Tazemetostat for tumors harboring SMARCB1/SMARCA4 or EZH2 alterations: results from NCI-COG pediatric MATCH APEC1621C

Paratesticular/inguinal SMARCB1/INI1 deficient carcinomas with yolk sac tumour-like differentiation are aggressive somatic malignancies

AIMS

Extragonadal yolk sac tumour (YST) is rare, and may present a diagnostic challenge. YST differentiation was recently reported in some somatically derived tumours in the sinonasal location and in the female genital tract, together with a SMARCB1/INI1 loss. We report two paratesticular/inguinal tumours with striking morphological and immunohistochemical similarities with YST, further expanding the spectrum of extragonadal tumours with YST-like morphology and SMARCB1/INI1 loss.

METHODS AND RESULTS

Patients were 13- and 27-year-old males who presented with a 1-cm inguinal mass and a 4.6-cm spermatic cord mass, respectively. Both neoplasms showed histological and immunohistochemical features in keeping with YST. Immunohistochemically, the neoplastic cells were diffusely positive for AE1/AE3, spalt-like transcription factor 4 (SALL4) and glypican-3; alpha-fetoprotein (AFP) was positive in one of two tumours. S100, SMA, CD34 and brachyury were negative in both tumours. Pre-operative serum AFP levels were normal in both patients. Although the initial diagnostic consideration was extragonadal YST, the diagnostic work-up revealed complete loss of SMARCB1/INI1 on immunohistochemistry and absence of isochromosome 12p by fluorescence in-situ hybridisation. Both patients had an aggressive clinical course with rapid disease progression and widespread metastatic spread.

CONCLUSIONS

Somatically derived tumours with YST-like morphology at an extragonadal location present a potential diagnostic pitfall. This type of neoplasm has not been previously reported in males at this location. Therefore, SMARCB1/INI1 should be included in the immunohistochemistry work-up of any neoplasm that morphologically resembles YST at an extragonadal site, even in the setting of positive germ cell tumour markers, as the correct diagnosis has prognostic and therapeutic implications.

Contemporary Biology, Management, and Outcomes of Renal Medullary Carcinoma in Children and Adults: A Pediatric Surgical Oncology Research Collaborative Study

BACKGROUND

Renal medullary carcinoma (RMC) is an aggressive tumor associated with sickle cell trait. Despite treatment advances for other rare renal tumors, RMC survival remains poor. We aimed to describe the contemporary management and survival of children and adults with RMC.

PROCEDURE

In this multicenter retrospective cohort study, Pediatric Surgical Oncology Research Collaborative sites searched their databases for patients diagnosed with RMC (2000-2022). Descriptive statistics were calculated and survival analyses performed using Kaplan-Meier and Cox regression.

RESULTS

Thirty-four patients with RMC were identified. Median age was 19 years (IQR: 15-28; range: 7-52). Most were male (24/34; 71%), Black (27/32; 84%), had sickle cell trait or disease (30/33; 91%), presented with metastatic disease (27/34; 79%), and were symptomatic at presentation (32/34; 94%). Median overall survival (OS) was 24 months from diagnosis (16 months for children, 28 months for adults, p = 0.6). Receipt of platinum-based chemotherapy (23/34; 68%) was associated with significantly higher OS than other regimens (35 vs. 5 months, p < 0.001). Nephrectomy (24/34; 71%) was associated with significantly improved OS compared with non-operative management (34 vs. 7 months, p = 0.001). Immunotherapy, targeted therapy, or radiation therapy were not associated with significant differences in OS, nor were age, sex, race, sickle cell status, SMARCB1/INI-1, stage, nephrectomy approach, retroperitoneal lymph node dissection, gross residual disease, margins, or tumor size.

CONCLUSIONS

RMC survival remains poor despite newer therapies. Nephrectomy and platinum-based chemotherapy should be considered in locally advanced and metastatic disease. Coordinated international cooperative group studies are needed to meaningfully improve RMC survival.

SMARCA4: Promises and challenges in the treatment of cancers

The SWI/SNF (switch/sucrose non-fermentable) related BAF (BRG1/BRM-related factor) chromatin remodeling complex subunit ATPase 4 (SMARCA4) is a gene with a high mutation frequency in the SWI/SNF complex. It plays a role as an ATP-dependent catalytic subunit, participates in remodeling chromatin structure and regulation of gene expression, and is closely related to the poor prognosis of malignant tumors. It is imperative to conduct a comprehensive investigation into the distinctive biological functions and mechanisms by which SMARCA4 contributes to cancer development and to devise targeted therapeutic strategies. Despite numerous studies associating SMARCA4 with the regulation of essential genes, ferroptosis, autophagy, lipid metabolism, and oxidative stress, the precise mechanisms of SMARCA4 in tumors remain unclear. Patients with SMARCA4 mutations exhibit a poor prognosis and demonstrate limited responsiveness to surgery, targeted therapies, immunotherapy, and chemotherapies. Thus, SMARCA4 emerges as a promising biomarker and therapeutic target. However, the development of more effective precision therapy tools remains an urgent unmet need. The unique molecular characteristics of SMARCA4 pose significant challenges for targeted drug development. Notably, the discovery of inhibitors targeting SMARCA4 synthetic lethal partners and associated pathways has marked a breakthrough in this field. Monotherapies directed against SMARCA4 face several limitations, including drug resistance, suboptimal objective response rates, and dose-limiting toxicities. Consequently, the exploration of combinatorial therapeutic strategies for SMARCA4 deficiency populations represents a critical direction for future clinical translation.

Elevated Bromide Levels due to Tazemetostat Therapy Treated With Salt and Water Supplementation in Two Children With Atypical Teratoid Rhabdoid Tumor

Atypical teratoid rhabdoid tumor (ATRT) is an embryonal CNS tumor that afflicts young children. The molecular process associated with ATRT is loss of SMARCB1 or SMARCA4, which causes EZH2 overactivation. Tazemetostat hydrobromide is an EZH2 inhibitor, which has shown efficacy in the treatment of ATRT. Tazemetostat is produced as a bromide salt and can cause increased bromide levels that may require therapy cessation or dose reduction. We report two children with ATRT, who developed elevated bromide levels secondary to tazemetostat, which were treated with chloride. We propose consideration of salt supplementation in children receiving tazemetostat to prevent bromide elevation and pauses or reductions in therapy.

Combinatorial therapies for epigenetic, immunotherapeutic, and genetic targeting of chordoma

PURPOSE

Chordoma, a rare malignancy of the axial skeleton and skull base, presents significant therapeutic challenges due to the high rates of tumor recurrence and resistance. While surgical resection and radiation therapy remain the gold standard of treatment, the lack of additional treatment options necessitates the exploration of novel therapies. Combinatorial therapies hold significant potential in shaping patient prognosis. By targeting the immunotherapeutic, epigenetic, and genetic landscapes of chordoma, these methods enable the more effective and personalized management of the diverse molecular mechanisms driving chordoma growth and resistance.

METHODS

To elucidate such potential, we conducted a literature review of all published articles on the usage of immunotherapeutic, epigenetic, and genetic approaches for chordoma treatment from 2014 to 2024.

RESULTS

Eighty-one papers were excluded based on our inclusion criteria. From the remaining thirty-nine publications, we found evidence supporting the efficacy of immune checkpoint inhibitors (ICIs), chimeric antigen receptor (CAR) T-cell therapies, and monoclonal antibodies; the roles of DNA methylation patterns, histone modification pathways, and miRNA regulation; and the contribution of cancer stem-like cells (CSCs) to chordoma progression.

CONCLUSION

Our findings underscore the importance of a multidirectional approach in chordoma treatment throughout the disease progression to reduce morbidity and improve patient outcomes despite the heterogeneity of chordoma.

SMARCB1-deficient Sinonasal Carcinoma: Expanding the Pathologic Spectrum With a Series of 32 Cases

SMARCB1-deficient sinonasal carcinoma (SDSC) is a recently recognized rare malignancy. Despite growing awareness, SDSC remains susceptible to misdiagnosis owing to its rarity and overlapping features with diverse mimics. A retrospective review of the clinical and pathologic features of 32 SDSC including 4 SMARCB-1 deficient adenocarcinoma (SDAC) cases was performed. The patients were aged 19 to 76 years with a male predominance. Most tumors arose in the naso-ethmoid (75%), and advanced stage (93.6%), with frequent multi-sinus (90.5%) involvement. Histologically, tumors exhibited diverse morphologies, including basaloid (50%), rhabdoid (25%), and undifferentiated (12.5%) types. SDAC cases showed glandular differentiation with intraluminal and stromal mucin. Empty vacuoles (62.5%), pagetoid spread (31.3%), eosinophilic-granular bodies (18.8%), hyaline globules (15.2%), and florid glomeruloid neovascularization (15.6%) were additional findings. Yolk sac-like areas were encountered in 18.6%. Immunohistochemically, tumors were defined by a complete loss of SMARCB1 (100%); a variable reactivity for p40 (65.6%), synaptophysin (13.6%), glypican3 (6.1%), and CD34 (6.1%) was present. Notably, >90% of our patients had different initial diagnoses before referral. Lymph node metastasis, locoregional recurrence, and distant metastasis were seen in 23.3%, 24.1%, and 27.6% patients, respectively; 37.9% died of disease. In conclusion, SDSCs are rare and aggressive sinonasal malignancies that display a wide histologic spectrum including glandular differentiation. This study expands on the morphologic spectrum of SDSC by analyzing a large cohort of 32 cases, adding comprehensive clinical, histopathologic, and immunohistochemical data, and highlighting features to improve diagnostic accuracy. The emergence of targeted therapies, such as EZH2 inhibitors, further underscores the importance of accurate diagnosis.

What Have We Learnt from the Recent Multimodal Managements of Young Patients with ATRT?

Atypical teratoid rhabdoid tumors are rare embryonal tumors of the nervous system mainly seen in very young children with aggressive behavior and dismal prognosis when treated with conventional chemotherapy only. More recent multimodal strategies combining, variably, high dose chemotherapy, radiotherapy and or intrathecal chemotherapy have led to some stride in survival. We present the results of the most recent clinical trials and registry data for patients treated with these multimodal approaches with survival ranging from 37.1% to 88.9%. We review the current consensus of the molecular characterization of these tumors into 3 subgroups (ATRT-TYR, ATRT-SHH and ATRT-MYC) and discuss the potential clinical impact of molecular subgrouping on survival. We explore other therapeutic tools including intrathecal chemotherapy and maintenance and possible new targeted agents for patients failing multimodal strategies.

Intrathoracic Rhabdoid Tumor: A Rare Site in a Jordanian Infant

Intrathoracic rhabdoid tumors in infants are rare and aggressive malignancies that pose significant diagnostic and therapeutic challenges. We report the case of a previously healthy six-month-old full-term infant admitted with severe respiratory distress and desaturation, requiring admission to the pediatric intensive care unit (PICU) and intubation. Initial evaluation suggested left upper lobe pneumonia, but the patient demonstrated minimal improvement with antibiotics and corticosteroids. Then a chest CT was done and revealed a large, heterogeneously enhancing pleural-based mass compressing the left lung, initially interpreted as an aggressive pleural tumor, such as bronchopleural blastoma. The findings led to the urgent initiation of chemotherapy, resulting in temporary clinical improvement that allowed for extubation and a biopsy to be taken. The initial biopsy indicated a germ cell tumor with yolk sac based on these immunohistochemical markers: SALL-4, cytokeratin, and vimentin. However, the patient's lack of a sustained response to chemotherapy and subsequent clinical deterioration prompted a repeat biopsy, which confirmed the diagnosis of an intrathoracic rhabdoid tumor. Despite aggressive multimodal therapy, the patient developed liver metastases five months after the initial diagnosis and was transitioned to palliative care. This case highlights the tumor's complex behavior and resistance to therapy, and underscores the diagnostic challenges associated with intrathoracic masses in infants, particularly the overlap between germ cell tumors and rhabdoid tumors.

Relapse-free survival in a pediatric patient with recurrent EZH2-mutant melanoma treated with adjuvant tazemetostat

Enhancer of zeste homolog 2 (EZH2) is an essential epigenetic regulator of H3K27 histone methylation and is mutated or overexpressed in a wide variety of cancers. In melanoma, EZH2 overexpression contributes to excessive trimethylation of H3K27 on tumor suppressor genes and has been proposed to be a mechanism of tumor progression and metastasis. EZH2-targeted therapies have been successfully used to treat patients with follicular lymphoma and epithelioid sarcoma, but their clinical use in melanoma has not been described. Here, we describe a pediatric patient with multiply relapsed melanoma harboring an EZH2 A692V missense mutation, treated adjuvantly with the EZH2 inhibitor tazemetostat, who experienced a prolonged relapse-free survival.

Hallmark discoveries in the biology of non-Wilms tumour childhood kidney cancers

Approximately 20% of paediatric and adolescent/young adult patients with renal tumours are diagnosed with non-Wilms tumour, a broad heterogeneous group of tumours that includes clear-cell sarcoma of the kidney, congenital mesoblastic nephroma, malignant rhabdoid tumour of the kidney, renal-cell carcinoma, renal medullary carcinoma and other rare histologies. The differential diagnosis of these tumours dates back many decades, when these pathologies were identified initially through clinicopathological observation of entities with outcomes that diverged from Wilms tumour, corroborated with immunohistochemistry and molecular cytogenetics and, subsequently, through next-generation sequencing. These advances enabled near-definitive recognition of different tumours and risk stratification of patients. In parallel, the generation of new renal-tumour models of some of these pathologies including cell lines, organoids, xenografts and genetically engineered mouse models improved our understanding of the development of these tumours and have facilitated the identification of new therapeutic targets. Despite these many achievements, paediatric and adolescent/young adult patients continue to die from such rare cancers at higher rates than patients with Wilms tumour. Thus, international coordinated efforts are needed to answer unresolved questions and improve outcomes.

Safety profile of EZH2 inhibitors for cancer: a systematic review and meta-analysis

Objective

To evaluate the safety profiles of EZH2-targeted inhibitors in cancer treatment, focusing on treatment-related adverse events (TRAEs) across various clinical trials.

Methods

We conducted a systematic review and meta-analysis using data from clinical trials involving EZH2 inhibitors reported up to May 31, 2024. Databases searched included PubMed, Embase, CENTRAL (Cochrane Central Register of Controlled Trials), and ClinicalTrials.gov. Studies included were those involving patients treated with EZH2 inhibitors as monotherapy or in combination, specifically detailing the incidence of TRAEs. Data on all-grade TRAEs, grade 3 or higher TRAEs, and severe TRAEs were extracted and analyzed using random-effects models.

Results

Our systematic review and meta-analysis included 22 studies encompassing 1,002 patients who met the inclusion criteria. TRAEs were commonly observed during EZH2 inhibitor therapy, affecting 86% of patients (95% CI [79-94%]%; I2 = 89.5%). The incidence of grade 3 or higher TRAEs was 33% (95% CI [21-44%]; I2 = 93.5%), while severe TRAEs occurred in 15% of the cases (95% CI [9-22%]; I2 = 87.5%). The most frequently reported grade 3 or higher TRAEs in the pooled analysis were neutropenia (8%), thrombocytopenia (8%), and anemia (6%). Specifically, for tazemetostat, the most common grade 3 or higher TRAE was neutropenia (5%). For SHR2554, the most prevalent grade 3 or higher TRAEs were thrombocytopenia (17%), neutropenia (8%), and anemia (7%). Notably, treatment-related fatalities were rare, with only 0.9% of patients experiencing potentially fatal outcomes due to therapy.

Conclusion

EZH2 inhibitors demonstrate a manageable safety profile with a low incidence of severe TRAEs, emphasizing their potential as safe therapeutic options in cancer treatment. The low rate of severe TRAEs and the rare occurrences of treatment-related deaths support the continued clinical use and further investigation of EZH2 inhibitors.

A novel case of glial transdifferentiation in renal medullary carcinoma brain metastasis

Renal medullary carcinoma is a rare undifferentiated tumor of the kidney associated with sickle cell trait and characterized by INI1 (SMARCB1) loss. Although metastasis to lungs, lymph nodes, and bone is commonly reported, distant spread to the central nervous system almost never occurs. Here we present an unusual case of a patient with renal medullary carcinoma with metastasis to the brain following treatment which included tazemetostat, an EZH2 inhibitor. The metastatic brain lesion harbored morphologic, immunohistochemical, and methylation profile supportive of a primary CNS phenotype with loss of the trimethylated lysine 27 residue of histone 3 while maintaining INI1 loss and a specific gene fusion shared with the patient's tumor prior to initiation of tazemetostat therapy. Therefore, given the common genetic signatures in the brain metastasis and the patient's prior tumor, this case represents a rare event of glial transdifferentiation in a brain metastasis of renal medullary carcinoma following the use of an epigenetic modulator. As renal medullary carcinoma has been known to cleverly utilize adaptive mechanisms for survival, we propose that such cell plasticity seen in this case may have been provoked by the use of a drug that alters the epigenetic signature of the tumor cells. Thus, careful assessment of tumor biology following novel therapeutic treatment options must be performed in order to note such unexpected consequences of treatment.

Brief Report: Clinical Characteristics and Outcomes of Patients With Thoracic SMARCA4-Deficient Undifferentiated Tumors

Introduction

Thoracic SMARCA4-deficient undifferentiated tumors (SMARCA4-UTs) are a recently defined group of aggressive cancers in which the effectiveness of standard treatments for lung cancer is unknown.

Methods

We collected clinical, pathologic, and demographic variables from five institutions for patients whose tumors met criteria for SMARCA4-UTs (undifferentiated phenotype and loss of SMARCA4 (BRG1) by immunohistochemistry).

Results

We identified 92 patients with SMARCA4-UTs; 58 (63%) had stage IV disease at diagnosis and 16 (17%) developed recurrent or metastatic disease after initial diagnosis. Median overall survival from metastatic diagnosis was 7.3 (95% confidence interval [CI]: 4.6-12.8) months. Of patients with metastatic disease, 58 (78%) received first-line systemic treatment. Most often, patients received chemo and immunotherapy combination (41%), chemotherapy alone (33%), or immunotherapy alone (16%). Median progression-free survival from start of systemic therapy was 1.9 (95% CI: 1.4-14.5) months for chemo and immunotherapy, 1.6 (95% CI: 1.1-5.8) months for chemotherapy, and 3.3 (95% CI: 1.2-undefined) months for immunotherapy alone. Five patients had durable responses (≥2 y); all received immunotherapy as part of first-line regimens. Nine (16%) of 55 tumor samples tested had programmed death-ligand 1 expression more than or equal to 50%, with 24 (44%) negative samples. Tumor mutational burden was available in 48 cases (52%), and median was 10.5 (range: 2-48) mutations per megabase.

Conclusions

This multi-institution retrospective cohort analysis revealed a population of patients with short progression-free survival to standard therapies and poor overall survival. A few patients had remarkable response to regimens including immunotherapy. Prospective clinical studies are urgently needed to identify better therapeutic approaches to treat this aggressive malignancy, and this analysis may serve as a benchmark for future clinical trial design.

Paediatric renal tumours: an update on challenges and recent developments

Paediatric renal tumours include a broad range of neoplasms which largely differ, but also overlap to a smaller extent, with adult kidney cancer. These include the embryonal tumour nephroblastoma, which accounts for the majority of cases of kidney cancer in the first decade of life and, despite boasting a cure in ~ 90% cases, still presents clinical challenges in a small proportion of cases. A variety of less common mesenchymal tumours, including the mostly indolent congenital mesoblastic nephroma, clear cell sarcoma of kidney which continues to be associated with poor outcomes for higher stage disease, and the typically lethal malignant rhabdoid tumour, form the bulk of the remaining presentations in the first decade. All three of these represent the intrarenal form of a wider 'family' of genetically related and histologically overlapping entities occurring in soft tissue and other anatomical locations. The latter two are examples of aggressive 'epigenetic' tumours driven by dysregulation of chromatin. In the second decade of life, renal cell carcinoma dominates, and with molecular characterisation many distinct subtypes are now described. Herein we discuss the developments in relation to diagnostic categorisation of paediatric renal cancers and how deeper understanding of the underlying biology is already providing therapeutic opportunity, while also focussing on the challenges that remain for the pathologist.

Progress Toward Epigenetic Targeted Therapies for Childhood Cancer

Among the most significant discoveries from cancer genomics efforts has been the critical role of epigenetic dysregulation in cancer development and progression. Studies across diverse cancer types have revealed frequent mutations in genes encoding epigenetic regulators, alterations in DNA methylation and histone modifications, and a dramatic reorganization of chromatin structure. Epigenetic changes are especially relevant to pediatric cancers, which are often characterized by a low rate of genetic mutations. The inherent reversibility of epigenetic lesions has led to an intense interest in the development of epigenetic targeted therapies. Additionally, the recent appreciation of the interplay between the epigenome and immune regulation has sparked interest in combination therapies and synergistic immunotherapy approaches. Further, the recent appreciation of epigenetic variability as a driving force in cancer evolution has suggested new roles for epigenetic therapies in limiting plasticity and resistance. Here, we review recent progress and emerging directions in the development of epigenetic targeted therapeutics and their promise across the landscape of childhood cancers.

Genomic and clinical characterization of pediatric lymphoepithelioma-like carcinoma

BACKGROUND

Pediatric lymphoepithelioma-like carcinoma (pLELC) is a rare neoplasm with unclear prognosis, genome, and tumor microenvironment. Our study aims to elucidate its genomic and clinical characteristics.

METHODS

Forty-one pLELC patients were enrolled at Sun Yat-sen University Cancer Center from 2012 to 2023. Kaplan-Meier analysis was utilized to estimate progression-free survival (PFS) and overall survival (OS). Baseline plasma protein levels from 16 patients and 9 health controls were analyzed using a Olink proteomic platform and whole exon sequence (WES) was performed on 11 tumor samples from 10 pediatric patients. Immunohistochemistry (IHC) for PD-L1was performed, and the infiltration of CD4+ or CD8+ T cells was evaluated.

RESULTS

Patients receiving anti PD-1 in combination with chemotherapy had a 1-year PFS of 100%, while the 2-year PFS was 72.92% (95%CI: 46.80‒100%). The 1-year OS for patients receiving anti PD-1 in combination with chemotherapy was 100%, and the 2-year OS was 87.5% (95%CI: 67.34-100%). Significant upregulation of immune checkpoint molecules was detected including LAG-3, PD-L1, and galectin-9 in LELC group by proteomic analysis (P < 0.05). The mutational landscape of pediatric LELC presented more genes mutated in pathways associated with immune, DNA repair, cell cycle and NOTCH. Pathway analysis of mutational profiles indicated DNA repair pathway and SWI/SNF complex were potential drug targets for pLELC patients. All the pediatric LELC patients evaluated exhibited positive PD-L1 expression and CD4+/CD8+ T cells infiltration.

CONCLUSIONS

Our findings indicate a promising response rate associated with the combination of PD-1 antibody treatment and chemotherapy in pediatric patients with LELC, providing a theoretical basis for targeting DNA repair pathways. These outcomes suggest that clinical trials involving immune checkpoint inhibitors are warranted in pediatric patients with LELC.

Pediatric Central Nervous System Embryonal Tumors: Presentation, Diagnosis, Therapeutic Strategies, and Survivorship-A Review

Central nervous system (CNS) embryonal tumors represent a diverse group of neoplasms and have a peak incidence in early childhood. These tumors can be located anywhere within the CNS, and presenting symptoms typically represent tumor location. These tumors display distinctive findings on neuroimaging and are staged using magnetic resonance imaging of the brain and spine as well as evaluation of cerebrospinal fluid. Diagnosis is made based on an integrated analysis of histologic and molecular features via tissue sampling. Risk stratification is based on integration of clinical staging and extent of resection with histologic and molecular risk factors. The therapeutic approach for these tumors is multimodal and includes surgery, chemotherapy, and radiation, tailored to the individual patient factors (including age) and specific tumor type. Comprehensive supportive care including management of nausea, nutrition support, pain, fertility preservation, and mitigation of therapy-related morbidity (including hearing protection) is imperative through treatment of CNS embryonal tumors. Despite advances in therapy and supportive care, the long-term consequences of current treatment strategies are substantial. Integration of less toxic, molecularly targeted therapies and a comprehensive, multidisciplinary approach to survivorship care are essential to improving survival and the overall quality of life for survivors.

Outcomes of SMARCB1-deficient sinonasal carcinoma: Largest single-center cross-sectional study

BACKGROUND

We evaluate outcomes of SMARCB1-deficient sinonasal carcinomas in the largest single-institution study.

METHODS

Retrospective cross-sectional study of patients with SMARCB1-deficient sinonasal carcinoma between 1998 and 2024. Disease-specific survival (DSS) and recurrence-free probability (RFP) at 1 and 5 years were measured by Kaplan-Meier method.

RESULTS

There were 47 patients with a median age of 53. Initial pathological diagnosis was altered in 33%. Twelve (34%) patients received neoadjuvant chemotherapy, with one partial response. Curative surgical approach was undertaken in 73%. Definitive chemoradiation was administered in 20%. DSS at 1 and 5 years was 93% and 45%, respectively. RFP at 1 and 5 years was 73% and 33%, respectively. On multivariate analysis, cranial nerve involvement (p = 0.01 for DSS) remained significantly worse for DSS and overall survival.

CONCLUSIONS

SMARCB1-deficient tumors had limited response to neoadjuvant chemotherapy. Cranial nerve involvement was associated with worse prognosis. Optimal treatment is unclear. Surgery should be offered to patients with resectable disease.

Effective treatment strategies and key factors influencing therapeutic efficacy in advanced SMARCA4-deficient non-small cell lung cancer

INTRODUCTION

SMARCA4/BRG1-deficient non-small cell lung cancer (SD-NSCLC) with high invasiveness and poor prognosis is associated with primary resistance to standard treatment, especially in late-stage patients. This study aimed to explore effective treatments and identify critical factors impacting therapeutic efficacy to enhance outcomes for SD-NSCLC patients.

METHODS

103 SD-NSCLC patients in stage III/IV diagnosed by immunohistochemistry from May 2019 to March 2024 were included in this study. We assessed the patients' clinical and genetic features, analyzed the clinical outcomes of local treatment and immunotherapy according to the TNM stage, and further evaluated the factors impacting therapeutic efficacy.

RESULTS

In stage III patients, no significant differences in the median progression-free survival (mPFS) and median overall survival (mOS) were observed between patients receiving local treatment at the primary site and those who did not (p > 0.05), while adding ICIs (immune checkpoint inhibitors) to local treatment significantly improved mPFS compared with non-ICIs (15.0 vs. 7.7 months, p = 0.033), though not mOS (p > 0.05). For stage IV patients, ICIs significantly improved mPFS (8.9 vs. 4.2 months, p = 0.006) and mOS (19.7 vs. 13.1 months, p = 0.007) compared to non-ICIs treatments. However, among ICIs-treated patients, the addition of local treatment to the primary lesion did not significantly affect mPFS and mOS (p > 0.05). Patients with STK11/KEAP1 mutations had significantly shorter mPFS (3.6 vs. 16.2 months, p = 0.001) and mOS (17.7 vs. 31.3 months, p = 0.002), while no significant difference was observed in mPFS and mOS in patients with different tumor mutation burden (TMB) and PD-L1 expression levels.

CONCLUSION

The addition of ICIs to local treatment shows promising results for locally advanced patients with SD-NSCLC, and first-line ICIs are associated with improved survival in metastatic SD-NSCLC. STK11/KEAP1 mutations may be linked to reduced efficacy of immunotherapy.

Consensus recommendations for systemic therapies in the management of relapsed Ewing sarcoma: A report from the National Ewing Sarcoma Tumor Board

Ewing sarcoma (ES) is a malignant tumor of bone and soft tissue that most often occurs in children, adolescents, and young adults. Debate and controversy remain in the management of relapsed/refractory ES (RR-ES). The authors leveraged the expertise assembled by the National Ewing Sarcoma Tumor Board, a multidisciplinary virtual tumor board that meets monthly to discuss challenging cases of ES. In this review, they focus on select topics that apply to the management of patients with RR-ES. The specific topics covered include the initial approach of such patients and discussion of the goals of care, the role of molecular testing, chemotherapy regimens and novel agents to consider, the role of maintenance therapy, and the use of high-dose chemotherapy with autologous stem cell rescue. The data referenced are often limited to subgroup analyses and/or compiled from multiple sources. Although not intended to replace the clinical judgement of treating physicians, these guidelines are intended to support clinicians and provide some clarity and recommendations for the management of patients with RR-ES. PLAIN LANGUAGE SUMMARY: Ewing sarcoma (ES) is a bone and soft tissue cancer that most often occurs in teenagers and young adults. This article uses the experience of the National Ewing Sarcoma Tumor Board, a multi-institution, multidisciplinary virtual tumor board that meets monthly to discuss challenging cases of ES and to address questions related to the treatment of patients with relapsed ES. Although not intended to replace the clinical judgement of treating physicians and limited by available data, these consensus recommendations will support clinicians who treat patients with this challenging malignancy, made even more difficult when it recurs.

Epigenetic therapies targeting histone lysine methylation: complex mechanisms and clinical challenges

As epigenetic therapies continue to gain ground as potential treatment strategies for cancer and other diseases, compounds that target histone lysine methylation and the enzyme complexes represent a major frontier for therapeutic development. Clinically viable therapies targeting the activities of histone lysine methyltransferases (HKMT) and demethylases (HKDMs) have only recently begun to emerge following FDA approval of the EZH2 inhibitor tazemetostat in 2020 and remain limited to compounds targeting the well-studied SET domain-containing HKMTs and their opposing HKDMs. These include the H3K27 methyltransferases EZH2/EZH1, the singular H3K79 methyltransferase DOT1L, and the H3K4 methyltransferase MLL1/COMPASS as well as H3K9 and H3K36 methyltransferases. They additionally include the H3K4/9-preferential demethylase LSD1 and the H3K4-, H3K27-, and H3K36-preferential KDM5, KDM6, and KDM2 demethylase subfamilies, respectively. This Review discusses the results of recent clinical and preclinical studies relevant to all of these existing and potential therapies. It provides an update on advancements in therapeutic development, as well as more basic molecular understanding, within the past 5 years approximately. It also offers a perspective on histone lysine methylation that departs from the long-predominant "histone code" metaphor, emphasizing complex-disrupting inhibitors and proximity-based approaches rather than catalytic domain inhibitors in the outlook for future therapeutic development.

Case report: Extraskeletal Ewing sarcoma with a germline pathogenic variant of SMARCA4

SMARCA4 (BRG1) is a core unit of the SWI/SNF complex, regulating gene transcription through chromatin remodeling. Germline SMARCA4 variants have been reported to be associated with various malignancies. Here, we report the first case of extraskeletal Ewing sarcoma in a young female patient with a germline pathogenic variant of SMARCA4 (c.3546 + 1G>A), diagnosed with next generation sequencing (NGS). This alteration was also identified in her familial lineage, including her sister who was previously diagnosed with small cell carcinoma of the ovary, hypercalcemic type, a malignancy highly associated with SMARCA4 mutations. Despite undergoing radical surgery and receiving systemic treatments including VeIP (vinblastine, ifosfamide, cisplatin), and VDC (vincristine, doxorubicin, cyclophosphamide) regimens, the patient succumbed to death due to disease progression. With the implementation of NGS, we anticipate that more cases with SMARCA4 mutations will be diagnosed in the future. Further research is necessary to unveil therapeutic targets associated for this oncogenic alteration.

Outcomes for children with recurrent/refractory atypical teratoid rhabdoid tumor: A single-institution study with molecular correlation

BACKGROUND

Survival data for recurrent pediatric atypical teratoid rhabdoid tumor (ATRT) and its association to molecular groups are extremely limited.

METHODS

Single-institution retrospective study of 64 children less than 21 years old with recurrent or treatment-refractory (progressive disease [PD]) ATRT treated at St. Jude Hospital from January 2000 to December 2020. Demographic, clinicopathologic, treatment, molecular grouping (SHH, TYR, and MYC) and germline data were collected. Progression-free survival (PFS2: time from PD to subsequent first progression) and overall survival (OSpostPD: time from PD to death/last follow-up) were estimated by Kaplan-Meier analysis.

RESULTS

Median age at and time from initial diagnosis to PD were 2.1 years (range: 0.5-17.9 years) and 5.4 months (range: 0.5-125.6 months), respectively. Only five of 64 children (7.8%) are alive at median follow-up of 10.9 (range: 4.2-18.1) years from PD. The 2/5-year PFS2 and OSpostPD were 3.1% (±1.8%)/1.6% (±1.1%) and 20.3% (±4.8%)/7.3% (±3.5%), respectively. Children with TYR group (n = 10) had a better OSpostPD compared to those with MYC (n = 11) (2-year survival estimates: 60.0% ± 14.3% vs. 18.2% ± 9.5%; p = .019), or those with SHH (n = 21; 4.8% ± 3.3%; p = .014). In univariate analyses, OSpostPD was better with older age at diagnosis (p = .037), female gender (p = .008), and metastatic site of PD compared to local or combined sites of PD (p < .001). Two-year OSpostPD for patients receiving any salvage therapy (n = 39) post PD was 33.3% ± 7.3%.

CONCLUSIONS

Children with recurrent/refractory ATRT have dismal outcomes. Older age at diagnosis, female gender, TYR group, and metastatic site of PD were associated with relatively longer survival in our study.

The genomic landscape of transformed splenic diffuse red pulp small B-cell lymphoma

The genetic landscape underlying the transformation of splenic diffuse red pulp small B-cell lymphoma (SDRPL) is not well understood. The present study aimed to unravel the genomic alterations involved in the progression and transformation of SDRPL. We performed genetic studies on both SDRPL and subsequent or synchronous diffuse large B cell lymphoma (DLBCL) samples in three SDRPL patients who eventually developed DLBCL. Our findings revealed that SDRPL cases progressing to DLBCL acquired genomic alterations in genes related to the cell cycle (CDKN2A/B, TP53, MYC and CCND3) and B cell development (BCL6).

Chromatin remodellers as therapeutic targets

Large-scale cancer genome sequencing studies have revealed that chromatin regulators are frequently mutated in cancer. In particular, more than 20% of cancers harbour mutations in genes that encode subunits of SWI/SNF (BAF) chromatin remodelling complexes. Additional links of SWI/SNF complexes to disease have emerged with the findings that some oncogenes drive transformation by co-opting SWI/SNF function and that germline mutations in select SWI/SNF subunits are the basis of several neurodevelopmental disorders. Other chromatin remodellers, including members of the ISWI, CHD and INO80/SWR complexes, have also been linked to cancer and developmental disorders. Consequently, therapeutic manipulation of SWI/SNF and other remodelling complexes has become of great interest, and drugs that target SWI/SNF subunits have entered clinical trials. Genome-wide perturbation screens in cancer cell lines with SWI/SNF mutations have identified additional synthetic lethal targets and led to further compounds in clinical trials, including one that has progressed to FDA approval. Here, we review the progress in understanding the structure and function of SWI/SNF and other chromatin remodelling complexes, mechanisms by which SWI/SNF mutations cause cancer and neurological diseases, vulnerabilities that arise because of these mutations and efforts to target SWI/SNF complexes and synthetic lethal targets for therapeutic benefit.

Phase II Study of Samotolisib in Children and Young Adults With Tumors Harboring Phosphoinositide 3-Kinase/Mammalian Target of Rapamycin Pathway Alterations: Pediatric MATCH APEC1621D

PURPOSE

Patients age 1-21 years with relapsed or refractory solid and CNS tumors were assigned to phase II studies of molecularly targeted therapies on the National Cancer Institute-Children's Oncology Group (NCI-COG) Pediatric Molecular Analysis for Therapy Choice (MATCH) trial. Patients whose tumors harbored predefined genetic alterations in the phosphoinositide 3-kinase (PI3K)/mammalian target of rapamycin (mTOR) pathway and lacked mitogen-activated protein kinase pathway activating alterations were treated with the PI3K/mTOR inhibitor samotolisib.

METHODS

Patients received samotolisib twice daily in 28-day cycles until disease progression or unacceptable toxicity. A rolling 6 limited dose escalation was performed as, to our knowledge, this was the first pediatric study of samotolisib. The primary end point was the objective response rate; secondary end points included progression-free survival (PFS) and the recommended phase II dose and toxicity of samotolisib in children.

RESULTS

A total of 3.4% (41/1,206) of centrally tested patients were matched to this arm. Seventeen patients were treated. Among treated patients, the most common diagnoses included osteosarcoma (n = 6) and high-grade glioma (n = 5) harboring alterations in phosphatase and tensin homolog (n = 6), PIK3CA (n = 5), and tuberous sclerosis complex 2 (n = 3). No objective responses or prolonged stable disease were observed. Three-month PFS was 12% (95% CI, 2 to 31). Two patients experienced dose-limiting toxicities (mucositis and pneumonitis). Dose level 2 (115 mg/m2/dose twice daily) was determined to be the recommended phase II dose of samotolisib in children.

CONCLUSION

This nationwide study was successful at identifying patients and evaluating the efficacy of molecularly targeted therapy for rare molecular subgroups of patients in a histology-agnostic fashion. Unfortunately, there was no activity of samotolisib against tumors with PI3K/mTOR pathway alterations. Prospective trials such as the NCI-COG Pediatric MATCH are necessary to evaluate the efficacy of molecularly targeted therapies given their increasing use in clinical practice.

Leading medulloblastoma to a differentiation end

Effective and less toxic therapies for medulloblastoma have proved to be highly elusive. In this issue of Cancer Cell, Yang et al. show that thyroid hormone treatment leads to the activation of neurogenic differentiation factor 1 (NeuroD1) and differentiation of medulloblastoma cells through reversing EZH2-mediated transcriptional repression of NeuroD1.

The New WHO Category of "Molecularly Defined Renal Carcinomas": Clinical and Diagnostic Features and Management Implications

The evolution of classification of renal tumors has been impacted since the turn of the millennium by rapid progress in histopathology, immunohistochemistry, and molecular genetics. Together, these features have enabled firm recognition of specific, classic types of renal cell carcinomas, such as clear cell renal cell carcinoma, that in current practice trigger histologic-type specific management and treatment protocols. Now, the fifth Edition World Health Classification's new category of "Molecularly defined renal carcinomas" changes the paradigm, defining a total of seven entities based specifically on their fundamental molecular underpinnings. These tumors, which include TFE3-rearranged, TFEB-altered, ELOC-mutated, fumarate hydratase-deficient, succinate dehydrogenase-deficient, ALK-rearranged, and SMARCB1-deficient renal medullary carcinoma, encompass a wide clinical and histopathologic phenotypic spectrum of tumors. Already, important management aspects are apparent for several of these entities, while emerging therapeutic angles are coming into view. A brief, clinically-oriented introduction of the entities in this new category, focusing on relevant diagnostic, molecular, and management aspects, is the subject of this review.

EZH2-driven immune evasion defines high-risk pediatric AML with t(16;21) FUS::ERG gene fusion

Despite decades of research, acute myeloid leukemia (AML) remains a remarkably lethal malignancy. While pediatric AML (pAML) carries a more favorable prognosis than adult AML, the past 25 years of large clinical trials have produced few improvements in pAML survival. Nowhere is this more evident than in patients carrying a t(16;21)(p11;q22) translocation, which yields the FUS::ERG fusion transcript. Patients with FUS::ERG-positive AML are often primary refractory, and most responders quickly relapse. In COG clinical trials, allogeneic stem cell transplantation was of no benefit to FUS::ERG pAML patients; 100% of transplanted patients succumbed to their disease. Expression of major histocompatibility complex (MHC) class I & II and costimulatory molecules is absent at diagnosis in FUS::ERG AML, mirroring the epigenetic mechanism of post-transplant relapse seen in adult AML and its associated dismal outcomes. Here we show that this class-defining immune-repressive phenotype is driven by overexpression of the EZH2 histone lysine methyltransferase in vitro and in multiple clinical cohorts. We show that treatment with the FDA-approved EZH2 inhibitor tazemetostat along with IFN-γ reverses this phenotype, re-establishes MHC presentation, and severely impairs the viability of FUS::ERG AML cells. EZH2 inhibitors may thus provide the first targeted therapeutic option for patients with this high-risk subtype of pAML, with particular benefit as a bridge to successful allogeneic stem cell transplantation.

Rhabdoid tumor predisposition syndrome: A historical review of treatments and outcomes for associated pediatric malignancies

Rhabdoid tumor predisposition syndrome (RTPS) is a rare disorder associated with malignant rhabdoid tumor of the kidney (RTK), atypical teratoid rhabdoid tumor (ATRT), and/or other extracranial, extrarenal rhabdoid tumors (EERT), and these pediatric malignancies are difficult to treat. Presently, most of the information regarding clinical manifestations, treatment, and outcomes of rhabdoid tumors comes from large data registries and case series. Our current understanding of treatments for patients with rhabdoid tumors may inform how we approach patients with RTPS. In this manuscript, we review the genetic and clinical features of RTPS and, using known registry data and clinical reports, review associated tumor types ATRT, RTK, and EERT, closing with potential new approaches to treatment. We propose collaborative international efforts to study the use of SMARC (SWI/SNF-related, matrix-associated, actin-dependent regulator of chromatin)-targeting agents, high-dose consolidative therapy, and age-based irradiation of disease sites in RTPS.

Marked Response to Nivolumab by a Patient With SMARCA4-Deficient Undifferentiated Urothelial Carcinoma Showing High PD-L1 Expression: A Case Report

BACKGROUND

SMARCA4 is a component gene of the SWI/SNF (SWItch/Sucrose NonFermentable) chromatin remodeling complex; undifferentiated tumors associated with its functional deletion have been described in several organs. However, no established treatment for these tumors currently exists.

CASE

In this study, we report a case of a SMARCA4-deficient undifferentiated urothelial carcinoma with high PD-L1 expression that was effectively treated with nivolumab after early relapse following treatment for non-invasive bladder cancer. The histological morphology of the rhabdoid-like undifferentiated tumor of unknown primary led us to suspect a SWI/SNF-deficient tumor, and subsequent immunostaining led to the diagnosis of a SMARCA4-deficient undifferentiated tumor. This effort also led to the identification of the developmental origin of this SMARCA4-deficient undifferentiated tumor as a non-invasive bladder cancer. We also carried out a detailed immune phenotypic assay on peripheral T cells. In brief, a phenotypic change of CD8+T cells from naive to terminally differentiated effector memory cells was observed.

CONCLUSION

Regardless of the organ of cancer origin or cancer type, SWI/SNF-deficient tumors should be suspected in undifferentiated and dedifferentiated tumors, and immune checkpoint inhibitors may be considered as a promising treatment option for this type of tumor. The pathogenesis of SMARCA4-deficient anaplastic tumors awaits further elucidation for therapeutic development.

Successful treatment with tislelizumab plus chemotherapy for SMARCA4-deficient undifferentiated tumor: a case report

SMARCA4-deficient undifferentiated tumor (SMARCA4-dUT) is a devastating subtype of thoracic tumor with SMARCA4 inactivation and is characterized by rapid progression, poor prognosis, and high risk of postoperative recurrence. However, effective treatments for SMARCA4-dUT are lacking. Herein, we describe a patient with SMARCA4-dUT who exhibited an impressive response to the anti-programmed cell death protein-1 (PD-1) antibody (tislelizumab) in combination with conventional chemotherapy (etoposide and cisplatin). To the best of our knowledge, this is the first case of SMARCA4-dUT treated with chemotherapy, comprising etoposide and cisplatin, combined with anti-PD-1 inhibitors. Immunotherapy combined with etoposide and cisplatin may be a promising strategy to treat SMARCA4-dUT.

Thoracic SMARCA4-deficient undifferentiated tumor: current knowledge and future perspectives

Thoracic SMARCA4-deficient undifferentiated tumor is a newly recognized disease entity characterized as a high-grade malignant neoplasm with an undifferentiated or rhabdoid phenotype. The tumor was initially identified as a subtype of thoracic sarcoma with SMARCA4 loss, but further investigation resulted in its classification as a subtype of epithelial malignancies in the current World Health Organization classification. SMARCA4-deficient undifferentiated tumor is highly aggressive and has a poor prognosis. Because of its rarity, an optimal treatment strategy has not yet been identified. In this review, we summarize the literature on SMARCA4-deficient undifferentiated tumor in terms of its clinical characteristics, diagnosis, treatment strategy and future perspectives.

Approaches for prevention of tumors in patients with rhabdoid tumor predisposition syndrome

Patients with rhabdoid tumor predisposition syndrome (RTPS) harbor germline alterations in the epigenetic regulator genes SMARCB1 or SMARCA4. Patients usually present with atypical teratoid/rhabdoid tumor (AT/RT) of the brain or malignant rhabdoid tumor (MRT) arising outside the central nervous system. Intensive treatment can lead to remissions, however tumors frequently recur or synchronous or metachronous tumors appear. A maintenance or secondary prevention regimen may prevent these aggressive tumors. Potential maintenance regimens may include low-dose traditional chemotherapy or different epigenetic therapies designed to target the epigenetic imbalance that drives RTs. We here review several potential maintenance regimens that may be useful in RTPS.

Current Molecular and Clinical Landscape of ATRT - The Link to Future Therapies

ATRT is a highly aggressive and rare pediatric CNS tumor of very young children. Its genetic hallmark is bi-allelic inactivation of SMARCB1 encoding INI1. Rarely SMARCA4 encoding BRG1 is affected. Up to 30% are associated with constitutional heterozygous pathogenic variants in one of the two genes, giving rise to the Rhabdoid-Tumor-Predisposition-Syndromes (RTPS) 1 and 2. Characteristic DNA methylation profiles distinguish ATRT from other SMARCB1-deficient entities. Three distinct subtypes ATRT-MYC, -TYR, and -SHH are on record. ATRT-SHH may be further divided into the subgroups ATRT-SHH1A, -SHH1B, and -SHH2. The cure of ATRT remains challenging, notwithstanding an increasing understanding of molecular pathomechanisms and genetic background. The implementation of multimodal institutional treatment protocols has improved prognosis. Regardless of treatment approaches, clinical risk factors such as age, metastases, and DNA methylation subtype affect survival probability. We provide a critical appraisal of current conventional multimodal regimens and emerging targeted treatment approaches investigated in clinical trials and entity-specific registries. Intense treatment approaches featuring radiotherapy (RT) and high-dose chemotherapy (HDCT) face the difficulty of balancing tumor control and treatment-related toxicity. Current approaches focus on minimizing radiation fields by proton beam therapy or to withhold RT in HDCT-only approaches. Still, a 40-75% relapse rate upon first-line treatment reveals the need for novel treatment strategies in primary and even more in recurrent/refractory (r/r) disease. Among targeted treatments, immune checkpoint inhibitors and epigenetically active agents appear most promising. Success remains limited in single agent approaches. We hypothesize that mechanism-informed combination therapy will enhance response, as the low mutational burden of ATRT may contribute to acquiring resistance to single targeted agents. As DNA methylation group-specific gene expression profiles appear to influence response to distinct agents, the future treatment of ATRT should respect clinical and biological heterogeneity in risk group adjusted treatment protocols.

Targeting EZH2 in SMARCB1-deficient sarcomas: Advances and opportunities to potentiate the efficacy of EZH2 inhibitors

Soft tissue sarcomas (STSs) are rare mesechymal malignancies characterized by distintive molecular, histological and clinical features. Many STSs are considered as predominatly epigenetic diseases due to underlying chromatin deregulation. Discovery of deregulated functional antagonism between the chromatin remodeling BRG1/BRM-associated (BAFs) and the histone modifying Polycomb repressor complexes (PRCs) has provided novel actionable targets. In epithelioid sarcoma (ES), extracranial, extrarenal malignant rhabdoid tumors (eMRTs) and synovial sarcoma (SS), the total or partial loss of the BAF core subunit SMARCB1, driven by different alterations, is associated with PRC2 deregulation and dependency on its enzymatic subunit, EZH2. In these SMARCB1-deficient STSs, aberrant EZH2 expression and/or activity emerged as a druggable vulnerability. Although preclinical investigation supported EZH2 targeting as a promising therapeutic option, clinical studies demonstrated a variable response to EZH2 inhibitors. Actually, whereas the clinical benefit recorded in ES patients prompted the FDA approval of the EZH2 inhibitor tazemetostat, the modest and sporadic responses observed in eMRT and SS patients highlighted the need to deepen mechanistic as well as pharmacological investigations to improve drug effectiveness. We summarize the current knowledge of different mechanisms driving SMARCB1 deficiency and EZH2 deregulation in ES, eMRT and SS along with preclinical and clinical studies of EZH2-targeting agents. Possible implication of the PRC2- and enzymatic-independent functions of EZH2 and of its homolog, EZH1, in the response to anti-EZH2 agents will be discussed together with combinatorial strategies under investigation to improve the efficacy of EZH2 targeting in these tumors.

Children's Oncology Group's 2023 blueprint for research: Developmental therapeutics

The Developmental Therapeutics Committee (DVL) identifies and develops new agents and treatment strategies for children/adolescents with cancer, through clinical and translational research. DVL has focused on evaluating the activity of targeted therapy and has evolved from trials with multiple histology strata to biomarker-selected phase 2 trials. These trials have included single-agent studies to evaluate agents such as cabozantinib in multi-disease cohorts, to trametinib, larotrectinib, and lorvotuzumab in disease-specific cohorts, as well as the pediatric Molecular Analysis for Therapy Choice (MATCH) study including multiple single agents targeted for biomarker-selected pediatric tumors. The ongoing vision and direction of DVL is to support the disease committees of COG to develop novel agents and combinations to advance the care of children with cancer.