OBJECTIVE: We aim to report the epidemiology, surgical outcomes, and survival rates of pediatric patients with posterior fossa tumors in a large single-center case series.
METHODS: A retrospective analysis was conducted on pediatric patients who underwent surgical treatment for posterior fossa tumors between January 2011 and January 2019.
RESULTS: A total of 135 pediatric patients, with an average age of 7.5 years at diagnosis and a mean follow-up of 35.7 months, were included in the study. Most tumors were located within the midline, with ventriculomegaly observed in 71.4% of the patients. Pilocytic astrocytomas encompassed the majority of tumors (34.1%), followed by medulloblastomas (27.4%) and ependymomas (11.8%). Gross total resection (GTR) was achieved in 71.8% of the patients, with a recurrence rate of 20%. Surgical complications were observed in 25.9% of the patients. GTR significantly impacted 5-year overall survival (OS) and 4-year progression-free survival (PFS) in patients with posterior fossa tumors. Patients who underwent GTR had a 5-year OS of 89.7%, compared to 72.7% for near-total resection and 70.8% for subtotal resection. The 4-year PFS for patients who underwent GTR was 82.5%, whereas it was 63.6% for patients who underwent near-total resection and 54.2% for patients who underwent subtotal resection.
CONCLUSIONS: Surgical resection remains the main treatment for pediatric posterior fossa tumors, and higher resection rates are linked to better survival outcomes. Despite limited resources for molecular diagnosis, our institution has demonstrated that a specialized neurooncological center with a high surgical volume can still achieve favorable survival outcomes for these patients.

SNCAIP duplication may promote Group 4 medulloblastoma via induction of PRDM6, a poorly characterized member of the PRDF1 and RIZ1 homology domain-containing (PRDM) family of transcription factors. Here, we investigated the function of PRDM6 in human hindbrain neuroepithelial stem cells and tested PRDM6 as a driver of Group 4 medulloblastoma. We report that human PRDM6 localizes predominantly to the nucleus, where it causes widespread repression of chromatin accessibility and complex alterations of gene expression patterns. Genome-wide mapping of PRDM6 binding reveals that PRDM6 binds to chromatin regions marked by histone H3 lysine 27 trimethylation that are located within, or proximal to, genes. Moreover, we show that PRDM6 expression in neuroepithelial stem cells promotes medulloblastoma. Surprisingly, medulloblastomas derived from PRDM6-expressing neuroepithelial stem cells match human Group 3, but not Group 4, medulloblastoma. We conclude that PRDM6 expression has oncogenic potential but is insufficient to drive Group 4 medulloblastoma from neuroepithelial stem cells. We propose that both PRDM6 and additional factors, such as specific cell-of-origin features, are required for Group 4 medulloblastoma. Given the lack of PRDM6 expression in normal tissues and its oncogenic potential shown here, we suggest that PRDM6 inhibition may have therapeutic value in PRDM6-expressing medulloblastomas.

Medulloblastoma is a frequent and aggressive pediatric tumor. It causes intracranial hypertension, necessitating ventriculoperitoneal shunting with surgical resection. Intraperitoneal metastases are rare and result from the migration of neoplastic cells through the shunt and into the peritoneal cavity. This metastatic form involving the ventriculoperitoneal shunt has a poor prognosis, making therapeutic management even more difficult. We report the case of a 14-year-old boy with a history of medulloblastoma of the cerebellum who was initially treated with complete resection of the tumor with placement of a ventriculoperitoneal shunt, followed by radiotherapy and chemotherapy, with good progression until he presented to the emergency department with acute abdominal symptoms. Imaging revealed multiple peritoneal masses with intra- and retroperitoneal lymphadenopathies. An ultrasound-guided biopsy revealed a metastatic medulloblastoma in the peritoneal cavity, and the patient underwent chemotherapy. The placement of the ventriculoperitoneal shunt in the tumor dissemination is therefore to blame.

Recent incorporation of the four primary medulloblastoma subgroups into the WHO Classification of Central Nervous System Tumors necessitates globally accessible methods to discern subgroups. In this issue of Cancer Cell, Wang et al. develop a rapid and reliable machine learning workflow for pre-operative subgroup determination using routine magnetic resonance imaging.

Medulloblastoma is the most common malignant tumor in the pediatric population. Its classification has incorporated key molecular variations alongside histological characterization. CD39 (also known as ENTPD1) and CD73 (also known as NT5E), enzymes of the purinergic signaling pathway, act in synergy to generate extracellular adenosine, creating an immunosuppressive tumor microenvironment. Our study examined the expression of mRNA of these genes in previously described transcriptome data sets of medulloblastoma patient samples from the Cavalli Cohort (n = 763). Survival distribution was estimated according to the Kaplan-Meier method using a median cut-off and log-rank statistics (p ≤ 0.05). In non-WNT and non-SHH medulloblastoma Group 4 (n = 264), the high expression of ENTPD1 and NT5E was significantly related to a lower overall survival (p = 2.7e-04; p = 2.6e-03). In the SHH-activated group (n = 172), the high expression of ENTPD1 was significantly related to lower overall survival (p = 7.8e-03), while the high expression of NT5E was significantly related to greater overall survival (p = 0.017). In the WNT group (n = 63), the expressions of ENTPD1 and NT5E were not significantly correlated with overall survival (p = 0.212; p = 0.101). In non-WNT and non-SHH medulloblastoma Group 3 (n = 113), the high expression of ENTPD1 was significantly related to greater survival (p = 0.034), while expression of NT5E was not significantly related to survival of patients (p = 0.124). This in silico analysis indicates that ENTPD1 (CD39) and NT5E (CD73) can be seen as potential prognostic markers and therapeutic targets for primary medulloblastomas in non-WNT and non-SHH Group 4.

Medulloblastoma (MB) cerebelli is a common brain tumor of the childhood. MB commonly spreads through cerebrospinal fluid; however, there are several reported cases of extracranial spread. The most common sites of extracranial metastasis are bones and bone marrow followed by peritoneum, liver, and lungs. Here, we report a case of pulmonary metastatic lesions of adult cerebellar MB that were discovered 1 year after the primary surgical treatment. We also tried to highlight similar reported cases in the literature.

BACKGROUND: Treatment of childhood medulloblastoma has evolved to reduce neurotoxicity while improving survival. However, the impact of evolving therapies on late neurocognitive outcomes and adult functional independence remains unknown.
METHODS: Adult survivors of childhood medulloblastoma (n=505; median[minimum-maximum] age, 29[18-46] years) and sibling controls (n=727; 32[18-58] years) from the Childhood Cancer Survivor Study completed surveys assessing neurocognitive problems and chronic health conditions (CHCs). Treatment exposures were categorized as historical (craniospinal irradiation [CSI]≥30 Gy, no chemotherapy), standard-risk (CSI>0 to <30 Gy +chemotherapy) and high-risk (CSI≥30 Gy +chemotherapy) therapy. Latent class analysis identified patterns of functional independence using employment, independent living, assistance with routine/personal care needs, driver\'s license, marital/partner status. Multivariable models estimated risk of neurocognitive impairment in survivors versus siblings and by treatment exposure group, and associations between neurocognitive impairment, CHCs, and functional independence.
RESULTS: Survivors in each treatment exposure group had 4- to 5-fold elevated risk of impaired memory and task efficiency compared to siblings. Contemporary risk-based therapies did not confer lower risk compared to historical therapy. Survivors treated in the 1990s had higher risk of memory impairment (relative risk [RR] 2.24, 95% confidence interval [CI] 1.39-3.60) compared to survivors treated in the 1970s. Sensorimotor, hearing problems and seizures were associated with 33%-34%, 25-26% and 21%-42% elevated risk of task efficiency and memory impairment, respectively. Treatment-related CHCs and neurocognitive impairment were associated with non-independence.
CONCLUSIONS: Despite treatment changes, long-term survivors of childhood medulloblastoma remain at risk for neurocognitive impairment, which was associated with CHCs. Neurocognitive surveillance after contemporary regimens is imperative.

The Hedgehog (Hh) signaling pathway plays important roles in various physiological functions. Several malignancies, such as basal cell carcinoma (BCC) and medulloblastoma (MB), have been linked to the aberrant activation of Hh signaling. Although therapeutic drugs have been developed to inhibit Hh pathway-dependent cancer growth, drug resistance remains a major obstacle in cancer treatment. Here, we show that the newly identified, 2-{3-[1-(benzylsulfonyl)-1,2,3,6-tetrahydropyridin-4-yl]-2-methyl-1H-indol-1-yl}-1-(pyrrolidin-1-yl)ethenone analog (LKD1214) exhibits comparable potency to vismodegib in suppressing the Hh pathway activation. LKD1214 represses Smoothened (SMO) activity by blocking its ciliary translocation. Interestingly, we also identified that it has a distinctive binding interface with SMO compared with other SMO-regulating chemicals. Notably, it maintains an inhibitory activity against the SmoD477H mutant, as observed in a patient with vismodegib-resistant BCC. Furthermore, LKD1214 inhibits tumor growth in the mouse model of MB. Collectively, these findings suggest that LKD1214 has the therapeutic potential to overcome drug-resistance in Hh-dependent cancers.

UNASSIGNED: ELP1 pathogenic variants (PV) have been recently identified as the most frequent variants predisposing to Sonic Hedgehog (SHH) medulloblastomas (MB); however, guidelines are still lacking for genetic counseling in this new syndrome.
UNASSIGNED: We retrospectively reviewed clinical and genetic data of a French series of 29 ELP1-mutated MB.
UNASSIGNED: All patients developed SHH-MB, with a biallelic inactivation of PTCH1 found in 24 tumors. Other recurrent alterations encompassed the TP53 pathway and activation of MYCN/MYCL signaling. The median age at diagnosis was 7.3 years (range: 3-14). ELP1-mutated MB behave as sporadic cases, with similar distribution within clinical and molecular risk groups and similar outcomes (5 y - OS = 86%); no unusual side effect of treatments was noticed. Remarkably, a germline ELP1 PV was identified in all patients with available constitutional DNA (n = 26); moreover, all tested familial trio (n = 11) revealed that the PVs were inherited. Two of the 26 index cases from the French series had a family history of MB; pedigrees from these patients and from 1 additional Dutch family suggested a weak penetrance. Apart from MB, no cancer was associated with ELP1 PVs; second tumors reported in 4 patients occurred within the irradiation fields, in the usual time-lapse for expected radiotherapy-induced neoplasms.
UNASSIGNED: The low penetrance, the \"at risk\' age window limited to childhood and the narrow tumor spectrum, question the actual benefit of genetic screening in these patients and their family. Our results suggest restricting ELP1 germline sequencing to patients with SHH-MB, depending on the parents\" request.

UNASSIGNED: Medulloblastoma (MB) is the most prevalent paediatric brain tumour. Despite improvements in patient survival with current treatment strategies, the quality of life of these patients remains poor owing to the sequelae and relapse risk. An alternative, or, in addition to the current standard treatment, could be considered immunotherapy, such as Natural Killer cells (NK). NK cells are cytotoxic innate lymphoid cells that play a major role in cancer immunosurveillance. To date, the mechanism of cytotoxicity of NK cells, especially regarding the steps of adhesion, conjugation, cytotoxic granule polarisation in the cell contact area, perforin and granzyme release in two and three dimensions, and therapeutic efficacy in vivo have not been precisely described.
UNASSIGNED: Each step of NK cytotoxicity against the three MB cell lines was explored using confocal microscopy for conjugation, Elispot for degranulation, flow cytometry, and luminescence assays for target cell necrosis and lysis and mediators released by cytokine array, and then confirmed in a 3D spheroid model. Medulloblastoma-xenografted mice were treated with NK cells. Their persistence was evaluated by flow cytometry, and their efficacy in tumour growth and survival was determined. In addition, their effects on the tumour transcriptome were evaluated.
UNASSIGNED: NK cells showed variable affinities for conjugation with MB target cells depending on their subgroup and cytokine activation. Chemokines secreted during NK and MB cell co-culture are mainly associated with angiogenesis and immune cell recruitment. NK cell cytotoxicity induces MB cell death in both 2D and 3D co-culture models. NK cells initiated an inflammatory response in a human MB murine model by modulating the MB cell transcriptome.
UNASSIGNED: Our study confirmed that NK cells possess both in vitro and in vivo cytotoxic activity against MB cells and are of interest for the development of immunotherapy.