Atypical teratoid rhabdoid tumor in the first year of life: the Canadian ATRT registry experience and review of the literature

Embryonal and pineal tumours

Embryonal and pineal tumours represent a diverse group of central nervous system (CNS) neoplasms. While many of the small round blue cell tumours that make up the embryonal neoplasms share similar histologic qualities, there are several morphologic and cytologic characteristics that are useful in distinguishing different tumour types. Similarly, pineal parenchymal tumours represent clinically diverse tumours, ranging from benign to overtly malignant. The most recent iteration of the World Health Organization Classification of CNS Tumours expanded greatly on the significance of molecular alterations in brain tumour diagnostics. In this article, we summarize the salient cytologic and histologic features of CNS embryonal and pineal tumours, and highlight diagnostically relevant molecular alterations within each tumour type.

Clinical factors, management, and outcomes of children under 3 years old with central nervous system tumors: single-center experience

PURPOSE

Children under 3 years old represent a notable portion, about 25 to 30%, of all central nervous system tumor (CNS) cases. Their clinical course, prognosis, and treatment significantly differ from older children. This single-center retrospective study aims to comprehensively analyze survival factors in children under three diagnosed with CNS tumors.

METHODS

Between April 2012 and December 2023, cases under 3 years of age with CNS tumors diagnosed at our center were retrospectively evaluated.

RESULTS

Among 279 CNS tumor cases, 42 (15%) were evaluated. The 5-year overall and event-free survival rates were 67.4% (95% CI 47.5-81.1) and 39.8% (95% CI 24.2-55.0), respectively. Gender, symptom onset to diagnosis time, pathological neurological findings at diagnosis, and tumor location did not significantly impact survival (p > 0.05). However, cases with neurological symptoms showed significantly higher event-free survival rates (p < 0.05). Patients with embryonal tumors, metastases, inability for total surgical excision, relapsed/progressive diseases, and who under 1 year old had significantly lower survival rates (p < 0.05). Radiotherapy timing did not affect survival (p > 0.05). Event-free survival rates remained unchanged after the third year.

CONCLUSION

The current treatments have been observed to have a positive impact on survival rates. Nonetheless, there is a need for novel treatments for patients with embryonal tumors, metastases, aged under 1 year, and those where total surgical excision is not feasible or in cases with progressive/relapse disease. This study underscores the importance of the first 3 years regarding relapse, progression, or mortality risk.

Radiation Therapy Plays an Important Role in the Treatment of Atypical Teratoid/Rhabdoid Tumors: Analysis of the EU-RHAB Cohorts and Their Precursors

PURPOSE

Atypical teratoid/rhabdoid tumor (AT/RT) is a rare malignancy of the central nervous system in young children with a dismal prognosis. Prognostic markers have been extensively investigated but have not been validated. The role of radiation therapy (RT) remains controversial. We evaluated the impact of RT as part of multimodality treatment by analyzing data of a European AT/RT cohort.

METHODS AND MATERIALS

We retrospectively analyzed data of the European Registry for Rhabdoid Tumors and its precursors. Primary endpoints were progression-free survival (PFS) and overall survival (OS). Potential impact of prognostic factors was analyzed using univariable and multivariable Cox regression analyses with RT as a time-dependent factor.

RESULTS

Data of 186 children (118 male, 68 female) treated from 1990 to 2016 were evaluable. The median age at diagnosis was 1.57 years (range, 0.01-26.70 years); 47% (87/186) of the patients were under the age of 18 months. Sixty-nine percent (128/186) received RT (focal RT, n = 93; craniospinal treatment with local boost, n = 34; spinal irradiation, n = 1). The median follow-up duration of the entire cohort was 1.73 years (range, 0.06-20.11 years). The estimated PFS and OS rates were 48% (95% CI, 41%-55%) and 72% (95% CI, 65%-78%) at 1 year and 33% (95% CI, 26%-40%) and 49% (95% CI, 41%-56%) at 2 years, respectively. On multivariable analysis, RT was an independent significant prognostic factor for PFS (hazard ratio, 0.45; 95% CI, 0.27-0.75; P = .002) and OS (hazard ratio, 0.54; 95% CI, 0.32-0.93; P = .025).

CONCLUSIONS

This analysis confirms the relevance of local therapies. RT was an independent prognostic factor for outcomes in children experiencing AT/RT. However, long-term sequelae have to be carefully evaluated and considered given the young age at time of RT.

Epidemiology, Characteristics, and Prognostic Factors of Primary Atypical Teratoid/Rhabdoid Tumors in the Spinal Canal: A Systematic Review

Primary atypical teratoid/rhabdoid tumors (AT/RTs) in the spinal canal are rare central nervous system (CNS) neoplasms that are challenging to diagnose and treat. To date, there has been no standard treatment regimen for these challenging malignant tumors. Thus, we conducted this research to explore potential prognostic factors and feasible treatment modalities for improving the prognosis of these tumors. Articles were retrieved from the PubMed, MEDLINE, and Embase databases, using the keywords "atypical teratoid/rhabdoid tumor," "rhabdoid tumor," "spine," "spinal," "spinal neoplasm", and "spinal cord neoplasm." All eligible cases demonstrated SMARCB1-deficient expression validated by pathological examination. We collected and analyzed data related to clinical presentation, radiological features, pathological characteristics, treatment modalities and prognosis via Kaplan-Meier and Cox regression analyses. Thirty-six articles comprising 58 spinal AT/RT patients were included in the study. The median progression-free survival (PFS) and overall survival (OS) were 18 and 22 months, respectively. Kaplan-Meier analysis demonstrated significant survival improvements for OS in the nonmetastasis, male, radiotherapy and intrathecal chemotherapy groups as well as for PFS in the chemotherapy and radiotherapy groups. Multivariate analysis revealed that chemotherapy and radiotherapy were prognostic factors for improved PFS, and that intrathecal chemotherapy reduced the risk of mortality. Spinal AT/RTs are uncommon malignant entities with a dismal survival rate. Although our review is limited by variability between cases, there is some evidence revealing potential risk factors and the importance of systematic chemotherapy, intrathecal chemotherapy and radiotherapy in spinal AT/RT treatment modalities.

Management of Atypical Teratoid/Rhabdoid Tumors in the Pediatric Population: A Systematic Review and Meta-Analysis

BACKGROUND

Atypical teratoid/rhabdoid tumors are rare and aggressive tumors that mainly affect children <3 years of age. Despite aggressive treatment, the overall survival rate for pediatric atypical teratoid/rhabdoid tumors remains poor. Due to their rarity, little is known regarding prognostic factors, and there is no official standard of treatment.

METHODS

A comprehensive database search was conducted following Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines. Search terms included "atypical teratoid rhabdoid tumor" and "atypical (teratoid OR rhabdoid) tumor." Variables of interest included, but were not limited to, age, sex, tumor location, treatment modality, extent of resection, and overall survival.

RESULTS

The study included 294 articles and 936 patients. The median age of patients was 22 months. There was a significant difference in survival among patients receiving surgery compared with patients receiving nonoperative treatment (50.3 months vs. 28 months; P < 0.005). Extent of resection did not significantly improve survival (P = 0.832 for gross total resection, P = 0.650 for partial resection). Combination therapy with surgical resection, radiotherapy, and chemotherapy demonstrated the largest median overall survival (54.9 months) and significantly improved survival on multivariate analysis (hazard ratio, 0.48; 95% confidence interval, 0.23-0.97; P = 0.042).

CONCLUSIONS

The results of this study indicate that while surgery is a crucial treatment modality for pediatric atypical teratoid/rhabdoid tumors, the effect of extent of resection is unclear. Multimodal therapy including surgery, radiotherapy, and chemotherapy is effective in improving overall survival. Future studies should focus on using larger datasets to efficiently account for confounding factors and biases.

Current status of DNA methylation profiling in neuro-oncology as a diagnostic support tool: A review

Over the last 2 decades, high throughput genome-wide molecular profiling has revealed characteristic genetic and epigenetic alterations associated with different types of central nervous system (CNS) tumors. DNA methylation profiling has emerged as an important molecular platform for CNS tumor classification with improved diagnostic accuracy and patient risk stratification in comparison to the standard of care histopathological analysis and any single molecular tests. The emergence of DNA methylation arrays have also played a crucial role in refining existing types and the discovery of new tumor types or subtypes. The adoption of methylation data into neuro-oncology has been greatly aided by the development of a freely accessible machine learning-based classifier. In this review, we discuss methylation workflow, address the utility of DNA methylation profiling in CNS tumors in a routine diagnostic setting, and provide an overview of the methylation-based tumor types and new types or subtypes identified with this platform.

Rhabdoid tumors in patients conceived following ART: is there an association?

STUDY QUESTION

In children affected by rhabdoid tumors (RT), are there clinical, therapeutic, and/or (epi-)genetic differences between those conceived following ART compared to those conceived without ART?

SUMMARY ANSWER

We detected a significantly elevated female predominance, and a lower median age at diagnosis, of children with RT conceived following ART (RT_ART) as compared to other children with RT.

WHAT IS KNOWN ALREADY

Anecdotal evidence suggests an association of ART with RT.

STUDY DESIGN, SIZE, DURATION

This was a multi-institutional retrospective survey. Children with RT conceived by ART were identified in our EU-RHAB database (n = 11/311 children diagnosed between January 2010 and January 2018) and outside the EU-RHAB database (n = 3) from nine different countries. A population-representative German EU-RHAB control cohort of children with RTs conceived without ART (n = 211) (EU-RHAB control cohort) during the same time period was used as a control cohort for clinical, therapeutic, and survival analyses. The median follow-up time was 11.5 months (range 0-120 months) for children with RT_ART and 18.5 months (range 0-153 months) for the EU-RHAB control cohort.

PARTICIPANTS/MATERIALS, SETTING, METHODS

We analyzed 14 children with RT_ART diagnosed from January 2010 to January 2018. We examined tumors and matching blood samples for SMARCB1 mutations and copy number alterations using FISH, multiplex ligation-dependent probe amplification, and DNA sequencing. DNA methylation profiling of tumor and/or blood samples was performed using DNA methylation arrays and compared to respective control cohorts of similar age (n = 53 tumors of children with RT conceived without ART, and n = 38 blood samples of children with no tumor born small for gestational age).

MAIN RESULTS AND THE ROLE OF CHANCE

The median age at diagnosis of 14 individuals with RT_ART was 9 months (range 0-66 months), significantly lower than the median age of patients with RT (n = 211) in the EU-RHAB control cohort (16 months (range 0-253), P = 0.03). A significant female predominance was observed in the RT_ART cohort (M:F ratio: 2:12 versus 116:95 in EU-RHAB control cohort, P = 0.004). Eight of 14 RT_ART patients were diagnosed with atypical teratoid rhabdoid tumor, three with extracranial, extrarenal malignant rhabdoid tumor, one with rhabdoid tumor of the kidney and two with synchronous tumors. The location of primary tumors did not differ significantly in the EU-RHAB control cohort (P = 0.27). Six of 14 RT_ART patients presented with metastases at diagnosis. Metastatic stage was not significantly different from that within the EU-RHAB control cohort (6/14 vs 88/211, P = 1). The incidence of pathogenic germline variants was five of the 12 tested RT_ART patients and, thus, not significantly different from the EU-RHAB control cohort (5/12 versus 36/183 tested, P = 0.35). The 5-year overall survival (OS) and event free survival (EFS) rates of RT_ART patients were 42.9 ± 13.2% and 21.4 ± 11%, respectively, and thus comparable to the EU-RHAB control cohort (OS 41.1 ± 3.5% and EFS 32.1 ± 3.3). We did not find other clinical, therapeutic, outcome factors distinguishing patients with RT_ART from children with RTs conceived without ART (EU-RHAB control cohort). DNA methylation analyses of 10 tumors (atypical teratoid RT = 6, extracranial, extrarenal malignant RT = 4) and six blood samples from RT_ART patients showed neither evidence of a general DNA methylation difference nor underlying imprinting defects, respectively, when compared to a control group (n = 53 RT samples of patients without ART, P = 0.51, n = 38 blood samples of patients born small for gestational age, P = 0.1205).

LIMITATIONS, REASONS FOR CAUTION

RTs are very rare malignancies and our results are based on a small number of children with RT_ART.

WIDER IMPLICATIONS OF THE FINDINGS

This cohort of patients with RT_ART demonstrated a marked female predominance, and a rather low median age at diagnosis even for RTs. Other clinical, treatment, outcome, and molecular factors did not differ from those conceived without ART (EU-RHAB control cohort) or reported in other series, and there was no evidence for imprinting defects. Long-term survival is achievable even in cases with pathogenic germline variants, metastatic disease at diagnosis, or relapse. The female preponderance among RT_ART patients is not yet understood and needs to be evaluated, ideally in larger international series.

STUDY FUNDING/COMPETING INTEREST(S)

M.C.F. is supported by the 'Deutsche Kinderkrebsstiftung' DKS 2020.10, by the 'Deutsche Forschungsgemeinschaft' DFG FR 1516/4-1 and by the Deutsche Krebshilfe 70113981. R.S. received grant support by Deutsche Krebshilfe 70114040 and for infrastructure by the KinderKrebsInitiative Buchholz/Holm-Seppensen. P.D.J. is supported by the Else-Kroener-Fresenius Stiftung and receives a Max-Eder scholarship from the Deutsche Krebshilfe. M.H. is supported by DFG (HA 3060/8-1) and IZKF Münster (Ha3/017/20). BB is supported by the 'Deutsche Kinderkrebsstiftung' DKS 2020.05. We declare no competing interests.

TRIAL REGISTRATION NUMBER

N/A.

Characterization of Switch/Sucrose Nonfermenting Complex Proteins and Nestin Expression in a Cohort of Pediatric Central Nervous System Tumors

Tumors of the central nervous system (CNS) in pediatric patients have undergone significant diagnostic refinement through the use of immunohistochemistry (IHC) and molecular techniques. The utility of these novel IHC antibodies has been demonstrated with the inactivation of the switch/sucrose nonfermenting (SWI/SNF) chromatin-remodeling complex in the diagnosis of atypical teratoid/rhabdoid tumors, predominantly through the loss of integrase interactor 1 (INI1; SMARCB1 ). Alternatively, these tumors may have inactivation of brahma-related gene 1 (BRG1; SMARCA4 ) in a subset of cases. The role of other SWI/SNF component proteins and their expression in pediatric brain tumors is not well established. Nestin, an intermediate filament, has been shown to be present in some pediatric CNS tumors, but of uncertain diagnostic and prognostic significance. We sought to explore the immunohistochemical expression profile for common SWI/SNF subunits and nestin in a pediatric CNS tumor cohort. Using a 118-sample tissue microarray, we performed IHC for INI1, BRG1, brahma (BRM), ARID1A, ARID1B, polybromo 1, and nestin. In 19 cases, INI1 was lost and BRG1 was lost in 2 cases. Interestingly, 6 cases originally diagnosed as primitive neuroectodermal tumors showed isolated loss of BRM. Other SWI/SNF proteins did not provide further diagnostic resolution. Nestin was positive in 76.2% of INI1/BRG1-deficient tumors, compared with 29.1% in INI1/BRG1-intact tumors yielding a sensitivity of 76.2%, specificity of 68.0%, and a P value of <0.001, but nestin positivity did not correlate specifically with poor outcomes. In conclusion, we confirm the utility of BRG1 IHC in the workup of pediatric CNS tumors, which may facilitate a difficult diagnosis when conventional markers are inconclusive, or as a first-line marker in cases where intraoperative smears are suggestive of atypical teratoid/rhabdoid tumor. Although nestin expression was associated with SWI/SNF inactivation, it did not yield statistically significant diagnostic or prognostic information in our study. Interestingly, we identified 6 tumors with isolated BRM IHC loss, the significance of which is uncertain but warrants further investigation.

Leptomeningeal dissemination in pediatric brain tumors

Leptomeningeal disease (LMD) in pediatric brain tumors (PBTs) is a poorly understood and categorized phenomenon. LMD incidence rates, as well as diagnosis, treatment, and screening practices, vary greatly depending on the primary tumor pathology. While LMD is encountered most frequently in medulloblastoma, reports of LMD have been described across a wide variety of PBT pathologies. LMD may be diagnosed simultaneously with the primary tumor, at time of recurrence, or as primary LMD without a primary intraparenchymal lesion. Dissemination and seeding of the cerebrospinal fluid (CSF) involves a modified invasion-metastasis cascade and is often the result of direct deposition of tumor cells into the CSF. Cells develop select environmental advantages to survive the harsh, nutrient poor and turbulent environment of the CSF and leptomeninges. Improved understanding of the molecular mechanisms that underlie LMD, along with improved diagnostic and treatment approaches, will help the prognosis of children affected by primary brain tumors.

MRI features of pediatric atypical teratoid rhabdoid tumors and medulloblastomas of the posterior fossa

BACKGROUND

Atypical teratoid rhabdoid tumor (AT/RT) occurs at a younger age and is associated with a worse prognosis than medulloblastoma; however, these two tumor entities are mostly indistinguishable on neuroimaging. The aim of our study was to differentiate AT/RT and medulloblastoma based on their clinical and MRI features to enhance treatment planning and outcome prediction.

METHODS

From 2005-2021, we retrospectively enrolled 16 patients with histopathologically diagnosed AT/RT and 57 patients with medulloblastoma at our institute. We evaluated their clinical data and MRI findings, including lesion signals, intratumoral morphologies, and peritumoral/distal involvement.

RESULTS

The age of children with AT/RT was younger than that of children with medulloblastoma (2.8 ± 4.9 [0-17] vs. 6.5 ± 4.0 [0-18], p < 0.001), and the overall survival rate was lower (21.4% vs. 66.0%, p = 0.005). Regarding lesion signals on MRI, AT/RT had a lower ADC_min (cutoff value ≤544.7 × 10^-6  mm² /s, p < 0.001), a lower ADC ratio (cutoff value ≤0.705, p < 0.001), and a higher DWI ratio (cutoff value ≥1.595, p < 0.001) than medulloblastoma. Regarding intratumoral morphology, the "tumor central vein sign" was mostly exclusive to medulloblastoma (24/57, 42.1%; AT/RT 1/16, 6.3%; p = 0.007). Regarding peritumoral invasion on T2WI, AT/RT was more prone to invasion of the brainstem (p < 0.001) and middle cerebellar peduncle (p < 0.001) than medulloblastoma.

CONCLUSIONS

MRI findings of a lower ADC value, more peritumoral invasion, and absence of the "tumor central vein sign" may be helpful to differentiate AT/RT from medulloblastoma. These distinct MRI findings together with the younger age of AT/RT patients may explain the worse outcomes in AT/RT patients.

Atypical teratoid rhabdoid tumours (ATRTs)-a 21-year institutional experience

PURPOSE

Atypical teratoid/rhabdoid tumours (ATRTs) are malignant embryonal tumours of childhood that affect the central nervous system (CNS). We aim to determine which factors, including patient age, extent of resection (EOR), presence of distal metastasis and use of adjuvant therapies, affect overall survival in children with atypical teratoid/rhabdoid tumours (ATRTs) treated at this single centre.

METHODS

Retrospective cohort review of patients with histological diagnosis of ATRT treated over 21 years (1999-2020) was conducted. Data on demographics, tumour location, presence of metastasis, use of adjuvant therapy, extent of resection (EOR), complications, neurological outcome post-surgery, and overall survival were collected. Kaplan-Meier survival analysis was performed.

RESULTS

A total of 45 children (mean age 2 years) underwent 64 operations. 25 patients were <1 year of age. Gross-total resection (GTR) pre-adjuvant therapy was achieved in 15, near-total resection (NTR) in 15, subtotal resection (STR) in 9, and biopsy in 6 children. Most children had good neurological outcomes post-operatively (28/45 with GOS 5). Fourteen patients survived longer than 4 years. Survival analysis showed a significant difference in median survival in favour of GTR and localised disease. There was no significant difference in median survival between patients <1 year vs >1 year of age (p=0.84).

CONCLUSION

We find that presence of metastasis was an important factor in poor survival in patients with ATRT. GTR, where possible, may confer significant survival benefit in ATRT. Children aged <1 year appear to have performed as well as those >1 year and therefore should still be considered for radical surgery.

Magnetic Resonance Imaging (MRI) and Positron Emission Tomography (PET)/Computed Tomography Features of Atypical Teratoid/Rhabdoid Tumors: Case Series and Review

Purpose: The purpose of this article is to explore the clinical and neuroradiologic properties of atypical teratoid/rhabdoid tumors. Methods: Data from 6 pediatric patients with atypical teratoid/rhabdoid tumors, which mainly contained the features of magnetic resonance imaging (MRI) and positron emission tomography (PET)/computed tomography (CT), was retrospectively analyzed. Follow-up was conducted in all patients through clinic services and/or telephone consultation. Results: The patients included 4 males and 2 females, aged from 3.2 to 83.1 months at the initial diagnosis. All patients had MRI scans. Two patients underwent ¹⁸F-fluorodeoxyglucose PET/CT scintigraphy preoperatively and 4 postoperatively. All primary lesions were located in the cranial cavity and the average diameter of lesions was 37.2 mm. Cerebrospinal fluid spread on enhanced T1-weighted images were found in 2 patients. Multiple metastases were found on MRI and PET/CT scans, which were located at cranial cavity, spinal cord, lung and lymph node. The primary and metastatic lesions showed evident uptake of ¹⁸F-fluorodeoxyglucose. Two patients underwent total tumor removal, and 4 patients underwent subtotal removal. None of the patients received shunt surgery. Follow-up was performed in all 6 patients. One patient survived event-free 38.4 months after resection. The mean overall survival of the remaining 5 patients was 5.1 months. Conclusion: We identified specific PET/CT and MRI features that can facilitate the recognition of atypical teratoid/rhabdoid tumors prior to biopsy.

Clinical predictors of survival for patients with atypical teratoid/rhabdoid tumors

PURPOSE

Atypical teratoid/rhabdoid tumors (AT/RTs) are malignant central nervous system (CNS) neoplasms of the young. Our study analyzed a large AT/RT cohort from the National Cancer Database (NCDB) to elucidate predictors of short-term mortality and overall survival (OS).

METHODS

Information was collected on patients with histologically confirmed AT/RT using the NCDB (2004-2016). Kaplan-Meier analysis indicated OS. Prognostic factors for 30-day mortality, 90-day mortality, and OS were determined via multivariate Cox proportional hazards (CPH) and logistic regression models.

RESULTS

Our cohort of 189 patients had a median age of 1 year (IQR [1, 4]) and tumor size of 4.7 ± 2.0 cm at diagnosis. Seventy-two percent were under 3 years old; 55.6% were male and 71.0% were Caucasian. Fifty (27.2%) patients received only surgery (S) (OS = 5.91 months), 51 (27.7%) received surgery and chemotherapy (S + CT) (OS = 11.2 months), and 9 (4.89%) received surgery and radiotherapy (S + RT) (OS = 10.3 months). Forty-five (24.5%) received S + CT + RT combination therapy (OS = 45.4 months), 13 (17.1%) received S + CT + BMT/SCT (bone marrow or stem cell transplant) (OS = 55.5 months), and 16 (8.70%) received S + CT + RT + BMT/SCT (OS = 68.4 months). Bivariate analysis of dichotomized age (HR = 0.550, 95% CI [0.357, 0.847], p = 0.0067) demonstrated significantly increased patient survival if diagnosed at or above 1 year old. On multivariate analysis, administration of S + CT + RT, S + CT + BMT/SCT, or S + CT + RT + BMT/SCT combination therapy predicted significantly (p < 0.05) increased OS compared to surgery alone.

CONCLUSION

AT/RTs are CNS tumors where those diagnosed under 1 year old have a significantly worse prognosis. Our study demonstrates that while traditional CT, RT, and BMT/SCT combination regimens prolong life, overall survival in this population is still low.

Epigenetic mechanisms in paediatric brain tumours: regulators lose control

Epigenetic mechanisms are essential to regulate gene expression during normal development. However, they are often disrupted in pathological conditions including tumours, where they contribute to their formation and maintenance through altered gene expression. In recent years, next generation genomic techniques has allowed a remarkable advancement of our knowledge of the genetic and molecular landscape of paediatric brain tumours and have highlighted epigenetic deregulation as a common hallmark in their pathogenesis. This review describes the main epigenetic dysregulations found in paediatric brain tumours, including at DNA methylation and histone modifications level, in the activity of chromatin-modifying enzymes and in the expression of non-coding RNAs. How these altered processes influence tumour biology and how they can be leveraged to dissect the molecular heterogeneity of these tumours and contribute to their classification is also addressed. Finally, the availability and value of preclinical models as well as the current clinical trials exploring targeting key epigenetic mediators in paediatric brain tumours are discussed.

Central Nervous System Tumor Classification: An Update on the Integration of Tumor Genetics

In 2016, the World Health Organization Classification of CNS Tumors introduced molecular abnormalities that refined tumor diagnoses. Around this time, the introduction of large scale genetic mutational analyses quickly advanced our knowledge of recurrent abnormalities in disease. In 2017, the C-IMPACT group was established to render expert consensus opinions regarding the application of molecular findings into central nervous system tumor diagnoses. C-IMPACT have presented their recommendations in 7 peer-reviewed publications; this article details those recommendations that are expected to be incorporated into the upcoming fifth edition of the World Health Organization classification.

Infantile Brain Tumors: A Review of Literature and Future Perspectives

Brain tumors in infants including those diagnosed in fetal age, newborns and under a year old represent less than 10% of pediatric nervous system tumors and present differently when compared with older children in terms of clinical traits, location and histology. The most frequent clinical finding is a macrocephaly but non-specific symptoms can also be associated. The prognosis is usually poor and depends on several factors. Surgery continues to be the main option in terms of therapeutic strategies whereas the role of chemotherapy is not yet well defined and radiotherapy is exceptionally undertaken. In view of this situation, a molecular characterization could assist in providing therapeutic options for these tumors. This review highlights the recent advances in the diagnosis and treatment of brain tumors in infants with a particular focus on the molecular landscape and future clinical applications.

Age and DNA methylation subgroup as potential independent risk factors for treatment stratification in children with atypical teratoid/rhabdoid tumors

BACKGROUND

Controversy exists as to what may be defined as standard of care (including markers for stratification) for patients with atypical teratoid/rhabdoid tumors (ATRTs). The European Rhabdoid Registry (EU-RHAB) recruits uniformly treated patients and offers standardized genetic and DNA methylation analyses.

METHODS

Clinical, genetic, and treatment data of 143 patients from 13 European countries were analyzed (2009-2017). Therapy consisted of surgery, anthracycline-based induction, and either radiotherapy or high dose chemotherapy following a consensus among European experts. Fluorescence in situ hybridization, multiplex ligation-dependent probe amplification, and sequencing were employed for assessment of somatic and germline mutations in SWItch/sucrose nonfermentable related, matrix associated, actin dependent regulator of chromatin, subfamily B (SMARCB1). Molecular subgroups (ATRT-SHH, ATRT-TYR, and ATRT-MYC) were determined using DNA methylation arrays, resulting in profiles of 84 tumors.

RESULTS

Median age at diagnosis of 67 girls and 76 boys was 29.5 months. Five-year overall survival (OS) and event-free survival (EFS) were 34.7 ± 4.5% and 30.5 ± 4.2%, respectively. Tumors displayed allelic partial/whole gene deletions (66%; 122/186 alleles) or single nucleotide variants (34%; 64/186 alleles) of SMARCB1. Germline mutations were detected in 26% of ATRTs (30/117). The patient cohort consisted of 47% ATRT-SHH (39/84), 33% ATRT-TYR (28/84), and 20% ATRT-MYC (17/84). Age <1 year, non-TYR signature (ATRT-SHH or -MYC), metastatic or synchronous tumors, germline mutation, incomplete remission, and omission of radiotherapy were negative prognostic factors in univariate analyses (P < 0.05). An adjusted multivariate model identified age <1 year and a non-TYR signature as independent negative predictors of OS: high risk (<1 y + non-TYR; 5-y OS = 0%), intermediate risk (<1 y + ATRT-TYR or ≥1 y + non-TYR; 5-y OS = 32.5 ± 8.7%), and standard risk (≥1 y + ATRT-TYR, 5-y OS = 71.5 ± 12.2%).

CONCLUSIONS

Age and molecular subgroup status are independent risk factors for survival in children with ATRT. Our model warrants validation within future clinical trials.

Age of diagnosis clinically differentiates atypical teratoid/rhabdoid tumors diagnosed below age of 3 years: a database study

BACKGROUND

Atypical teratoid/rhabdoid tumor (ATRT) is a rare and largely pediatric diagnosis, with poor survival. Diagnosis below the age of 3 years is characteristically seen as a poor prognostic sign. However, elucidating if clinical differences exist within this niche age group has never been attempted before. Correspondingly, we sought to characterize clinical profile of ATRT diagnoses before the age of 3 years based on separate ages of diagnosis.

METHODS

All pediatric ATRT patients aged < 3 years in the US National Cancer Database (NCDB) between 2005 and 2016 were retrospectively reviewed. Age groups were divided based on diagnoses at ages 0-1 years in group 1, 1-2 years in group 2, and 2-3 years in group 3. Data were summarized, and overall survival (OS) was modeled using Kaplan-Meier and Cox regression analyses.

RESULTS

A total of 354 ATRT diagnoses were made before the age of 3 years, with surgery used in 316 (89%) cases, chemotherapy in 242 (68%) cases, and radiation therapy in 118 (33%) cases. In terms of diagnosis age, there were 153 (43%) in group 1, 137 (39%) in group 2, and 64 (18%) in group 3. With respect to OS, median value was 9.9 months in group 1, 28.4 months in group 2, and 15.9 months in group 3. Upon multivariate analysis, receiving radiation therapy was the only parameter shared amongst all three groups as independently prognostic of longer OS (HR 0.53, P = 0.01 in group 1; HR 0.34, P < 0.01 in group 2; HR 0.31, P < 0.01 in group 3). In group 1, surgery (HR 0.47, P < 0.01) and chemotherapy (HR 0.44, P < 0.01) were also independently prognostic of longer OS. In group 3, multiple socioeconomic parameters were identified to independently predict longer OS. There were no additional predictive parameters identified in group 2.

CONCLUSION

Although ATRT diagnosed before the age of 3 is typically viewed a poor prognostic age category, our findings demonstrate that the clinical profile of this pediatric niche is highly heterogeneous based on age of diagnosis. Survival of only those diagnosed between 0 and 1 years is independently prognosticated by all three treatment modalities; patients diagnosed between 1 and 2 years trend towards longest survival, and socioeconomic parameters are most influential in those diagnosed between 2 and 3 years.

Cancer Predisposition in Neonates and Infants: Recognition, Tumor Types, and Surveillance

Pediatric cancer is rare, and malignancy during the neonatal period even rarer. However, several malignancies can present in infancy, most commonly in the form of solid tumors. Specific cancer types, bilateral or multifocal disease, associated congenital malformations, and/or cancers in close relatives may herald a diagnosis of an underlying cancer predisposition syndrome. For many patients, surveillance protocols are recommended beginning at birth or during the course of maternal prenatal care. Advantages and disadvantages of genetic testing and surveillance should be discussed with families using a multidisciplinary approach, with input from a genetic counselor with expertise in pediatric cancer predisposition.

Current recommendations for clinical surveillance and genetic testing in rhabdoid tumor predisposition: a report from the SIOPE Host Genome Working Group

The rhabdoid tumor (RT) predisposition syndromes 1 and 2 (RTPS1 and 2) are rare genetic conditions rendering young children vulnerable to an increased risk of RT, malignant neoplasms affecting the kidney, miscellaneous soft-part tissues, the liver and the central nervous system (Atypical Teratoid Rhabdoid Tumors, ATRT). Both, RTPS1&2 are due to pathogenic variants (PV) in genes encoding constituents of the BAF chromatin remodeling complex, i.e. SMARCB1 (RTPS1) and SMARCA4 (RTPS2). In contrast to other genetic disorders related to PVs in SMARCB1 and SMARCA4 such as Coffin-Siris Syndrome, RTPS1&2 are characterized by a predominance of truncating PVs, terminating transcription thus explaining a specific cancer risk. The penetrance of RTPS1 early in life is high and associated with a poor survival. However, few unaffected carriers may be encountered. Beyond RT, the tumor spectrum may be larger than initially suspected, and cancer surveillance offered to unaffected carriers (siblings or parents) and long-term survivors of RT is still a matter of discussion. RTPS2 exposes female carriers to an ill-defined risk of small cell carcinoma of the ovaries, hypercalcemic type (SCCOHT), which may appear in prepubertal females. RT surveillance protocols for these rare families have not been established. To address unresolved issues in the care of individuals with RTPS and to propose appropriate surveillance guidelines in childhood, the SIOPe Host Genome working group invited pediatric oncologists and geneticists to contribute to an expert meeting. The current manuscript summarizes conclusions of the panel discussion, including consented statements as well as non-evidence-based proposals for validation in the future.

Adult Sellar Region Atypical Teratoid/Rhabdoid Tumor: A Retrospective Study and Literature Review

Background: Adult sellar region atypical teratoid/rhabdoid tumor (AT/RT) is a rare lesion. We aimed to elucidate clinical, radiologic, and pathological characteristics, treatment strategies, and outcomes of this disease.

Methods: Five adult sellar AT/RT patients were retrospectively analyzed between January 2015 and December 2018. In addition, we performed a review of the reported data on adult sellar AT/RT.

Results: Patients (n = 5) were female with a median age of 50 years. The mean duration of symptoms, of which headache was the most frequent, was 1.6 months (range, 2 weeks−8 months). The average tumor size was 2.82 cm (range, 1.9–4.5 cm). All lesions were irregularly shaped. MRI showed heterogeneous enhancement in three of five lesions. Four of five patients underwent subtotal resection (STR) and one gross total resection (GTR). Whereas, one patient received post-operative adjuvant radiotherapy, one patient received post-operative combination of radio- and chemotherapy. The review of the reported data showed that 39 cases of adult sellar AT/RT had been reported. The estimated median overall survival (OS) was 23 months with a 1-year survival estimate of 59.7%. The median OS for patients with GTR was 28 months and 17 months for patients with STR. Kaplan–Meier analysis showed that patients with high (≥35%) MIB-1/Ki67 index value had a significantly shorter OS compared with those with low (<35%) index value (p = 0.033), and that patients who received post-operative combination radio- and chemotherapy had longer OS than that of those who did not (p < 0.001).

Conclusion: Adult sellar region AT/RT is a rapidly growing tumor with a poor prognosis. High levels of MIB1/Ki-67 on histology may indicate aggressive feature of the tumor. Maximal safe resection followed by adjuvant radiotherapy combined with chemotherapy may be the optimal therapeutic strategy for adult sellar region AT/RT.

[Influence of resection quality on postoperative outcomes in children with atypical teratoid-rhabdoid tumor of the central nervous system]

The purpose of this study was to assess the influence of resection quality on overall survival and disease-free survival in children with atypical teratoid-rhabdoid tumors (ATRT). The study included children younger than 18 years old for the period from 2008 to 2019. There were 134 interventions in 105 patients with ATRT including 11 redo resections («second-look» surgery) and 18 procedures for tumor recurrence. Age of patients ranged from 2 to 168 months (median 21 months). Patients with supratentorial tumors prevailed (50.5%), infratentorial neoplasms were diagnosed in 45.7% of patients, spinal cord lesion - 3.8% of cases. At the first stage, all patients underwent surgical treatment. Total resection was achieved in 34 (32.4%) patients, subtotal - 37 (35.2%) patients, partial resection - 30 (28.6%) patients. Biopsy was performed in 4 (3.8%) patients. Quality of resection and age at surgery significantly influenced overall and disease-free survival. Extended resection of tumor followed by adjuvant chemo- and radiotherapy are required to improve survival although ATRTs are high-grade neoplasms with poor prognosis.

Atypical Teratoid/Rhabdoid Tumor of the Central Nervous System in Children under the Age of 3 Years

Purpose

Atypical teratoid/rhabdoid tumor (ATRT) is a highly aggressive malignancy with peak incidence in children aged less than 3 years. Standard treatment for central nervous system ATRT in children under the age of 3 years have not been established yet. The objective of this study was to analyze characteristics and clinical outcomes of ATRT in children aged less than 3 years.

Materials and Methods

A search of medical records from seven centers was performed between January 2005 and December 2016.

Results

Forty-three patients were enrolled. With a median follow-up of 90 months, 27 patients (64.3%) showed at least one episode of disease progression (PD). The first date of PD was at 160 days after diagnosis. The 1- and 3-year progression-free survivals (PFS) were 51.2% and 28.5%, respectively. The 1- and 3-year overall survivals were 61.9% and 38.1%, respectively. The 3-year PFS was improved from 0% in pre-2011 to 47.4% in post-2011. Excluding one patient who did not receive any further therapy after surgery, 27 patients died due to PD (n=21), treatment-related toxicity (n=5), or unknown cause (n=1). In univariate analysis, factors associated with higher 3-year PFS were no metastases, diagnosis after 2011, early adjuvant radiotherapy, and high-dose chemotherapy (HDCT). In multivariate analysis, the use of HDCT and adjuvant radiotherapy remained significant prognostic factors for PFS (both p < 0.01).

Conclusion

Aggressive therapy including early adjuvant radiotherapy and HDCT could be considered to improve outcomes of ATRT in children under the age of 3 years.

Atypical teratoid rhabdoid tumor: molecular insights and translation to novel therapeutics

INTRODUCTION

Atypical teratoid rhabdoid tumor (ATRT) is a rare, often lethal brain tumor of childhood characterized by a complex epigenetic landscape amongst a simple genetic background. Recent molecular studies have defined key biologic events that contribute to tumorigenesis and molecular subtypes of ATRT.

METHODS

Seminal studies on ATRT are reviewed with an emphasis on molecular pathogenesis and its relevance to novel therapeutics.

RESULTS

In this review, we summarize the key clinicopathologic and molecular features of ATRT, completed and ongoing clinical trials and outline the translational potential of novel insights into the molecular pathogenesis of this tumor.

CONCLUSIONS

SMARCB1 loss is the key genetic event in ATRT pathogenesis that leads to widespread epigenetic dysregulation and loss of lineage-specific enhancers. Current work is defining subtype-specific treatments that target underlying molecular derangements that drive tumorigenesis.

Outcomes with respect to extent of surgical resection for pediatric atypical teratoid rhabdoid tumors

PURPOSE

To evaluate overall survival for atypical teratoid rhabdoid tumors (ATRTs) in relation to extent of surgical resection.

METHODS

The neurosurgical tumor databases from three UK Pediatric centers (University Hospital of Wales, Alder Hey and Royal Manchester Children's Hospital) were analyzed. Patients with a diagnosis of ATRT were identified between 2000 and 2018. Data was collected regarding demographics, extent of resection, complications, and overall survival.

RESULTS

Twenty-four patients diagnosed with ATRT underwent thirty-eight operations. The age range was 20 days to 147 months (median 17.5 months). The most common location for the tumor was the posterior fossa (nine patients; 38%). Six patients (25%) underwent a complete total resection (CTR), seven (29%) underwent a near total resection (NTR), eight (33.3%) underwent a subtotal resection (STR), and three patients (12.5%) had biopsy only. Two-thirds of patients who underwent a CTR are still alive, as of March 2019, compared to 29% in the NTR and 12.5% in the STR groups. Out of the thirty-eight operations, there were a total of twenty-two complications, of which the most common was pseudomeningocele (27%). The extent of surgical resection (p = 0.021), age at surgery (p = 0.00015), and the presence of metastases at diagnosis (0.015) significantly affected overall survival.

CONCLUSIONS

Although these patients are a highly vulnerable group, maximal resection is recommended where possible, for the best chance of long-term survival. However, near total resections are likely beneficial when compared with subtotal resections and biopsy alone. Maximal surgical resection should be combined with adjuvant therapies for the best long-term outcomes.

Effect of early radiotherapy initiation and high-dose chemotherapy on the prognosis of pediatric atypical teratoid rhabdoid tumors in different age groups

PURPOSE

The optimal treatment strategy for pediatric atypical teratoid rhabdoid tumor (ATRT) is inconclusive. This study evaluated the prognostic value of early radiotherapy (RT) and high-dose chemotherapy with autologous stem cell rescue (HDC/ASCR) in pediatric ATRT.

METHODS

This pooled analysis included ATRT patients treated at our institution and from other studies who were identified by a search of the PubMed electronic database. The effect of patient demographics and treatment profiles on progression-free survival (PFS) and overall survival (OS) were analyzed using Cox regression.

RESULTS

Overall, 34 patients from our institution and 436 patients from 35 published studies were included. In multivariable analysis, patients with gross total resection (GTR), early RT (time to RT interval < 2 months), and HDC/ASCR had both better PFS [hazard ratio (HR) 0.46, p[Formula: see text] 0.001; HR 0.64, p = 0.011; and HR 0.51, p = 0.005, respectively] and OS (HR 0.55, p = 0.002; HR 0.48, p = 0.004; and HR 0.42, p < 0.001, respectively). For patients aged < 3 years, both RT and HDC/ASCR were significant favorable factors for PFS (HR 0.32 and 0.46, respectively) and OS (HR 0.40 and 0.36, respectively), while early RT was not prognostic. For patients aged ≥ 3 years, early RT was significantly associated with better PFS (HR 0.51) and HDC/ASCR did not affect PFS, and neither was related to OS.

CONCLUSION

Both early RT initiation and HDC/ASCR were important components in the treatment of pediatric ATRT. However, the optimal treatment strategies might differ by age.

Efficacy of High-Dose Chemotherapy and Three-Dimensional Conformal Radiation for Atypical Teratoid/Rhabdoid Tumor: A Report From the Children's Oncology Group Trial ACNS0333

PURPOSE

Atypical teratoid/rhabdoid tumor (AT/RT) is an aggressive, early-childhood brain tumor without standard effective treatment. To our knowledge, we conducted the first AT/RT-specific cooperative group trial, ACNS0333, to examine the efficacy and safety of intensive postoperative chemotherapy and focal radiation to treat AT/RT.

PATIENTS AND METHODS

Patients from birth to 22 years of age with AT/RT were eligible. After surgery, they received 2 courses of multiagent chemotherapy, followed by 3 courses of high-dose chemotherapy with peripheral blood stem cell rescue and involved-field radiation therapy. Timing of radiation was based on patient age and disease location and extent. Central testing of tumor and blood for SMARCB1 status was mandated. Tumor molecular subclassification was performed retrospectively. The primary analysis was event-free survival (EFS) for patients < 36 months of age compared with a cooperative groups' historical cohort. Although accrual was based on the therapeutic question, potential prognostic factors, including age, tumor location, M stage, surgical resection, order of therapy, germline status, and molecular subtype, were explored.

RESULTS

Of 65 evaluable patients, 54 were < 36 months of age. ACNS0333 therapy significantly reduced the risk of EFS events in patients < 36 months of age compared with the historical cohort (P < .0005; hazard rate, 0.43; 95% CI, 0.28 to 0.66). Four-year EFS and overall survival for the entire cohort were 37% (95% CI, 25% to 49%) and 43% (95% CI, 31% to 55%), respectively. Timing of radiation did not affect survival, and 91% of relapses occurred by 2 years from enrollment. Treatment-related deaths occurred in 4 patients.

CONCLUSION

The ACNS0333 regimen dramatically improved survival compared with historical therapies for patients with AT/RT. Clinical characteristics and molecular subgrouping suggest prognostic differences. ACNS0333 results lay a foundation on which to build future studies and incorporate testing of new therapeutic agents.

Role of early and aggressive post-operative radiation therapy in improving outcome for pediatric central nervous system atypical teratoid/rhabdoid tumor

PURPOSE

The purpose of the study is to evaluate possible prognostic factors and optimal management for pediatric atypical teratoid/rhabdoid tumor (AT/RT) of the central nervous system (CNS).

METHODS

Twenty-eight pediatric patients with CNS AT/RT who were treated with radiation therapy (RT) as part of multimodality treatment regimens at a single institution (1996-2015) were reviewed. Survival outcomes were analyzed in relation to possible prognostic factors.

RESULTS

The 28 patients analyzed were followed up for a median 48-month period. Median progression-free survival (PFS) was 11 months, and overall survival (OS) was 57 months. Patients < 3 years old had RT delayed for a longer period after surgery (p = 0.04), and the mean RT dose to tumor bed was lower (p < 0.01) than in patients ≥ 3 years old. In multivariate analysis, a higher primary tumor bed RT dose was identified as a favorable prognostic factor for both PFS (hazard ratio [HR] = 0.85 per gray, p < 0.01) and OS (HR = 0.92 per gray, p = 0.02). In addition, an interval between surgery and RT initiation > 2 months, with disease progression observed before RT, as compared with an interval ≤ 2 months without disease progression prior to RT, was associated with worse PFS (HR = 8.50, p < 0.01) and OS (HR = 5.27, p < 0.01).

CONCLUSIONS

Early and aggressive RT after surgery is critical for successful disease control in AT/RT patients. Conversely, a delay in RT until disease progression is observed that leads to unfavorable outcomes.

Spontaneous Regression of Atypical Teratoid Rhabdoid Tumor Without Therapy in a Patient With Uncommon Regional Inactivation of SMARCB1 ( hSNF5/INI1)

Atypical teratoid/rhabdoid tumor (ATRT) is a high-grade central nervous system tumor, with poor prognosis despite intensive multimodal therapy. Loss of nuclear immunostaining for INI1 due to inactivation of the hSNF5/INI1 tumor suppressor gene is pathognomonic of ATRT. We present a patient with congenital ATRT, who had spontaneous tumor regression without therapy, and is disease-free 4 years later. Tumor histopathology showed rhabdoid cells characteristic of ATRT, but immunohistochemistry revealed heterogeneous loss of nuclear INI1 staining. The populations of INI1-intact and INI1-deficient cells were separated by laser microdissection, for molecular analysis with DNA sequencing and fluorescence in situ hybridization. The INI1-negative cells were found to harbor a heterozygous deletion and truncating mutation of the hSNF5/INI1 locus, while the INI1-intact cells had 2 copies of the wild-type INI1 gene. To our knowledge, this is the first report of spontaneous regression of ATRT, with molecular heterogeneity for SMARCB1 inactivation, with no radiographic signs of recurrence at 4 years after diagnosis.

Advances in the classification of pediatric brain tumors through DNA methylation profiling: From research tool to frontline diagnostic

Despite significant improvements in pediatric brain tumor therapy and outcome, too many children still die of disease, and too many survivors experience significant sequelae as a result of conventional therapies. The molecular characterization of pediatric brain tumors has afforded tremendous insight into the basic biology and clinical management of these deadly childhood diseases. Genomic, epigenomic, and transcriptional profiling have facilitated the identification of significant heterogeneity among previously uniform disease entities. In particular, DNA methylation profiling has emerged as a robust tool for identifying key disease-specific subgroups that can exhibit distinct clinical outcomes. These approaches, which also complement classic histologic techniques, can suggest key mechanistic underpinnings of tumorigenesis and open the door for better informed and more tailored therapy. By leveraging the results of large-scale classifications of disease cohorts, novel driver mutations and pathways can be uncovered, enabling the generation of faithful animal models, promoting targeted drug design, informing developmental biology, and ultimately translating into improved clinical management. In this review, progress in the epigenetic classification of common malignant pediatric brain tumors, namely medulloblastoma, ependymoma, high-grade glioma, atypical teratoid/rhabdoid tumor, and central nervous system embryonal tumors, will be discussed, and the potential role of DNA methylation profiling as a frontline diagnostic modality will be emphasized.

Case-based review: atypical teratoid/rhabdoid tumor

Atypical teratoid/rhabdoid tumor (AT/RT) is a rare CNS cancer that typically occurs in children younger than 3 years of age. Histologically, AT/RTs are embryonal tumors that contain a rhabdoid component as well as areas with primitive neuroectodermal, mesenchymal, and epithelial features. Compared to other CNS tumors of childhood, AT/RTs are characterized by their rapid growth, short symptomatic prodrome, and large size upon presentation, often leading to brain compression and intracranial hypertension requiring urgent intervention. For decades, the mainstay of care has been a combination of maximal safe surgical resection followed by adjuvant chemotherapy and radiotherapy. Despite advances in each of these modalities, the relative paucity of data on these tumors, their inherently aggressive course, and a lack of molecular data have limited advances in treatment over the past 3 decades. Recent large-scale, multicenter interdisciplinary studies, however, have significantly advanced our understanding of the molecular pathogenesis of these tumors. Multiple clinical trials testing molecularly targeted therapies are underway, offering hope for patients with AT/RT and their families.

Pediatric Brain Tumors

PURPOSE OF REVIEW

This article describes the most common pediatric brain tumors and highlights recent developments in their diagnosis and treatment strategies.

RECENT FINDINGS

We are in the midst of a molecular era for pediatric brain tumors. Genetic and epigenetic profiling of tumors has impacted their diagnosis, allowing for the subgrouping of heterogeneous tumor groups and leading to the complete renaming of some tumor types. These advances are reflected in the new 2016 World Health Organization classification. For example, primitive neuroectodermal tumors have been completely eliminated and replaced by subgroups defined by the absence or presence of specific chromosomal amplification. Medulloblastomas, diffuse astrocytomas, and ependymomas now have specific subtypes that are based on defining molecular features. More recent epigenetic-based subgrouping of atypical teratoid/rhabdoid tumors have not yet made it into the official classification system, but will surely have an impact on how these tumors are regarded in future preclinical and clinical trials.

SUMMARY

Genetic and epigenetic data are changing how pediatric brain tumors are diagnosed, are leading to new guidelines for how treatment outcome analyses can be organized, and are offering molecular targets that can be used for the development of novel therapies.

The extraordinary challenge of treating patients with congenital rhabdoid tumors-a collaborative European effort

BACKGROUND

Congenital rhabdoid tumors are rare and highly aggressive malignancies. In general, patients are considered to be incurable and are often treated using an exclusive, primarily palliative approach.

METHODS

A prospective and retrospective collection of 42 patients from the European Rhabdoid Registry (EU-RHAB), France and Moscow (2006-2016) diagnosed within the first 28 days of life was evaluated. Genetic and clinical reference evaluation included SMARCB1 and/or SMARCA4 (fluorescence-in-situ-hybridization, multiplex ligation-dependent probe amplification, and sequencing) mutation analysis and immunohistochemistry. Forty-eight percent (20/42) of patients were treated according to the EU-RHAB therapy, 7% (3/42) according to the pilot approach Rhabdoid 2007, 33% (14/42) with individual schedules, and 12% (5/42) received no chemotherapy at all.

RESULTS

Forty point five percent (17/42) of patients presented with extracranial rhabdoid tumors, 33.5% (14/42) with rhabdoid tumors of the central nervous system (atypical teratoid/rhabdoid tumor), and the remainder 26% (11/42) demonstrated synchronous tumors. Metastases at diagnosis were present in 52% (22/42) of patients. A germline mutation was detected in 66% (25/38) and was associated with a poor prognosis (4.2 ± 4.1% vs. 48 ± 16.4%, P < 0.00005). A gross total resection (GTR) was realized in 17%. A GTR (42.9 ± 18.7% vs. 4.9 ± 4.3%, P = 0.04), therapy according to a standardized approach (20.9 ± 8.7% vs. 7.1 ± 6.9 %, P = 0.0018), and a complete remission (CR) (23.6 ± 9.8% vs. 1.3 ± 3.6%, P = 0.04) were significant prognostic factors.

CONCLUSIONS

The management of patients with congenital rhabdoid tumors requires a major multidisciplinary effort. In many instances, cure is not possible and a palliative approach is warranted. Our data indicate a positive impact of standardized therapeutic approaches on survival, making a tailored approach toward affected patients and their families mandatory.

Incorporating Advances in Molecular Pathology Into Brain Tumor Diagnostics

Recent advances in molecular pathology have reshaped the practice of brain tumor diagnostics. The classification of gliomas has been restructured with the discovery of isocitrate dehydrogenase (IDH) 1/2 mutations in the vast majority of lower grade infiltrating gliomas and secondary glioblastomas (GBM), with IDH-mutant astrocytomas further characterized by TP53 and ATRX mutations. Whole-arm 1p/19q codeletion in conjunction with IDH mutations now define oligodendrogliomas, which are also enriched for CIC, FUBP1, PI3K, NOTCH1, and TERT-p mutations. IDH-wild-type (wt) infiltrating astrocytomas are mostly primary GBMs and are characterized by EGFR, PTEN, TP53, NF1, RB1, PDGFRA, and CDKN2A/B alterations, TERT-p mutations, and characteristic copy number alterations including gains of chromosome 7 and losses of 10. Other clinically and genetically distinct infiltrating astrocytomas include the aggressive H3K27M-mutant midline gliomas, and smaller subsets that occur in the setting of NF1 or have BRAF V600E mutations. Low-grade pediatric gliomas are both genetically and biologically distinct from their adult counterparts and often harbor a single driver event often involving BRAF, FGFR1, or MYB/MYBL1 genes. Large scale genomic and epigenomic analyses have identified distinct subgroups of ependymomas tightly linked to tumor location and clinical behavior. The diagnosis of embryonal neoplasms also integrates molecular testing: (I) 4 molecularly defined, biologically distinct subtypes of medulloblastomas are now recognized; (II) 3 histologic entities have now been reclassified under a diagnosis of "embryonal tumor with multilayered rosettes (ETMR), C19MC-altered"; and (III) atypical teratoid/rhabdoid tumors (AT/RT) now require SMARCB1 (INI1) or SMARCA4 (BRG1) alterations for their diagnosis. We discuss the practical use of contemporary biomarkers for an integrative diagnosis of central nervous system neoplasia.

BRD9 Inhibition, Alone or in Combination with Cytostatic Compounds as a Therapeutic Approach in Rhabdoid Tumors

Rhabdoid tumors (RT) are malignant neoplasms of early childhood. Despite intensive therapy, survival is poor and new treatment approaches are required. The only recurrent mutations in these tumors affect SMARCB1 and less commonly SMARCA4, both subunits of the chromatin remodeling complex SWItch/Sucrose Non-Fermentable (SWI/SNF). Loss of these two core subunits alters the function of the SWI/SNF complex, resulting in tumor development. We hypothesized that inhibition of aberrant SWI/SNF function by selective blockade of the BRD9 subunit of the SWI/SNF complex would reduce tumor cell proliferation. The cytotoxic and anti-proliferative effects of two specific chemical probes (I-BRD9 and BI-9564) which target the bromodomain of SWI/SNF protein BRD9 were evaluated in 5 RT cell lines. Combinatorial effects of I-BRD9 and cytotoxic drugs on cell proliferation were evaluated by cytotoxicity assays. Single compound treatment of RT cells with I-BRD9 and BI-9564 resulted in decreased cell proliferation, G1-arrest and apoptosis. Combined treatment of doxorubicin or carboplatin with I-BRD9 resulted in additive to synergistic inhibitory effects on cell proliferation. In contrast, the combination of I-BRD9 with vincristine demonstrated the antagonistic effects of these two compounds. We conclude that the BRD9 bromodomain is an attractive target for novel therapies in this cancer.