Gross, Andrea M

Abstract Purpose: Combined mTOR and MEK inhibition, critical components of the RAS effector pathway underlying the pathogenesis of neurofibromatosis type 1 (NF1)–related tumors, caused regression in a malignant peripheral nerve sheath tumor (MPNST) transgenic mouse model. The primary objective was to determine the clinical benefit rate in patients with unresectable/metastatic MPNST. Patients and Methods: The study design was a multi-institutional, open-label, Simon two-stage, phase II study of the MEK inhibitor selumetinib and mTOR inhibitor sirolimus. Patients ≥12 years with histologically confirmed MPNST received selumetinib 50 mg twice daily and sirolimus 4 mg once daily, in continuous 28-day cycles. Correlative studies evaluated patient-reported pain, immune signature in peripheral blood, and cell-free DNA (cfDNA). Results: A total of 21 heavily pretreated patients [seven females; median age, 41 years (range, 16–72); and 14 with NF1] with advanced disease enrolled at five participating sites. Clinical benefit was observed in only one of seven in stage 1 and one of 14 patients in stage 2. The median number of cycles was two (range, 1–6). Most common adverse events (AE) were grade ≤2 gastrointestinal toxicity, acneiform rash, hypertriglyceridemia, mucositis, and transaminase elevation. Unlike the preclinical model, early 18F-fluorodeoxyglucose PET scan performed during cycle 1 demonstrated partial metabolic responses in five patients (24%), but these did not correlate with objective responses after cycle 2. cfDNA was able to detect MPNST with the potential to be a biomarker of response. Conclusions: The combination was safe, with manageable and expected AEs, but did not meet study parameters for further evaluation in MPNST. Correlative studies were informative and may guide future therapeutic trials of MPNST.

Abstract Purpose: Early detection of neurofibromatosis type 1 (NF1)–associated peripheral nerve sheath tumors (PNST) informs clinical decision-making, enabling early definitive treatment and potentially averting deadly outcomes. In this study, we describe a cell-free DNA (cfDNA) fragmentomic approach that distinguishes nonmalignant, premalignant, and malignant forms of PNST in the cancer predisposition syndrome, NF1. Experimental Design: cfDNA was isolated from plasma samples of a novel cohort of 101 patients with NF1 and 21 healthy controls and underwent whole-genome sequencing. We investigated diagnosis-specific signatures of copy-number alterations with in silico size selection as well as fragment profiles. Fragmentomics were analyzed using complementary feature types: bin-wise fragment size ratios, end motifs, and fragment non-negative matrix factorization signatures. Results: The novel cohort of patients with NF1 validated that our previous cfDNA copy-number alteration–based approach identifies malignant PNST (MPNST) but cannot distinguish between benign and premalignant states. Fragmentomic methods were able to differentiate premalignant states including atypical neurofibromas (AN). Fragmentomics also adjudicated AN cases suspicious for MPNST, correctly diagnosing samples noninvasively, which could have informed clinical management. Conclusions: Novel cfDNA fragmentomic signatures distinguish AN from benign plexiform neurofibromas and MPNST, enabling more precise clinical diagnosis and management. This study pioneers the early detection of malignant and premalignant PNST in NF1 and provides a blueprint for decentralizing noninvasive cancer surveillance in hereditary cancer predisposition syndromes.

Neurofibromatosis type 1 is a genetic syndrome characterized by a wide variety of tumor and non-tumor manifestations. Bone-related issues, such as scoliosis, tibial dysplasia, and low bone mineral density, are a significant source of morbidity for this population with limited treatment options. Some of the challenges to developing such treatments include the lack of consensus regarding the optimal methods to assess bone health in neurofibromatosis type 1 and limited data regarding the natural history of these manifestations. In this review, the Functional Committee of the Response Evaluation in Neurofibromatosis and Schwannomatosis International Collaboration: (1) presents the available techniques for measuring overall bone health and metabolism in persons with neurofibromatosis type 1, (2) reviews data for use of each of these measures in the neurofibromatosis type 1 population, and (3) describes the strengths and limitations for each method as they might be used in clinical trials targeting neurofibromatosis type 1 bone manifestations. The Response Evaluation in Neurofibromatosis and Schwannomatosis International Collaboration supports the development of a prospective, longitudinal natural history study focusing on the bone-related manifestations and relevant biomarkers of neurofibromatosis type 1. In addition, we suggest that the neurofibromatosis type 1 research community consider adding the less burdensome measurements of bone health as exploratory endpoints in ongoing or planned clinical trials for other neurofibromatosis type 1 manifestations to expand knowledge in the field.

Background: Spinal conditions, such as scoliosis and spinal tumors, are prevalent in neurofibromatosis type 1 (NF1). Despite the recognized importance of their early detection and treatment, there remain knowledge gaps in how to approach these manifestations. The purpose of this study was to utilize the experience of a multidisciplinary committee of experts to establish consensus-based best practice guidelines (BPGs) for spinal screening and surveillance, surgical intervention, and medical therapy in pediatric patients with NF1. Methods: Using the results of a prior systematic review, 10 key questions that required further assessment were first identified. A committee of 20 experts across medical specialties was then chosen based on their clinical experience with spinal deformity and tumors in NF1. These were 9 orthopaedic surgeons, 4 neuro-oncologists/oncologists, 3 neurosurgeons, 2 neurologists, 1 pulmonologist, and 1 clinical geneticist. An initial online survey on current practices and opinions was conducted, followed by 2 additional surveys via a formal consensus-based modified Delphi method. The final survey involved voting on agreement or disagreement with 35 recommendations. Items reaching consensus (≥70% agreement or disagreement) were included in the final BPGs. Results: Consensus was reached for 30 total recommendations on the management of spinal deformity and tumors in NF1. These were 11 recommendations on screening and surveillance, 16 on surgical intervention, and 3 on medical therapy. Five recommendations did not achieve consensus and were excluded from the BPGs. Conclusion: We present a set of consensus-based BPGs comprised of 30 recommendations for spinal screening and surveillance, surgical intervention, and medical therapy in pediatric NF1.

Abstract Plexiform Neurofibromas (PN) are a common manifestation of the genetic disorder neurofibromatosis type 1 (NF1). These benign nerve sheath tumors often cause significant morbidity, with treatment options limited historically to surgery. There have been tremendous advances over the past two decades in our understanding of PN, and the recent regulatory approvals of the MEK inhibitor selumetinib are reshaping the landscape for PN management. At present, there is no agreed upon PN definition, diagnostic evaluation, surveillance strategy, or clear indications for when to initiate treatment and selection of treatment modality. In this review, we address these questions via consensus recommendations from a panel of multidisciplinary NF1 experts.