Pediatric Rhabdomyosarcoma Research Articles

Abstract 2355: Intratumoral translocation positive heterogeneity in pediatric alveolar rhabdomyosarcoma tumors correlates to changes in genes predicted to inhibit the immunological response

Abstract Alveolar rhabdomyosarcoma (ARMS) is characterized by one of three translocation states: t(2;13)(q35;q14) producing PAX3-FOXO1, t(1;13)(p36;q14) producing PAX7-FOXO1, or translocation-negative. Tumors with t(2;13) are associated with greater disease severity and mortality than t(1;13) positive or translocation negative patients. We demonstrated that ARMS tumor samples contain intratumoral genetic heterogeneity with respect to the presence of t(2;13). Further, we demonstrated that this heterogeneity had an inverse correlation with tumor aggressiveness, with tumors containing higher translocation positivity having lower failure-free survival of patients. However, it is not yet known whether a correlation exists between percent t(2;13) positivity and changes in gene expression, in particular genes whose function contributes to immune invasion in the tumor microenvironment. Of fifty-five rhabdomyosarcoma patient tumor samples received from Children’s Hospital in New Orleans, nine were confirmed to contain t(2;13) ranging from 16 - 98% cells positive for the translocation. We used aged-matched normal muscle tissue derived from autopsies as a control. RNA was isolated from whole tissue samples and analyzed using the Nanostring nCounter®️ PanCancer IO 360™ Panel. This panel contains 770 genes that specifically analyze tumor immunogenicity, tumor sensitivity to immune attack, inhibitory immune mechanisms, stromal factors, inhibitory metabolism, anti-tumor immune activity, inhibitory immune signaling, immune cell population and abundance, and tumor inflammation. We found 487 genes have an average change in expression ≥ 1.5-fold relative to the control. Of these genes 31 (6.4%) have a statistically significant positive correlation and nearly 25% (114 genes) had a statistically significant negative correlation to percent intratumoral translocation positivity. A closer examination indicated that genes with a negative correlation had biological functions that target a variety of different immunological processes. These include the recognition of antigen by T cells; the activation, maturation, and differentiation of lymphocytes and myeloid cells; adhesion of immune responsive cells; promotion of the inflammatory response; and activation of the innate immune response. These results suggest that increased intratumoral t(2;13) positivity negatively impacts the immunological response thereby increasing the ability for immune evasion of the tumors with higher levels of the translocation, a result consistent with our previously published work. Citation Format: Andrew D. Hollenbach, Matthew Stark, Jovanny Zabaleta, Fern Tsien. Intratumoral translocation positive heterogeneity in pediatric alveolar rhabdomyosarcoma tumors correlates to changes in genes predicted to inhibit the immunological response [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 2355.

Abstract 5429: Therapeutic targeting of oncogenic long non-coding RNAs utilizing antisense oligonucleotides

Abstract Non-coding RNAs (ncRNAs) are emerging as potent regulators of biological process including human diseases such as cancer. Long non-coding RNAs (lncRNAs) are a dynamic and versatile class of ncRNAs for which there is extensive evidence of these transcripts modulating epigenetic programs to affect cellular phenotypes. Our initial studies using a model of glioblastoma (GBM) tumor recurrence has revealed a number of oncogenic lncRNAs associated with therapy resistance and/or tumor recurrence. We have validated the expression of these oncogenic lncRNAs in another cancer, pediatric rhabdomyosarcoma (RMS). There have been few effective therapeutic advances made in past decades for either RMS or GBM. Radiation therapy is commonly employed alongside surgery and standard chemotherapy, especially in the case of unresectable disease, advanced disease, or upon tumor recurrence. Tumors may inherently possess or acquire resistance to radiation therapy and other treatment modalities over the course of disease. Tumor therapy resistance and recurrence are mediated by complex epigenetic programs which lead to increased capacity for DNA damage repair or tolerance of double stranded breaks. LncRNAs may regulate mechanisms of tumor recurrence and therapy resistance across multiple cancer types. The functional roles of ZFAS1 modulating epithelial to mesenchymal transition in colon cancers and SAMMSON which drives aberrant mitochondrial function in melanoma have been described. CASC19/PCAT2, ZFAS1, DUXAP9, and SOX2-OT are overexpressed in multiple cancers with CASC19 having a significant negative association with GBM patient survival. In silico analysis identifies DNA-binding capacities harbored by these lncRNA transcripts, and their predicted binding sites are proximal to several cancer hallmark genes. We have verified the expression of isoforms of these lncRNA transcripts that contain DNA-binding domains through sequencing and qPCR. We hypothesize that these lncRNAs regulate transcriptional networks via recruitment of transcriptional or epigenetic machinery to genomic loci to modulate oncogenic programs and/or tumor suppressor pathways. As potent epigenetic regulators, lncRNAs present an attractive class of therapeutic targets that could complement standard treatments to reduce disease burden and improve patient survival. It is possible that acquired radiation resistance mediated by lncRNAs is conserved across multiple malignancies. We are developing chemically modified, novel antisense oligonucleotides to target these transcripts in GBM and RMS patient-derived xenografts. Using these systems, we hope to reveal novel associations with disease progression and oncogenic mechanisms that could be exploited through the direct targeting of lncRNAs. We hope our work will lead to the development of novel clinical agents to treat patients with RMS, GBM, and potentially other intractable cancers. Citation Format: Christian Tyler Stackhouse, Corinne Linardic, Malaika Kimmons, Samantha Weitzel. Therapeutic targeting of oncogenic long non-coding RNAs utilizing antisense oligonucleotides [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 5429.

Abstract 2503: Identification of clinically relevant gene fusions in archived pediatric solid and liquid tumor samples using Arima-HiC sequencing

Abstract Gene fusions are known to have oncogenic effects in various cancers and serve as disease biomarkers. Obtaining gene-level resolution of these large structural variants is not possible with lower resolution karyotyping approaches and can be challenging using RNA sequencing approaches due to low transcript abundance or low-quality RNA. Furthermore, the ability of fluorescence in situ hybridization (FISH) techniques to detect fusions is limited by the targeted nature of these assays and subject to which probes were run. Here, we used a novel method, Arima-HiC sequencing, on 6 archived pediatric cancer samples to determine the technique’s effectiveness in detecting gene fusions. We first adapted the Arima Hi-C method for use with formalin-fixed paraffin-embedded (FFPE) tissue. We then selected four archived pediatric alveolar rhabdomyosarcoma (ARMS) tumors (FFPE archival period range: 8-12 years)—known to be fusion-positive via prior clinical testing—for Arima-HiC sequencing. Briefly, FFPE tissue scrolls were dewaxed, and the tissue rehydrated; it then underwent chromatin digestion, end-labeling, and proximity ligation prior to DNA purification per the Arima-HiC FFPE protocol. Purified DNA was next prepared as a short-read sequencing library and sequenced on a HiSeq 2500. The raw reads were aligned and deduplicated, and structural variants were called using the HiC-Breakfinder software. We additionally selected 2 non-FFPE cases, both pediatric leukemia cases with cryopreserved blasts (archival period range: 1-3 years), for Arima-HiC sequencing (as above). These cases had undergone standard of care cytogenetic (karyotyping, FISH) and molecular (targeted cancer NGS sequencing panel) testing clinically and a genetic driver/known gene fusion had not been identified. Using Arima-HiC sequencing, we identified either a PAX3-FOXO1 (n=2) or PAX7-FOXO1 (n=2) gene fusion in each of our 4 ARMS cases, consistent with the original diagnostic cytogenetic finding. HiC data was additionally able to provide partner gene information (PAX3 or PAX7) in 2 of the 4 cases where this was unknown. We also test two cases of leukemia, one, a case of precursor B-cell acute lymphoblastic leukemia (B-ALL) in a 3-year-old male, and the other, a case of acute myeloid leukemia (AML) in a 2-year-old female. In the first case, we detected an EP300-ZNF384 gene fusion, which is a known, but rare, gene fusion seen in B-ALL. This finding is clinically relevant as ZNF384 fusions are associated with a more favorable prognosis. In the second case, we detected a SCN4B-MLLT10 gene fusion. This finding is also clinically relevant as MLLT10 fusions are rare in AML but indicate an unfavorable prognosis. In summary, this study demonstrates how Arima-HiC sequencing provides molecular diagnostic value in archived pediatric solid and liquid tumor specimens via the identification of clinically relevant gene fusions. Citation Format: Midhat S. Farooqi, Kristin Sikkink, Derek Reid, Tomi Pastinen, Anthony Schmitt, Atif Ahmed. Identification of clinically relevant gene fusions in archived pediatric solid and liquid tumor samples using Arima-HiC sequencing [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 2503.

Abstract 683: Identification of common germline variants associated with pediatric rhabdomyosarcoma survival: A report from the Children's Oncology Group (COG)

Abstract Background: Rhabdomyosarcoma (RMS) is the most common soft tissue sarcoma in children and has one of the poorest survival rates among pediatric cancers, underscoring the need to identify factors which may be leveraged to improve therapeutic options for these individuals. Methods: We carried out a genome-wide association study of overall survival (OS) and event-free survival (EFS) in 920 RMS patients from COG protocols and randomly divided them into discovery (n=642) and replication (n=278) cohorts. Genotyping was conducted using the Illumina OmniExpress or Global Screening Array and imputed using the Haplotype Reference Consortium. We used Cox proportional hazards regression to calculate an adjusted hazard ratio (aHR) and P value for each common variant (minor allele frequency [MAF]>5%) for OS and EFS while adjusting for age at diagnosis, tumor stage, histological subtype, and the top five principal components. Analyses were also conducted by histological subtype: embryonal RMS (ERMS, n=544) and alveolar RMS (ARMS, n=268). Finally, we performed a meta-analysis of the results from the discovery and replication cohorts to generate a summary aHR and P value for each single nucleotide polymorphism (SNP). Results: We identified an intergenic SNP at chr8q21.13 associated with worse RMS EFS across subtypes (aHR=2.08, P=2.80x10-9), which had consistent effects across the discovery (aHR=1.91, P=5.05x10-6) and replication (aHR=2.62, P=7.16x10-5) cohorts. This SNP lies in a region which spans the genomic binding site for GATA2 and GATA3, transcription factors that are recognized to contribute to cancer development. We also identified a significant association between a SNP at chr12q21.1 and worse EFS (aHR=2.04, P=3.35x10-8) with consistent effects across the discovery and replication cohorts. Based on data from the Genotype-Tissue Expression project (GTEx), this SNP is associated with expression of SLCO1B1, a gene which encodes a liver anion transporter linked to RMS treatment-related toxicities. In subtype-specific analyses, we identified a SNP at chr17q21.32 that was significantly associated with worse ARMS OS (129 events; aHR=3.18, P=3.12x10-8; discovery: aHR=3.19, P=6.23x10-4; replication: aHR=3.16, P=1.43x10-3). In GTEx, this SNP is associated with expression and splicing of genes including PITPNM3, KIAA0753, and MED31 across various tissues. No SNPs were significantly associated with ERMS OS or EFS. Conclusion: In the first GWAS of RMS survival outcomes, we identified two SNPs that were significantly associated with worse EFS across RMS subtypes. Further, we identified a SNP that was associated with OS in ARMS patients, a subtype that is associated with worse outcomes. Additional investigation of the impact of these SNPs may further support their consideration for novel risk stratification protocols. Citation Format: Bailey A. Martin-Giacalone, Michael E. Scheurer, Javed Khan, Stephen J. Chanock, Shengchao Alfred Li, Meredith Yeager, Deborah A. Marquez-Do, Donald A. Barkauskas, David Hall, Matthew T. McEvoy, Melissa A. Richard, Pagna Sok, Austin L. Brown, Aniko Sabo, Stephen X. Skapek, Douglas S. Hawkins, Rajkumar Venkatramani, Lisa Mirabello, Philip J. Lupo. Identification of common germline variants associated with pediatric rhabdomyosarcoma survival: A report from the Children's Oncology Group (COG) [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 683.

Abstract 1679: Single-cell profiling reveals a conserved myogenic hierarchy in pediatric rhabdomyosarcomas amenable to differentiation therapy

Abstract Rhabdomyosarcoma (RMS) is a highly aggressive pediatric soft tissue cancer, associated with the skeletal muscle lineage. Despite undoubted expression of key myogenic regulatory factors, RMS cells are blocked in a proliferative state and do not complete terminal differentiation. The extent to which the skeletal muscle lineage is represented in RMS tumors, as well as the mechanisms leading to developmental arrest, remain elusive. We therefore aimed to identify RMS subpopulations, understand why RMS cells are stalled in their differentiation path, and determine mechanisms to pharmacologically restore myogenic differentiation. Using single-cell RNA sequencing and mass cytometry analysis, we profiled cells from 14 PDX-derived primary cultures and three cell lines of alveolar (aRMS) and embryonal RMS (eRMS) subtypes. We discovered that both RMS subtypes contain different cell subpopulations distributed along the myogenic lineage. aRMS tumors recapitulate a yet unrecognized branched myogenic trajectory, where progenitor cells either commit to differentiation or give rise to actively cycling myoblasts. Following in vitro exposure to chemotherapy, aRMS cells show compositional shifts towards undifferentiated states, consistent with a model where treatment rewires cellular trajectories. To quantify aRMS cellular states, we developed an automated image-based single-cell approach and applied it to identify pro-differentiating agents among a library of >240 FDA-approved drugs. We identified the RAS pathway as an important mediator of myogenic differentiation in several aRMS cultures, demonstrating the potential for differentiation therapy. Current studies are ongoing to validate these results in vivo and to uncover drug combinations that completely overcome the differentiation block. Taken together, this study reveals possible cellular origins for RMS and identifies a potential novel treatment strategy for aRMS that targets cellular differentiation. Citation Format: Sara G. Danielli, Ermelinda Porpiglia, Andrea J. De Micheli, Ingrid Bechtold, Joana G. Marques, Stephanie Kasper, Helen M. Blau, Marco Wachtel, Beat W. Schäfer. Single-cell profiling reveals a conserved myogenic hierarchy in pediatric rhabdomyosarcomas amenable to differentiation therapy [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 1679.

Case - Salvage nerve-sparing radical cystectomy for pediatric rhabdomyosarcoma of the bladder.

Case - Salvage nerve-sparing radical cystectomy for pediatric rhabdomyosarcoma of the bladder.

Adolescents and young adults with rhabdomyosarcoma treated in the European paediatric Soft tissue sarcoma Study Group (EpSSG) protocols: a cohort study

Adolescent and young adult patients with rhabdomyosarcoma often have poorer outcomes than do children. We aimed to compare the findings of adolescent and young adult patients with children enrolled in two prospective clinical protocols. This retrospective observational analysis was based on data from the European paediatric Soft tissue sarcoma Study Group (EpSSG) rhabdomyosarcoma 2005 trial (phase 3 randomised trial for localised rhabdomyosarcoma, open from April, 2006, to December, 2016) and the EpSSG MTS 2008 protocol (prospective, observational, single-arm study for metastatic rhabdomyosarcoma, open from June, 2010, to December, 2016), which involved 108 centres from 14 different countries in total. For this analysis, patients were categorised according to their age into children (age 0-14 years) and adolescents and young adults (age 15-21 years). For the analysis of adherence to treatment and toxicity, only patients with high-risk localised rhabdomyosarcoma included in the randomised part of the rhabdomyosarcoma 2005 study were considered. The primary outcome of event-free survival (assessed in all participants) was defined as the time from diagnosis to the first event (eg, tumour progression, relapse) or to the latest follow-up. Secondary outcomes were overall survival, response to chemotherapy, and toxicity. Our analysis included 1977 patients, 1720 children (median age 4·7 years; IQR 2·6-8·4) and 257 adolescents and young adults (16·6 years; 15·8-18·0). 1719 patients were from the EpSSG rhabdomyosarcoma 2005 study (1523 aged <15 years and 196 aged 15-21 years) and 258 patients were from the EPSSG MTS 2008 study (197 aged <15 years and 61 aged 15-21 years). Adolescent and young adult patients were more likely than were children to have metastatic tumours (61 [23·7%] of 257 vs 197 [11·5%] of 1720; p<0·0001), unfavourable histological subtypes (119 [46·3%] vs 451 [26·2%]; p<0·0001), tumours larger than 5 cm (177 [68·9%] vs 891 [51·8%]; p<0·0001), and regional lymph node involvement (109 [42·4%] vs 339 [19·7%]; p<0·0001). Adolescent and young adult patients had lower 5-year event-free survival (52·6% [95% CI 46·3-58·6] vs 67·8% [65·5-70·0]; p<0·0001) and lower 5-year overall survival (57·1% [50·4-63·1] vs 77·9% [75·8-79·8]; p<0·0001) than did children. The multivariable analysis confirmed the inferior prognosis of patients aged 15-21 years (hazard ratios 1·48 [95% CI 1·20-1·83; p=0·0002] for poorer event-free survival and 1·73 [1·37-2·19; p<0·0001] for poorer overall survival). Modifications of administered chemotherapy occurred in 13 (15·3%) of 85 adolescents and young adults, and in 161 (21·4%) of 754 children. Grade 3-4 haematological toxicity and infection were observed more frequently in children than in adolescent and young adult patients. This study found better outcomes for adolescent and young adult patients than those reported in epidemiological studies (eg, the EUROCARE-5 study reported 5-year overall survival of 39·6% for patients aged 15-19 years in the 2000-07 study period), suggesting that adolescent and young adult patients, at least up to age 21 years, can be treated with intensive paediatric therapies with no major tolerability issues and should be included in paediatric rhabdomyosarcoma trials. However, the inferior outcomes in adolescent and young adult patients compared with those in children, despite receiving similar therapy, suggest that a tailored and intensive treatment strategy might be warranted for these patients. Fondazione Città della Speranza.

The future of rhabdomyosarcoma trials

Rhabdomyosarcoma is a rare tumour but the most frequent soft tissue sarcoma in the first two decades of life. Major progress in survival has been achieved by multicentre international cooperative studies with multimodal treatment.1 Over the past 30 years, survival has improved for patients with localised disease and now exceeds 70%. Many prognostic factors (eg, histological subtype, tumour site and size, and age) have been defined and included in risk-adapted stratification systems.2 Age as a risk group was divided between 10 years or younger versus older than 10 years in all past paediatric rhabdomyosarcoma trials and protocols.

Evaluating the effects of critical metabolite depletion in pediatric rhabdomyosarcoma (RMS) using a novel inhibitor of nicotinamide phosphoribosyltransferase (NAMPT).

e22004 Background: RMS is the most common pediatric cancer of the soft tissues. Patients who present with metastatic disease or experience recurrence have a poor prognosis; survivors often suffer from long-term systemic effects resulting from cytotoxic chemotherapy. Thus, novel therapies are needed. NAMPT inhibitors are a class of drugs targeting a key metabolic enzyme in the production of NAD+, a coenzyme critical to energy generation in some cancer cells. In this study, we evaluated the mechanism and functional outcomes of treatment with the clinical NAMPT inhibitor, OT-82, in preclinical models of RMS. Methods: Live cell analysis via IncuCyte was used to determine the temporal effects of OT-82 on cell growth in a diverse panel of ten fusion positive and negative RMS cell lines. Analysis of the proposed mechanism of action was performed using NAD/NADH detection assays and rescue experiments with nicotinamide mononucleotide (NMN), the product of NAMPT. Markers of cellular apoptosis and necrosis were quantified with flow cytometric assays. Specific metabolic effects of OT-82 were determined with ATP quantification and real-time extracellular flux analysis of oxidative phosphorylation and glycolysis. In vivo studies were performed in orthotopic RMS models. Tumor dimensions were measured with calipers, and toxicity was assessed by observation and body weight measurement. Results: Treatment of RMS cell lines with OT-82 dosed in the low nanomolar range resulted in time- and dose-dependent decreases in NAD+ levels and proliferation in all cell lines tested. Addition of NMN rescued cell growth, confirming the on-target activity and functional effect of OT-82. Flow cytometric assays revealed cell-line dependent differences in cell fates, with a subset of cell lines staining positive for markers of necrosis, and the other subset staining negative for markers of necrosis and apoptosis. Functional investigation verified that necrotic cell lines did not regrow after withdrawal of OT-82 in culture (durable responders), whereas non-necrotic cell lines recovered growth (transient responders). Additionally, ATP levels in durable responders decreased with OT-82 treatment but remained stable in transient responders. Extracellular flux analysis revealed that both durable and transient responders experienced inhibition of glycolysis, but that oxidative phosphorylation was only reduced in the durable responders. In vivo studies using OT-82 on a clinically-relevant schedule demonstrated that all RMS xenografts underwent complete tumor regression, with durable responder models experiencing a longer tumor-free period following discontinuation of treatment. Conclusions: In vitro and in vivo efficacy of OT-82 suggest that targeting NAD+ metabolism through NAMPT inhibition may be a promising approach for the treatment of RMS.

Racial and ethnic differences in presentation and clinical outcomes for pediatric rhabdomyosarcoma (RMS).

10017 Background: Race and ethnicity are recognized risk factors for many cancer types, including several pediatric cancers. Though racial and ethnic disparities in the presentation, treatment, and survival of certain cancers have been widely demonstrated, there is conflicting evidence about whether such disparities exist in RMS, the most common pediatric soft tissue sarcoma. Understanding the role of race and ethnicity in the presentation, treatment, and prognosis of RMS is important to promote improved survival in patients of all racial and ethnic groups. Methods: Patient, tumor, and treatment characteristics of patients enrolled on Children’s Oncology Group studies D9602, D9802, D9803, ARST0331, ARST0431, ARST0531, and ARST08P1 were compared across racial and ethnic groups using a chi-square test. Significant characteristics underwent pairwise analysis, comparing the Non-Hispanic Black (NHB) and Non-Hispanic White (NHW) groups. Outcome analyses were performed using the Kaplan-Meier method and Wilcoxon signed-rank test. Results: Race and ethnicity incidence among the 2157 study patients were as follows: 8 (0.4%) American Indian or Alaska Native, 56 (2.6%) Asian, 271 (12.6%) Hispanic, 4 (0.2%) Native American or other Pacific Islander, 275 (12.8%) Non-Hispanic Black, 1335 (61.9%) Non-Hispanic White, and 208 (9.6%) unknown. Thirteen patient and tumor factors relating to presentation and treatment were evaluated for differences by race and ethnicity; the following five were significant: age, IRS group, tumor invasiveness, metastatic disease, and FOXO1 fusion partner. Pairwise comparison of NHB and NHW patients for these factors demonstrated that NHBs are more likely than NHWs to present at age 10 years or greater (p = 0.002) and that NHB patients are more likely to present with invasive tumors (p = 0.012). Incidence of metastatic disease at diagnosis was not significantly different between the groups (p = 0.202). No differences in treatment, including extent of surgical resection (p = 0.259) or use of radiation therapy (p = 0.920), were found. Neither event free survival nor overall survival were significantly different across the entire cohort (EFS p = 0.457, OS p = 0.159) or in subset analysis by risk group (low risk: EFS p = 0.856, OS p = 0.558; intermediate risk: EFS p = 0.907, OS p = 0.493; high risk: EFS p = 0.218, OS p = 0.397), by age (&lt; 1y: EFS p = 0.489, OS p = 0.546; 1-9y: EFS p = 0.417, OS p = 0.112; ≥10y: EFS p = 0.556, OS p = 0.609), in invasive tumors (EFS p = 0.704, OS p = 0.872), or in metastatic disease (EFS p = 0.270, OS p = 0.373). Conclusions: These data indicate that while differences in the presenting features of RMS exist between racial groups, with NHB patients exhibiting higher risk features, patients treated on these clinical trials did not experience differences in outcomes by racial group. This suggests NHB patients may experience a survival benefit from clinical trial enrollment.

Efficacy and prognostic analysis of 125I brathytherapy combined with chemotherapy for pediatric parameningeal rhabdomyosarcoma

Objective: To analyze the efficacy and prognostic factors in children with parameningeal rhabdomyosarcoma (PMRMS) treated by 125I brachytherapy combined with chemotherapy. Methods: A retrospective analysis of the clinical data of 33 pediatric patients treated with 125I brachytherapy combined with chemotherapy in Peking University Stomatological Hospital from July 2013 to October 2018 was carried out to analyze the efficacy and prognostic factors. Results: Among the 33 patients, 19 were males and 14 were females; the median age was 4 years old (1-12 years old). There were 17 cases with embryonic type, 9 cases with alveolar type, and 7 with undifferentiated type; 26 cases with original PMRMS, and 7 cases with recurrent PMRMS. The tumors occurred in subtemporal-mastoid area in 15 patients, while nasopalatine-paranasal area in 6 cases, and parapharyngeal-submandibular area in 12 cases. There were 28 patients in IRS Ⅲ, and 5 patients in IRS Ⅳ. As for the risk level, 28 cases were in the middle-risk group and 5 cases in the high-risk group. The median follow-up time was 52 months. The 1, 3, and 5-year local control rates were 87.9%, 58.6%, and 49.9%, and the 1, 3, and 5-year survival rates were 93.8%, 60.5%, and 47.5%, respectively. The 5-year local control rate and 5-year survival rate of 12 patients with the tumor in the parapharyngeal-submandibular area were 91.7% and 100%, respectively. The 5-year local control rate and 5-year survival rate of the 6 patients with tumor in the nasopalatine-paranasal area were both 83.3%. The 3-year local control rate and 3-year survival rate of the 15 patients with tumor in the subtemporal-mastoid area were 17.5% and 21.4%. The multivariate survival analysis using Cox proportional risk regression model showed that the tumor located in the subtemporal-mastoid area was an independent risk factor affecting the 5-year overall survival rate (HR=38.40, 95%CI: 4.87-302.52, P=0.001). Within 3 months after 125I seed implantation, the incidence of acute radiotherapy adverse reactions in all patients was 84.8% (28/33). Twenty-one patients (63.6%) had a grade 1 acute radiotherapy reaction, and 7 cases (21.2%) had a grade 2 acute radiotherapy reaction. No acute radiotherapy adverse reactions of grade 3 or 4 occurred. Three months after 125I seed implantation, the adverse reactions were significantly alleviated, and no adverse reactions of grade 3 or above such as skin ulcer or salivary gland fibrosis occurred, and no serious cranio-maxillofacial deformities occurred. Conclusions: 125I seed brachytherapy combined with chemotherapy has a definite clinical effect in the treatment of children with parameningeal rhabdomyosarcoma. The prognosis of rhabdomyosarcoma in the parapharyngeal-submandibular area and nasopalatine-paranasal area is better than that in the subtemporal-mastoid area.

A Web-Based Prognostic Model for Pediatric Genitourinary Rhabdomyosarcoma: Analysis of Population-Based Cohort With External Validation.

BackgroundWe conduct an analysis of data from the Surveillance, Epidemiology, and End Results (SEER) database, intending to identify prognostic factors of pediatric genitourinary rhabdomyosarcoma (PGU–RMS). Prognostic nomogram and web-based calculator were developed for potential clinical use.MethodsData of PGU–RMS patients were extracted from the SEER database as training and internal validation cohort, patients diagnosed as PGU–RMS from 2001 to 2015 in Beijing Children's Hospital were collected as an external validation cohort. We used log-rank tests to seek risk factors on the overall survival (OS) in the overall SEER cohort, tumor site subgroups, radiation subgroups, and metastasis subgroups. The univariable and multivariate Cox regression analyses were applied to establish the prognosis model.ResultsA total of 372 PGU-RMS patients in SEER and 84 patients from our center were included. 1-, 3-, and 5-year OS of the overall SEER cohort were 95.8, 82.1, and 78.8%. Subgroup analysis indicated that tumors located in the prostate/bladder were associated with a worse prognosis than the paratesticular, female genital system, and other sites (P < 0.001). Tumors of the T1/T2 stage, without regional lymph node, involvement or metastasis, can benefit from radiotherapy (P < 0.05). For patients without metastasis, younger age, T1/T2 stage, and undergoing radiation were associated with better prognosis (P < 0.05). The prognosis nomogram was well-calibrated, the concordance index (C-index) for the OS prediction was 0.823, 0.803, and 0.768 in training, internal and external validation cohort, the area under the receiver operating characteristic curve for 3-, and 5-year OS were 0.84, 0.84 in the training cohort, 0.90, 0.84 in internal validation cohort and 0.75, 0.80 in the external validation cohort. Decision curve analysis showed good clinical utility. The predictive performance of the nomogram was higher than the Intergroup Rhabdomyosarcoma Study Group (IRSG) pretreatment stage system based on the comparison of overtime C-index, net reclassification index, and integrated discriminatory index (P < 0.001).ConclusionA comprehensive analysis of OS for PGU–RMS patients was conducted based on population cohort. The established prognosis nomogram has been fully validated and evaluated, exhibits better performance than the IRSG pretreatment stage system. Furthermore, a web-based risk calculator was developed to optimize clinical decisions.

An unusual case of pediatric embryonal rhabdomyosarcoma with subsequent diagnosis of neurofibromatosis type 1

A 10-month-old girl presented with a 4-month history of a rapidly growing lesion on the lower lip. Initial assessment and Doppler ultrasound supported a diagnosis of pyogenic granuloma. However, emergent biopsy revealed an embryonal rhabdomyosarcoma, a highly malignant tumor commonly associated with cancer-susceptible syndromes including neurofibromatosis type 1 (NF1). Despite having no apparent clinical features of NF1 at initial presentation, she was later found to have multiple café-au-lait spots and a subsequent diagnosis of NF1 was made.

Optimizing Rhabdomyosarcoma Treatment in Adolescents and Young Adults.

Simple SummaryDue to their rarity, we still know comparatively little about rhabdomyosarcomas (RMS) in adolescents and young adults (AYA). Factors responsible for the significantly poor outcomes in AYA-RMS are tumor biology, physiological factors specific to the age group concerned, refractoriness to multimodal treatments, and various psychosocial and medical care issues. The present review aims to examine these issues and offers possible solutions based on integrating new developments and findings with older, fundamental evidence regarding pediatric RMS.Rhabdomyosarcoma (RMS) is the most common form of soft tissue sarcoma in children, but can also develop in adolescents and young adults (AYA). The mainstay of treatment is multi-agent chemotherapy, ideally with concomitant local treatment, including surgical resection and/or radiation therapy. Although most treatment decisions for RMS in AYA are based on scientific evidence accumulated through clinical studies of pediatric RMS, treatment outcomes are significantly inferior in AYA patients than in children. Factors responsible for the significantly poor outcomes in AYA are tumor biology, the physiology specific to the age group concerned, refractoriness to multimodal treatments, and various psychosocial and medical care issues. The present review aims to examine the various issues involved in the treatment and care of AYA patients with RMS, discuss possible solutions, and provide an overview of the literature on the topic with several observations from the author’s own experience. Clinical trials for RMS in AYA are the best way to develop an optimal treatment. However, a well-designed clinical trial requires a great deal of time and resources, especially when targeting such a rare population. Until clinical trials are designed and implemented, and their findings duly analyzed, we must provide the best possible practice for RMS treatment in AYA patients based on our own expertise in manipulating the dosage schedules of various chemotherapeutic agents and administering local treatments in a manner appropriate for each patient. Precision medicine based on state-of-the-art cancer genomics will also form an integral part of this personalized approach. In the current situation, the only way to realize such a holistic treatment approach is to integrate new developments and findings, such as gene-based diagnostics and treatments, with older, fundamental evidence that can be selectively applied to individual cases.

The myogenesis program drives clonal selection and drug resistance in rhabdomyosarcoma.

Rhabdomyosarcoma (RMS) is a pediatric cancer with features of skeletal muscle; patients with unresectable or metastatic RMS fare poorly due to high rates of disease recurrence. Here, we use single-cell and single-nucleus RNA sequencing to show that RMS tumors recapitulate the spectrum of embryonal myogenesis. Using matched patient samples from a clinical trial and orthotopic patient-derived xenografts (O-PDXs), we show that chemotherapy eliminates the most proliferative component with features of myoblasts within embryonal RMS; after treatment, the immature population with features of paraxial mesoderm expands to reconstitute the developmental hierarchy of the original tumor. We discovered that this paraxial mesoderm population is dependent on EGFR signaling and is sensitive to EGFR inhibitors. Taken together, these data serve as a proof of concept that targeting each developmental state in embryonal RMS is an effective strategy for improving outcomes by preventing disease recurrence.

A rare case of paediatric oral rhabdomyosarcoma presenting with respiratory distress.

A rare case of paediatric oral rhabdomyosarcoma presenting with respiratory distress.

Clinical significance of circulating tumor cells and cell-free DNA in pediatric rhabdomyosarcoma.

Liquid biopsy analysis represents a powerful and noninvasive tool to uncover biomarkers for disseminated disease assessment and longitudinal monitoring of patients. Herein, we explored the value of circulating and disseminated tumor cells (CTC and DTC, respectively) and cell‐free DNA (cfDNA) in pediatric rhabdomyosarcoma (RMS). Peripheral blood and bone marrow samples were analyzed to detect and enumerate CTC and DTC, respectively. We used the epithelial cellular adhesion molecule (EpCAM)‐based CellSearch platform coupled with an automatic device to collect both EpCAM‐positive and EpCAM‐low/negative CTCs. The standard assay was implemented, including the mesenchymal marker desmin. For selected cases, we molecularly profiled primary tumors and liquid biopsy biomarkers using whole‐exome sequencing and droplet digital PCR, respectively. RMS patients with metastatic disease had a significantly higher number of CTCs compared to those with localized disease, whereas DTCs were detected independently of disease presentation. The use of the desmin marker remarkably increased the identification of CTCs and DTCs in RMS samples. Of note, CTC clusters were detected in RMS patients with disseminated disease. Further, cfDNA and CTC molecular features closely reflected the molecular makeup of primary tumors and informed of disease course.

D,L-Methadone enhances the cytotoxic activity of standard chemotherapeutic agents on pediatric rhabdomyosarcoma

PurposeIn advanced tumor stages, pediatric rhabdomyosarcoma (RMS) shows an intrinsic resistance to standard chemotherapy, which is associated with a dismal prognosis. Alternative therapeutic approaches and optimization of already existent treatment protocols are urgently needed in these conditions. The µ-opioid receptor (OPRM1) agonist, D,L-methadone is frequently used for analgesia in oncological patients. Recent evidence has shown that D,L-methadone in combination with chemotherapeutic agents may enhance their cytotoxic effect against cancer cells. There are no related data in pediatric rhabdomyosarcoma (RMS).MethodsAntitumor effects of combined D,L-methadone and doxorubicin, carboplatin, and vincristine on RMS cell lines RD and RH30 were analyzed using following outcome data: expression of the OPRM1 receptor (Western blot), cell growth inhibition (MTT assay), cell migration (wound-healing assay), apoptosis induction (caspase-3/7 assay), and reactive oxygen species (ROS) production (flow cytometry).ResultsIn both cell lines, OPRM1 expression was significantly increased after combined treatment of D,L-methadone with all three cytotoxic drugs tested, which resulted in suppression of tumor cell growth and increase of apoptosis rates. These effects were mediated by increased ROS production and up-regulation of caspase-3/7 activity. Doxorubicin combined with D,L-methadone significantly reduced cell migration in both cell lines. Carboplatin or vincristine in combination with D,L-methadone had only an impact on cell migration in RH30 cells.ConclusionsThis new therapeutic approach in RMS provides strong antitumor effects in vitro. The combination of standard chemotherapy and D,L-methadone requires further investigation. Especially advanced tumors with a limited effectiveness of conventional treatment regimens seem a potential target of this approach.

Locoregional Control and Survival in Children, Adolescents, and Young Adults With Localized Head and Neck Alveolar Rhabdomyosarcoma-The French Experience.

IntroductionThe head and neck (HN) are the most frequent sites of pediatric rhabdomyosarcoma (RMS). Alveolar RMS (ARMS) represents ~20% of all RMS cases and frequently spread to lymph nodes (LNs). The aim was to report locoregional control, event-free survival (EFS), and overall survival (OS), according to clinical and pathological features, LN staging, and treatment modalities.MethodsThe study included all patients prospectively enrolled in EpSSG RMS 2005 study under 21 years of age with localized HN ARMS and diagnosed between 2005 and 2016 in France. Medical data including imaging, surgical report, and radiation therapy planes were analyzed.ResultsForty-eight patients (median age 6 years; range 4 months−21 years), corresponding to 30 parameningeal and 18 non-parameningeal ARMS, were included. There were 33 boys (69%). Tumor locations included the following: orbit (n = 7) among which four cases had bone erosion, paranasal sinuses and nasal cavity (n = 16), deep facial spaces (n = 10), nasolabial fold (n = 8), and other non-parameningeal HN sites (n = 7). A fusion transcript of PAX3-FOXO1 or PAX7-FOXO1 was expressed in 33 of the 45 cases (73%) with molecular analysis. At diagnosis, 10 patients had primary resection of the primary tumor (PRPT) (none with microscopic complete resection) and 9 had LN staging. After induction chemotherapy, 26 patients (54%) had secondary resection of the primary tumor (SRPT) and 13 patients (27%) had cervical LN dissection. A total of 43 patients (90%) were treated with radiation therapy.With a median follow-up of 7 years (range 2–13 years), 5-year OS and EFS were 78% (95% CI, 63–88%) and 66% (95% CI, 51–78%), respectively. We observed 16 events (10 deaths): 4 local, 4 regional, 1 local and regional, and 7 metastatic. In univariate analysis, OS was only superior for patients under 10 years of age (p = 0.002), while FOXO1-negative ARMS, SRPT for parameningeal ARMS, and LN surgery were associated with significantly better EFS.ConclusionOur study confirms a better outcome for fusion-negative ARMS and ARMS in children under 10 years. Moreover, LN surgery and SRPT of parameningeal tumor may improve EFS of ARMS. Larger studies are needed to confirm our findings.

Anaplasia in childhood rhabdomyosarcoma: An under reported entity.

Rhabdomyosarcoma (RMS) is the most common soft tissue sarcoma in children. Anaplasia is a rare phenomenon seen in childhood RMS. The most common histologic subtype was Embryonal followed by Alveolar and spindle subtype. A total of 11 cases of pediatric RMS were selected from January 2017 to June 2019 presenting at various sites. Out of 11 cases, 2 were further diagnosed as Embryonal, 2 as Alveolar, 2 as Pleomorphic, 1 as Spindle subtype and rest 4 as RMS-NOS based on morphology. All cases were positive for Desmin. The presence of cells with lobated, hyperchromatic nuclei at least three times larger than the tumor cell (anaplastic cells) was selected as the main criterion to diagnose Anaplasia. Out of the total 11 cases, anaplasia was seen in 7 cases. Out of these seven, five cases showed Focal Anaplasia (FA) (71.4%) and 2 cases showed Diffuse Anaplasia (DA) (28.6%). Out of 2 cases of Embryonal RMS one exhibited focal anaplasia (50%). One case of Spindle RMS showed diffuse anaplasia, 2 cases of pleomorphic RMS showed focal anaplasia. Out of 3 cases of RMS- NOS, 2 exhibited focal anaplaisa and one displayed Diffuse anaplasia. Both Alveolar RMS had no features of anaplasia. Presence of Anaplasia is a frequent observation in pediatric RMS. Anaplasia is often under reported in pediatric RMS. Pathologist should be more aware of this rare phenomenon.