Citations

Abstract Diffuse hemispheric glioma, H3 G34‐mutant (DHG‐H3 G34) has been primarily molecularly characterized by methylation profiling and sequencing studies. We describe an integrated histomolecular evaluation including high‐resolution copy number profiling of a series of 60 DHG‐H3 G34 to further our understanding of the spectrum of genetic changes associated with this tumor type. Cases were clinically tested using an 187‐gene mutation and fusion targeted neuro‐oncology next‐generation sequencing panel ( n = 60) and Oncoscan chromosomal microarray ( n = 26) by a single laboratory (2018–2022). A subset of cases had immunohistochemical results for OLIG2 ( n = 42), p53 ( n = 48), and ATRX ( n = 46), and methylation array data ( n = 8). Median age at testing was 21 years (range, 12–50). No significant difference was noted in clinical, histopathological, and mutational profile between pediatric and adult patients. H3‐3A G34 mutations included G34R ( n = 56; 94%), G34V ( n = 3), and a non‐canonical G34E ( n = 1). Concurrent mutations most often involved TP53 ( n = 55; 92%), ATRX ( n = 50; 83%), and PDGFRA ( n = 34; 57%). A reportedly primary tumor was confirmed to be hypermutant and had a PMS2 mutation. A single case also showed an FGFR3::FAM184B fusion. All cases with available chromosomal microarray data had unbalanced genomes, which were often complex (14/26; 54%). The most frequent recurrent copy number abnormalities were losses involving 3q, 4q, 10q, 13q, and 18q, and 17p copy‐neutral loss of heterozygosity (cnLOH) encompassing TP53 . This copy number profile was reminiscent of that seen in Grade 4 IDH‐mutant astrocytomas. Collectively, a TP53 abnormality at copy number (12/26, all cnLOH), sequence (55/60) and protein expression (46/48) level was detected in all 60 cases. In conclusion, integrated high‐resolution copy number and histomolecular analysis expanded the spectrum of genetic changes associated with DHG‐H3 G34, including the presence of universal TP53 abnormalities with frequent cnLOH—a copy number abnormality that has been largely unrecognized—for this new 2021 World Health Organization central nervous system tumor type.

TPS486 Background: Hepatocellular carcinoma (HCC) is a major cause of cancer-related death in the U.S. HCC surveillance is associated with improved early detection and receipt of curative treatment. However, current surveillance strategies suffer from low adherence and suboptimal sensitivity. The multi-target HCC blood test (mt-HBT) is a novel early detection assay that provides a qualitative result based on a multiparametric algorithm that incorporates information from methylation markers ( HOXA1, TSPYL5, and B3GALT6), AFP, and patient sex. Here, we describe the protocol for a prospective, multicenter clinical trial designed to investigate the performance of the mt-HBT in patients at risk for HCC. Methods: ALTernative to U/S (ALTUS) is a longitudinal, multicenter, prospective study with a targeted enrollment of 3,000 participants. The main inclusion and exclusion criteria are described in the table. Participants will receive HCC surveillance imaging (either U/S or CT/MRI) and blood collection for the mt-HBT. Those with positive U/S are anticipated to receive standard-of-care imaging follow-up with a multiphase CT or MRI, and those with a negative U/S will receive a study CT/MRI within 30 days of blood collection. Imaging interpretation is based on the CT/MRI LI-RADS (LR) v2018 categories. The primary endpoints are the overall sensitivity and specificity of the mt-HBT to detect HCC, defined as pathology-confirmed HCC or hepatocellular cholangiocarcinoma (cHCC-CCA), LR-4/5, or LR-TIV/M plus definite/probable HCC or cHCC-CCA. The secondary endpoints are mt-HBT early-stage sensitivity, and performance in a) participants with LR-5 or biopsy-confirmed HCC and b) participants confirmed non-HCC. Participants not diagnosed with a liver malignancy at visit one will continue to receive HCC surveillance, returning for a second visit ̃6 months from first blood collection. Blood will be collected after the second visit for the mt-HBT. Data on treatment will be collected for those diagnosed with HCC. Study participants and providers will be blinded to the mt-HBT results. Participants are currently enrolling across the U.S., with 60 targeted sites and an anticipated 12-month enrollment window. Clinical trial information: NCT05064553. [Table: see text]