Systemic Treatment for Advanced and Metastatic Malignant Peripheral Nerve Sheath Tumors-A Sarcoma Reference Center Experience

Pharmacogenomic synthetic lethal screens reveal hidden vulnerabilities and new therapeutic approaches for treatment of NF1-associated tumors

Neurofibromatosis Type 1 (NF1) is a common cancer predisposition syndrome, caused by heterozygous loss of function mutations in the tumor suppressor gene NF1. Individuals with NF1 develop benign tumors of the peripheral nervous system (neurofibromas), originating from the Schwann cell linage after somatic loss of the wild type NF1 allele, some of which progress further to malignant peripheral nerve sheath tumors (MPNST). There is only one FDA approved targeted therapy for symptomatic plexiform neurofibromas and none approved for MPNST. The genetic basis of NF1 syndrome makes associated tumors ideal for using synthetic drug sensitivity approaches to uncover therapeutic vulnerabilities. We developed a drug discovery pipeline to identify therapeutics for NF1-related tumors using isogeneic pairs of NF1-proficient and deficient immortalized human Schwann cells. We utilized these in a large-scale high throughput screen (HTS) for drugs that preferentially kill NF1-deficient cells, through which we identified 23 compounds capable of killing NF1-deficient Schwann cells with selectivity. Multiple hits from this screen clustered into classes defined by method of action. Four clinically interesting drugs from these classes were tested in vivo using both a genetically engineered mouse model of high-grade peripheral nerve sheath tumors and human MPNST xenografts. All drugs tested showed single agent efficacy in these models as well as significant synergy when used in combination with the MEK inhibitor selumetinib. This HTS platform yielded novel therapeutically relevant compounds for the treatment of NF1-associated tumors and can serve as a tool to rapidly evaluate new compounds and combinations in the future.

Brain metastases of sarcoma: a rare phenomenon in rare tumours

The usual site for distant metastases of sarcoma is lungs, while brain metastasis (BM) occurs much less frequently and usually late in the disease progression. Despite the advancement in cancer treatment, the outcome for patients with brain metastasis is poor, and their lifespan is short. The frequency of BM in sarcoma seems to be affected by the location and histology of the primary tumour. Sarcoma subtypes with a high propensity for brain metastasis are ASPS, leiomyosarcoma and osteosarcoma. There are no clear guidelines for the treatment of sarcoma brain metastasis. However, therapeutic options include surgery, radiotherapy and chemotherapy, and are often combined. Targeted therapies are a promising treatment option for sarcoma but require investigation in patients with BM. The following review presents the data on sarcoma brain metastasis incidence, treatment and prognosis.

The quest for effective immunotherapies against malignant peripheral nerve sheath tumors: Is there hope?

Immune-based therapies represent a new paradigm in the treatment of multiple cancers, where they have helped achieve durable and safe clinical responses in a growing subset of patients. While a wealth of information is available concerning the use of these agents in treating the more common malignancies, little has been reported about the use of immunotherapies against malignant peripheral nerve sheath tumors (MPNSTs), a rare form of soft tissue sarcoma that arises from the myelin sheaths that protect peripheral nerves. Surgical resection has been the mainstay of therapy in MPNSTs, but the recurrence rate is as high as 65%, and chemotherapy is generally ineffective. The immune contexture of MPNSTs, replete with macrophages and a varying degree of T cell infiltration, presents multiple opportunities to design meaningful therapeutic interventions. While preliminary results with macrophage-targeting strategies and oncolytic viruses are promising, identifying the subset of patients that respond to immune-based strategies will be a milestone. As part of our effort to help advance the use of immunotherapy for MPNSTs, here we describe recent insights regarding the immune contexture of MPNSTs, discuss emerging immune-based strategies, and provide a brief overview of potential biomarkers of response.

Metastatic Multifocal Malignant Peripheral Nerve Sheath Tumour in the Cervicothoracic Spinal Cord of a Dog Initially Mimicking Meningomyelitis

A nine year old cross-breed dog was presented with a two week history of ambulatory tetraparesis and proprioceptive ataxia affecting all four limbs. Meningomyelitis of Unknown Origin (MUO) was presumptively diagnosed based on the magnetic resonance imaging (MRI) findings and cerebrospinal fluid (CSF) analysis. The dog received a tapering dose of glucocorticoids and cyclosporine, showing significant improvement and the stabilization of the clinical signs for seven months. After this period, the dog showed an acute clinical deterioration and a follow-up MRI revealed new multiple lesions affecting different spinal nerve roots along the cervicothoracic spinal cord. Following euthanasia, a final diagnose of multiple malignant peripheral nerve sheath tumors (MPNSTs) was made based on the histopathological examination. MPNSTs can affect the cranial nerves, spinal nerves or the associated nerve roots at any location and can lead to secondary spinal cord compression. The aim of the present case report is to describe the clinical presentation and atypical MRI findings of a dog with histologically confirmed multiple MPNSTs. According to the reviewed literature, this is the first reported case of simultaneous MPNSTs in the cervicothoracic spinal cord of a dog.

Metastatic malignant peripheral nerve sheath tumour in a patient with neurofibromatosis 1 and review of contemporary systemic treatments

Malignant peripheral nerve sheath tumours are rare soft tissue sarcomas commonly seen in patients with neurofibromatosis type 1. They typically manifest in the fibrous sheaths of major nerve trunks in the extremities or in an axial location. Presenting symptoms are generally non-specific, including pain and weakness, and survival is dependent on size and location of the tumour. Surgical resection is the primary treatment modality followed by radiotherapy or chemotherapy; however, prognosis is poor. Medications such as tyrosine kinase inhibitors and mitogen-activated protein kinase (MAPK)/extracellular signal-regulated kinase (ERK) pathway inhibitors are increasingly being recognised as potentially effective therapy for these malignancies. We report a case of a patient with neurofibromatosis type 1 presenting with a malignant peripheral nerve sheath tumour along the tibial nerve that was initially diagnosed as a muscle strain. We discuss the utility of diagnostic imaging and pathology in correctly identifying this aggressive tumour as well as review the drugs used in her care.

In search of effective therapies: the current landscape of phase II trials in patients with advanced soft tissue sarcoma

PURPOSE

Soft tissue sarcomas (STS) are diagnosed in 4-6 cases per 100 000 people a year and are associated with an unfavorable prognosis. Around one-third of patients will develop metastatic disease that requires palliative systemic therapy. Current therapeutic options have limited activity, and new treatments are tested, mainly in phase II trials. There is high variability and no standardization of phase II designs. We aimed to analyze the current landscape of phase II studies in STS and evaluate how its statistical design can affect the results.

METHODS

Full-text phase II studies published in STS patients between 2005 and 2020 were identified and analyzed.

RESULTS

We have identified 102 trials, of which 77.4% were single-arm trials, 16.7% were randomized comparative trials (RCT), and 5.9% were randomized noncomparative trials. Including multiple cohorts, 22 randomized and 128 single-arm cohorts were analyzed. Nearly 80% of trials reported full statistical bases of the design. Over 20 different primary endpoints were used, with PFS as the most common in RCT trials (81.8%) and ORR (36.7%) and 3-months progression-free survival (PFS) rate (21.9%) in single-arm trials. Overall, 27.3% of RCT and 37.5% of single-arm trials were positive. Among single-arm trials, studies using 3- or 6-month rates were more often positive than those based on ORR.

CONCLUSIONS

There is high heterogeneity in sarcoma trial designs, mainly in primary-endpoint and hypotheses used for size calculation. There is an unmet need for standardization that will incorporate factors associated with the rarity of the disease, outcomes detected in previous trials and real-life studies, and specific characteristics of new therapeutic agents.

The clinical course and role of surgery in pediatric malignant peripheral nerve sheath tumors: a database study

OBJECTIVE

Malignant peripheral nerve sheath tumors (MPNSTs) are rare tumors found throughout the body, with their clinical course in children still not completely understood. Correspondingly, this study aimed to determine survival outcomes and specific clinical predictors of survival in this population from a large national database.

METHODS

All patients with MPNSTs aged ≤ 18 years in the US National Cancer Database (NCDB) between 2005 and 2016 were retrospectively reviewed. Data were summarized, and overall survival was modeled using Kaplan-Meier and Cox regression analyses.

RESULTS

A total of 251 pediatric patients with MPNSTs (132 [53%] females and 119 [47%] males) were identified; the mean age at diagnosis was 13.1 years (range 1-18 years). There were 84 (33%) MPNSTs located in the extremities, 127 (51%) were smaller than 1 cm, and 22 (9%) had metastasis at the time of diagnosis. In terms of treatment, surgery was pursued in 187 patients (74%), chemotherapy in 116 patients (46%), and radiation therapy in 129 patients (61%). The 5-year overall survival rate was estimated at 52% (95% CI 45%-59%), with a median survival of 64 months (range 36-136 months). Multivariate regression revealed that older age (HR 1.10, p < 0.01), metastases at the time of diagnosis (HR 2.14, p = 0.01), and undergoing biopsy only (HR 2.98, p < 0.01) significantly and independently predicted a shorter overall survival. Chemotherapy and radiation therapy were not statistically significant.

CONCLUSIONS

In this study, the authors found that older patient age, tumor metastases at the time of diagnosis, and undergoing only biopsy significantly and independently predicted poorer outcomes. Only approximately half of patients survived to 5 years. These results have shown a clear survival benefit in pursuing maximal safe resection in pediatric patients with MPNSTs. As such, judicious workup with meticulous resection by an expert team should be considered the standard of care for these tumors in children.

Cutaneous Findings in Neurofibromatosis Type 1

Neurofibromatosis type 1 (NF1) is a complex autosomal dominant disorder associated with germline mutations in the NF1 tumor suppressor gene. NF1 belongs to a class of congenital anomaly syndromes called RASopathies, a group of rare genetic conditions caused by mutations in the Ras/mitogen-activated protein kinase pathway. Generally, NF1 patients present with dermatologic manifestations. In this review the main features of café-au-lait macules, freckling, neurofibromas, juvenile xanthogranuloma, nevus anemicus and other cutaneous findings will be discussed.