioblastoma (GBM), but previous studies suggest that patients with tumors harboring an unmethylated MGMT promoter derive minimal benefit. The aim of this open-label, phase III CheckMate 498 study was to evaluate the efficacy of nivolumab (NIVO) + RT compared with TMZ + RT in newly diagnosed GBM with unmethylated MGMT promoter.

METHODS

Patients were randomized 1:1 to standard RT (60 Gy) + NIVO (240 mg every 2 weeks for eight cycles, then 480 mg every 4 weeks) or RT + TMZ (75 mg/m2 daily during RT and 150-200 mg/m2/day 5/28 days during maintenance). The primary endpoint was OS.

RESULTS

A total of 560 patients were randomized, 280 to each arm. Median OS (mOS) was 13.4 months (95% CI, 12.6 to 14.3) with NIVO + RT and 14.9 months (95% CI, 13.3 to 16.1) with TMZ + RT (hazard ratio [HR], 1.31; 95% CI, 1.09 to 1.58; P = .0037). Median progression-free survival was 6.0 months (95% CI, 5.7 to 6.2) with NIVO + RT and 6.2 months (95% CI, 5.9 to 6.7) with TMZ + RT (HR, 1.38; 95% CI, 1.15 to 1.65). Response rates were 7.8% (9/116) with NIVO + RT and 7.2% (8/111) with TMZ + RT; grade 3/4 treatment-related adverse event (TRAE) rates were 21.9% and 25.1%, and any-grade serious TRAE rates were 17.3% and 7.6%, respectively.

CONCLUSIONS

The study did not meet the primary endpoint of improved OS; TMZ + RT demonstrated a longer mOS than NIVO + RT. No new safety signals were detected with NIVO in this study. The difference between the study treatment arms is consistent with the use of TMZ + RT as the standard of care for GBM.ClinicalTrials.gov NCT02617589.

PATH-22. CLINICAL FEATURES AND MOLECULAR CHARACTERIZATION OF LEPTOMENINGEAL DISEASE IN PATIENTS WITH HIGH GRADE GLIOMA

INTRODUCTION

Leptomeningeal disease (LMD) is a challenging complication of high grade glioma (HGG) and critical questions remain unanswered regarding clinicopathologic risk factors, molecular associations, and optimal treatment.

METHODS

Patients with molecularly-profiled HGG (Caris Life Sciences; Phoenix, AZ) with LMD at two institutions were included. Medical records were reviewed for clinicopathological characteristics, treatment, and outcome. Kaplan-Meier estimates of patient survival were performed on censored data using Cox’s proportional hazard model.

RESULTS

43 patients (male: 33, female: 10; median age: 56 years) were identified, comprising 41 grade 4 (glioblastoma: 38; gliosarcoma: 2; H3K27M diffuse midline glioma: 1) and 2 grade 3 tumors (astrocytoma: 1; pleomorphic xanthoastrocytoma: 1). LMD diagnosed at HGG diagnosis (n=18) versus recurrence (n=22) was associated with longer post-LMD survival [pLMD-OS: 15.3m vs. 4.8m, HR: 0.07, 95% CI: 0.02-0.29, p=0.0004] but similar overall survival [mOS: 15.3m vs. 12.3m; HR: 0.82; 95% CI: 0.36-1.85; p=0.63]. Pathology-diagnosed LMD (n=15) versus MRI-diagnosed LMD (n=26) was associated with longer post-LMD survival [pLMD-OS: 15.4m vs. 5.2m, HR: 14.9, 95% CI: 0.01-0.30, p=0.0004] but similar overall survival [mOS: 17.1m vs. 12.3m; HR: 0.66; 95% CI: 0.3-1.58; p=0.38]. Post-LMD survival was significantly prolonged for supratentorial (n=28) versus infratentorial/spinal (n=4) locations regardless of the diagnostic modality [pLMD-OS: 2.6m vs. 11.3m, HR: 14.4, 95% CI: 2.73-75.7, p=0.0017], and did not significantly differ between symptomatic (n=20) and asymptomatic (n=23) patients [pLMD-OS: 4.8m vs. 11.2m, HR: 1.75, 95% CI: 0.82-3.77, p=0.15). pTERT mutation (81%), EGFR amplification (43%), and MGMT methylation (33%) were prevalent but IDH1 mutation was rare (2.8%). Comparison with a separate glioblastoma cohort (n=1400) suggested more frequent amplification of CHIC2, MDM4, and KDR, higher mutation rates of RUNX1, APC, and RAD51C, colder tumor microenvironment (TME), and lower expression of immune checkpoint-related genes.

CONCLUSIONS

Clinicopathological characteristics affect post-LMD survival, and cohort comparison suggests molecular and TME differences in LMD-HGG tumors.

CTNI-61. CLINICAL EFFICACY AND PREDICTIVE BIOMARKERS OF ONC201 IN H3K27M-MUTANT DIFFUSE MIDLINE GLIOMA

Patients with H3K27M-mutated diffuse midline glioma (DMG) have no proven effective therapies beyond radiation. ONC201, a DRD2 antagonist and mitochondrial ClpP agonist, has shown promise in this population. Clinical and genetic variables associated with ONC201 response in H3K27M-mutant DMG continue to be investigated. A combined clinical and genetic study evaluated patients with H3K27M-DMG treated with single-agent ONC201 at the established phase 2 dose. Clinical outcomes of patients treated on two recently completed multi-site clinical studies (NCT03416530 and NCT03134131, n = 75) were compared with historical control data from patients with confirmed H3K27M-DMG (n = 391 total, n = 119 recurrent). Patients treated with ONC201 monotherapy following initial radiation, but prior to recurrence, demonstrated a median overall survival (OS) of 25.6 months from diagnosis and recurrent patients demonstrated a median OS of 16.2 months from recurrence, both of these more than doubling historical outcomes. Using a Cox model to correct for age, gender and tumor location, OS of ONC201-treated patients with H3K27M-mutant tumors remained significantly better than non-ONC201-treated historical controls (p = 0.0001). A survival and radiographic analysis based on tumor location, revealed stronger responses in thalamic patients. In patients with thalamic tumors treated after initial radiation (n = 16), median OS was not reached with median follow up of 22.1 months (historical control median OS of 12.5 months, n = 83, p = 0.0001). Significant correlations were found between baseline cerebral blood flow (CBF) on perfusion imaging and OS (Pearson’s r = 0.75, p = 0.003) and between nrCBF and PFS (r = 0.77, p = 0.002). Baseline tumor sequencing from treated patients (n = 20) demonstrates EGFR mutation (n = 3) and high EGFR expression as a marker of resistance and improved response in tumors with MAPK-pathway alterations (n = 5). In conclusion, ONC201 demonstrates unprecedented clinical and radiographic efficacy in H3K27M-mutant DMG with outcomes enriched in patients with thalamic tumors, treatment prior to recurrence, MAPK-pathway alterations, and patients with relatively high CBF.

BIOM-43. THE GENOMIC, TRANSCRIPTOMIC, AND EPIGENOMIC LANDSCAPE OF ISOCITRATE DEHYDROGENASE WILD TYPE GLIOBLASTOMA ACROSS THE AGE CONTINUUM

BACKGROUND

Older age is a poor prognostic factor for glioblastoma (GBM) patients. We tested whether the intrinsic molecular landscape of the tumor may contribute to this poor prognosis.

METHODS

In accordance with the 2021 WHO classification scheme, we included only isocitrate dehydrogenase (IDH) wild type GBM. Based on published literature, we defined older as age > 65. RNA expression, gene amplification, tumor mutational burden (TMB) and mutational profiles were analyzed in three unique datasets: Tempus (n = 1,410), Caris (n = 1,432), and TCGA (n = 557). Comparison were made between < 65 and ³ 65 year olds using Pearson’s Chi-squared tests, Fisher’s exact tests, or Wilcoxon rank-sum where appropriate.

RESULTS

From our evaluable gene sets, TERT promoter mutations were more prevalent in patients ³ 65 years old (Caris 82.64 vs 77.27%, p = 0.016; Tempus 58.0 vs 49.0%, p = 0.002). There were no significant differences in PDCD1, CD274, CD3E, TNFRSF18, CD40, CD8A, TNFRSF4, CTLA4, HAVCR2, TNFSF9, CD274, or CDKN2A; PDL-1 (by IHC); dMMR/MSI-H, TMB; CDK6 amplification, EGFR amplification, EGFR, EGFRvIII, EGFR fusions, MET fusions, PTEN, TP53, or NF-1. MGMT promoter methylation (Caris data) was more common in the older group (49.73 v 34.14%, p < 0.001). TGCA data demonstrated that gene expression, TMB, and methylation did not change significantly with age. Additionally, PCOLCE2 and SLC10A4 were differentially methylated, and missense mutations, of any type, were more common in the older group (p=0.006).

CONCLUSION

Despite worse survival outcomes for older patients with IDHwt GBM as compared to younger counterparts, the molecular landscape is similar at the genomic, transcriptomic and epigenomic levels. The key exception is TERT promoter mutations that are more common in older GBM patients. Poorer survival is therefore not likely to be attributable solely to intratumoral factors.

Phase III trial of chemoradiotherapy with temozolomide plus nivolumab or placebo for newly diagnosed glioblastoma with methylated MGMT promoter

BACKGROUND

Nearly all patients with newly diagnosed glioblastoma experience recurrence following standard-of-care radiotherapy (RT) + temozolomide (TMZ). The purpose of the phase III randomized CheckMate 548 study was to evaluate RT + TMZ combined with the immune checkpoint inhibitor nivolumab (NIVO) or placebo (PBO) in patients with newly diagnosed glioblastoma with methylated MGMT promoter (NCT02667587).

METHODS

Patients (N = 716) were randomized 1:1 to NIVO [(240 mg every 2 weeks × 8, then 480 mg every 4 weeks) + RT (60 Gy over 6 weeks) + TMZ (75 mg/m2 once daily during RT, then 150-200 mg/m2 once daily on days 1-5 of every 28-day cycle × 6)] or PBO + RT + TMZ following the same regimen. The primary endpoints were progression-free survival (PFS) and overall survival (OS) in patients without baseline corticosteroids and in all randomized patients.

RESULTS

As of December 22, 2020, median (m)PFS (blinded independent central review) was 10.6 months (95% CI, 8.9-11.8) with NIVO + RT + TMZ vs 10.3 months (95% CI, 9.7-12.5) with PBO + RT + TMZ (HR, 1.1; 95% CI, 0.9-1.3) and mOS was 28.9 months (95% CI, 24.4-31.6) vs 32.1 months (95% CI, 29.4-33.8), respectively (HR, 1.1; 95% CI, 0.9-1.3). In patients without baseline corticosteroids, mOS was 31.3 months (95% CI, 28.6-34.8) with NIVO + RT + TMZ vs 33.0 months (95% CI, 31.0-35.1) with PBO + RT + TMZ (HR, 1.1; 95% CI, 0.9-1.4). Grade 3/4 treatment-related adverse event rates were 52.4% vs 33.6%, respectively.

CONCLUSIONS

NIVO added to RT + TMZ did not improve survival in patients with newly diagnosed glioblastoma with methylated or indeterminate MGMT promoter. No new safety signals were observed.

P11.17.B Molecular characterization of primary central nervous system lymphoma vs non-CNS lymphoma and correlation between mutational profile and treatment response

Background

Primary central nervous system lymphoma (PCNSL) is a unique type of non-Hodgkin lymphoma restricted to the central nervous system. Most cases are diffuse large B-cell lymphomas, but prognosis is far less favorable compared to extracerebral cases. Many mutations found in PCNSL converge on the NF-κB signaling pathway, leading to downstream activation of B-cell receptor (BCR) and NF-κB pathway. The differences in mutation frequency when compared to non-CNS lymphoma and how mutational profiles affect treatment response are not well understood. We compared the genomic profile of PCNSL and non-CNS lymphoma, evaluated the association between specific molecular alterations and survival, and analyzed the association between various mutations and response to therapy.

Materials and Methods

A total of 60 patients with PCNSL, 8 with secondary CNS lymphoma, and 202 with non-CNS B-cell lymphomas underwent molecular profiling at Caris Life Sciences (Phoenix, AZ). Analyses included next-generation sequencing of DNA (592 Genes, NextSeq or WES, NovaSeq) and RNA (WTS, NovaSeq). X2/Fisher’s-exact U tests were used for comparison, and significance was determined as p-value adjusted for multiple comparison by the Benjamini-Hochberg method (q<0.05). Overall survival (OS) was calculated from the start of temozolomide (TMZ) or tissue collection to last contact using insurance claims data.

Results

When compared to non-CNS lymphomas, PCNSL tumors showed significantly higher mutation rates in MYD88 (70% vs. 7%), PIM-1 (58% vs. 7%), CD79B (42% vs. 3%) and higher rates of TMB-High (cutoff 10mut/MB; 28% vs. 10%) (q<0.01). In addition, mutations in CARD11 (12% vs. 4%) and IRF4 (8% vs. 1%) trended to be more prevalent in PCNSL (p<0.05). In contrast, mutations in KMT2D (35% vs. 16%), EZH2 (13% vs. 2%), CREBBP (22% vs. 7%), TNFRSF14 (10% vs. 0) and BCL2 (19% vs. 2%) trended to be more prevalent in non-CNS lymphomas compared to PCNSL (p<0.05). In patients with PCNSL, there was no difference in survival in those with or without MYD88, PIM1 or CD79B mutations. No between-group differences were observed in the small cohort of patients with secondary CNS lymphoma (n=8). In the subgroup in whom these data were available, 25% of tumors were MGMT methylated, 71% had a “high or intermediate” tumor mutational burden, 8% were MSI high, and 54% were PD-L1 expression positive when tested by immunohistochemistry. Patients with PCNSL had worse overall survival (OS) than non-CNS lymphomas (30 vs 81 months, p<0.001).

Conclusion

MYD88, PIM-1, and CD79B mutations are more frequent in PCNSL compared to non-CNS lymphomas, but none of these mutations affected OS. Only 25% of PCNSL patients are MGMT methylated, but a majority have expression of PD-L1 suggesting a benefit from PD-1-targeted therapy. Response and survival in patients with mutation-guided therapy will be presented.

SYST-14 CLINICAL EFFICACY OF ONC201 IN RECURRENT H3 K27M-MUTANT DIFFUSE MIDLINE GLIOMA (DMG) PATIENTS

BACKGROUND

H3 K27M-mutant DMG predominantly affects children and young adults; no effective therapy is known. ONC201 is a first-in-class, anti-cancer DRD2 antagonist and ClpP agonist.

METHODS

Fifty pediatric and adult patients with recurrent H3 K27M DMG who received oral ONC201 monotherapy in clinical trials and expanded access were selected for a planned efficacy analysis. Eligibility criteria included measurable contrast-enhancing disease by RANO-HGG criteria (excluding pontine and spinal cord tumors), KPS/LPS≥60, ≥90 days from prior radiation, and adequate washout from prior anti-cancer therapy. The primary endpoint was overall response rate (ORR) by RANO-HGG criteria. Secondary endpoints included duration of response, time to response, progression-free survival (PFS), overall survival (OS), corticosteroid response rate, performance status response rate, and ORR by RANO-LGG criteria. Radiographic endpoints were assessed by dual-reader blinded independent central review. Data cutoff was May 31, 2021.

RESULTS

ORR was 20.0% (95%CI, 10.0–33.7) by RANO-HGG criteria. Median duration of response was 11.2 months (95%CI, 3.8–not reached) and median time to response was 8.3 months (range, 1.9–15.9). PFS at 6 months was 35.1% (95%CI, 21.2–49.3). The ORR was 26.0% (95%CI, 14.6–40.3) by RANO-LGG criteria. Fifteen patients (30.0%; 95%CI, 17.9–44.6) achieved an objective response by RANO-HGG and/or RANO-LGG criteria. Of 15 patients receiving ≥4 mg daily dexamethasone at baseline, 7 (46.7%; 95%CI, 21.3–73.4) achieved ≥50% confirmed reduction in dose. Of 34 patients with baseline KPS/LPS <80, 7 (20.6%; 95%CI, 8.7–37.9) achieved a confirmed performance status improvement. With a median follow-up of 18.8 months, median OS was 13.7 months (95%CI, 8.0–20.3) and OS at 24 months was 34.7% (95%CI, 20.7–49.2). Twenty-five patients had serious adverse events with one possibly related to ONC201 by investigator assessment.

CONCLUSIONS

ONC201 monotherapy exhibits durable and clinically meaningful efficacy in recurrent H3 K27M-mutant DMG.

Abstract PD6-06: Comprehensive characterization of neurotransmitters and neuronal signaling gene alterations in invasive breast cancers

BACKGROUNDIt has been reported that the sympathetic nervous system and associated neurotransmitters (NTs) play a pivotal role in driving breast cancer (BC) tumorigenesis and metastasis, however, comprehensive characterization of these pathways in BC is lacking. The purpose of this study was to retrospectively characterize NTs and neuronal signaling (NTNS) gene alterations in a large real-world BC cohort. METHODS A total of 6464 BC tumors were analyzed by next generation sequencing (NextSeq, 592 genes and WES, NovaSEQ, 720 genes) and whole transcriptome sequencing (WTS, NovaSeq) at Caris Life Sciences. Gene set variation analysis (GSVA) scores were calculated (positive: higher gene expressions in a selected gene set compared to genes outside that gene set in each tumor specimen, vice versa for negative) to assess expression of major NTNS genes, including GABA, nicotinic (NIC), muscarinic (MUS), dopamine (DA), reelin (RELN), and glial cell line-derived neurotrophic factor (GDNF). GSVA scores were compared by histologic subtype, primary or metastatic site, and hormone receptor (HR) and HER2 status with corrected Wilcoxon-Mann-Whitney testing. All significance levels were p<0.01. RESULTS The 6464 BC specimens in this cohort included 2520 primary sites and 3944 metastasis (mets) (liver: 1012; lymph node: 714; bone: 575; lung: 420; brain: 196). Predictive biomarker status in this cohort was HR+/HER2-: 3705; HR+/HER2+: 238; HR-/HER2+: 189; TNBC: 1654. Invasive ductal carcinomas (IDC) were the most common histologic subtype and demonstrated significantly higher GSVA scores for RELN and NIC pathways with respect to invasive lobular carcinomas (ILC) (Table). TNBC tumors had significantly higher enrichment overall (GABA, -0.04 vs -0.14; RELN, -0.05 vs -0.31; DA, -0.03 vs -0.08; MUS, 0.13 vs -0.16; NIC, 0.01 vs -0.12; and GDNF, 0.04 vs -0.04). HR-/HER2+ had significantly higher scores in GABA, -0.04 vs -0.14; RELN, -0.03 vs -0.31; MUS, 0.12 vs -0.16; and NIC, -0.01 vs -0.12 genes. Brain mets had significantly enriched pathway scores for GABA, 0.30 vs -0.13; MUS, 0.15 vs -0.08; and NIC, 0.13 vs -0.09 compared to primary tumors. Similarly, GABA,0.09 vs -0.13; DA, 0.07 vs -0.05; MUS, 0.17 vs -0.08; and NIC, 0.02 vs -0.09 pathways were enriched in bone mets compared to those from primary tumors. CONCLUSION Our results demonstrate that NTNS pathways are significantly enriched in IDC, TNBC tumors, and particularly in brain and bone mets. Our data advance the current understanding of the role of NTNS pathways in BC tumorigenesis and metastasis. Further investigation on genetic. determinants and signaling alternations associated with the observed NTNS pathway deregulation is warranted and could inform the development of novel therapeutic strategies. Significant comparisons with Bonferroni corrected p values are shown with an asterisk.

Citation Format: Irene Kang, Krutika Deshpande, Sarah Persing, Jun Yin, Joanne Xiu, Wolfgang Michael Korn, Jia Zeng, Evanthia T Roussos-Torres, Janice Lu, Darcy Spicer, Stephen F Sener, Antoinette R Tan, Ashley Sumrall, David SB Hoon, Cynthia X Ma, Carey K Anders, Heather L McArthur, Reva Basho, Heinz-Josef Lenz, Josh Neman. Comprehensive characterization of neurotransmitters and neuronal signaling gene alterations in invasive breast cancers [abstract]. In: Proceedings of the 2021 San Antonio Breast Cancer Symposium; 2021 Dec 7-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2022;82(4 Suppl):Abstract nr PD6-06.

Molecular alterations associated with improved outcome in patients with glioblastoma treated with Tumor-Treating Fields

Background

The genomic and overall biologic landscape of glioblastoma (GB) has become clearer over the past 2 decades, as predictive and prognostic biomarkers of both de novo and transformed forms of GB have been identified. The oral chemotherapeutic agent temozolomide (TMZ) has been integral to standard-of-care treatment for nearly 2 decades. More recently, the use of non-pharmacologic interventions, such as application of alternating electric fields, called Tumor-Treating Fields (TTFields), has emerged as a complementary treatment option that increases overall survival (OS) in patients with newly diagnosed GB. The genomic factors associated with improved or lack of response to TTFields are unknown.

Methods

We performed comprehensive genomic analysis of GB tumors resected from 55 patients who went on to receive treatment using TTFields, and compared results to 57 patients who received standard treatment without TTFields.

Results

We found that molecular driver alterations in NF1, and wild-type PIK3CA and epidermal growth factor receptor (EGFR), were associated with increased benefit from TTFields as measured by progression-free survival (PFS) and OS. There were no differences when stratified by TP53 status. When NF1, PIK3CA, and EGFR status were combined as a Molecular Survival Score, the combination of the 3 factors significantly correlated with improved OS and PFS in TTFields-treated patients compared to patients not treated with TTFields.

Conclusions

These results shed light on potential driver and passenger mutations in GB that can be validated as predictive biomarkers of response to TTFields treatment, and provide an objective and testable genomic-based approach to assessing response.

CTNI-27. SINGLE AGENT ACTIVITY OF ONC201 IN NON-MIDLINE H3 K27M-MUTANT DIFFUSE GLIOMAS

BACKGROUND

H3 K27M-mutant diffuse midline glioma is an invariably lethal form of brain cancer that disproportionately affects children and young adults and has no effective treatment following front-line radiation. The initial disease definition in the 2016 WHO Classification of Tumors of the Central Nervous System regarded the H3 K27M mutation as pathognomonic, though the definition was updated in 2018 restricting the diagnosis to histologically diffuse gliomas that involve midline CNS structures (cIMPACT-NOW update 2). ONC201 is an investigational anti- cancer small molecule, DRD2 antagonist and ClpP agonist that has induced durable tumor regressions by RANO-HGG criteria in a registration cohort of recurrent diffuse midline glioma, H3 K27M-mutant patients treated with single agent ONC201.

METHODS

We present 7 patients with H3 K27M-mutant diffuse gliomas were enrolled in ONC201 clinical studies, excluded from the registration cohort due to involvement of non-midline CNS structures, all within the cerebral hemispheres (3 frontal, 1 temporal, 1 frontotemporal, 1 parietal, and 1 corona radiata).

RESULTS

Two of the 7 patients underwent objective responses by RANO-HGG criteria as assessed by investigator, which was associated with clinical benefit that included increased mobility and level of alertness.

CONCLUSIONS

These results demonstrate that H3 K27M-mutant diffuse gliomas occur outside of midline CNS structures, and suggest that ONC201 has single agent activity in H3 K27M-mutant gliomas irrespective of CNS location.

HGG-18. CLINICAL EFFICACY OF ONC201 IN THALAMIC H3 K27M-MUTANT GLIOMA

ONC201, a bitopic DRD2 antagonist and allosteric ClpP agonist, has shown encouraging efficacy in H3 K27M-mutant glioma. Given that the thalamus has the highest extra-striatal expression of DRD2, we performed an integrated preclinical and clinical analysis of ONC201 in thalamic H3 K27M-mutant glioma. ONC201 was effective in mouse intra-uterine electroporation (IUE)-generated H3 K27M-mutant gliomas, with an in vitro IC₅₀ of 500 nM and 50% prolongation of median survival in vivo (p=0.02, n=14). We analyzed thalamic H3 K27M-mutant glioma patients treated with ONC201 on active clinical trials as of 5/22/19 enrollment (n=19 recurrent and 10 post-radiation, non-recurrent; 5–70 years old). As of 12/18/2019, PFS6 and OS12 are 26.3% and 36.8%, respectively, in the recurrent group. For non-recurrent patients, with median follow up of 21.9 months (8.6–26.6) from diagnosis, median PFS or OS have not been reached. This surpasses historical OS of 13.5 months. Best response by RANO includes 1 CR, 3 PR, 4 SD, 8 PD for recurrent patients and 2 PR, 4 SD, 1 PD for non-recurrent patients (4 on-trial patients experienced regressions that are yet unconfirmed responses). Median duration of response for recurrent patients is 14.0 months (2.0–33.1). Furthermore, H3 K27M cell-free tumor DNA in plasma and CSF correlated with MRI response. In summary, single agent ONC201 administered at recurrence, or adjuvantly following radiation, demonstrates promising clinical efficacy in thalamic H3 K27M-mutant glioma patients who currently have no effective treatments following radiation. Investigations are ongoing to assess whether micro-environmental DRD2 expression explains the early exceptional responses in thalamic H3 K27M-mutant glioma.

NCOG-43. NEUROCOGNITIVE IMPAIRMENT AND FRAILTY IN GERIATRIC PATIENTS WITH HIGH GRADE GLIOMA AND THORACIC MALIGNANCY

BACKGROUND

The median age at diagnosis for high grade glioma is 64 years. With peak incidence 75-84, malignant glial tumors are frequently a disease of the elderly. Common assessment measures fail to accurately gauge geriatric cancer patient fitness. Comprehensive Geriatric Assessment (CGA) is recommended in patients older than 65 to gauge risk of toxicity and tolerance of therapeutic intervention. We reviewed data for older patients with high grade glioma (HGG) and thoracic malignancy (TM) who underwent CGA via Senior Oncology Clinic (SOC) at Levine Cancer Institute.

METHODS

From 2015 to 2019 104 thoracic malignancy patients and 19 high grade glioma patients completed CGA via SOC before treatment or a required change in therapy. Data was incorporated into the LCI Senior Oncology Database by the REDCap secure web application, allowing for both quantitative and qualitative data analysis.

RESULTS

The median age was 77 in the HGG cohort compared to 80 years with TM. The physician rated Karnofsky Performance Status (KPS) for HGG and TM were similar (76% v 79%) as were the percentages of patients that were frail or prefrail (90% v 87%). Montreal Cognitive Assessment scores were lower in HGG (20 v 23). Considerably more HGG had falls in the 6 months before their assessment (58% v 30%) and gait speed was slower (0.76 m/s v 0.85 m/s).

CONCLUSIONS

Older patients with high grade gliomas compared to similar thoracic malignancies had more neurocognitive impairment, falls in the preceding 6 months, and slower gait speed. Physician rated KPS and frailty were similar in both groups. The results illustrate the limitations of physician-rated performance measures and highlight the importance of CGA in older brain tumor patients.

CTNI-17. CLINICAL EFFICACY AND PREDICTIVE BIOMARKERS OF ONC201 IN H3 K27M-MUTANT DIFFUSE MIDLINE GLIOMA

Patients with diffuse midline glioma (DMG) harboring H3 K27M mutation rarely survive longer than two years and have no proven therapies following first-line radiation. ONC201, a bitopic DRD2 antagonist and allosteric ClpP agonist, has shown encouraging efficacy in early phase studies in H3 K27M-mutant DMG. In order to define response rates in H3 K27M DMG patients and to clarify the genomic, anatomic and molecular predictors of response, we performed an integrated pre-clinical and clinical analysis of ONC201 treatment. ONC201 was effective in intra-uterine electroporation (IUE)-generated H3 K27M-mutant murine glioma models with excellent CNS penetration and survival benefit. Patients with H3 K27M-mutant DMG treated with ONC201 on active clinical trials (n=50, 27 thalamic, 23 brainstem) showed an overall survival (OS) of 28.1 (range: 5.9–105) months from diagnosis (enrollment by 4/29/19, data cut-off 12/28/19), compared to historical median OS of 12 months. Median OS for non-recurrent patients has not been reached (n=16, median follow-up: 16.8 from diagnosis). For non-recurrent thalamic patients (n=8), median PFS is 20.1 (range: 9.3–27.6) months from diagnosis (median time on drug: 14.5 months). Best response for thalamic patients by RANO: 1 CR, 5 PR, 7 SD, 8 PD, 6 not reported. Decreased H3 K27M cell-free tumor DNA in plasma and CSF at 6 months correlated with long-term response. Baseline tumor gene expression profiling in patients treated with ONC201 (n=14) identified EGFR and the cortical developmental transcription factor FOXG1 as the strongest biomarkers of radiographic response to ONC201. Analysis of 541 ONC201-treated human cancer cell lines from DepMap, provided evidence for an EGFR-dependent ONC201 resistance mechanism. Analysis of 38 glioma cell lines further supports FOXG1 as a glioma-specific predictive biomarker of ONC201 response. The unprecedented survival results and radiographic responses to ONC201 in H3K27M DMG make a compelling case for later phase and combinatorial studies.

BIOM-17. BRAF MUTATION IS AN EARLY EVENT IN THE EVOLUTION OF A SUBSET OF GLIOBLASTOMAS AND IS ASSOCIATED WITH INCREASED PD-L1 EXPRESSION

INTRODUCTION

BRAF is a RAF-family kinase that regulates MAPK/ERK signaling. Activating BRAF mutations, including V600E, are common in circumscribed low-grade gliomas of childhood and young adulthood, but are uncommon in infiltrative astrocytomas, including glioblastoma. Their role in glioblastoma initiation and progression requires analysis of large datasets given the low frequency (1.0%) in TCGA IDH-wild-type glioblastomas.

METHODS

Molecular profiling was done on 4679 FFPE gliomas by next-generation sequencing at Caris Life Sciences, of which 3170 underwent RNA-sequencing for gene fusion and 4603 DNA-sequencing for mutations. MGMT promoter methylation was tested by pyrosequencing and PD-L1 IHC was performed using the SP142 clone.

RESULTS

Excluding variants of uncertain significance, BRAF mutations/fusions were most common in pleomorphic xanthoastrocytoma (PXA; N=12/24, 50%), glioneuronal tumors (N=6/13, 46%), pilocytic astrocytoma (PA; N=15/48, 31%), and ganglioglioma (n=5/18, 28%). BRAF fusions were uncommon (N=17), most frequent in PA (N=8/31, 26%) where they were associated with older age at daignosis (P=0.043), and typically involved KIAA1549 as fusion partner (70%). BRAF-mutated/fused glioblastoma patients (N=59/3126, 2%) were younger than BRAF-wild-type glioblastoma patients (54 versus 59 years, P=3.5x10-3); more likely to be MGMT-unmethylated (75% versus 56%, P=5.0x10-3); and 3x more likely to express PD-L1 (55% versus 17%, P=2.1x10-10). In tumors harboring a V600E mutation, the variant allele frequency (VAF) was similar in glioblastoma as in PXA, PA, ganglioglioma, and glioneuronal tumors (median VAF=35%).

CONCLUSIONS

BRAF-mutated glioblastoma were 3x more likely to express PD-L1 than BRAF-wild-type glioblastoma. We observed no differences in BRAF V600E clonality in BRAF-mutated glioblastoma compared to BRAF-mutated PXA, PA, ganglioglioma, and glioneuronal tumors, suggesting BRAF mutation is an initiating event in the clonal evolution of a subset of glioblastoma. There is rationale to evaluate combined BRAF inhibition with checkpoint inhibition in BRAF-mutated glioblastoma, potentially synergizing the complete response profile of the former with the durable response profile of the latter.

Single-agent ONC201 in recurrent H3 K27M-mutant diffuse midline glioma

3615

Background: Recurrent H3 K27M-mutant diffuse midline glioma is a lethal brain tumor that predominantly affects children and young adults and has no effective therapy. ONC201 is a first-in-class orally administered, anti-cancer small molecule that selectively antagonizes the dopamine receptors DRD2/DRD3 and agonizes ClpP, a mitochondrial protease. Prior studies have indicated dysregulated dopamine receptor expression and enhanced ONC201 sensitivity among H3 K27M-mutant gliomas. Methods: Adults with midline H3 K27M-mutant glioma patients were enrolled to a dedicated Phase II clinical trial (NCT03295396), a multi-arm Phase II clinical trial (NCT02525692), and expanded access protocols under the Sponsor’s IND. Results were pooled among patients treated with ONC201 monotherapy through any of these trial with H3 K27M confirmed glioma, progressive and measurable disease by RANO, > 90 days from completion of prior radiation, no evidence of leptomeningeal dissemination, midline location other than primarily pons or spinal cord, and baseline KPS > 60. Using an enrollment cutoff of February 15, 2019 and data cutoff of July 31, 2019, there were 20 patients (NCT03295396, 12; NCT02525692, 7; expanded access, 1). Dosage was 625 mg weekly in 19 and once every 3 weeks in 1. Results: No DLTs or treatment discontinuations due to toxicity occurred. Midline gliomas can exhibit minimal contrast enhancement or exhibit a mixture of contrast-enhancing and non-contrast enhancing regions in the tumor. As a result, blinded independent central review (BICR) of tumor response by MRI was assessed by RANO-HGG and RANO-LGG for each patient to capture contrast-enhancing lesions by T1 post-contrast and non-contrast-enhancing assessments by T2/FLAIR, respectively, in the object response rate. The best response by RANO-HGG or RANO-LGG is 30% (95% CI, 11.9-54.3%). Duration of response by RANO-HGG is median 52.7 weeks (range 15.9-138.3). One patient with stable disease as of this data cutoff has continued on treatment beyond 12 months and recently underwent an investigator-reported PR by RANO-HGG that is pending confirmation. Conclusions: Single agent ONC201 is well tolerated and clinically active in recurrent H3 K27M-mutant diffuse midline glioma patients. Clinical trial information: NCT03295396, NCT02525692 .

Anticonvulsant prophylaxis and steroid use in adults with metastatic brain tumors: summary of SNO and ASCO endorsement of the Congress of Neurological Surgeons guidelines

BACKGROUND

The Congress of Neurological Surgeons (CNS) has developed a series of guidelines on the treatment of adults with metastatic brain tumors, including systemic therapy and supportive care topics. ASCO has a policy and set of procedures for endorsing clinical practice guidelines that have been developed by other professional organizations.

METHODS

Two CNS Guidelines were reviewed for developmental rigor by methodologists and an independent multi-disciplinary Expert Panel was formed to review the content and assess agreement with the recommendations. The expert panel voted to endorse the two guidelines and ASCO and SNO independently reviewed and approved the ASCO/SNO guideline endorsement.

RESULTS

The ASCO/SNO Expert Panel determined that the recommendations from the CNS anticonvulsants and steroids guidelines, published January 9, 2019, are clear, thorough, and based upon the most relevant scientific evidence. ASCO/SNO endorsed these two CNS guidelines, with minor alterations.

CONCLUSIONS

Key recommendations include: prophylactic anti-epileptic drugs were not recommended for routine use; corticosteroids (specifically dexamethasone) were recommended for temporary symptomatic relief in patients with neurologic symptoms and signs related to mass effect from brain metastases.

Primary CNS lymphoma commonly expresses immune response biomarkers

Background

Primary central nervous system lymphoma (PCNSL) is rare and there is limited genomic and immunological information available. Incidental clinical and radiographic responses have been reported in PCNSL patients treated with immune checkpoint inhibitors.

Materials and Methods

To genetically characterize and ascertain if the majority of PCNSL patients may potentially benefit from immune checkpoint inhibitors, we profiled 48 subjects with PCNSL from 2013 to 2018 with (1) next-generation sequencing to detect mutations, gene amplifications, and microsatellite instability (MSI); (2) RNA sequencing to detect gene fusions; and (3) immunohistochemistry to ascertain PD-1 and PD-L1 expression. Tumor mutational burden (TMB) was calculated using somatic nonsynonymous missense mutations.

Results

High PD-L1 expression (>5% staining) was seen in 18 patients (37.5%), and intermediate expression (1-5% staining) was noted in 14 patients (29.2%). Sixteen patients (33.3%) lacked PD-L1 expression. PD-1 expression (>1 cell/high-power field) was seen in 12/14 tumors (85.7%), uncorrelated with PD-L1 expression. TMB of greater than or equal to 5 mutations per megabase (mt/Mb) occurred in 41/42 tumors, with 19% (n = 8) exhibiting high TMB (≥17 mt/Mb), 71.4% (n = 30) exhibiting intermediate TMB (7-16 mt/Mb), and 9.5% (n = 4) exhibiting low TMB (≤6 mt/Mb). No samples had MSI. Twenty-six genes showed mutations, most frequently in MYD88 (34/42, 81%), CD79B (23/42, 55%), and PIM1 (23/42, 55%). Among 7 cases tested with RNA sequencing, an ETV6-IGH fusion was found. Overall, 18/48 samples expressed high PD-L1 and 38/42 samples expressed intermediate to high TMB.

Conclusions

Based on TMB biomarker expression, over 90% of PCNSL patients may benefit from the use of immune checkpoint inhibitors.

GENE-41. UNDERSTANDING THE DIFFERENCES IN ADOLESCENT AND YOUNG ADULT (AYA) GLIOMAS AND OLDER ADULT (OA) GLIOMAS BASED ON FUNCTIONAL MOLECULAR SUBGROUPS

BACKGROUND

Gliomas in the AYA population (15–39 years of age) have unique biological characteristics and need to be better characterized.

METHODS

Glioma tumors in AYA subjects and subjects >65 years of age (OA) were analyzed by next generation sequencing using a 592 gene panel. Pathogenic mutations were classified into five functional groups, viz. metabolic pathways genes (IDH1/2, FH), tumor suppressor genes (TP53, RB1, APC, NF1/2, PTEN, TSC1/2), genes involved in DNA repair (MMR genes, BRCA1/2, POLE, ARID1A, CHEK2, ATM, BLM, BRIP1, WRN, BARD1, POT1, MUTYH), oncogenes (BRAF, NRAS, HRAS, EGFR, PDGFRA, FGFR1, NOTCH1, MYCN), and genes involved in transcriptional regulation (SETD2, H3F3A, KMTD2A/2C/2D, KDM6A, PIK3CA). Mutation frequency in AYA tumors and OA tumors were compared using Chi-squared analysis (Pearson’s score χ2; likelihood ratio LR).

RESULTS

720 unique gliomas tumors were analyzed: 118 AYA, 602 OA; 420 males, 300 females. When both groups are considered together, glioblastoma was the most common histology (75%), followed by grade 3 astrocytoma (13%), glioma NOS (3.8%), oligodendrogliomas (3%), low grade gliomas (2.9%) and other (2.3%). AYA tumors harbored more metabolic pathway gene mutations (χ2 137.7, p< 0.0001) driven primarily by IDH1 mutations, while OA tumors had a higher mutation frequency in oncogenes (χ2 9.22, p=0.0024) driven by EGFR mutations (LR 27.567) and tumor suppressor genes (χ2 40.35, p< 0.0001) driven by NF1 (LR 18.147) and PTEN (LR 66.216). No significant differences were noted in mutation frequency in DNA repair or transcriptional regulation genes. However, AYA glioblastoma tumors had a significant increase in mutations in genes involved in chromatin remodeling, (χ2 11.43, p=0.0007) even after excluding H3F3A.

CONCLUSIONS

Functional genomic classification of AYA tumors may help develop better targeted therapies, especially focused on genes involved in metabolic pathways and transcriptional regulation.

ACTR-34. SINGLE AGENT ONC201 IN PREVIOUSLY-TREATED, PROGRESSIVE ADULT H3 K27M-MUTANT GLIOMA

H3 K27M-mutant gliomas often manifest as midline gliomas, have a dismal prognosis, and have no established or effective treatments at recurrence. ONC201 is the first clinical bitopic DRD2 antagonist/ClpP agonist and is under evaluation in Phase II trials for gliomas and other cancers. We previously reported in vitro studies suggesting dysregulated dopamine receptor expression and enhanced ONC201 sensitivity among H3 K27M-mutant gliomas. Following these observations, adults with midline H3 K27M-mutant glioma patients were enrolled to a dedicated Phase II clinical trial (NCT03295396), a multi-arm Phase II trial (NCT0252569), and expanded access protocols under the Sponsor’s IND. An integrated radiographic analysis with an objective response rate primary endpoint in patients who received ONC201 monotherapy with confirmed H3 K27M-mutant glioma (not primarily in the pons or spinal cord and without leptomeningeal spread) that was progressive and measurable disease by RANO criteria, >90 days from completion of prior radiation, and had KPS >60. As of December 15, 2018, 15 patients have received single agent ONC201 who meet these criteria (n=9 NCT03295396; n=5 NCT0252569; n=1 expanded access). ONC201 was orally administered at 625 mg weekly, except for one patient dosed once every 3 weeks. As midline gliomas can exhibit a mixture of contrast-enhancing and non-contrast-enhancing disease, objective response was assessed by blinded independent central review using RANO-HGG and RANO-LGG criteria for each patient. Best response to date by RANO-HGG criteria is at least 27%: 1 CR, 3 PR, 7 SD, and 4 PD; by RANO-LGG is at least 36%: 1 CR, 1 PR, 3 minor response (MR), 4 SD, 5 PD, 1 unevaluable. By RANO-HGG, median onset of response is 2.6 months (range 1.3–3.4); median duration of response has not been reached with a median follow-up of 7.7 months (range 1.8–29.8). Updated radiographic response, pharmacodynamics, safety, and other clinical outcomes will be reported.

PATH-55. MUTATIONS OF H3.3 AND H3.1 IN A LARGE COHORT OF GLIOMAS

Mutations in the histone genes H3.3 and H3.1 are driver events in pediatric and adult gliomas and carry diagnostic and prognostic importance for tumors originating from midline structures. Patients with tumors affected by these mutations are difficult to treat. We surveyed a large cohort of gliomas for H3-mutations, including H3K27m. Consecutive gliomas submitted for tumor profiling at Caris Life Sciences from 2015- 2019 were analyzed. NextGen sequencing was done on 592 genes; MGMT promoter methylation was tested by pyrosequencing; and EGFRvIII and gene fusions were tested by RNA-sequencing. Of nearly 1800 tumors analyzed, 41 harbored H3F3A alterations, including 33 with the K27M mutation (4 arose from the spinal cord, 1 from cerebellum, 1 from brain stem, 4 from thalamus, and 23 from brain, NOS). Eight G34R mutations were identified. A HIST1H3B-K27M was detected in a tumor from the brain stem. H3 mutations were more prevalent in pediatric tumors, and all H3 mutations seen in pediatric tumors were from grade IV tumors. Among the H3-mutated adult tumors, histology differed. There were 2 grade II tumors, 1 low grade glioma, 1 anaplastic ganglioglioma, and 2 anaplastic astrocytomas. In the investigated cohort, H3-mutations were mutually exclusive of IDH1/2 mutations and EGFR alterations. Significantly higher mutation rates were seen in H3-mutated tumors for TP53, ATRX, NF1, PDGFRA, FGFR1, FBXW7, BLM, and TSC2 compared with H3-WT. The H3-WT tumors were more enriched for MGMT-methylation and PTEN mutation. In H3-mutated tumors that were MGMT-methylated, most H3-mutations seen were G34R while K27M was largely exclusive. There was a heterogeneous distribution of H3 mutations, and the co-occurring molecular alterations seen in H3-mutated tumors further support the hypothesis that these tumors are a distinct molecular entity. By better characterizing these associations, we can develop insight into novel treatment strategies for a class of tumors with historically dismal prognosis.

PDCT-12. CLINICAL EFFICACY OF ONC201 IN THALAMIC H3 K27M-MUTANT GLIOMA

ONC201, the first bitopic DRD2 antagonist for clinical oncology, has shown efficacy in H3 K27M-mutant glioma. We performed an integrated preclinical and clinical analysis of ONC201 in thalamic H3 K27M-mutant glioma. ONC201 was effective in mouse intra-uterine electroporation (IUE)-generated H3 K27M-mutant gliomas, with an in vitro IC50 of 500 nM and 50% prolongation of median survival in vivo (p=0.02, n=14). Elevated DRD2 expression was found in the thalamus of non-malignant brain tissue, leading to the hypothesis that thalamic tumors may be a particularly ONC201-sensitive sub-group. We analyzed thalamic H3 K27M-mutant glioma patients treated with ONC201 as of the 05/22/2019 cutoff date, which included patients who had recurrent disease prior to initiating ONC201 (n=20; 15–73 years old) and post-radiation non-recurrent patients (n=11; 5–19 years old). As of 5/22/2019, 10 of 20 recurrent patients and 9 of 11 non-recurrent patients remain on-treatment. Median PFS has not been reached for either cohort: median follow-up of 2.2 months (range: 0.6–37.9) for recurrent patients and 10.6 months (range: 4.3–20.5) from diagnosis for non-recurrent patients. Best response so far by RANO includes 1 CR, 2 PR, 7 SD, 9 PD, 1 NE for recurrent patients and 1 PR, 7 SD, 3 PD for non-recurrent patients. Additionally, 3 recurrent (-66%, -47%, -34%) and 2 non-recurrent (-40%, -10%) patients experienced regressions but are not yet confirmed PRs. For recurrent patients, median onset of response is 3.5 months (range: 2.2–3.8) and median duration of response has not been reached with a median follow-up of 12.5 months (range: 8.1–32.8). Preliminary analyses demonstrated a strong correlation of cell-free tumor DNA in plasma and CSF with MRI response. In summary, ONC201 demonstrates promising clinical efficacy in thalamic H3 K27M-mutant glioma patients, regardless of age. Micro-environmental DRD2 expression may enhance the overall ONC201 response and extend its therapeutic utility beyond H3 K27M-mutant glioma.

MLTI-08. AN EXCEPTIONAL INTRACRANIAL RESPONSE TO REPEAT RADIATION AND IMMUNOTHERAPY IN A PATIENT WITH METASTATIC, POORLY DIFFERENTIATED ADENOCARCINOMA OF THE LUNG

We report an unusual case of a long-term survivor of metastatic, poorly differentiated adenocarcinoma of the lung (EGFR- ALK-) who developed intracranial disease after definitive treatment of a stage IIIB lung cancer. He received a complex course of RT which began with SRS to his intracranial disease in 2012 and included: brainstem (pontine) mass, left parietal mass, left frontal, left lateral temporal, and left insular lesions. The left temporal mass progressed and was resected. Subsequently, SRS was given to a right anterior frontal lesion. Additional SRS was given to progressive right superior frontal mass & left temporal tumor bed was given fractionated RT to the left temporal tumor bed. Later, he developed bilateral cerebellar masses and right-sided progression. More SRS was given to right frontal area, and then to bilateral cerebellar lesions. Surprisingly, he did well neurologically until seizures developed. His repeat biopsy was sent for NGS and noted to be PDL1+, APC mutated, and KRAS mutated. This gentleman was started on pembrolizumab in May 2016. Due to colitis, his therapy stopped in January 2017. His colitis progressed such that immunotherapy could not be restarted. Now, after observation only for the past 2.5 years. his disease has disappeared. He is doing well neurologically. We propose that the use of radiation and immunotherapy worked to produce an exceptional, durable response.

RADI-16. ECONOMIC IMPLICATIONS OF PREOPERATIVE VERSUS POSTOPERATIVE STEREOTACTIC RADIOSURGERY FOR BRAIN METASTASES

OBJECTIVE: Retrospective data suggests preoperative stereotactic radiosurgery (preSRS) reduces radiation necrosis (RN) and leptomeningeal disease (LMD) failure after resection of brain metastases (BM) as compared to postoperative SRS (postSRS). We evaluated the potential financial impact of a reduction in symptomatic RN (SRN) and LMD, should preSRS become a national standard. METHODS: A decision tree was designed to evaluate the two strategies: preSRS vs. postSRS. We assumed no difference in survival and that a reduction in SRN and LMD exists on par with retrospective data. Effectiveness was not considered given unclear health utilities. Treatments for SRN considered were dexamethasone, bevacizumab, surgical resection, or hyperbaric oxygen (HBO). Treatments for LMD considered included conventional radiation, SRS, systemic therapy (lapatinib/capecitabine), or no therapy. Probabilities were extracted from the 2-year LMD/SRN rates and subsequent treatment patterns observed in retrospective data. Treatment costs were based on the 2019 Medicare physician fee schedule and published data in 2019 US dollars without discounting. National costs to the healthcare system were estimated by assuming 200,000 BM cases per year with a surgical utilization rate of 16%. Deterministic and probabilistic sensitivity analyses (PSA) were performed. RESULTS: The incorporated rate of LMD and SRN for postSRS was 22.4% and 16.4% and 4.3% and 4.9% for preSRS, respectively. The expected mean costs were $3,129 for postSRS and $810 for preSRS. Deterministic sensitivity analysis demonstrated that the model was sensitive to only LMD/SRN rates. PSA demonstrated that in 95% of simulations, the expected savings ranged from $770-$6,429/patient. Therefore, the national healthcare system stands to save approximately $74 million per year if preSRS was a national standard (range $25–206 million). CONCLUSIONS: A prospective randomized trial demonstrating the effectiveness of preSRS in the reduction of LMD and/or SRN would carry a significant return on investment through the reduction of subsequent treatment costs.

Single agent ONC201 in adult recurrent H3 K27M-mutant glioma

3005

Background: H3 K27M-mutant glioma is associated with a poor prognosis and there is no effective therapy following radiation. We report the clinical experience with single agent ONC201, the first small molecule DRD2 antagonist in oncology, in adults with recurrent H3 K27M-mutant glioma. Methods: Twenty-nine adult patients with recurrent H3 K27M-mutant glioma have been treated with single agent ONC201 as of January 20, 2019: 19 patients on NCT03295396; 8 patients on NCT02525692; 2 patients on compassionate use protocols under the Sponsor’s IND. Median age was 57 years old (range: 17-74), median prior lines of therapy was 2 (range: 1-4) and all patients received prior radiation (median 8.5 months from radiation completion to ONC201 initiation). ONC201 was orally administered at 625 mg weekly, except for one patient dosed once every 3 weeks. Results: As of February 5, 2019, 13 of 29 patients remain on-trial within median follow up of 6.5 months (range: 0.6-33.6), 8 patients are alive but off-trial with median follow up of 2.4 months (range: 0.2-9), and 8 patients have expired. Nine of 29 patients (31%) remain progression-free on ONC201 with a median follow up of 6.5 months (range 0.6-33.6). No dose-limiting toxicities or treatment discontinuations due to toxicity occurred. Three patients have experienced durable partial responses by RANO (4.3-28.5 months). In addition, one patient experienced complete regression that continues for > 14 months of all < 1 cm tumor lesions that are not measurable by RANO. Furthermore, 10 patients had a best response of stable disease by RANO, 12 patients experienced progressive disease, and 3 patients are not yet evaluable. Among the patients with a best response of stable disease by RANO, one patient had > 50% tumor regression in the basal ganglia that did not qualify as a partial response by RANO due to a new lesion on a confirmatory scan. Another patient with stable disease by RANO has had 37% tumor regression so far in the brainstem and remains on-treatment for 6 months. All tumor regressions remain durable to date and some were associated with improvements in disease-associated neurological symptoms. Conclusions: Single agent ONC201 is well tolerated and clinically active in adult recurrent H3 K27M-mutant glioma patients. Clinical trial information: NCT03295396; NCT02525692.

Anticonvulsant Prophylaxis and Steroid Use in Adults With Metastatic Brain Tumors: ASCO and SNO Endorsement of the Congress of Neurological Surgeons Guidelines

PURPOSE

The Congress of Neurological Surgeons (CNS) has developed a series of guidelines for the treatment of adults with metastatic brain tumors, including systemic therapy and supportive care topics. ASCO has a policy and set of procedures for endorsing clinical practice guidelines that have been developed by other professional organizations.

METHODS

Two CNS guidelines were reviewed for developmental rigor by methodologists, and an independent multidisciplinary Expert Panel was formed to review the content and assess agreement with the recommendations. The Expert Panel voted to endorse the two guidelines, and ASCO and Society for Neuro-Oncology (SNO) independently reviewed and approved the ASCO/SNO guideline endorsement.

RESULTS

The ASCO/SNO Expert Panel determined that the recommendations from the CNS anticonvulsants and steroids guidelines, published January 9, 2019, are clear, thorough, and based on the most relevant scientific evidence. ASCO/SNO endorsed these two CNS guidelines with minor alterations.

RECOMMENDATIONS

Key recommendations include the following: prophylactic antiepileptic drugs were not recommended for routine use; and corticosteroids, specifically dexamethasone, were recommended for temporary symptomatic relief in patients with neurologic symptoms and signs related to mass effect from brain metastases. Additional information is available at www.asco.org/neurooncology-guidelines .

Comparing pre-operative stereotactic radiosurgery (SRS) to post-operative whole brain radiation therapy (WBRT) for resectable brain metastases: a multi-institutional analysis

Pre-operative stereotactic radiosurgery (pre-SRS) has been shown as a viable treatment option for resectable brain metastases (BM). The aim of this study is to compare oncologic outcomes and toxicities for pre-SRS and post-operative WBRT (post-WBRT) for resectable BM. We reviewed records of consecutive patients who underwent resection of BM and either pre-SRS or post-WBRT between 2005 and 2013 at two institutions. Overall survival (OS) was calculated using the Kaplan-Meier method. Cumulative incidence was used for intracranial outcomes. Multivariate analysis (MVA) was performed using the Cox and Fine and Gray models, respectively. Overall, 102 patients underwent surgical resection of BM; 66 patients with 71 lesions received pre-SRS while 36 patients with 42 cavities received post-WBRT. Baseline characteristics were similar except for the pre-SRS cohort having more single lesions (65.2% vs. 38.9%, p = 0.001) and smaller median lesion volume (8.3 cc vs. 15.3 cc, p = 0.006). 1-year OS was similar between cohorts (58% vs. 56%, respectively) (p = 0.43). Intracranial outcomes were also similar (2-year outcomes, pre-SRS vs. post-WBRT): local recurrence: 24.5% vs. 25% (p = 0.81), distant brain failure (DBF): 53.2% vs. 45% (p = 0.66), and leptomeningeal disease (LMD) recurrence: 3.5% vs. 9.0% (p = 0.66). On MVA, radiation cohort was not independently associated with OS or any intracranial outcome. Crude rates of symptomatic radiation necrosis were 5.6 and 0%, respectively. OS and intracranial outcomes were similar for patients treated with pre-SRS or post-WBRT for resected BM. Pre-SRS is a viable alternative to post-WBRT for resected BM. Further confirmatory studies with neuro-cognitive outcomes comparing these two treatment paradigms are needed.

Outcome after bevacizumab clinical trial therapy among recurrent grade III malignant glioma patients

Although outcome following bevacizumab among recurrent grade IV malignant glioma patients is documented as poor by several analyses, outcome for recurrent grade III patients following bevacizumab therapy has not been specifically evaluated. We performed a pooled analysis of 96 recurrent grade III malignant glioma patients enrolled on three consecutive phase II bevacizumab salvage trials to evaluate overall outcome following bevacizumab trial discontinuation. Outcome on the three bevacizumab trials, which included similar eligibility, treatment and assessment criteria, was comparable. Forty-nine patients who progressed on bevacizumab trial therapy and remained alive for at least 30 days elected to receive additional therapy. These patients achieved a median PFS-6 and OS of 30.6% (95% CI: 18.4, 43.6) and 10.3 months (95% CI: 5.2, 11.7), respectively. Among patients who continued bevacizumab therapy (n = 23) after study progression, PFS-6 and median OS were 39.1% (95% CI: 19.9, 58.0) and 9.2 months (95% CI: 5.2, 13.6), respectively, compared to 23.1% (95% CI: 9.4, 40.3; P = 0.51) and 10.3 months (95% CI: 2.5, 14.4; P = 0.91) for patients who initiated non-bevacizumab containing therapy (n = 26). Outcome after discontinuation of bevacizumab therapy for recurrent grade III malignant glioma patients is associated with improved outcome compared to historical data for recurrent grade IV malignant glioma patients. Salvage therapies following bevacizumab failure have modest activity for grade III malignant glioma patients that is independent of further bevacizumab continuation.

Recurrent, transformed non-Hodgkin's lymphoma presenting as chiasmal syndrome with hyperprolactinemia and hypopituitarism

A 69-year-old white female with past medical history of follicular cell lymphoma presented to her local physician with new neurological findings. She was subsequently diagnosed with a pituitary lesion comprised of diffuse large B cell lymphoma. Non-Hodgkin's lymphoma (NHL) affecting the pituitary uncommonly appears as metastatic disease from a concurrent systemic lymphoma. This case represents the first case of recurrent, transformed NHL as chiasmal syndrome with hyperprolactinemia and hypopituitarism in the American medical literature.

Pneumococcal septic arthritis as the initial presentation of multiple myeloma

Septic arthritis induced by Streptococcus pneumoniae is an uncommon manifestation of pneumococcal infection. Pneumococcus has been identified as the inciting pathogen in only 6% of cases of septic arthritis in recent retrospective studies (Ross et al., 2003). Approximately 50% of patients with pneumococcal septic arthritis have a preceding or concurrent extra-articular focus of infection. The septic joint evolves from hematogenous seeding of the highly vascular synovial membrane by bacteria. Polyarticular disease occurs in only approximately 36% of patients. Most pneumococcal septic arthritis occurs with coexistant joint disease, prosthesis, alcoholism, HIV infection, or rheumatoid arthritis (Baraboutis & Skoutelis, 2004; Raad & Peacock, 2004). We report a case of polyarticular septic arthritis as the first manifestation of an underlying disease. Our literature review discloses that this is the first reported case of multiple myeloma initially presenting as pneumococcal septic arthritis in the USA and the third internationally (Cuesta et al., 1992; Renou et al., 2007).

A case of severe hemorrhagic diarrhea

A 50-year-old white female presented to the emergency department with diarrhea, abdominal pain, and hematochezia. The illness started four days prior to presentation and escalated to 10-15 bowel movements daily. She was tachycardic and hypotensive upon presentation with a diffusely tender abdomen. Her anemia and persistent hematochezia prompted endoscopy by a gastroenterologist. Flexible sigmoidoscopy was performed to the splenic flexure and revealed evidence of severe active colitis. The mucosa was friable and severely ulcerated. Numerous biopsies were obtained that revealed acute colitis with fibrinopurulent exudates. A stool culture showed Escherichia coli O157:H7, which was confirmed by the Mississippi State Board of Health. Infection with E. coli O157:H7 affects nearly 1.1 per 100,000 Americans annually. It accounts for about 3% of all bacterial and protozoal causes of foodborne illnesses and possesses a mortality rate of about 1-2%.

Therapy-related acute nonlymphoblastic leukemia following mitoxantrone therapy in a patient with multiple sclerosis

A 58-year-old male with migraine headaches, complex partial epilepsy, and secondary progressive multiple sclerosis treated with mitoxantrone was admitted to our facility in August 2005 with febrile neutropenia, worsening ataxia, aphasia, cough, and declining mental status. Bone marrow aspirate was consistent with acute nonlymphoblastic leukemia. Review of the literature reveals ten reported cases of nonlymphoblastic leukemias following treatment with mitoxantrone. Although de novo leukemia cannot be fully excluded, the likelihood of de novo disease is low given the patient's medical history. This case continues the important discussion of efficacy versus toxicity when selecting mitoxantrone as a therapeutic option for patients with multiple sclerosis. Although leukemia is rarely seen, the potential for this outcome warrants careful consideration before initiating this therapy.