Predictors of postoperative complications and functional outcomes in pediatric patients with surgically treated fourth ventricle tumors

BACKGROUND

Tumors of the fourth ventricle are frequently treated pathologies in pediatric neurosurgery. Data regarding predictors for permanent neurological deficits, long-term functional outcomes, cerebellar mutism (CM), the extent of resection (EOR), and oncological outcomes are scarce. We attempt to contribute to this topic with an analysis of our institutional cohort.

METHODS

A retrospective single-center study of patients aged ≤ 19 years who underwent primary surgical resection of a fourth ventricular tumor over a 15-year period (2006-2021). Predictors analyzed included age, gender, surgical approach, anatomical pattern, tumor grade, EOR, tumor volume, and others as appropriate.

RESULTS

One hundred six patients were included (64 males, mean age 7.3 years). The rate of permanent neurological deficit was 24.2%; lateral tumor extension (p = 0.036) and tumor volume greater than 38 cm3 (p = 0.020) were significant predictors. The presence of a deficit was the only significant predictor of reduced (less than 90) Lansky score (p = 0.005). CM occurred in 20.8% of patients and was influenced by medulloblastoma histology (p = 0.011), lateral tumor extension (p = 0.017), and male gender (p = 0.021). No significant difference between the transvermian and telovelar approach in the development of CM was detected (p = 0.478). No significant predictor was found for the EOR. EOR was not found to be a significant predictor of overall survival for both low-grade and high-grade tumors; however, gross total resection (GTR) was protective against tumor recurrence compared to near-total or subtotal resection (p < 0.001). In addition, survival was found to be better in older patients (≥ 7.0 years, p = 0.019).

CONCLUSION

The overall rate of postoperative complications remains high due to the eloquent localization. Older patients (> 7 years) have been found to have better outcomes and prognosis. Achieving GTR whenever feasible and safe has been shown to be critical for tumor recurrence. CM was more common in patients with medulloblastoma and in patients with tumors extending through the foramen of Luschka. The telovelar approach uses a safe and anatomically sparing corridor; however, it has not been associated with a lower incidence of CM and neurological sequelae in our series, showing that each case should be assessed on an individual basis.

HGG-14. Molecular characterization of unique biological subgroups among H3 wild type high-grade gliomas

INTRODUCTION: Paediatric high-grade gliomas (HGG) are characterised by the aggressive biological behaviour with dismal prognosis of long-term survival 10-15%. Current molecular-biological diagnostic approaches allow for more precise characterization and determination of new unique subgroups of HGG. Our aim was to identify novel and rare HGG subgroups within our institution cohort. PATIENTS AND METHODS: Our reference centre patients′ cohort consisted of 97 clinically annotated patients with HGG diagnosed between 2000 and 2021. Sanger sequencing was used for screening of the most common HGG-related oncogenic drivers; furthermore we employed whole genome methylation array (Illumina Infinium MethylationEPIC BeadChip) and for selected samples RNA sequencing and expression profiling. RESULTS: Based on H3 status and previous radiotherapy we separated our HGG cases into the RIG, H3mut and H3wt groups. In contrast to H3mut(n=35) and RIG(n=11) that were uniformly fatal, H3wt group contained a proportion of long-term survivors. In the H3wt group we found patients carrying driver mutations in IDH1/2 (n=2) and BRAFV600E (7). Five young patients (under 3) consisted of 3 infant hemispheric gliomas (with NTRK and ROS1 fusions), one gliomatosis cerebri and one brainstem anaplastic astrocytoma with MYB/QKI fusion. We also identified a rare EWSR1-PATZ1 gene fusion in one patient. Importantly, long-term survivors recruited from these subgroups. On the contrary, four cases of MYCN GBM with poor prognosis presented in various locations: one disseminated, one gliomatosis cerebri and two with hemispheric tumour. We identified one patient with “hypermutated” glioblastoma and used targeted therapy with Nivolumab. In three samples of our patients with thalamic glioblastomas, we detected “loss of H3K27-trimethylation” caused by EZHIP overexpression. These tumours proved to be very aggressive with early metastatic recurrence and dismal prognosis. SUMMARY: Detailed characterization of H3 wild-type HGG is very important for further understanding of their biological behaviour, diagnostics, prognostication and identification of therapeutic targets.

Methylation pattern in the diagnosis and prognosis of brain cancer

Examination of changes in the methylation profile of DNA in cancer is currently used to determine the diagnosis or prognostic and predictive biomarkers. It complements histological or molecular biological examinations. At the same time, it helps to identify new diagnostic groups and subgroups. Currently, this diagnosis is most common in brain tumors, where it has become a routine examination. The established methylation profile may help even where the diagnosis or subgroup classification of the disease cannot be determined in any other way, as is the case with medulloblastoma.

HGG-31. UNIQUE BIOLOGICAL CHARACTERISTICS OF RADIATION-INDUCED GLIOMAS

Radiation-induced gliomas (RIGs) are the most common secondary solid tumours with very unfavourable prognosis. We aimed to describe different clinical and molecular biological characteristic of RIGs from primary gliomas. We reviewed clinical data of ten patients with RIGs. In patients with available samples, we used the whole genome methylation array and performed targeted sequencing for specific mutations. Between 2000–2018, we diagnosed RIG in 10 patients (M/F 2/8) aged 5–12 years at primary diagnosis of different solid tumours and acute leukaemia. These patients developed RIG with a median 9.5 years (ranging 3–31) after primary diagnosis. Eight patients died within 1 year after diagnosis of RIG and 2 patients are still alive more than 4 years from this diagnosis. According to Heidelberg DNA methylation-based classification, most RIGs belong to the IDH-wild type glioblastoma subclass midline which biologically corresponds to diffuse midline glioma (DMG). However, compared to primary DMGs they do not carry the characteristic H3K27M mutation. One patient developed anaplastic ganglioglioma with BRAF-V600E mutation and methylation profile identical to pleomorphic xanthoastrocytoma (alive for 4 years after diagnosis of RIG). In half of the patients from the group DMGs IDH wild type, examined by methylation array, PDGFRA amplification was found. Our data shows that most RIGs are midline IDH-wild type glioblastomas with poor prognosis that are biologically different from primary DMGs. PDGFRA amplifications are potentially targetable by kinase inhibitors in order to order to prognosis of these patients.

LGG-46. MOLECULAR CHARACTERIZATION OF HEMISPHERIC LOW-GRADE GLIOMAS IN CHILDREN

BACKGROUND

Heterogeneous pathology in hemispheric low-grade gliomas (hemLGG) stress the importance of molecular testing in terms of prognosis prediction and targeted therapy options.

METHODS

Demographic data was collected and targeted genomic approach was employed in the single institutional study. RT-PCR was used to screen for KIAA1549-BRAF fusion and FGFR1 tyrosine-kinase domain duplication (FGFR1-ITD). Direct sequencing evaluated point mutations (BRAF ex15 and ex11, FGFR1 ex12 and ex14). Samples with no detected alteration were subjected to panel RNA-sequencing (FusionPlex Archer Diagnostics).

RESULTS

Within 2000–2019 were diagnosed 76 patients with hemLGG (median age 11.1y, range 0.0y–18.5y) comprising predominantly of ganglioglioma, dysembryoplastic neuroepithelial tumors, and diffuse astrocytoma. 40 % of hemLGG were characterized by BRAF alterations with over 2/3 of those cases harboring BRAF point mutations (two BRAFex11, 12 BRAFV600E). Notably, BRAF fusions were uncommon and detected only in six patients (two KIAA-BRAF fusion, two minor oncogenic BRAF variants, two non-KIAA BRAF fusion). 25 % of alterations were found in genes for receptor tyrosine kinases, consisting of seven patients with FGFR1-ITD, three FGFR2/3 fusions, two FGFR1 mutations, two ALK fusions, and one ROS fusion. Out of MAP kinase pathway, the most frequent alteration was IDH1 mutations (n=9). Two angiocentric gliomas were characterized by MYB-QKI fusion.

CONCLUSION

Targeted sequencing combined with RNA-sequencing is feasible to establish molecular diagnosis in majority of cases and reveal new and rare alterations. Significant prevalence of non-BRAF alterations explains heterogeneity among hemLGG.

Two cases of improvement of smooth pursuit eye movements after selective posterior rhizotomy

OBJECTIVE

Selective posterior rhizotomy (SPR) represents a standard neurosurgical approach in the treatment of spasticity in children with cerebral palsy (CP). Beside the reduction of spasticity in lower limbs, SPR may have suprasegmental effects, considerably above the surgery site. In this communication, we report on the improvement of smooth pursuit eye movements (SPEM) in two children after SPR.

MATERIAL AND METHODS

Four children with CP underwent SPR. Eye movements were registered by infrared video-oculography before and after the surgery.

RESULTS

The analysis of SPEM showed the improvement of the correlation coefficient of the eye response to the stimulus after SPR in two subjects. Improvement of SPEM performance was largely due to suppression of spontaneous fixation nystagmus.

CONCLUSION

SPR may lead to the improvement of SPEM in children with CP. The influence of SPEM improvement on quality of life in a group of severely disabled nonambulant children with CP remains to be assessed.

BIR-1, the homologue of human Survivin, regulates expression of developmentally active collagen genes in C. elegans

BIR-1 and Survivin are highly conserved members of the inhibitor of apoptosis protein family that regulate cell division in nematodes and mammals and inhibit apoptosis in mammals. In the C. elegans genome, bir-1 is organized in an operon together with transcription and splicing cofactor CeSKIP (skp-1) and is highly expressed during embryogenesis as well as in non-dividing cells during larval development. Previously we have shown that BIR-1 regulates transcription and development and its loss-of-function phenotype overlaps with loss of function of CeSKIP and nuclear hormone receptor CHR3 (NHR-23). Here we searched for genes whose expression is affected by BIR-1 loss of function using whole-genome microarray experiments and identified several collagen genes as candidate targets of bir-1 inhibition in L1 larval stage. The decreased expression of selected collagen genes in bir-l-inhibited larvae was confirmed by quantitative RT-PCR. Next, we generated transgenic lines expressing bir-1 mRNA under a heat shock-regulated promoter and tested whether bir-1 overexpression has the potential to augment the expression of genes that showed decreased expression in worms treated with bir-1 RNAi. Overexpression of bir-1 resulted in a pronounced increase (2 to 5 times) of the expression of these genes. Our findings support the concept that BIR-1, a protein generally regarded as a mitotic factor, is involved in the regulation of transcription during normal development of C. elegans and has a strong ability to affect transcription of developmentally active genes if overexpressed.

Elevated and deregulated expression of HDAC3 in human astrocytic glial tumours

Abnormal expression of histone deacetylases may contribute to the establishment of a cancer specific transcription profile. We examined expression of HDAC3 in human non-malignant gliosis and glial astrocytic tumours. Samples from four non-malignant gliosis and 17 astrocytic gliomas (six of grade II, one of grade III and ten of grade IV) removed for therapeutic purposes were assayed for HDAC3 expression at mRNA and protein levels. HDAC3 mRNA was detected in non-tumorous gliosis as well as in all examined glial tumours. Seven out of eleven examined high-grade tumours showed an elevated number of copies of HDAC3 mRNA. Western blot analysis detected high levels of expression of HDAC3 in the majority of the examined tumours. Immunohistochemistry and immunofluorescence made on a collection of 35 astrocytic tumours detected nuclear as well as cytoplasmic HDAC3 expression in all of those tumours. While the distribution of HDAC3 was both nuclear as well as cytoplasmic and moderate in intensity in non-malignant tissues and low-grade gliomas, high-grade tumours expressed HDAC3 in a focally deregulated pattern that included strongly pronounced cytoplasmic localization. Confocal microscopy and additional co-localization analysis detected nuclear HDAC3 in all tumours examined. We conclude that HDAC3 expression is elevated in human astrocytic tumours and its expression pattern is deregulated at the cellular level in high-grade gliomas.