The prevalence and severity of lower back pain in South African university rowers

Background

Low back pain (LBP) is a condition prevalent among rowers due to the repetitive and physically demanding nature of rowing. Information concerning LBP among university-level rowers is, however, outdated and not widely available.

Objective

To determine the prevalence, severity and disabilities of LBP among university-level rowers in South Africa.

Methods

An online questionnaire, including the Athlete Disability Index (ADI) Questionnaire, was distributed to nine South African university rowing clubs. One-hundred participants aged between 18 to 30 years completed the online questionnaires.

Results

Eighty-seven rowers admitted to sustaining LBP either at the time of the study or previously in their university rowing career. These rowers (n=87) completed the Athlete Disability Index (ADI) Questionnaire which provided a moderate LBP disability score (ADI score: 8.1±6.0; ADI %: 24.7%±18.1). Rowers who had been rowing for a longer duration reported a higher severity of LBP (p=0.001). There was no statistically significant difference for LBP prevalence (p=0.584), or severity (p=0.445) between the sexes. A small significant correlation between age and the ADI score (r=0.25, p= 0.021) was reported. The high prevalence and moderate severity highlight the significance of LBP among university rowers.

Conclusion

This study illustrates the prevalence of LBP with moderate severity among university rowers. Future research on LBP risk factors and aetiology is recommended to decrease the negative impact of this condition.

The physical attributes of sub-elite rugby union referees of inland provinces in South Africa

Background

The purpose of the on-field referee is to implement the laws of the game. For the referee to do this successfully, he is required to keep up with the pace of play.

Objectives

The aim of this study was to determine the physical attributes of sub-elite rugby union referees of inland provinces in South Africa.

Methods

A total of 82 referees (age: 26.5 ± 6.4 years; stature: 177.3 ± 6.8 cm; body mass: 79.1 ± 14.7 kg) were assessed with a reliable testing battery.

Results

The participants showed a refined aerobic capacity (VO_2max: 61.8 ± 11.0 mL·min^-1·kg^-1) and good agility (Illinois Agility Test: 17.2 ± 3.8 s). A two-way unbalanced ANOVA was performed for all referees' attributes between qualification levels (levels 1-4) and union affiliations (three unions) at a significance level of p<0.05. The results yielded significant differences across the three unions in age (p=0.002), Yo-Yo distance (p=0.0001), aerobic capacity (p=0.0001), plank time (p=0.0001) and agility (p=0.027). Similarly, differences were reported across the four qualifications in aerobic capacity (p=0.0001) and agility (p=0.037).

Conclusion

These differences may be due to the diverse training programmes offered by the various unions. Additionally, an increased level of physical fitness may occur when progressing up the qualification levels.

Association Between Early Treatment With Tocilizumab and Mortality Among Critically Ill Patients With COVID-19

IMPORTANCE

Therapies that improve survival in critically ill patients with coronavirus disease 2019 (COVID-19) are needed. Tocilizumab, a monoclonal antibody against the interleukin 6 receptor, may counteract the inflammatory cytokine release syndrome in patients with severe COVID-19 illness.

OBJECTIVE

To test whether tocilizumab decreases mortality in this population.

DESIGN, SETTING, AND PARTICIPANTS

The data for this study were derived from a multicenter cohort study of 4485 adults with COVID-19 admitted to participating intensive care units (ICUs) at 68 hospitals across the US from March 4 to May 10, 2020. Critically ill adults with COVID-19 were categorized according to whether they received or did not receive tocilizumab in the first 2 days of admission to the ICU. Data were collected retrospectively until June 12, 2020. A Cox regression model with inverse probability weighting was used to adjust for confounding.

EXPOSURES

Treatment with tocilizumab in the first 2 days of ICU admission.

MAIN OUTCOMES AND MEASURES

Time to death, compared via hazard ratios (HRs), and 30-day mortality, compared via risk differences.

RESULTS

Among the 3924 patients included in the analysis (2464 male [62.8%]; median age, 62 [interquartile range {IQR}, 52-71] years), 433 (11.0%) received tocilizumab in the first 2 days of ICU admission. Patients treated with tocilizumab were younger (median age, 58 [IQR, 48-65] vs 63 [IQR, 52-72] years) and had a higher prevalence of hypoxemia on ICU admission (205 of 433 [47.3%] vs 1322 of 3491 [37.9%] with mechanical ventilation and a ratio of partial pressure of arterial oxygen to fraction of inspired oxygen of <200 mm Hg) than patients not treated with tocilizumab. After applying inverse probability weighting, baseline and severity-of-illness characteristics were well balanced between groups. A total of 1544 patients (39.3%) died, including 125 (28.9%) treated with tocilizumab and 1419 (40.6%) not treated with tocilizumab. In the primary analysis, during a median follow-up of 27 (IQR, 14-37) days, patients treated with tocilizumab had a lower risk of death compared with those not treated with tocilizumab (HR, 0.71; 95% CI, 0.56-0.92). The estimated 30-day mortality was 27.5% (95% CI, 21.2%-33.8%) in the tocilizumab-treated patients and 37.1% (95% CI, 35.5%-38.7%) in the non-tocilizumab-treated patients (risk difference, 9.6%; 95% CI, 3.1%-16.0%).

CONCLUSIONS AND RELEVANCE

Among critically ill patients with COVID-19 in this cohort study, the risk of in-hospital mortality in this study was lower in patients treated with tocilizumab in the first 2 days of ICU admission compared with patients whose treatment did not include early use of tocilizumab. However, the findings may be susceptible to unmeasured confounding, and further research from randomized clinical trials is needed.

Emergency preparedness, resilience and response to a biological outbreak

Major disease outbreaks continue to be a significant risk to public health, with pandemic influenza or an emerging infectious disease outbreak at the top of the UK National Risk Register. The risk of deliberate release of a biological agent is lower but remains possible and may only be recognised after casualties seek medical attention. In this context the emergency preparedness, resilience and response (EPRR) process protects the public from high consequence infectious diseases, other infectious disease outbreaks and biological agent release. The core elements of the EPRR response are recognition of an outbreak, isolation of patients, appropriate personal protective equipment for medical staff and actions to minimise further disease spread. The paper discusses how high-threat agents may be recognised by clinicians, the initial actions to be taken on presentation and how the public health system is notified and responds. It draws on the national pandemic influenza plans to describe the wider response to a major disease outbreak and discusses training requirements and the potential role of the military.

DIPG-79. H3K27M INDUCES EPIGENETIC AND ONCOGENIC CHANGES THAT ARE PARTIALLY REVERSED BY SMALL MOLECULE AURORA KINASE B/C INHIBITION

Diffuse intrinsic pontine glioma (DIPG) is a fatal pediatric brain tumor with no curative treatments. Approximately 80% of DIPGs contain an H3K27M mutation. The implications of the mutation and how they may be targeted are not fully understood. We established an H3K27M effect-isolating model by transducing H3K27-wildtype lines (HSJD-GBM-001, normal human astrocytes) with lentiviral-packaged H3K27M. We characterized H3K27M-related changes through western blot, phenotypic assays, and RNA-seq. Drug screening of H3K27-wildtype and matched H3K27M-transduced lines was used to identify targets more effective with H3K27M present. Patient-derived pediatric glioblastoma and DIPG lines (BT-245, SU-DIPG-IV, HSJD-DIPG-007, SU-DIPG-XIII*, SF7761) were used for validation. We observed increased H3K27ac and decreased H3K27me3, as well as increased proliferative and migratory abilities, with the addition of H3K27M to H3K27-wildtype lines. RNA-seq showed downregulation of cell cycle regulation and upregulation of epithelial-mesenchymal transition. GSK1070916, an Aurora kinase B/C inhibitor, was isolated from a synthetic lethality screen with H3K27M. GSK1070916 showed strong efficacy in native H3K27M lines (IC₅₀s=60nM-1250nM), superior to the Aurora kinase A inhibitor alisertib, to which all cell lines showed substantial resistance. Combination of both drugs was not synergistic. GSK1070916 treatment caused increased H3K27me3 and decreased H3S10ph and H3S28ph. GSK1070916 induced apoptosis and S-phase stall. The H3K27M mutation induces epigenetic, phenotypic, and cell cycle regulation changes resulting in relaxation of transcriptional controls and more aggressive growth. Aurora kinase B/C inhibition is a novel therapeutic modality for DIPG that appears capable of reversing some H3K27M-related epigenetic changes, inducing apoptosis, and repressing uncontrolled cellular division.

EPID-13. A POPULATION-BASED ANALYSIS OF CNS TUMOR DIAGNOSES, TREATMENT, AND SURVIVAL IN CONGENITAL AND INFANT AGE GROUPS

BACKGROUND

Congenital (<3 months) and infant (3 to 11 months) brain tumors are biologically different from tumors in older children, but epidemiology of these tumors has not been studied comprehensively. Insight into epidemiological differences could help tailor treatment recommendations by age and increase overall survival (OS).

METHODS

Population-based data from the SEER 18 registries was obtained for 14,493 0-19-year-olds diagnosed with CNS tumors between 1990 and 2015. Incidence, treatment, and survival were analyzed using Chi-square and Kaplan-Meier analyses.

RESULTS

Between the <3 month, 3–5 month, 6–11 month, and 1–19 year age groups, tumor type distribution differed significantly (p<0.001); high-grade glioma (HGG) was most common in the <3-month-olds, while low-grade glioma (LGG) was most common in the other groups. 5-year OS for all tumors was 36.7% (<3 months), 56.0% (<3–5 months), 63.8% (6–11 months), and 74.7% (1–19 years) (log rank p<0.001). OS by tumor type was worst for <3-month-olds with LGG, medulloblastoma, and other embryonal tumors; OS was worst for 3-5-month-olds with ependymoma, <1-year-olds collectively with atypical teratoid-rhabdoid tumor, and 1-19-year-olds with HGG (log rank p<0.02 for all tumor types). <3-month-olds were least likely to receive any treatment for each tumor type and least likely to undergo surgery for all except HGG. <1-year-olds were far less likely than 1-19-year-olds to undergo radiation for embryonal tumors, as expected, but were also less likely to undergo chemotherapy.

CONCLUSIONS

Congenital/infant CNS tumors differ pathologically, therapeutically, and prognostically from those in older children. Treatment changes could help address poorer outcomes for these young patients.

IMG-17. RADIOMICS CHARACTERIZATION OF FOUR PEDIATRIC BRAIN TUMOR SUBTYPES IN PDX MOUSE MODELS

BACKGROUND

Previously, we have reported on the development of advanced magnetic resonance imaging (MRI) protocols for mouse brain tumors. The goal of this follow-up pre-clinical study was to develop a machine-learning MRI classifier (radiomics) for four subtypes of childhood brain tumor in patient-derived xenograft (PDX) mice.

METHODS

MRI scans on orthotopic medulloblastoma, ependymoma, ATRT and DIPG PDX (each n=12 animals) were performed on the animal 9.4 Tesla scanner with an in-plane resolution of 47 microns. Image segmentation, as well as shape and texture based radiomics descriptors were modeled using a modified COLIAGE software for tumor classification and to characterize tumor habitat of each tumor subtype.

RESULTS

The mean tumor volumes were 11.2 mm3. Each MRI scan was segmented into three regions: (i) well defined tumor (including distant metastases); (ii) peritumoral edema; (iii) tumor necrosis. 360 radiomics features (capturing co-occurrence, grey-level dependence and directional gradients) were obtained for each region. The model classified four subtypes with high accuracy while achieving sufficient segmentation accuracy despite the small lesion size. A subset of fourteen tumoral, six peritumoral and five distant MRI radiomics features were found to be predictive of the tumor sub-type (p=0.0017) independently of tumor anatomical location.

CONCLUSIONS

MRI protocols followed by radiomics feature analysis discriminated among specific radiological features for four distinct orthotopic PDX models: medulloblastomas exhibit low ADC values, high angiogenesis and cortical metastases as compared to ependymomas (high levels of edema and olfactory bulb metastases), ATRT (the highest level of necrosis) and DIPG (highest T2 signal intensities and spinal metastases).

QOL-36. USE OF CANNABINOIDS IN THE PEDIATRIC CENTRAL NERVOUS SYSTEM TUMOR POPULATION

BACKGROUND

Cannabinoids, including cannabidiol (CBD) and tetrahydrocannabinol (THC), are a class of compounds found in marijuana. Numerous studies in adults have examined cannabinoid use in management of cancer-related symptoms such as nausea, anorexia, and pain. Less is known about the use in the pediatric oncology population.

METHODS

A prospective observational study has been ongoing since 2016 at Children’s Hospital Colorado to evaluate cannabinoids’ impact using PedsQL™ modules on quality of life of pediatric patients with central nervous system (CNS) tumors who are 2–18 years old. Laboratory assessments of T-cell activity and pharmacokinetics of CBD, THC and associated metabolites are in process. Diaries with exploratory information on cannabinoid use patterns are being collected.

RESULTS

Thirty-three patients (14:19; male:female) have been enrolled with a median age of 6.4 years (range, 2.9–17.7 years). The most common tumor type in enrolled patients is embryonal tumors (13/33; 39%). Nine (27%) patients have low-grade glial/glioneuronal tumors, and eight (24%) had high-grade/diffuse midline gliomas. The remaining patients had ependymoma or craniopharyngioma. The median time on cannabinoids is 9 months. Most (n=20) patients have used oral products with CBD and THC. One patient continues on cannabinoid therapy in follow up. Preliminary immune function analyses identified impaired neutrophil superoxide anion production and chemotaxis in patients taking cannabinoids at early time points on therapy.

CONCLUSIONS

Families of children with various CNS tumors are pursuing cannabinoid therapy for both antitumor and supportive care purposes. Analysis of the impact of cannabinoids on patients’ quality of life is ongoing.

HGG-57. WHOLE-GENOME SEQUENCING, METHYLATION ANALYSIS, AND SINGLE-CELL RNA-SEQ DEFINE UNIQUE CHARACTERISTICS OF PEDIATRIC TREATMENT-INDUCED HIGH-GRADE GLIOMA AND SUGGEST ONCOGENIC MECHANISMS

BACKGROUND

Pediatric treatment-induced high-grade glioma (TIHGG) is among the most severe late effects observed in childhood cancer survivors and is uniformly fatal. We previously showed that TIHGG are divergent from de novo pediatric high-grade glioma (pHGG) and cluster into two gene expression subgroups, one stemlike and the other inflammatory. Here we systematically compared TIHGG molecular profiles to pHGG and evaluated expression and single cell sequencing profiles in order to identify oncogenic mechanisms and the cellular basis for the observed TIHGG gene expression subgroups. MATERIALS/

METHODS

450/850K methylation and mutational signature analysis was conducted in 36 TIHGG samples. Resultant data were analyzed for the presence of chromothripsis, distinct molecular alterations, and mutational signatures in a subset of 10 samples with whole genome sequencing data. Five TIHGGs underwent single-cell RNA-Seq analysis (scRNAseq).

RESULTS

26/36 TIHGG clustered with the pedRTK1 methylation class. TIHGG were characterized by an increased frequency of chromothripsis relative to pHGG (67% vs. 31%, p=0.036). FISH and WGS revealed frequent PDGFRA amplification secondary to enrichment in ecDNA. TIHGG were enriched for COSMIC mutational signatures 5 and 19 (p=0.0003) relative to pHGG. scRNAseq data showed that TIHGG tumors are composed of stem-like, neuronal, and inflammatory cell populations which may contribute to the previously described dominant expression profiles.

CONCLUSIONS

TIHGG represents a distinct molecular subtype of pHGG. Chromothripsis, leading to enriched expression of genes in extrachromosomal DNA, likely contribute to TIHGG oncogenesis. The dominant cell type (stem-like vs. inflammatory) may define the expression subgroup derived from bulk RNA-seq in heterogeneous tumors.

LGG-48. PROLIFIC GROWTH OF BRAF V600E MUTANT PILOCYTIC ASTROCYTOMA WHILE ON KETOGENIC DIET: CASE REPORT

Epilepsy is a common diagnosis among pediatric patients with supratentorial tumors, particularly infiltrating gliomas. The ketogenic diet can be a successful antiepileptic therapy for patients with medically intractable epilepsy. Acetoacetate, a main ketone released during ketosis, has been shown to increase BRAF^V600E binding to MEK1 and MEK1 phosphorylation in BRAF^V600E mutant melanoma cells, thereby promoting proliferation and tumor growth (Kang et al, 2015, Xia et al, 2017). BRAF^V600E mutation is common in pediatric low-grade gliomas. Therefore, use of a ketogenic diet to manage coincident epilepsy could, in theory, promote tumor growth. However, this has not been previously reported in a human patient. We present a 3 year-old male with a non-NF1 optic pathway BRAF^V600E mutant pilocytic astrocytoma and medically intractable epilepsy. He was treated with carboplatin and bevacizumab for 1 year, with good tumor response and vision recovery. He showed stable, non-progressive disease for several months. He was placed on a ketogenic diet 9 months into treatment and became seizure free. Tumor recurrence occurred at 8 months off therapy, at which time a biopsy demonstrated BRAF^V600E mutation. The tumor progressed rapidly despite treatment with Trametinib and Dabrafenib, leading to salvage therapy with carboplatin, vinblastine, bevacizumab, and XRT, without tumor control. We discuss the potential effect of the ketogenic diet on this patient’s outcome.

DIPG-34. SUPER ELONGATION COMPLEX AS A TARGETABLE DEPENDENCY IN H3K27M+ DIFFUSE MIDLINE GLIOMA

Mutations in the histone 3 gene (H3K27M) are the eponymous driver in diffuse intrinsic pontine gliomas (DIPGs) and other diffuse midline gliomas (DMGs), aggressive pediatric brain tumors for which no curative therapy currently exists. To identify specific epigenetic dependencies within the context of the H3K27M mutation, we performed an shRNA screen targeting 408 genes classified as epigenetic/chromatin-associated molecules in patient-derived DMG cultures. This identified AFF4, a component of the super elongation complex (SEC), as necessary for DMG cells to maintain growth and self-renewal. We hypothesized that aberrant SEC expression occurs as a consequence of the H3K27M mutation and that this dysregulated SEC signaling overcomes repressive transcriptional regulation in order to suppresses differentiation and promote self-renewal of DMG tumor stem cells. We interrogated the role of AFF4 in DMG using an shRNA lentiviral approach. We demonstrate a significant decrease in in vitro clonogenicity and stem cell maintenance following AFF4 depletion. We employed RNA-seq-based gene set enrichment analysis to delineate differentiation programs under SEC regulatory control. Finally, we sought to determine whether CDK9, the catalytic subunit of the SEC, represents a therapeutic vulnerability in DMG. Using RNA polymerase II ChIP-seq, we demonstrate that CDK9 pharmacologic inhibition restores regulatory Pol II pausing, promotes cellular differentiation, and leads to potent anti-tumor effect both in vitro and in patient-derived xenograft models. These studies present a biologic rationale for the translational exploration of CDK9 inhibition as a promising therapeutic approach.

DIPG-73. SENESCENCE ASSOCIATED SECRETORY PHENOTYPE AS A MECHANISM OF RESISTANCE AND THERAPEUTIC VULNERABILITY IN BMI1 INHIBITOR TREATED DIPG

BACKGROUND

Diffuse intrinsic pontine gliomas (DIPGs) driven by mutations in the histone 3 (H3) gene (H3K27M) are aggressive pediatric brain tumors for which there is no curative therapy.

METHODS

To identify novel therapeutic targets we performed a high throughput drug screen combined with an epigenetically targeted RNAi screen using H3K27M and H3.3 WT DIPG cells.

RESULTS

Chemical and genetic depletion of BMI1 in vitro resulted in inhibition of clonogenicity and cell self-renewal consistent with previous studies. We show for the first time that clinically relevant BMI1 inhibitors attenuates growth of orthotopic DIPG xenografts as measured by MRI and prolong survival in vivo. We found that BMI1 inhibition drives phenotypic cellular senescence and that the senescent cells were able reactivate to form new neurospheres in vitro and tumor growth in vivo. RNA-seq, ChIP-Seq and immuno-proteomic analysis revealed that the senescent cells induced the expression of the Senescence Associated Secretory Phenotype (SASP) cytokines by increasing occupancy of activated histone marks at SASP factor promoters. The SASP results in increased expression of anti-apoptotic BH3 proteins including BCLxl, and BCL2. Treatment of the PTC028 treated senescent DIPG cells with BH3 mimetics induces apoptosis and clears the senescent cells. Combining BH3 mimetics with BMI1 inhibition attenuates tumor growth in vivo synergistically and significantly prolongs survival of DIPG bearing mice compared to BMI1 inhibition alone.

CONCLUSION

These data inform the current trial of BMI1 inhibition as a monotherapy and predict the need for adding BH3 mimetics to achieve efficacy.

IMMU-21. INVESTIGATION OF WHITE BLOOD CELL CHARACTERISTICS IN CSF SAMPLES AT PEDIATRIC BRAIN TUMOR DIAGNOSIS

BACKGROUND

There has been a recent surge in investigation of immunity and immunotherapy, but their role in pediatric brain tumors is incompletely defined. We hypothesized that investigating an understudied dataset, WBC and differential results in CSF drawn at the time of pediatric brain tumor diagnosis to look for microscopic metastases, would provide insight into the role of immunology and potential for immunotherapy in these diseases and correlate with prognosis and/or metastasis.

METHODS

We conducted a retrospective comparison analysis of CSF values in 349 patients at our institution from samples drawn within 60 days of initial CNS tumor diagnosis from 1998–2018. We examined total nucleated cell count, absolute counts and percentages for WBC subtypes. We compared CSF values by tumor cell presence, patient vital status, and disease group: atypical teratoid rhabdoid tumor, ependymoma, germinoma, high-grade glioma (HGG), low-grade glioma (LGG), medulloblastoma, non-germinomatous germ cell tumor, and other embryonal tumors (OET). We used Wilcoxon and Kruskal-Wallis tests for comparisons.

RESULTS

Overall, higher lymphocyte percentage (p=0.002) and lower monocyte percentage (p=0.007) were associated with survival. WBC characteristics did not differ significantly based on tumor cell presence. Compared to medulloblastoma, ependymoma showed a more active CSF immune response, while LGG, HGG, and OET showed a less active response, based on total WBC and/or absolute neutrophil count (p=0.001–0.007).

CONCLUSIONS

Higher lymphocyte and lower monocyte percentages in CSF correlated with better prognosis overall; causality requires further investigation. Tumor subtypes varied in their immune stimulation, offering potential insight into which will be amenable to immunotherapy.

LGG-34. CLINICAL AND MOLECULAR CHARACTERIZATION OF A MULTI-INSTITUTIONAL COHORT OF PEDIATRIC SPINAL CORD LOW-GRADE GLIOMAS

BACKGROUND

The MAPK/ERK pathway is involved in cell growth and proliferation, and mutations in the BRAF paralog of this pathway have made it an oncogene of interest in pediatric cancer. Previous studies have identified that BRAF mutations as well as BRAF-KIAA1549 fusions are common in intracranial low-grade gliomas (LGGs). Fewer studies have tested for the presence of these genetic aberrations in spinal LGGs. The aim of this study was to better understand the prevalence of BRAF and other genetic aberrations in spinal LGG.

METHODS

We analyzed 46 spinal LGGs from children age 1–25 years from two institutions, Children’s Hospital Colorado (CHCO) and The Hospital for Sick Children (Sick Kids) for the presence of BRAF fusions or mutations. Data was correlated with clinical information. A 67 gene panel additionally screened for other possible genetic abnormalities of interest in the patient cohort from CHCO. In the Sick Kids cohort, BRAFV600E was tested for by ddPCR and IHC while BRAF fusions where detected by FISH, RT-PCR or Nanostring platform.

RESULTS

Of the 31 patient samples who underwent fusion analysis, 13 (42%) harbored the BRAF-KIAA1549 fusion. Overall survival (OS) for patients confirmed positive for BRAF-KIAA1549 was 100% compared to 76% for fusion negative patients. Other mutations of interest were also identified in this patient cohort including BRAFV600E, STK11, PTPN11, H3F3A, APC, TP53, PIK3CA (polymorphism), FGFR1, and CDKN2A deletion.

CONCLUSION

BRAF-KIAA1549 was seen in higher frequency than BRAFV600E or other genetic aberrations in pediatric spinal LGGs and trends towards longer OS although not statistically significant.

Patients as teachers: Evaluating the experiences of volunteer inpatients during medical student clinical skills training

PURPOSE

Early patient encounters in medical education are an important element of clinical skill development. This study explores the experiences of volunteer inpatients (VIPs) participating in clinical skills training with junior medical students (JMS) solely for educational purposes.

METHODS

Following first-year medical students practicing history taking and clinical examinations with VIPs at Toronto General Hospital (TGH) and Toronto Western Hospital (TWH), patients completed a questionnaire and a short audio-recorded interview. This study used a mixed methodological approach. A 5-point Likert-scaled survey queried satisfaction regarding the recruitment process, student and faculty interactions and patient demographics (e.g. age and educational background). A 10-minute follow-up interview investigated patient perspectives. Survey responses were correlated to patient demographics and descriptive thematic analysis summarized trends in patient perspectives.

RESULTS

Of 93 consenting VIPs, 66% were male and 58% participated at TGH. The mean overall experience was positive (4.76 and 4.93 at TGH and TWH, respectively). Three themes emerging through thematic analysis were Not "Just" a Medical Student, Patient as Teacher, and Promoting Best Practices. VIPs reported positive experiences when they were adequately informed of the VIP role during recruitment, and when students exhibited confidence, interest, and respect throughout the session.

CONCLUSION

Study results provide clarity about VIP experiences with JMS and lay a foundation for improved patient satisfaction and best practices within clinical skills curricula in the health professions.

CTNI-18. FINAL RESULTS OF A PHASE 2 STUDY OF EFFICACY, SAFETY AND INTRATUMORAL PHARMACOKINETICS (PK) OF SELINEXOR MONOTHERAPY IN RECURRENT GLIOBLASTOMA (rGBM)

BACKGROUND

Selinexor is an FDA-approved first-in-class, oral selective nuclear export inhibitor which forces nuclear retention of many tumor suppressor proteins.

METHODS

We conducted a phase 2 trial of selinexor monotherapy for adults with recurrent GBM including a surgical arm to explore intratumoral PK and 3 medical arms to optimize dosing. Prior treatment with radiotherapy and temozolomide was required; prior bevacizumab was exclusionary. The primary endpoint was 6-month progression-free survival (6mPFS) rate.

RESULTS

Selinexor administered ~2 hours pre-operatively yieleded average intratumoral concentration (136 nM, n=6) comparable to the in vitro IC50 (130 nM) from 7 primary human GBM cell lines. Among all 68 patients accrued to 3 medical arms (~85 mg BIW, n=24; 60 mg BIW, n=14; 80 mg QW, n=30), median age was 56 years (21–78). Median number of prior lines of therapies was 2 (1–7). At 80 mg QW, 28% patients were progression-free at the end of cycle 6; the 6mPFS was 17%; disese control rate by RANO was 37% (1 CR, 2 PRs, 7 SD) among 27 evaluable patients; responses were durable (median 11.1 months), and treatment lasted for 442, 547 and 1282 days in 3 responders, as of data lock, with one responder remaining on treatment off study; median overall survival was 10.2 months with 95% CI (7.0, 15.4). The ~85 mg BIW-schedule was abandoned due to poor tolerability. The related adverse events (all grades) in patients on ~85 mg BIW/60 mg BIW/80 mg QW were nausea (41.7%/64.3%/66.7%), fatigue (70.8%/71.4%/50.0%), neutropenia (29.2%/14.3%/33.3%), decreased appetite (45.8%/71.4%/26.7%), thrombocytopenia (66.7%/28.6%/23.3%) and weight loss (16.7%,/42.9%/6.7%).

CONCLUSION

Selinexor monotherapy demonstrated encouraging intratumoral penetration and efficacy, with durable disease control in rGBM. Monotherapy dose at 80 mg QW is recommended for further development in rGBM. A phase 1/2 study of combination therapy for newly diagnosed or rGBM has been initiated (NCT04421378).

DDRE-13. DECONVOLUTING MECHANISMS OF RESISTANCE TO BRAF INHIBITORS IN BRAF V600E HUMAN GLIOMA

BACKGROUND

While BRAF-targeted therapy can be effective in a subset of patients with glioma, resistance to treatment can emerge over time. The description and validation of mechanisms of resistance in BRAF-mutant glioma are not previously described.

METHODS

Pre- and post- BRAF inhibitor (BRAFi) or BRAFi/MEK inhibitor (MEKi) treated patient samples were obtained under IRB-approved protocols at University of Colorado Denver, UCSF, and Johns Hopkins. Targeted DNA sequencing or whole exome sequencing (WES), and RNA-seq were conducted on paired samples. Functional validation of putative resistance mechanisms was performed using established glioma cell lines with BRAF V600E mutation (DBTRG-5MG, AM38, B76).

RESULTS

Analysis of 15 tissue sample pairs identified point mutations in 15 genes (including CBL, NF1, PTEN, and MAP2K1) and expression changes in RAF1 leading to putative mechanisms of resistance. We performed functional validation of loss of NF1 and CBL as resistance mechanisms and demonstrated growth inhibition and cell death in response to BRAFi with siRNA/sgRNA-mediated knockdown of each gene. Knockdown of CBL resulted in increased EGFR expression and phosphorylation, a possible mechanism for maintaining ERK signaling within the cell. Combination therapy with a MEKi or EGFR inhibitor was able to overcome resistance to BRAFi, in NF1 knockdown and CBL knockdown, respectively. Restoration of wild-type PTEN in B76 cells (PTEN-/-) restored sensitivity to BRAFi. Ingenuity pathway analysis suggested that a switch from BRAF to CRAF dependence mediated resistance in some tumors. Indeed, inhibition of CRAF expression using siRNA in a patient-derived glioma cell line re-sensitized cells to BRAFi.

CONCLUSIONS

Analysis of pre-/post-treatment BRAF mutant glioma sample pairs, primarily from pediatric patients, identified a variety of putative resistance mechanisms, some of which have been validated in vitro. Resistance mechanisms to BRAFi in glioma are varied and may be susceptible to different combinations of targeted therapy, highlighting the importance of a personalized approach.

BIOM-26. MOLECULAR PREDICTORS OF RESPONSE TO SELINEXOR IN RECURRENT GLIOBLASTOMA (GBM)

The nuclear export protein exportin 1 (XPO1) is overexpressed in many cancers, including GBM. Selinexor is an inhibitor of XPO1 that crosses the blood-brain-barrier and targets cancer cells by sequestering tumor suppressor proteins and oncoprotein mRNAs in the nucleus, inducing cancer cell apoptosis. We previously reported encouraging results from a phase II trial of selinexor for molecularly unselected patients with recurrent GBM (ASCO 2019). Pre-treatment tumors from 57 patients were exome and RNA sequenced to explore molecular correlates of response, in a hypothesis generating, post-hoc, exploratory analysis. We compared overall survival (OS) and progression-free survival (PFS) between mutated and wild-type patients. Two mutated genes were associated with longer survival in selinexor treated patients: DOCK8 (n=7; PFS, P=0.013, hazard ratio [HR]=3.75 [1.32–10.62]; overall survival, P=0.009, HR=15.39 [2.00–118.34]) and PDX1 (n=5, PFS, P=0.014, HR=4.468 [1.361–14.670]). Other commonly mutated genes in glioma, including IDH1 (n=9) were observed but not associated with survival. RNAseq data were used to infer differential protein activities, which were input into a machine learning model that compared patients with selinexor sensitive disease (best response of partial or complete response, n=7) and resistant disease (best response of progressive disease, n=23). We found the inferred activities of three proteins emerged as the most associated with response and could be combined in a model to accurately predict benefit from selinexor treatment (area under the ROC curve from leave one out cross validation = 0.89 permutation test P&lt; 0.04). The three proteins were ZC3H12A (also called MCPIP-1), a negative regulator of inflammation; RAB43, a member of the RAS family that binds GTP and regulates vesicle trafficking, and SOCS3, a suppressor of cytokine signaling that can antagonize JAK/STAT signaling. Together these data identified mutations and proteins activities for identifying patients most likely to benefit from selinexor treatment. Further studies are required for validation. ClinicalTrials.gov:NCT01986348.

Factors Associated With Death in Critically Ill Patients With Coronavirus Disease 2019 in the US

Importance

The US is currently an epicenter of the coronavirus disease 2019 (COVID-19) pandemic, yet few national data are available on patient characteristics, treatment, and outcomes of critical illness from COVID-19.

Objectives

To assess factors associated with death and to examine interhospital variation in treatment and outcomes for patients with COVID-19.

Design, Setting, and Participants

This multicenter cohort study assessed 2215 adults with laboratory-confirmed COVID-19 who were admitted to intensive care units (ICUs) at 65 hospitals across the US from March 4 to April 4, 2020.

Exposures

Patient-level data, including demographics, comorbidities, and organ dysfunction, and hospital characteristics, including number of ICU beds.

Main Outcomes and Measures

The primary outcome was 28-day in-hospital mortality. Multilevel logistic regression was used to evaluate factors associated with death and to examine interhospital variation in treatment and outcomes.

Results

A total of 2215 patients (mean [SD] age, 60.5 [14.5] years; 1436 [64.8%] male; 1738 [78.5%] with at least 1 chronic comorbidity) were included in the study. At 28 days after ICU admission, 784 patients (35.4%) had died, 824 (37.2%) were discharged, and 607 (27.4%) remained hospitalized. At the end of study follow-up (median, 16 days; interquartile range, 8-28 days), 875 patients (39.5%) had died, 1203 (54.3%) were discharged, and 137 (6.2%) remained hospitalized. Factors independently associated with death included older age (≥80 vs <40 years of age: odds ratio [OR], 11.15; 95% CI, 6.19-20.06), male sex (OR, 1.50; 95% CI, 1.19-1.90), higher body mass index (≥40 vs <25: OR, 1.51; 95% CI, 1.01-2.25), coronary artery disease (OR, 1.47; 95% CI, 1.07-2.02), active cancer (OR, 2.15; 95% CI, 1.35-3.43), and the presence of hypoxemia (Pao2:Fio2<100 vs ≥300 mm Hg: OR, 2.94; 95% CI, 2.11-4.08), liver dysfunction (liver Sequential Organ Failure Assessment score of 2-4 vs 0: OR, 2.61; 95% CI, 1.30-5.25), and kidney dysfunction (renal Sequential Organ Failure Assessment score of 4 vs 0: OR, 2.43; 95% CI, 1.46-4.05) at ICU admission. Patients admitted to hospitals with fewer ICU beds had a higher risk of death (<50 vs ≥100 ICU beds: OR, 3.28; 95% CI, 2.16-4.99). Hospitals varied considerably in the risk-adjusted proportion of patients who died (range, 6.6%-80.8%) and in the percentage of patients who received hydroxychloroquine, tocilizumab, and other treatments and supportive therapies.

Conclusions and Relevance

This study identified demographic, clinical, and hospital-level risk factors that may be associated with death in critically ill patients with COVID-19 and can facilitate the identification of medications and supportive therapies to improve outcomes.