Kaspar Draaisma

Background: The T2-FLAIR mismatch sign is defined by signal loss of the T2-weighted hyperintense area with Fluid-Attenuated Inversion Recovery (FLAIR) on magnetic resonance imaging, causing a hypointense region on FLAIR. It is a highly specific diagnostic marker for IDH-mutant astrocytoma and is postulated to be caused by intercellular microcystic change in the tumor tissue. However, not all IDH-mutant astrocytomas show this mismatch sign and some show the phenomenon in only part of the lesion. The aim of the study is to determine whether the T2-FLAIR mismatch phenomenon has any prognostic value beyond initial noninvasive molecular diagnosis. Methods: Patients initially diagnosed with histologically lower-grade (2 or 3) IDH-mutant astrocytoma and with at least 2 surgical resections were included in the GLASS-NL cohort. T2-FLAIR mismatch was determined, and the growth pattern of the recurrent tumor immediately before the second resection was annotated as invasive or expansive. The relation between the T2-FLAIR mismatch sign and tumor grade, microcystic change, overall survival (OS), and other clinical parameters was investigated both at first and second resection. Results: The T2-FLAIR mismatch sign was significantly related to Grade 2 (80% vs 51%), longer post-resection median OS (8.3 vs 5.2 years), expansive growth, and lower age at second resection. At first resection, no relation was found between the mismatch sign and OS. Microcystic change was associated with areas of T2-FLAIR mismatch. Conclusions: T2-FLAIR mismatch in IDH-mutant astrocytomas is correlated with microcystic change in the tumor tissue, favorable prognosis, and Grade 2 tumors at the time of second resection.

INTRODUCTION. Diffuse gliomas are the most frequent and devastating primary CNS tumors in adults. Standard treatment has limited efficacy and without exception these gliomas recur. The evolutionary processes that drive progression in glioma of the IDH-mutant astrocytoma subgroup, remain unclear. The GLASS-NL consortium was initiated to gain insight into the molecular mechanisms underlying glioma evolution and to identify markers of progression in IDH-mutant astrocytomas. Such markers can ultimately assist clinical decision making. Here, we present the results of genome wide DNA-methylation profiling of samples included in the GLASS-NL study. METHODS. 110 adult patients were identified with an IDH-mutant, 1p19q non-codeleted, astrocytoma at first diagnosis. All patients underwent surgical resection of the tumor at least twice, separated by >6 months with a median of 41.9 months (IQR:26.5-65.9). After surgical resection of the initial tumor, 63% and 22% of the patients were treated with radiotherapy or chemotherapy respectively. DNA-methylation profiling was performed on 235 samples from 103 patients, using the Illumina Infinium MethylationEPIC BeadChip array. Copy number alterations (CNAs) were extracted from these data. Methylation subclasses were determined according to Capper et al. (Nature, 2018). Overall survival (OS) was measured from date of initial surgery. RESULTS. Of all primary tumors, 85 (87%) of the tumor samples were assigned to the A_IDH (‘low grade’) methylation subclass and 10 (10%) to the A_IDH_HG (‘high grade’) subclass. The relative proportion of high grade tumors increased ~three-fold at tumor recurrence (32/101, 32%) and even further in the second recurrence (15/29, 52%). The high grade subclass of the recurrent, but not the initial tumor sample, was negatively associated with OS (p < 0.0001). The overall DNA-methylation levels of recurrent samples were lower than that of initial samples. This difference is explained by the increased number of high grade samples at recurrence, since near identical DNA-methylation levels were observed in samples that remained low grade. Analysis of CNAs revealed several chromosomal arms and bands that were more frequently altered in samples of the high grade methylation subclass compared to low grade. In addition, gains and losses of specific genes, such as homozygous deletion (HD) of CDKN2A/B, were more frequent in high grade samples. Overall DNA-methylation levels of recurrent samples with CDKN2A/B HD were lower than that of samples without this deletion. However, CDKN2A/B HD alone does not fully explain DNA-demethylation at malignant progression and other molecular aberrations are likely to contribute as well. CONCLUSION. Longitudinal methylation profiling analysis of IDH-mutant astrocytoma reveals a shift towards a higher grade at tumor recurrence coinciding with reduced genome-wide DNA-methylation levels. Citation Format: Wies Rijan Vallentgoed, Anneke Niers, Karin van Garderen, Martin van den Bent, Erik van Dijk, Kaspar Draaisma, Paul van Eijk, Iris de Heer, Mathilde Kouwenhoven, Johan Kros, Wendy de Leng, Ivonne Martin, Pierre Robe, Marion Smits, Mircea Tesileanu, Hinke van Thuijl, Roel Verhaak, Bart Westerman, Mark van de Wiel, Bauke Ylstra, Pieter Wesseling, Pim French. Methylation analysis of matched primary and recurrent IDH-mutant astrocytoma; an update from the GLASS-NL consortium [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 4020.

Background: Glioblastoma is the most prevalent and severe type of malignant brain tumor in adults. Although the genetic make-up initiating glioblastoma is increasingly better understood, a better understanding in the mechanisms that drive its evolution, heterogeneity and therapy resistance may reveal new directions for therapy development. To get better insights into glioblastoma evolution, we analyzed and de-convoluted transcriptomes of primary and recurrent glioblastoma resections. Material and Methods: Matching primary and secondary resections from n=185 glioblastoma patients were collected as part of EORTC Study 1542. The study was extended with tumor pairs from n=51 patients from the international GLASS study. The datasets were subjected to differential and deconvolution analysis using in-house algorithms. Results: When mapping the tumor samples into a reduced Glioblastoma Intrinsic Transcriptional Subtype space, we visualized subtype traversal, indicating that the CL subtype most often switches. As we found no more transitions from MES to other subtypes than to be expected by chance, we concluded that MES is an end-state. On average, tumor cell percentages decreased from ~67% to ~50% mostly due to an increase in TAM/microglia. Differential expression analysis was performed with correction for tumor cell percentages. While expression of most known oncogenes did not change considerably over time, marker genes of TAM/microglia, neurons and oligodendrocytes were up-regulated whereas endothelial cell markers were down-regulated over time. Furthermore, a cluster of ~30 extracellular matrix-associated genes increase significantly over time. A signature representing the gene-set was significantly associated with poor survival; high signatures were in particular associated to survival in secondary resections (P = 6.613e-06, Kaplan-Meier estimator). This suggests that the increase of extracellular matrix expression fulfils an important role in glioblastoma evolution. Conclusion: Using a large cohort, we interrogated changes in the glioblastoma transcriptome over time and found that in particular the composition of the tumor and its environment changes. The tumor cell percentage drops, suggesting more invasion or recruitment of non-malignant cells or a combination of both. This change is independent of an increase in the prognostic increase in extracellular matrix expression. Citation Format: Youri Hoogstrate, Kaspar Draaisma, Santoesha A. Ghisai, Iris de Heer, Levi van Hijfte, Wouter Coppieters, Melissa Kerkhof, Astrid Weyerbrock, Marc Sanson, Ann Hoeben, Slávka Lukacova, Giuseppe Lombardi, Sieger Leenstra, Monique Hanse, Ruth Fleischeuer, Colin Watts, Joseph McAbee, Nicos Angelopoulos, Thierry Gorlia, Vassilis Golfinopoulos, Johan M. Kros, Vincent Bours, Martin J. van den Bent, Pierre A. Robe, Pim J. French. Transcriptional evolution of glioblastoma reveals changes in bulk composition, mesenchymal sub-type as end-state, and a prognostic association with increased extracellular matrix gene expression [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 6140.