Faculty Bibliography

Fusions involving CRAF (RAF1) are infrequent oncogenic drivers in pediatric low-grade gliomas, rarely identified in tumors bearing features of pilocytic astrocytoma, and involving a limited number of known fusion partners. We describe recurrent TRAK1::RAF1 fusions, previously unreported in brain tumors, in three pediatric patients with low-grade glial-glioneuronal tumors. We present the associated clinical, histopathologic and molecular features. Patients were all female, aged 8 years, 15 months, and 10 months at diagnosis. All tumors were located in the cerebral hemispheres and predominantly cortical, with leptomeningeal involvement in 2/3 patients. Similar to previously described activating RAF1 fusions, the breakpoints in RAF1 all occurred 5' of the kinase domain, while the breakpoints in the 3' partner preserved the N-terminal kinesin-interacting domain and coiled-coil motifs of TRAK1. Two of the three cases demonstrated methylation profiles (v12.5) compatible with desmoplastic infantile ganglioglioma (DIG)/desmoplastic infantile astrocytoma (DIA) and have remained clinically stable and without disease progression/recurrence after resection. The remaining tumor was non-classifiable; with focal recurrence 14 months after initial resection; the patient remains symptom free and without further recurrence/progression (5 months post re-resection and 19 months from initial diagnosis). Our report expands the landscape of oncogenic RAF1 fusions in pediatric gliomas, which will help to further refine tumor classification and guide management of patients with these alterations.

Stimulated Raman histology (SRH) is an ex vivo optical imaging method that enables microscopic examination of fresh tissue intraoperatively. The conventional intraoperative method uses frozen section analysis, which is labor and time intensive, introduces artifacts that limit diagnostic accuracy, and consumes tissue. SRH imaging allows rapid microscopic imaging of fresh tissue, avoids tissue loss, and enables remote telepathology review. This improves access to expert neuropathology consultation in both low- and high-resource practices. We clinically validated SRH by performing a blinded, retrospective two-arm telepathology study to clinically validate SRH for telepathology at our institution. Using surgical specimens from 47 subjects, we generated a data set composed of 47 SRH images and 47 matched whole slide images (WSIs) of formalin-fixed, paraffin-embedded tissue stained with hematoxylin and eosin, with associated intraoperative clinicoradiologic information and structured diagnostic questions. We compared diagnostic concordance between WSI and SRH-rendered diagnoses. Also, we compared the 1-year median turnaround time (TAT) of intraoperative conventional neuropathology frozen sections with prospectively rendered SRH-telepathology TAT. All SRH images were of sufficient quality for diagnostic review. A review of SRH images showed high accuracy in distinguishing glial from nonglial tumors (96.5% SRH vs 98% WSIs) and predicting final diagnosis (85.9% SRH vs 93.1% WSIs). SRH-based diagnosis and WSI-permanent section diagnosis had high concordance (κ = 0.76). The median TAT for prospectively SRH-rendered diagnosis was 3.7 minutes, approximately 10-fold shorter than the median frozen section TAT (31 minutes). The SRH-imaging procedure did not affect ancillary studies. SRH generates diagnostic virtual histologic images with accuracy comparable to conventional hematoxylin and eosin-based methods in a rapid manner. Our study represents the largest and most rigorous clinical validation of SRH to date. It supports the feasibility of implementing SRH as a rapid method for intraoperative diagnosis complementary to conventional pathology laboratory methods.

BACKGROUND/UNASSIGNED:Central nervous system (CNS) cancer is the 10th leading cause of cancer-associated deaths for adults, but the leading cause in pediatric patients and young adults. The variety and complexity of histologic subtypes can lead to diagnostic errors. DNA methylation is an epigenetic modification that provides a tumor type-specific signature that can be used for diagnosis. METHODS/UNASSIGNED:We performed a prospective study using DNA methylation analysis as a primary diagnostic method for 1921 brain tumors. All tumors received a pathology diagnosis and profiling by whole genome DNA methylation, followed by next-generation DNA and RNA sequencing. Results were stratified by concordance between DNA methylation and histopathology, establishing diagnostic utility. RESULTS/UNASSIGNED:Of the 1602 cases with a World Health Organization histologic diagnosis, DNA methylation identified a diagnostic mismatch in 225 cases (14%), 78 cases (5%) did not classify with any class, and in an additional 110 (7%) cases DNA methylation confirmed the diagnosis and provided prognostic information. Of 319 cases carrying 195 different descriptive histologic diagnoses, DNA methylation provided a definitive diagnosis in 273 (86%) cases, separated them into 55 methylation classes, and changed the grading in 58 (18%) cases. CONCLUSIONS/UNASSIGNED:DNA methylation analysis is a robust method to diagnose primary CNS tumors, improving diagnostic accuracy, decreasing diagnostic errors and inconclusive diagnoses, and providing prognostic subclassification. This study provides a framework for inclusion of DNA methylation profiling as a primary molecular diagnostic test into professional guidelines for CNS tumors. The benefits include increased diagnostic accuracy, improved patient management, and refinements in clinical trial design.

BACKGROUND: While most meningiomas are considered benign tumors, a subset of these tumors are characterized by a more aggressive clinical course and require multimodal treatment. Beyond surgical and radiotherapeutic options, there are no effective medical treatments available. Somatostatin receptor 2 (SSTR2) is expressed by the majority of meningiomas. 177Lu-DOTATATE is a SSTR2-targeting radionuclide that has been successful in neuroendocrine tumors. Here we report the results of the interim analysis of an ongoing clinical trial (NCT03971461) that is evaluating the effect of 177Lu-DOTATATE in treating progressive intracranial meningiomas.
METHOD(S): In this Simon two-stage design phase II study, adults with advanced intracranial meningiomas received 177Lu-DOTATATE 7.4 GBq (200 mCi) every eight weeks for four doses. 68Ga-DOTATATE PET-MRI was performed before and at the end of treatment. The primary endpoint was progression-free survival at 6 months (PFS-6). Correlative studies evaluated the association of PFS-6, objective response rate, progression-free survival, overall survival with radiographic tumor measurements, 68Ga-DOTATATE uptake on PET-MRI, SSTR2 expression in tumor, and meningioma methylation subclass.
RESULT(S): Fourteen patients (F = 11, M = 3) with progressive meningiomas (WHO I = 3, II = 10, III = 1) have been enrolled. Median age was 63.1 (range 49-78) years. All patients previously underwent tumor resection and at least one course of radiation. Treatment with 177Lu-DOTATATE was well tolerated, no treatment-limiting toxicities were observed. Six of 14 patients (42%) achieved PFS-6. Radiographically, all six patients had achieved Stable Disease. A functional alteration of tumoral SSTR2 expression by 68Ga-DOTATATE PET-MR imaging was observed in three patients.
CONCLUSION(S): Treatment with SSTR2- targeting 177Lu-DOTATATE is well tolerated. In this interim analysis, six of 14 patients achieved PFS-6. This exceeds the predefined threshold to continue to stage two of this study. This clinical trial is now open to patient enrollment at two study sites in the US

Diffuse spinal cord gliomas (SCGs) are rare tumors associated with a high morbidity and mortality that affect both pediatric and adult populations. In this retrospective study, we sought to characterize the clinical, pathological, and molecular features of diffuse SCG in 22 patients with histological and molecular analyses. The median age of our cohort was 23.64 years (range 1-82) and the overall median survival was 397 days. K27M mutation was significantly more prevalent in males compared to females. Gross total resection and chemotherapy were associated with improved survival, compared to biopsy and no chemotherapy. While there was no association between tumor grade, K27M status (p = 0.366) or radiation (p = 0.772), and survival, males showed a trend toward shorter survival. K27M mutant tumors showed increased chromosomal instability and a distinct DNA methylation signature.

OBJECTIVE:Silent corticotroph adenomas (SCAs) behave more aggressively than other non-functioning adenomas (NFAs). This study aims to expand the body of knowledge of the behavior of SCAs. METHODS:Retrospective analysis of 196 non-corticotroph NFAs and 20 SCAs from 2012-2017 was completed. Demographics, clinical presentation, imaging and biochemical data were gathered. The primary endpoint was to identify features of SCAs vs. other NFAs that suggest aggressive disease, including pre-surgical comorbidities, postoperative complications, extent of tumor and recurrence. GRASP MRI images were obtained from a subset of SCAs and NFAs. Permeability data was obtained to compare signal-to-time curve variation between the two groups. RESULTS:With multivariate regression analysis, SCAs showed higher rates of hemorrhage on preoperative imaging than NFAs (p=0.017). SCAs presented more frequently with headache, vision changes and fatigue (p=0.012, p=0.041, p=0.028). SCAs exhibited greater extent of tumor burden with increased occurrence of stalk deviation, suprasellar invasion, optic chiasm compression and cavernous sinus invasion (p=0.008, p=0.021, p=0.022, p=0.015). On GRASP imaging, SCAs had significantly lower permeability of contrast than NFAs (p=0.001). 30% of SCAs were noted to recur with a 14% recurrence rate in other NFAs, though this difference was not of statistical significance (p=0.220). CONCLUSIONS:SCAs exhibit features of more aggressive disease. Interestingly, a significant increase in recurrence was not seen despite these features. The results of this study support the growing body of evidence that SCAs behave more aggressively than other NFPAs and was able to provide some insight into factors that may contribute to recurrence.

The prognostic value of mutations in G-protein genes GNAQ and GNA11 in patients with intracranial and orbital melanocytomas is unknown. The authors present a case of GNA11 mutation (GNA11Q209L) in a 32-year-old male suffering from a meningeal melanocytoma with orbital involvement and ipsilateral Nevus of Ota. The patient underwent gamma knife stereotactic radiosurgery without biopsy and later partial transcranial resection of the melanocytic tumor that was subject to immunohistochemical and molecular analysis. A 50-gene next-generation sequencing panel revealed a 626A>T mutation in the GNA11 gene. One year later, intracranial extension of the melanocytoma necessitated a ventriculoperitoneal shunt and immunotherapy. Future work is needed to determine how GNA11 mutations in melanocytomas influence prognosis and monitoring strategies.