Malignant Peripheral Nerve Sheath Tumors Patients Research Articles

Linking FOXM1 and PD-L1 to CDK4/6-MEK targeted therapy resistance in malignant peripheral nerve sheath tumors.

Malignant peripheral nerve sheath tumors (MPNSTs) are aggressive, Ras-driven sarcomas characterized by loss of the NF1 tumor suppressor gene and hyperactivation of MEK and CDK4/6 kinases. MPNSTs lack effective therapies. We recently demonstrated remarkable efficacy of dual CDK4/6-MEK inhibition in mice with de novo MPNSTs, which was heightened by combined targeting of the immune checkpoint protein, PD-L1. The triple combination therapy targeting CDK4/6, MEK, and PD-L1 led to extended MPNST regression and improved survival, although most tumors eventually acquired drug resistance. Here, we consider the immune activation phenotype caused by CDK4/6-MEK inhibition in MPNSTs that uniquely involved intratumoral plasma cell accumulation. We discuss how PD-L1 and FOXM1, a tumor-promoting transcription factor, are functionally linked and may be key mediators of resistance to CDK4/6-MEK targeted therapies. Finally, the role of FOXM1 in suppressing anti-tumor immunity and potentially thwarting immune-based therapies is considered. We suggest that future therapeutic strategies targeting the oncogenic network of CDK4/6, MEK, PD-L1, and FOXM1 represent exciting future treatment options for MPNST patients.

MEK inhibitors lead to PDGFR pathway upregulation and sensitize tumors to RAF dimer inhibitors in NF1-deficient malignant peripheral nerve sheath tumor (MPNST).

Malignant peripheral nerve sheath tumor (MPNST) is a highly aggressive subtype of soft tissue sarcoma with a high propensity to metastasize and extremely limited treatment options. Loss of the RAS-GAP NF1 leads to sustained RAF/MEK/ERK signaling in MPNST. However, single-agent MEK inhibitors (MEKi) have failed to elicit a sustained inhibition of the MAPK signaling pathway in MPNST. We employed pharmacological, biochemical, and genetic perturbations of the receptor tyrosine kinase (RTK) and MAPK signaling pathway regulators to investigate the mechanisms of MEKi resistance and evaluated combination therapeutic strategies in various preclinical MPNST models in vitro and in vivo. Here, we report that MEKi treatment resistance in MPNST involves two adaptive pathways: direct transcriptional upregulation of the receptor tyrosine kinase (RTK) PDGFRβ, and MEKi-induced increase in RAF dimer formation and activation of downstream signaling. While the pharmacological combination of MEKi with a PDGFRβ specific inhibitor was more effective than treatment with MEKi alone, the combination of MEKi and RAF-dimer inhibitors led to a robust inhibition of the MAPK pathway signaling. This combination treatment was effective in vitro and in vivo, as demonstrated by the significant increase in drug synergism and its high effectiveness in decreasing MPNST viability. Our findings suggest that the combination of MEKi and PDGFR and/or RAF dimer inhibitors can overcome MEKi resistance and may serve as a novel targeted therapeutic strategy for NF1-deficient MPNST patients, which in turn could impact future clinical investigations for this patient population.

Preoperative Classification of Peripheral Nerve Sheath Tumors on MRI Using Radiomics.

Malignant peripheral nerve sheath tumors (MPNSTs) are aggressive soft-tissue tumors prevalent in neurofibromatosis type 1 (NF1) patients, posing a significant risk of metastasis and recurrence. Current magnetic resonance imaging (MRI) imaging lacks decisiveness in distinguishing benign peripheral nerve sheath tumors (BPNSTs) and MPNSTs, necessitating invasive biopsies. This study aims to develop a radiomics model using quantitative imaging features and machine learning to distinguish MPNSTs from BPNSTs. Clinical data and MRIs from MPNST and BPNST patients (2000-2019) were collected at a tertiary sarcoma referral center. Lesions were manually and semi-automatically segmented on MRI scans, and radiomics features were extracted using the Workflow for Optimal Radiomics Classification (WORC) algorithm, employing automated machine learning. The evaluation was conducted using a 100× random-split cross-validation. A total of 35 MPNSTs and 74 BPNSTs were included. The T1-weighted (T1w) MRI radiomics model outperformed others with an area under the curve (AUC) of 0.71. The incorporation of additional MRI scans did not enhance performance. Combining T1w MRI with clinical features achieved an AUC of 0.74. Experienced radiologists achieved AUCs of 0.75 and 0.66, respectively. Radiomics based on T1w MRI scans and clinical features show some ability to distinguish MPNSTs from BPNSTs, potentially aiding in the management of these tumors.

Survival outcomes of malignant peripheral nerve sheath tumors (MPNSTs) with and without neurofibromatosis type I (NF1): a meta-analysis

IntroductionMalignant peripheral nerve sheath tumors (MPNSTs) are malignancies that demonstrate nerve sheath differentiation in the peripheral nervous system. They can occur sporadically or be associated with neurofibromatosis type 1 (NF1), an autosomal dominant neurocutaneous disorder, with up to 13% of patients developing MPNSTs in their lifetimes. Previous studies have suggested conflicting findings regarding the prognosis of NF1 for patients with MPNSTs. The elucidation of NF1 as an independent prognostic factor on mortality has implications for clinical management. We aim to investigate the role of NF1 status as an independent prognostic factor of overall survival (OS) and disease-specific survival (DSS) in MPNSTs.MethodsAn electronic literature search of PubMed and MEDLINE was performed on studies reporting OS or DSS outcomes of MPNSTs with and without NF1. A grey literature search by reviewing bibliographies of included studies and review articles was performed to find pertinent studies. Data was extracted and assessed in accordance with the PRISMA guidelines. A meta-analysis was performed to calculate hazard ratios (HRs) using a random-effects model. The primary and secondary outcomes were all-cause and disease-specific mortality, respectively, with NF1 as an independent prognostic factor of interest.ResultsA total of 59 retrospective studies involving 3602 patients fulfilled the inclusion criteria for OS analysis, and 23 studies involving 704 MPNST patients were included to evaluate DSS outcomes. There was a significant increase in the hazard of all-cause mortality (HR 1.63, 95% CI 1.45 to 1.84) and disease-specific mortality (HR 1.52, 95% CI 1.24 to 1.88) among NF1 as compared to sporadic cases. Subgroup analyses and meta-regression showed that this result was consistent regardless of the quality of the study and year of publication.ConclusionNF1 is associated with a substantially higher risk of all-cause and disease-specific mortality. This finding suggests that closer surveillance is required for NF1 patients at risk of developing MPNSTs.

Cell-Free DNA Fragmentomics for Early Detection of Malignant Transformation in NF1 Patients Harboring Plexiform Neurofibromas

Malignant peripheral nerve sheath tumors (MPNST) are aggressive soft tissue sarcomas that are resistant to radiotherapy and chemotherapy, and are associated with poor survival. MPNST typically arise from benign or atypical plexiform neurofibromas (PN) in the setting of neurofibromatosis type 1 (NF1). Unfortunately, early detection by imaging and clinical examination remains very challenging. We hypothesize that cell-free DNA fragmentomic analysis can be used to precisely detect the risk for developing MPNST in NF1 patients, which could significantly improve clinical outcomes in the future through early cancer detection. We performed low-pass whole genome sequencing of plasma cell-free DNA samples from healthy controls (n = 21), patients with PN (n = 113), AN (n = 39) and MPNST (n = 71). Cell-free DNA was analyzed at a per-fragment level by tracking 4-nucleotide end motifs, and using a bin-wise fragmentomic machine learning approach called DELFI, which integrates across ratios of short (100-150 bp) versus long (151-220 bp) fragments in 5 megabase bins across the genome. End motif frequencies were compared between MPNST and PN patients, and receiver operating characteristic (ROC) analysis was used to classify disease states using DELFI fragmentomic scores. Using DELFI for genome-wide fragmentomics, followed by ROC analysis, we obtained the following accuracies: MPNST vs. AN (acc 0.62), MPNST vs. PN (acc 0.83), MPNST vs. healthy (acc 0.86), AN vs. PN (acc 0.87), AN vs. healthy (acc 0.72) and PN vs. healthy (acc 0.88). DELFI-based cell-free DNA fragmentomics was superior to the ichor CNA-based copy number alteration classifier that we published previously (Szymanski et al. PLOS Medicine, 2021) for all the aforementioned group comparisons (p < 0.001 by McNemar's test). Strikingly, the two AN cases with DELFI scores most closely resembling MPNST were separately identified by independent clinical care teams to have very high-risk features and recent history warranting short-interval follow up. Specifically, one patient had a paraspinal AN exhibiting new onset pain and rapid growth on imaging, while the other had increased FDG uptake of multiple AN lesions in a supraclavicular field treated years earlier with radiotherapy. We also measured fragment end motifs across different patient groups, and found that the CTCA end motif was more commonly present in cell-free DNA from MPNST and PN patients compared to healthy donors (Bonferroni-corrected p-value < 0.001). This study suggests that fragmentomic analysis of cell-free DNA can accurately risk-stratify NF1 patients with plexiform neurofibromas. Cell-free DNA fragmentomics outperformed our previously published copy number alteration method for distinguishing closely related patient subgroups with different malignancy risks. Atypical neurofibroma patients with cell-free DNA fragmentomic scores suggestive of MPNST were deemed clinically very high-risk for malignant transformation.

Analysis of demographic characteristics of malignant peripheral nerve sheath tumor in adults: A National Cancer Database study.

e23555 Background: Malignant peripheral nerve sheath tumor (MPNST) is a rare cancer involving the peripheral nerve sheath. Even though the 5-year post-surgical resection survival rate is only 30 to 40%, the epidemiology is not well understood, and looking at trends in demographics could provide insight into factors potentially contributing to poor prognosis. A previous National Cancer Database (NCDB) study investigated demographics in pediatric patients with MPNST. This study analyzed NCDB data to investigate the demographics of adults with MPNST. Methods: Adult patients with a histologic diagnosis of MPNST were retrospectively examined in a cohort analysis using demographic information from the NCDB from 2004 – 2020 (N = 414). Regression analysis was used to describe incidence trends. Demographics (age, sex, race, Hispanic origin, income, insurance status, area of residence, facility type, distance from facility, and Charlson-Deyo score) were explored through descriptive statistics. Palliative care enrollment and mortality rate was examined. Results: 414 patients with age &gt; 18 were identified in the NCDB database with a confirmed diagnosis of MPNST between the years 2004 – 2020. There was a slight increase in incidence of patients diagnosed per year (R2 = 0.254). The average age of diagnosis was 47.0 years (SD = 17.2, range = 19 – 88 years) with more males (51.4%) affected than females (48.6%). The most common primary sites were the retroperitoneum (32.4%), spinal cord (24.4%), and cranial nerves (15.0%). A majority of individuals (82.6%) had Charlson-Deyo comorbidity scores of 0. Individuals most commonly affected were White (79.7%) or Black (14.3%), and non-Hispanic (87.4%). Patients most commonly were in the top quartile of household income (31.6%), had private insurance (53.6%), lived in metropolitan counties (83.8%), and received treatment at an academic/research program (62.2%). Patients lived on average 61.6 miles (SD = 145.7, range = 0.5 – 1454.9) from the facility. The 90-day mortality rate post-surgery was 10.5%. The overwhelming majority of patients did not receive palliative care (94.4%). Conclusions: This is the first NCDB analysis on the demographics of MPNST in adults, providing information that bridges the gap in knowledge. This analysis showed that the retroperitoneum was the most common tumor site, and that the average age of diagnosis was 47 years, consistent with previous reports. Patients were most likely to be White, non-Hispanic, upper quartile income earners, privately insured, treated at an academic facility, and live in metropolitan counties. With the majority of patients receiving no palliative care, it’s possible that palliative care is underutilized and may benefit MPNST patients given the poor prognosis. Additional research on the relationship between socioeconomic status and palliative care access may provide information on this discrepancy.

202 Molecular Signature of Malignant Peripheral Nerve Sheath on Tumor Site

INTRODUCTION: Malignant peripheral nerve sheath tumors (MPNSTs) are rare, highly aggressive soft tissue sarcomas that may occur sporadically, in association with neurofibromatosis type I (NF1) or after radiotherapy (RT). High recurrence rates and distant metastases are common, with lung and bone being the most common sites, yet the anatomic distribution of molecular changes is largely unknown. METHODS: Using the cBioPortal platform and systematic bioinformatical-analysis of the Cancer Genome Atlas (MSKCC) Nature Genetics 2014 dataset, we screened the dataset for the ADAM3A gene in the completed gene panel and twelve MPNST patients [pulmonary (6), neck (1), chest-wall (2), calf (1), arm (2)] with were included in the study. Broadly, these twelve patients were categorized as primary-pulmonary MPNST (6) and non-pulmonary MPNST (6) subgroups. RESULTS: The putative copy-number alteration pattern involving the ADAM3A gene based on the primary site was distinct (p &lt;0.0001). All six patients with primary-pulmonary MPNST showed ADAM3A amplification while all six patients with non-pulmonary MPNST demonstrated ADAM3A homodeletion. Remarkably, regardless of the underlying etiology and pathogenesis, ADAM3A amplification in primary-pulmonary MPNST was invariably noted across the board in sporadic (3), NF1-associated (2), and RT-associated (1) tumor samples (p &lt;0.0001). CONCLUSIONS: The findings in this study highlight the site-specificity of the MPNST molecular landscape. Further studies are essential for understanding the underlying molecular implications, pathways, and the specific role of ADAM3A in pulmonary and non-pulmonary MPNSTs.

Preclinical Assessment of MEK Inhibitors for Malignant Peripheral Nerve Sheath Tumors Reveals Differences in Efficacy and Adaptive Response.

Malignant peripheral nerve sheath tumors (MPNSTs) are rare soft-tissue sarcomas refractory to standard therapies. Inactivation of NF1 and subsequent upregulation of RAS/RAF/MEK/ERK signaling exist in the majority of MPNSTs. However, the lack of preclinical assessment of MEK inhibitors in MPNSTs hinders the clinical application as well as the development of combination therapy. To guide further clinical studies, we evaluated different MEK inhibitors in terms of efficacy, safety, and mechanism of adaptive response in treating MPNSTs. Using a MPNST tissue microarray, we found that p-ERK could serve as a biomarker for predicting the prognosis of MPNST patients as well as an effective therapeutic target. Through in vitro and in vivo experiments, we identified trametinib as the most potent MEK inhibitor for the treatment of MPNSTs. Mechanistically, reduced reactivation of the MAPK pathway and compensatory activation of the parallel pathways contributed to better efficacy. Our results provide a basis for the further clinical application of MEK inhibitors as single agents or combinational therapies.

Cell-free DNA ultra-low-pass whole genome sequencing to distinguish malignant peripheral nerve sheath tumor (MPNST) from its benign precursor lesion: A cross-sectional study.

BackgroundThe leading cause of mortality for patients with the neurofibromatosis type 1 (NF1) cancer predisposition syndrome is the development of malignant peripheral nerve sheath tumor (MPNST), an aggressive soft tissue sarcoma. In the setting of NF1, this cancer type frequently arises from within its common and benign precursor, plexiform neurofibroma (PN). Transformation from PN to MPNST is challenging to diagnose due to difficulties in distinguishing cross-sectional imaging results and intralesional heterogeneity resulting in biopsy sampling errors.Methods and findingsThis multi-institutional study from the National Cancer Institute and Washington University in St. Louis used fragment size analysis and ultra-low-pass whole genome sequencing (ULP-WGS) of plasma cell-free DNA (cfDNA) to distinguish between MPNST and PN in patients with NF1. Following in silico enrichment for short cfDNA fragments and copy number analysis to estimate the fraction of plasma cfDNA originating from tumor (tumor fraction), we developed a noninvasive classifier that differentiates MPNST from PN with 86% pretreatment accuracy (91% specificity, 75% sensitivity) and 89% accuracy on serial analysis (91% specificity, 83% sensitivity). Healthy controls without NF1 (participants = 16, plasma samples = 16), PN (participants = 23, plasma samples = 23), and MPNST (participants = 14, plasma samples = 46) cohorts showed significant differences in tumor fraction in plasma (P = 0.001) as well as cfDNA fragment length (P < 0.001) with MPNST samples harboring shorter fragments and being enriched for tumor-derived cfDNA relative to PN and healthy controls. No other covariates were significant on multivariate logistic regression. Mutational analysis demonstrated focal NF1 copy number loss in PN and MPNST patient plasma but not in healthy controls. Greater genomic instability including alterations associated with malignant transformation (focal copy number gains in chromosome arms 1q, 7p, 8q, 9q, and 17q; focal copy number losses in SUZ12, SMARCA2, CDKN2A/B, and chromosome arms 6p and 9p) was more prominently observed in MPNST plasma. Furthermore, the sum of longest tumor diameters (SLD) visualized by cross-sectional imaging correlated significantly with paired tumor fractions in plasma from MPNST patients (r = 0.39, P = 0.024). On serial analysis, tumor fraction levels in plasma dynamically correlated with treatment response to therapy and minimal residual disease (MRD) detection before relapse. Study limitations include a modest MPNST sample size despite accrual from 2 major referral centers for this rare malignancy, and lack of uniform treatment and imaging protocols representing a real-world cohort.ConclusionsTumor fraction levels derived from cfDNA fragment size and copy number alteration analysis of plasma cfDNA using ULP-WGS significantly correlated with MPNST tumor burden, accurately distinguished MPNST from its benign PN precursor, and dynamically correlated with treatment response. In the future, our findings could form the basis for improved early cancer detection and monitoring in high-risk cancer-predisposed populations.

Adrenergic signaling promotes the expansion of cancer stem-like cells of malignant peripheral nerve sheath tumors

Malignant peripheral nerve sheath tumor (MPNST), a highly malignant tumor that arises in peripheral nerve tissues, is known to be highly resistant to radiation and chemotherapy. Although there are several reports on genetic mutations and epigenetic changes that define the pathogenesis of MPNST, there is insufficient information regarding the microenvironment that contributes to the malignancy of MPNST. In the present study, we demonstrate that adrenaline increases the cancer stem cell population in MPNST. This effect is mediated by adrenaline stimulation of beta-2 adrenergic receptor (ADRB2), which activates the Hippo transducer, YAP/TAZ. Inhibition and RNAi experiments revealed that inhibition of ADRB2 attenuated the adrenaline-triggered activity of YAP/TAZ and subsequently attenuated MPNST cells stemness. Furthermore, ADRB2-YAP/TAZ axis was confirmed in the MPNST patients’ specimens. The prognosis of patients with high levels of ADRB2 was found to be significantly worse. These data show that adrenaline exacerbates MPNST prognosis and may aid the development of new treatment strategies for MPNST.

Surgical strategies and the use of functional reconstructions after resection of MPNST: An international survey on surgeons’ perspective

Malignant peripheral nerve sheath tumors (MPNST) are aggressive and possibly morbid sarcomas because of their tissue of origin. However, postoperative functional status of MPNST patients has been understudied. Reconstructions may play a role in restoring lost function, but are still infrequently carried out. This study investigated how surgical considerations and the use of functional reconstructions differed among surgeons treating MPNST. This survey was distributed among members of multiple surgical societies. Survey responses were analyzed overall and between surgical subspecialties (surgical oncology/neurosurgery/plastic surgery/other). A total of 30 surgical oncologists, 30 neurosurgeons, 85 plastic surgeons, and 29 ‘others’ filled out the survey. Surgical oncologists had the highest case load (p < 0.001). Functional status was usually considered preoperatively among all subspecialties (65.1%); 42.2% never considered performing less extensive resections to preserve function. Neuropathic pain and motor deficits are seen in 40.9 ± 22.9% and 36.7 ± 25.5% respectively. Functional reconstructions for motor and sensory deficits were more commonly considered by plastic surgeons and ‘others’. Relative contraindications for reconstructions did not differ between subspecialties (p > 0.05). Most surgeons would reconstruct directly or directly unless radiotherapy would be administered (62.7%). On average, surgeons would consider functional reconstructions when estimated survival is 3.0 ± 2.0 years. Surgical treatment of MPNSTs differs slightly among subspecialties. Neuropathic pain, motor deficits, and sensory deficits are commonly acknowledged postoperative morbidities. Functional reconstructions are varyingly considered by surgeons. Surgical oncologists and neurosurgeons treat most patients, yet may be least likely to consider functional reconstructions. A multidisciplinary surgical and reconstructive approach may be beneficial in MPNSTs. • Neuropathic pain, motor deficits, and sensory deficits are common postoperative morbidities after the resection of MPNSTs. • Surgical considerations for function preservation varies among surgeons. • Surgical oncologists and neurosurgeons treat most MPNST patients but are least likely to consider functional reconstructions. • Functional reconstructions can be considered in MPNST patients with a life expectancy of three or more years.

Systemic Options for Malignant Peripheral Nerve Sheath Tumors.

Malignant peripheral nerve sheath tumors (MPNSTs) are rare mesenchymal neoplasms that represent a profound therapeutic challenge due to their high proclivity for recurrence and metastasis and relatively poor response to systemic therapy regimens. While our understanding of the pathophysiology of MPNST is growing, including loss of the tumor suppressor gene neurofibromin and subsequent activation of the Ras pathway, targeted therapy to modify the poor prognosis seen in MPNST patients has thus far been without success. Correspondingly, MPNST patients are treated as per soft tissue sarcoma treatment algorithms with anthracycline-based therapy as the front-line therapy of choice for patients with unresectable, locally advanced, or metastatic MPNST. Beyond first-line anthracycline-based therapy, other standard cytotoxic chemotherapy agents used in advanced MPNST include the alkylating agent ifosfamide and the topoisomerase II inhibitor etoposide. Notably, soft tissue sarcoma regimens are used in MPNST despite distinct systemic therapy sensitivity and prognosis. This is particularly notable for neurofibromatosis type 1 (NF1)-associated MPNST, which is associated with poorer response to systemic therapy and prognosis than sporadic MPNST. As such, NF1-associated MPNST is a particular area in need of novel therapeutic strategies. Given the lack of benefit in the targeting of unique aspects of MPNST disease biology thus far, pre-clinical studies to identify novel rational therapies are critical to inform future clinical trials.

Activation of Receptor Tyrosine Kinases Mediates Acquired Resistance to MEK Inhibition in Malignant Peripheral Nerve Sheath Tumors.

Malignant peripheral nerve sheath tumors often arise in patients with neurofibromatosis type 1 and are among the most treatment-refractory types of sarcoma. Overall survival in patients with relapsed disease remains poor, and thus novel therapeutic approaches are needed. NF1 is essential for negative regulation of RAS activity and is altered in about 90% of malignant peripheral nerve sheath tumors (MPNST). A complex interplay of upstream signaling and parallel RAS-driven pathways characterizes NF1-driven tumorigenesis, and inhibiting more than one RAS effector pathway is therefore necessary. To devise potential combination therapeutic strategies, we identified actionable alterations in signaling that underlie adaptive and acquired resistance to MEK inhibitor (MEKi). Using a series of proteomic, biochemical, and genetic approaches in an in vitro model of MEKi resistance provided a rationale for combination therapies. HGF/MET signaling was elevated in the MEKi-resistant model. HGF overexpression conferred resistance to MEKi in parental cells. Depletion of HGF or MET restored sensitivity of MEKi-resistant cells to MEKi. Finally, a combination of MEK and MET inhibition demonstrated activity in models of MPNST and may therefore be effective in patients with MPNST harboring genetic alterations in NF1. SIGNIFICANCE: This study demonstrates that MEKi plus MET inhibitor may delay or prevent a novel mechanism of acquired MEKi resistance, with clinical implications for MPNST patients harboring NF1 alterations.

Limitations and benefits of FDG-PET/CT in NF1 patients with nerve sheath tumors: A cross-sectional/longitudinal study.

The purposes of this study were to re‐confirm the usefulness of PET/CT in the differentiation of benignity/malignancy of neurogenic tumors in NF1 patients, and to analyze the natural course of plexiform neurofibroma (pNF) and clarify whether PET/CT is also useful for detecting tumors other than neurogenic tumors. PET/CT was prospectively imaged in 36 NF1 patients. There were 14 malignant peripheral nerve sheath tumors (MPNSTs) in 14 patients, and 54 pNFs in 30 patients. Nine patients had both MPNST and pNF. Maximal standardized uptake value (SUVmax) was significantly higher in MPNST (median 7.6: range 4.1‐10.4) (P < .001) compared with that of pNF (median 3.7: range 1.6‐9.3). The cut‐off value of 5.8 resulted in a sensitivity of 78.6% and specificity of 88.9%. Median age was 29 y, and median maximum tumor diameter was 82 mm in 14 MPNST patients. The 5‐y overall survival rate was 46.8%. Three patients with low‐grade MPNST were alive without disease at the time of this report. In 9 patients in which pNF and MPNST co‐existed, 2 showed a higher SUVmax of pNF than that of MPNST. Natural history analysis of pNF (n = 43) revealed that no factors significantly correlated with increased tumor size. Nine lesions other than neurogenic tumors were detected by PET/CT including 5 thyroid lesions and 3 malignant neoplasms. This study revealed the usefulness and limitation of PET/CT for NF1 patients. In the future, it will be necessary to study how to detect over time the malignant transformation of pNF to MPNST, via an intermediate tumor.

Incidence and prognosis of distant metastasis in malignant peripheral nerve sheath tumors.

Malignant peripheral nerve sheath tumors (MPNSTs) are a type of soft tissue sarcomas (STS) with recurrence and metastatic potential. We aimed to investigate the risk factors for developing distant metastases (DM) and to identify the prognostic factors in patients with DM. Based on the Surveillance, Epidemiology, and End Result (SEER) database, MPNST patients diagnosed between 2010 and 2016 were extracted in our study. The logistic regression model was performed for predicting DM development while the Cox proportional hazard regression model was conducted for revealing the prognostic factors. Eventually, 764 patients diagnosed with MPNSTs were included with 109 cases presenting with metastases at initial diagnosis. Larger tumor size and lymph node metastases were independent risk factors for developing DM. The median overall survival (OS) for patients with metastases was 8.0 (95% CI: 6.1-9.9) months. Multiple metastatic sites and no surgical treatment were prognostic factors for worse survival. Tumors located in non-head and neck region were related with better survival. The incidence of DM was 14.3% with a dismal median OS of 8.0months for metastatic MPNSTs. More evaluation should be applied for patients with large tumor size and lymph metastases. Tumors located in head and neck region and the presence of multiple metastases predicted worse survival outcome. Surgical treatment can significantly improve the survival of MPNST patients with distant metastasis.

Primary adult retroperitoneal sarcoma (RS): Comprehensive genomic profiling (CGP) study.

11541 Background: We performed CGP on 315 cases of RS to discover targetable genomic alterations (GA) and their potential impact on potential targeted and immunotherapy (IO) selection. Methods: FFPE tissues from 315 clinically advanced RS tissues underwent hybrid-capture based CGP (DNA and RNA). Tumor mutational burden (TMB) was determined on up to 1.2 Mbp of sequenced DNA, and tumor cell PD-L1 expression was determined by IHC (Dako 22C3) (low = 1-49%; High = &gt;50% tumor cell staining). Results: 155 liposarcomas (LPS), 74 leiomyosarcomas (LMS), 46 pleomorphic sarcomas (PLS), 7 solitary fibrous tumors (SFT), 6 malignant peripheral nerve sheath tumors (MPNST), 5 synovial sarcomas (SS) and 5 dendritic follicular cell sarcomas (DFCS) were studied; 17 cases were excluded. Median age was 59. There were 5.1 GA/tumor, none were MSI-high, median TMB was low at 2.4; PD-L1 IHC staining was low-positive in 21% and high-positive in 5%. MPNST patients were younger (median 28 years vs. 59 years). LPS was more frequent in men and LMS in women. LPS had more GA/tumor than LMS, with DFCS having the highest and SS the lowest. TP53 and RB1 GA were the highest in LMS and CDK4/6 and MDM2 GA the highest in LPS. Molecular targets in mTOR pathway were most frequently altered. Targetable gene fusions in ALK, ROS1 and NTRK1-3 were rare. Non-targetable fusions in HMGA2 (LPS and some PLS), STAT6 (SFT) and SS18 (SS) were also identified. Conclusions: RS in our cohort are predominantly composed of LPS, LMS and PLS and we identified a small proportion with “actionable” genomic targets on CGP, albeit in association with uncertain mTOR pathway inhibitor benefit and uncommon targetable kinase fusions. Our analysis suggests that a small subset of RS may respond to immunotherapy based on putative biomarker expression. [Table: see text]

Integrated genomic and functional analysis of patient-derived sarcoma cell lines validates their use for candidate treatment discovery including knockdown of a novel BCOR fusion gene.

e23572 Background: Malignant peripheral nerve sheath tumors (MPNST) are rare, biologically-aggressive soft tissue sarcomas of neural origin, characterized by high risk of recurrence, metastases, treatment resistance and lethality. Preclinical models accurately reflecting underlying genetics are needed for exploring the tumor’s biology and developing novel therapeutic approaches. Using genomic, biochemical and bioinformatic approaches we generated and deeply characterized a patient-derived MPNST cell-line model (PDCL) and functionally validated identified therapeutic targets including a novel BCOR fusion gene. Methods: Under IRB consent, two geographically distinct metastatic tumor samples were obtained from a right peritoneal nodule (PN) and the pelvis (P) of a 63-year-old woman, with recurrent uterine MPNST to generate PDCL. Whole exome (WES) and RNA sequencing was performed on all samples. Data and bioinformatic analysis was performed using the QIAGEN software suite (CLC Genomic Workbench, Ingenuity Variant and Pathway Analysis, OmicSoft-ArrayStudio). Results: To define the degree of shared genomic diversity, WES and RNAseq of tumors and PDCL was performed. WES of metastatic samples identified both shared (n = 39) and novel (98 and 116, respectively) cancer driver variants, which were also present in the paired PDCL (38% and 39%, respectively). Furthermore, somatic copy number alterations (SCNAs) were also shared between tissue and paired PDCL. These SCNAs are present in the MPNST TCGA dataset suggesting broad biologic significance. Finally, a novel and expressed BCOR-CREBRF fusion was present in all samples. With the potential to identify and validate candidate therapies, bioinformatic analysis was used to identify shared canonical signaling pathways (Ephrin receptor signaling) and upstream regulators (HBEGF, VEGFA, and ERBB2) between tumors and PDCL. Based upon this analysis, the inhibitory effects of a targeted list of candidate drugs was performed: Dasatinib, Pazopanib, PD153035, and Lapatinib all selectively resulted in tumor cell death. Moreover, siRNA-mediated BCOR-CREBRF knockdown significantly inhibited PDCL growth. Conclusions: We demonstrate that MPNST PDCL capture the genomic diversity inherent in their founder tumor tissues and potentially other MPNST. Moreover, using a bioinformatic approach for therapeutic discovery, demonstrate the use of these PDCL for testing treatment candidates for possible use in MPNST patients.

Aberrations of TBX2-CHK2-p53 Signaling Pathway and its Role in Malignant Peripheral Nerve Sheath Tumors

Background and Objectives: The dismal outcome of malignant peripheral nerve sheath tumor (MPNST) highlights the necessity of identifying new biomarkers and pathogenesis for this aggressive sarcoma. Therefore, it is necessary to detect the aberrations of the TBX2-CHK2-p53 pathway and investigate its biological role in MPNST. Methods: Genetic aberrations of TBX2, CHK2 and p53 were detected by next generation sequencing (NGS) in 10 MPNST samples. Protein expression of TBX2, CHK2, p53, Ki-67 and cyclin D1 were assessed by immunohistochemistry (IHC) in 63 MPNST samples. Results: Our present data demonstrated that there were gene mutations of TBX2, CHK2 and p53 in MPNST samples. TBX2 expression was correlated with American Joint Committee on Cancer (AJCC) stage, recurrence and metastasis. Correlation analysis found that TBX2 was positively correlated with CHK2 (p=0.045) and CHK2 was positively correlated with p53 (p=0.006). Furthermore, both CHK2 and p53 were positively correlated with Ki-67 (p&lt;0.05), which is related to tumor differentiation, metastasis and prognosis. As for survival analyses, patients with high TBX2, CHK2 and p53 expression exhibited shorter disease-free survival (DFS) and overall survival (OS), respectively (p&lt;0.05) and TBX2 and CHK2 were independent prognostic factors for MPNST patients (p&lt;0.05). Conclusion: There are genetic aberrations of the TBX2-CHK2-p53 signaling pathway in MPNST, which might promote the progression of MPNST by increasing Ki-67 expression. Thus, TBX2 and CHK2 might be useful markers for MPNST.

Interdisciplinary approach allows minimally invasive, nerve-sparing removal of retroperitoneal peripheral nerve sheath tumors

PurposeEn bloc resection of retroperitoneal peripheral nerve sheath tumors (PNST) is advocated by a variety of surgical disciplines. Yet, microsurgical, nerve-sparing tumor resection might be better suited to improve symptoms and maintain neurological function, especially in cases where patients present with preoperative neurological deficits. However, neurosurgeons, versed in nerve-sparing techniques to remove PNST, are generally unfamiliar with the visceral approaches to retroperitoneal PNST.MethodsWe retrospectively evaluate a series of 16 patients suffering from retroperitoneal PNST. Patients were treated by a unique interdisciplinary approach, combining the visceral surgeon’s skills to navigate the complex anatomy of the retroperitoneal space and the neurosurgeon’s familiarity with microsurgical, nerve-sparing tumor removal. Specifically, we assess whether our interdisciplinary approach is suited to improve preoperative symptoms and maintain neurological function and study whether oncological outcome, surgical morbidity, and operative times are comparable to those reported for “classical” retroperitoneal PNST resection. In addition, we study two cases of suspected PNST that were diagnosed as malignant peripheral nerve sheath tumors (MPNST) after surgery.ResultsTotal macroscopic tumor resection was achieved in 14/16 PNST patients. Mean intraoperative blood loss was 680.6 ml (95% CI, 194.3–1167.0 ml) and mean operative time was 162.5 min (95% CI, 121.6–203.4 min). We did not record any major postoperative surgical or neurological complications. A total of 8/11 patients with preoperative pain symptoms reported long-lasting improvement of their symptoms. In terms of oncological outcome, all patients that had been subjected to total tumor removal and for whom follow-up was available, were tumor-free after a mean follow-up of 761.9 days (95% CI, 97.6–1426.0 days). One of the two MPNST patients, who presented with tumor progress 15 months after initial surgery, was subjected to radical re-resection.ConclusionsInterdisciplinary, nerve-sparing removal of retroperitoneal PNST is well suited to improve preoperative symptoms and maintain neurological function, while achieving an oncological outcome and a surgical morbidity similar to previously reported results for radical retroperitoneal PNST resection. Radical re-resection was feasible in a patient with post hoc MPNST diagnosis.

Neurofibromatosis-associated malignant peripheral nerve sheath tumors in children have a worse prognosis: A nationwide cohort study.

Malignant peripheral nerve sheath tumors (MPNST) are rare and aggressive non-rhabdomyoblastic soft-tissue sarcomas (NRSTS) in children. This study set out to investigate clinical presentation, treatment modalities, and factors associated with survival in pediatric MPNST using Dutch nationwide databases. Data were obtained from the Netherlands Cancer Registry (NCR) and the Dutch Pathology Database (PALGA) from 1989 to 2017. All primary MPNSTs were collected. Demographic differences were analyzed between adult and pediatric (age ≤18 years) MPNST. In children, demographic and treatment differences between neurofibromatosis type 1 (NF1) and non-NF1 were analyzed. A Cox proportional hazard model was constructed for localized pediatric MPNSTs. A total of 70/784 MPNST patients were children (37.1% NF1). Children did not present differently from adults. In NF1 children, tumor size was more commonly large (>5cm, 92.3% vs 59.1%). Localized disease was primarily resected in 90.6%, and radiotherapy was administered in 37.5%. Non-NF1 children tended to receive chemotherapy more commonly (39.5% vs 26.9%). Overall, estimated five-year survival rates of localized NF1-MPNST was 52.4% (SE: 10.1%) compared with 75.8% (SE: 7.1%) in non-NF1 patients. The multivariate model showed worse survival in NF1 patients (HR: 2.98; 95% CI, 1.17-7.60, P=0.02) and increased survival in patients diagnosed after 2005 (HR: 0.20; 95% CI, 0.06-0.69, P=0.01). No treatment factors were independently associated with survival. Pediatric MPNSTs have presentations similar to adult MPNSTs. In children, NF1 patients present with larger tumors, but are treated similarly to non-NF1 MPNSTs. In localized pediatric MPNST, NF1 is associated with worse survival. Promisingly, survival has increased for pediatric MPNSTs after 2005.