Risk-Adapted Treatment Strategies with Pre-Irradiation Chemotherapy in Pediatric Medulloblastoma: Outcomes from the Polish Pediatric Neuro-Oncology Group.

Craniospinal irradiation (CSI) has been a major component of the standard of care treatment backbone for childhood medulloblastoma. However, chemotherapy regimens have varied based on protocol, patient age, and molecular subtyping. In one of the largest studies to date, we analyzed treatment outcomes in children with newly-diagnosed medulloblastoma treated with pre-irradiation chemotherapy followed by risk-adapted radiotherapy and maintenance chemotherapy. A total of 153 patients from the Polish Pediatric Neuro-Oncology Group were included in the analysis. The median age at diagnosis was 8.0 years, and median follow-up time was 6.4 years. Sixty-seven patients were classified as standard-risk and eighty-six as high-risk. Overall survival (OS) and event-free survival (EFS) for standard-risk patients at 5 years (±standard error) were 87 ± 4.3% and 84 ± 4.6%, respectively, while 5-year OS and EFS for high-risk patients were 81 ± 4.3% and 79 ± 4.5%, respectively. Only one patient had disease progression prior to radiotherapy. This study demonstrates promising survival outcomes in patients treated with pre-irradiation chemotherapy followed by risk-adapted CSI and adjuvant chemotherapy. Such an approach may be useful in cases where the initiation of radiotherapy may need to be delayed, a common occurrence in many institutions globally.

Transcriptional profiling of paediatric ependymomas identifies prognostically significant groups.

The majority of supratentorial ependymomas in children contain oncogenic fusions, such as ZFTA-RELA or YAP1-MAMLD1. In contrast, posterior fossa (PF) ependymomas lack recurrent somatic mutations and are classified based on gene expression or methylation profiling into group A (PFA) and group B (PFB). We have applied a novel method, NanoString nCounter Technology, to identify four molecular groups among 16 supratentorial and 50 PF paediatric ependymomas, using 4-5 group-specific signature genes. Clustering analysis of 16 supratentorial ependymomas revealed 9 tumours with a RELA fusion-positive signature (RELA+), 1 tumour with a YAP1 fusion-positive signature (YAP1+), and 6 not-classified tumours. Additionally, we identified one RELA+ tumour among historically diagnosed CNS primitive neuroectodermal tumour samples. Overall, 9 of 10 tumours with the RELA+ signature possessed the ZFTA-RELA fusion as detected by next-generation sequencing (p = 0.005). Similarly, the only tumour with a YAP1+ signature exhibited the YAP1-MAMLD1 fusion. Among the remaining unclassified ependymomas, which did not exhibit the ZFTA-RELA fusion, the ZFTA-MAML2 fusion was detected in one case. Notably, among nine ependymoma patients with the RELA+ signature, eight survived at least 5 years after diagnosis. Clustering analysis of PF tumours revealed 42 samples with PFA signatures and 7 samples with PFB signatures. Clinical characteristics of patients with PFA and PFB ependymomas corroborated the previous findings. In conclusion, we confirm here that the NanoString method is a useful single tool for the diagnosis of all four main molecular groups of ependymoma. The differences in reported survival rates warrant further clinical investigation of patients with the ZFTA-RELA fusion.

Immunohistochemical detection of ALK protein identifies APC mutated medulloblastoma and differentiates the WNT-activated medulloblastoma from other types of posterior fossa childhood tumors.

Expression of the ALK gene strongly correlates with the WNT-activated medulloblastomas, which are routinely identified by detection of CTNNB1 mutation. However, some tumors have mutations in other than CTNNB1 genes. Therefore, we investigated if ALK expression may identify WNT-activated tumors without CTNNB1 mutation. In addition, we examined if ALK expression may differentiate WNT-activated medulloblastoma from other malignant posterior fossa tumors. ALK expression was analyzed using immunohistochemistry (clone D5F3) in 70 patients with posterior fossa tumours. Among 55 medulloblastomas, 6 tumors showed ALK expression in > 50% of tumor cells. In one tumor, with ALK positive reaction, negative nuclear reaction against ß-catenin and the lack of CTNNB1 mutation, next generation sequencing revealed a presence of pathogenic variant c.3366_3369del in the APC gene, with homozygous deletion leading to inactivation of both copies in tumor cells. MLPA analysis displayed the presence of chromosome 6 monosomy, therefore, confirming the WNT type of this tumor. All analyzed 19 anaplastic ependymomas, 4 choroid plexus carcinomas and 2 atypical teratoid rhabdoid tumors were immunonegative for ALK expression. Therefore, we propose, that immunohistochemical detection of ALK protein should be highly recommended in routine investigation, in parallel to already established methods for identification and differentiation of WNT-activated medulloblastoma.

Analysis of Newly Identified and Rare Synonymous Genetic Variants in the RET Gene in Patients with Medullary Thyroid Carcinoma in Polish Population.

Gain-of-function germline mutations of the RET proto-oncogene are responsible for initiation of carcinogenesis within the thyroid gland and development of hereditary form of medullary thyroid carcinoma and MEN2 syndrome. Genotype-phenotype correlations are established for most RET mutations, but the importance of the synonymous changes in this gene remains debatable. We aimed to analyze RET gene variants in Polish population. Genetic testing for the RET gene variants was performed with standard methods in 585 people aged 1-85, including 448 patients with medullary thyroid carcinoma and 131 of their first- and second-degree relatives, as well as six patients suspected of MTC/MEN2. Besides the most frequent synonymous changes, p.Leu769Leu, p.Ser836Ser, and p.Ser904Ser, four rare changes-c.1827C>T (p.Cys609Cys), c.2364C>T (p.Ile788Ile), c.2418C>T (p.Tyr806Tyr), and c.2673G>A (p.Ser891Ser)-were found in the RET gene, in the Polish population. Two of the rare changes, p.Cys609Cys and p.Ile788Ile, had not been previously described. The frequency of molecular synonymous variants in the general population was evaluated by testing 400 anonymous blood samples of neonates. Our findings may contribute to a better understanding of the genetic diversity of the RET gene and the involvement of synonymous variants in this diversity.

ALK Expression Is a Novel Marker for the WNT-activated Type of Pediatric Medulloblastoma and an Indicator of Good Prognosis for Patients.

ALK gene rearrangements were identified in a variety of cancers, including neuroblastoma, where the presence of ALK expression is associated with adverse prognosis. ALK mutations have recently been found in the pediatric brain tumor medulloblastoma, and microarray data indicate that ALK is highly expressed in a subset of these tumors. Therefore, we investigated whether ALK expression correlates with transcriptional profiles and clinical features of medulloblastoma. Tumors from 116 medulloblastoma patients were studied at diagnosis for the detection of ALK expression at the RNA level by an application of NanoString technology and at the protein level by immunohistochemistry using antibody ALK clone D5F3. The results indicate that ALK expression, at both the RNA and the protein levels, is strongly associated with the WNT-activated type of tumors and therefore may serve as a useful marker for the detection of this type of medulloblastoma. Importantly, ALK protein expression alone is also an indicator of good prognosis for medulloblastoma patients.