Ewing Sarcoma Research Articles

Abstract A009: Synthetic lethality in the context of STAG2-mutant Ewing sarcoma

Abstract Introduction: Ewing sarcoma is an aggressive type of pediatric bone cancer, characterized by a fusion transcription factor (EWSR1-FLI1 in 85% of cases1,2). Recurrent secondary mutations are limited to alterations in TP53, CDKN2A and most frequently STAG2 (15-22%3-6). STAG2-loss-of-function (LOF) mutations correlate with poor prognosis, metastasis and relapse3,5,6, and are shown to induce a metastatic phenotype in preclinical studies7,8. Despite intensive multimodal treatment (surgery, radiation and chemotherapy), the estimated 5-year survival is a mere 65-75% for patients with localized disease, and below 30% for those presenting with metastasis or relapse9. Targeted treatment is currently not available. Our current work aims at identifying synthetic lethal (SL) interactions with STAG2-LOF mutations in the context of Ewing sarcoma, which could represent potential avenues for targeted therapy. Methods: In order to identify STAG2-SL interactions, we have performed genome-wide and subsequent targeted CRISPR knockout (KO) screening in Ewing sarcoma cell lines and their isogenic CRISPR-engineered STAG2-KO clones. To capture Ewing sarcoma inter- and intra-tumoral heterogeneity, we engineered additional bulk STAG2-KO populations across a wide range of cell lines and primary samples, using a lentiviral approach. These isogenic (STAG2 +/-) models are used for high throughput drug screening, validation of screening results and investigation of underlying SL mechanisms. Results: The quality of our genetic screening is validated by the recurrent emergence of (untargetable) paralog STAG1 as the top STAG2-SL hit. Additional preliminary results include a targetable candidate that emerged from both CRISPR- and drug-based screens in most of our tested models. Validation experiments across a broader panel of isogenic cell lines and primary models are currently ongoing. Conclusion: In this work, we employ genetic and drug-based screening approaches across a panel of isogenic (STAG2+/-) Ewing sarcoma cell lines, aiming to identify STAG2-SL interactions. These approaches have yielded potential hits that are currently being investigated across a broader panel of Ewing cell lines and primary models. Ultimately, this work aims to identify novel targeted therapeutic strategies for this aggressive subtype of Ewing sarcoma.

Abstract A015: Exploiting endogenous replication stress with a novel targeted therapy in Ewing sarcoma

Abstract Ewing sarcoma (EwS) is a rare and aggressive disease that typically affects the bone of children and young adults. Although there are moderate 5-year survival rates for primary disease, there is a high rate of recurrence and a lack of targeted therapies in this setting. Furthermore, pediatric exposure to chemotherapies leads to an increased risk of long-term complications, including secondary cancers, cardiomyopathy, and infertility. Therefore, there is a desperate need for targeted therapies which improve therapeutic outcomes and reduce exposure to chemotherapy in these patients. Like many pediatric cancers, EwS has a low mutational burden. Instead, it is driven by chromosomal translocation between a FET family member, EWSR1, and an ETS family member, usually FLI1. The EWSR1-FLI1 fusion protein acts as an aberrant and oncogenic transcription factor, disrupting cell cycle control, cell migration, and proliferation. ETS family members in these fusions retain their ability to bind to the SWI/SNF chromatin remodeling complex, further dysregulating DNA methylation and gene expression. Although targeting of the EWSR1 fusion has not yet been successful, these elevated levels of replication stress (RS) present a unique element of vulnerability within the cell. To this end, our lab has previously identified replication stress response (RSR) inhibitors, DDKi and WEE1i, which can be utilized to exploit the characteristic ability of EwS to maintain high levels of replication stress (RS) and push EwS cells into mitotic catastrophe in vitro. Here, we evaluate the efficacy of the replication stress response inhibitors (RSRi) TAK931 (DDKi) and MK1775 (WEE1i) with chemotherapy regimens commonly utilized in the relapsed/refractory setting in vivo. Using cell line derived xenografts in NSG mice, we show that DDKi and WEE1i with irinotecan limits tumor growth significantly more than existing therapy (temozolomide + irinotecan). Dosing schedules are optimized through dosing de-escalation and alternative-day dosing strategies. We further demonstrate the ability of our RSRi combination to effectively limit tumor growth over time in vivo even when irinotecan dosage is decreased. We go on to investigate the RSRi combination in the presence of ultra-low dose irinotecan. Finally, we utilize reduced representation bisulfite sequencing to examine the epigenetic effects of these treatment regimens. Overall, the exploitation of high endogenous replication stress in EwS by targeted RSRi presents a promising potential therapeutic option for this pediatric patient population. Citation Format: Emily Isenhart, Ajay Gupta, Bryan Gillard, Kristopher Attwood, Joyce Ohm. Exploiting endogenous replication stress with a novel targeted therapy in Ewing sarcoma [abstract]. In: Proceedings of the AACR Special Conference in Cancer Research: Expanding and Translating Cancer Synthetic Vulnerabilities; 2024 Jun 10-13; Montreal, Quebec, Canada. Philadelphia (PA): AACR; Mol Cancer Ther 2024;23(6 Suppl):Abstract nr A015.

Abstract IA019: Identification of metabolic adaptation mechanisms that confer resistance to glutathione depletion in Ewing sarcoma

Abstract Aggressive cancer cells must overcome diverse stress forms in the tumor microenvironment and circulation, such as oxidative stress, to survive and metastasize. One adaptive process to counter oxidative stress is to upregulate glutathione (GSH), a tripeptide consisting of glutamate, cysteine, and glycine, which is a powerful antioxidant in cells, including in tumor cells. A rate-liming step in GSH production is the availability of the amino acid, cysteine. Tumor cells can either import cystine, a dimer of cysteine, through the xCT antiporter system, for conversion to the reduced cysteine monomer, or in some tumor types, they can synthesize cysteine de novo from methionine and serine through the transsulfuration pathway. GSH is not only critical for redox homeostasis, but is taken up into mitochondria where is acts as a source of sulphur to generate iron-sulphur (Fe-S) clusters that are essential for many mitochondrial enzymes including electron transport complexes. We wished to determine if Ewing sarcoma cells could tolerate reduced levels of GSH, using either xCT genetic or pharmacologic inhibition, or by blocking downstream enzymes in the GSH synthesis pathway, including GCLC using buthionine sulfoximine (BSO), or glutaminase using CB-839. To our surprise, we were able to generate BSO and CB-839 resistant cells with vanishingly low levels of GSH. These cells somehow maintained not only redox homeostasis, but also showed functional mitochondrial respiration (oxidative phosphorylation). We then performed CRISPR dropout screens to identify how these cells might be surviving in the absence of GSH, and to tease out specific dependencies of these BSO and CB-839 resistant cells. These studies revealed unexpected dependencies, and opportunities for synthetic lethal interventions, as will be discussed. Citation Format: Poul H. Sorensen, Hai-Feng Zhang, Christopher Hughes, Alberto Delaidelli, Samuel Aparicio. Identification of metabolic adaptation mechanisms that confer resistance to glutathione depletion in Ewing sarcoma [abstract]. In: Proceedings of the AACR Special Conference in Cancer Research: Expanding and Translating Cancer Synthetic Vulnerabilities; 2024 Jun 10-13; Montreal, Quebec, Canada. Philadelphia (PA): AACR; Mol Cancer Ther 2024;23(6 Suppl):Abstract nr IA019.

Ewing Sarcoma of Kidney: A Rare Entity

AbstractPrimary renal origin of Ewing sarcoma/PNET (primitive neuroectodermal tumor) is a rare entity in the adult population and has an aggressive outcome. The entity was first coined by Arthur Purdy stout in 1918 and recognized under family of small round cell tumor. Radiologically it is difficult to distinguish from primary clear cell carcinoma of kidney from Ewing/PNET. Diagnosis of this requires histopathology, immunohistochemistry (IHC), and cytogenetics studies.A 40-year-old female presented with hematuria and radiology found a mass lower pole of left kidney with extension into renal hilum. Nephrectomy was done for the case and the histopathology diagnosis of small round cell tumor of left kidney was given. Followed by IHC, diagnosis of malignant round cell tumor was suggestive of Ewing sarcoma.Microscopy showed cells with small, round, hyperchromatic nuclei, scant cytoplasm, and inconspicuous nucleoli. Increased mitosis was noted (15/10 high power field). Multiple foci of pseudorosettes, areas of hemorrhage, and necrosis lymphovascular emboli were seen.IHC done outside showed NKX 2-2, synaptophysin positivity, CD99 diffuse membranous positivity, cytokeratin perinuclear dot like positivity, and negative for CD20, CD3, desmin, CD34, S100, and Pax8. Impression of malignant round cell tumor was suggestive of Ewing sarcoma.Ewing sarcoma is one of the rare yet highly aggressive tumors. This should be kept as differential diagnosis in young adults with renal mass, as on radiologically it cannot be differentiated from renal cell carcinoma. Diagnosis of Ewing sarcoma is done using histopathology, IHC, and cytogenetic study. Early diagnosis helps in initiation of surgery, chemotherapy, and radiotherapy and helps in increasing the survival rate.

AMH levels after initial cycles of chemotherapy in female adolescents with Ewing sarcoma and implications for preservation of fertility.

10067 Background: Anti-Müllerian hormone (AMH) has been recommended as the primary surveillance modality for evaluation of ovarian insufficiency in females. Patients with Ewing sarcoma receive VDC-IE chemotherapy which is estimated high risk of gonadotoxic injury. Previous studies have shown that only a small part of female patients with Ewing sarcoma show signs of ovarian recovery during long-term follow-up, similar to those treated with SCT or abdominal radiotherapy. Time to start preservation of fertility should be defined in this group of patients. Methods: In this observational study, we prospectively investigated AMH as a measure of ovarian function in female adolescents (less than 18 years old) with Ewing sarcoma who received initial chemotherapy in our hospital. Patients previously treated with systemic treatment were excluded. Serum levels of AMH were measured at the laboratory of Peking University People’s Hospital. Blood samples were collected at the first day of the initial two cycles of VDC-IE treatment, before local therapy including surgical resection and radial radiation, and at the end of chemotherapy. All statistical analyses were performed using SPSS 19.0 version. Results: A total of 53 female adolescents with Ewing sarcoma who received initial chemotherapy in our hospital were analyzed from February 1, 2021 to December 31, 2023, including 35 patients aging from 6 to 12 (group 1), 18 patients aging from 12 to 18 (group 2). 255 blood samples from unique time points were measured. The baseline mean AMH were 4.16 (90% CI, 1.88 – 9.42) ng/mL in all patients, 3.58 (90% CI, 1.40 – 6.91) ng/mL for group1 and 5.28 (90% CI, 3.10 – 9.48) ng/mL for group 2. The mean AMH level after first cycle of chemotherapy was 0.43 (90% CI, 0.03 – 0.81) ng/mL in all patients, 0.40 (90% CI, 0.03 – 0.69) ng/mL and 0.47 (90% CI, 0.12 – 1.09) ng/mL for each group at a mean time of 16.5 days after initial chemotherapy. The mean AMH level before local therapy was 0.17 (90% CI, 0.03 – 0.37) ng/mL and 0.07 (90% CI, 0.01 – 0.32) ng/mL at the end of chemotherapy. Conclusions: Female adolescents with Ewing sarcoma treated by VDC-IE regimen showed a rapid reduction of AMH after initial cycles. Methods for preservation of fertility should be implemented as soon as possible but not at the same time of local therapy.

Epidemiology of bone tumors in children and adolescents: a retrospective study of 266 patients in the south of Tunisia.

Although bone tumors (BT) are relatively uncommon among the human neoplasm, they constitute the most frequent tumors in children and adolescents (CAA). Little information is available about the epidemiologic features of BT in CAA. We aimed to present and discuss epidemiological characteristics of BT in CAA in southern Tunisia, regarding the different histological types. This is a retrospective study including cases of BT in CAA collected in the pathology department at the Habib Bourguiba university hospital over a period of 15 years (2006- 2020). A total of 266 BT was diagnosed in our institution (42,7% among all BT in Southern Tunisia) divided into 200 benign bone tumors (BBT) (75,2%) and 66 malignant bone tumors (MBT) (24,8%). The mean age for all BT was 14,2 years (3-20 years) with male predominance (sex ratio: 1,48). The most common tumor was osteochondroma (42.2%) followed by osteosarcoma (14.6%) and Ewing sarcoma (6.4%). For BBT, the most affected age group was the 16 to 20 year - old - group (50,7%) with a male predominance (59.8%) and a predilection for lower limb (66.8%) then the upper limb (16,8%). Osteochondroma was the most common histological type (56.5%) followed by aneuvrysmal cyst (8,5%) and osteoid osteoma (6,5%). For MBT, the mean age was 12,5 years (5-20 years) and the most affected age group was the 11 to 15 year -old -group (59%). Boys were more affected (60.6%), with a preference for the lower limb (57%) followed by the pelvis (15,6%). Osteosarcoma was the most common MBT (60%) followed by Ewing sarcoma (24%). Given their rarity and heterogeneity, the diagnosis of BT is particular in CAA and requires a multidisciplinary approach. The reporting of epidemiological studies remains essential in order to expand our knowledge regarding these uncommon tumors.

HER2 expression-independent antitumor effect of trastuzumab deruxtecan (T-DXd) on pediatric solid tumors.

e15016 Background: Treatment of pediatric solid tumors shows limited improvement even with intensification of conventional chemotherapy, suggesting novel approaches such as targeted therapies are needed. Trastuzumab Deruxtecan (T-DXd), a HER2-targeting antibody–drug conjugate, exhibits significant anti-cancer activity in breast cancers with a broad range of HER2 expression. T-DXd might be a promising agent for refractory or relapsed pediatric solid tumors, but its efficacy in pediatric tumors needs to be studied. Methods: Anti-cancer efficacy of T-DXd and its payload DXd were assessed in vitro by utilizing our in-house cancer cell line models. Cytotoxicity assays were performed for 60 pediatric cancer cell lines, including Neuroblastoma (NB) = 25, Ewing sarcoma / Ewing sarcoma family of tumors (EWS / EWSFT) = 17, Rhabdomyosarcoma (RMS) = 10, Others (Osteosarcoma, Brain tumor, Wilms tumor, Hepatoblastoma, and Malignant rhabdoid tumor (MRT) = 8, and 2 breast cancer cell lines expressing HER2 high or low (IHC score 2+ or 0) as positive or low control, respectively. We analyzed HER2 expression on the cell surface by flow cytometry and evaluated relative mean fluorescence intensity (MFI) values. Results: In the flow cytometric assessment, pediatric cancer cell lines showed smaller median MFI of 1.40 (0.67 - 2.71) compared with breast cancer control with HER2 high expression (33.77). The median MFI of each cell lines were 0.94 in NB, 1.76 in EWS / EWSFT, 1.42 in RMS, 1.52 in other pediatric cancers. Although low or no expression of HER2, certain inhibitory activities to the cell growth were observed for T-DXd against a part of NB, EWS, RMS and MRT cell lines, with the minimum IC50 values of 14.5 nM, 6.5 nM, 10.2 nM, 8.1 nM, respectively. In NB, EWS and RMS, a wide range of sensitivity to T-DXd were seen among different cell lines in the same disease. Most of cell lines showed high sensitivity to DXd (Median IC50 value: 0.90 nM [0.08 - 6.46 nM]), but, among them, cell lines with lower sensitivity to DXd tend to show less sensitivity to T-DXd. There was no clear correlation between sensitivity to T-DXd and HER2 expression among pediatric cancer cell lines, indicating that other mechanism such as intrinsic sensitivity to payload might affect antitumor activity of T-DXd. Conclusions: T-DXd exhibited antitumor efficacy against pediatric solid tumors in vitro irrespective of HER2 expression. Our results suggest that T-DXd might be an alternative therapy for pediatric solid tumor cases for whom conventional chemotherapies and other targeting therapies are ineffective. This study supports further investigation for T-DXd in this population.

Association of elevated ctDNA burden following one cycle of chemotherapy with inferior outcomes for patients with metastatic Ewing sarcoma: A report from the Children’s Oncology Group (COG).

10018 Background: All patients with Ewing sarcoma (EWS) currently receive the same intensive chemotherapy and novel risk-adapted approaches to therapy are needed. We have previously shown that elevated baseline ctDNA burden is prognostic among patients with EWS. Here we investigate the prognostic impact of on-treatment ctDNA burden in patients with metastatic EWS treated on COG AEWS1221. Methods: AEWS1221 was a randomized phase 3 trial evaluating ganitumab plus interval compressed chemotherapy (vincristine/doxorubicin/cyclophosphamide alternating with ifosfamide/etoposide given every 2 weeks) for patients with newly diagnosed metastatic EWS. We evaluated 680 serial blood samples and data from 273 patients enrolled to AEWS1221. We utilized a custom NGS hybrid-capture assay for ctDNA quantification that detects EWSR1 and FUSfusions. We used log rank tests to compare event-free survival (EFS) from the designated timepoint according to ctDNA burden post cycle 1 of VDC (planned day 14) and post cycle 2 VDC+IE (planned day 28) of chemotherapy. We dichotomized patients by ≥0.5% ctDNA at each timepoint. A P-value of ≤0.05 was considered evidence of a significant association. Results: Of 298 eligible patients with metastatic EWS, 273 provided blood samples for ctDNA analysis. Three patients had non-FET-ETS family fusions ( CIC::DUX4, EWSR1::WT1 and EWSR1::GTDC1) and were excluded from further analysis. Eighty-five percent of patients were < 21, 56% were male, 33% had pelvic bone primary tumors, and 40% had lung only metastatic disease. ctDNA was ≥0.5% in 86% of patients at baseline (median 25%, range 0-113%, n = 264), in 53% (median 0.53%, range 0-15%, n = 34) after 1 cycle (median day 14, range 11-20), and in 14% (median 0, range 0-53%, n = 130) after 2 cycles (median day 29, range 25-36). Baseline ctDNA burden ≥0.5% was associated with an increased risk of EFS-event (3-year EFS 35% [95% CI 29-41%] vs. 61% [95% CI 43-76%], HR = 2.2, P= 0.002). ctDNA ≥0.5% after cycle 1 was also associated with an increased risk of EFS-event (3-year EFS 6% [95% CI 0.4-22%] vs. 56% [95% CI 29-76%], HR = 6.0, P< 0.0001). ctDNA ≥0.5% after cycle 2 was not associated with an increased risk of EFS-event (28% [95% CI 10-49%] vs. 34% [95% CI 25-43%], HR = 1.2, P= 0.55). Conclusions: ctDNA burden ≥0.5% following one cycle of chemotherapy identifies patients highly likely to relapse, albeit in a small cohort with available data at that timepoint. Conversely, ctDNA at a cutpoint of ≥0.5% after two cycles of chemotherapy was not prognostic, suggesting either more sensitive assays are needed or the prognostic value of ctDNA burden is diminished following additional therapy. These findings will enable novel trials of risk-adapted therapy focused on baseline and early ctDNA burden.

Impact of age on clinical trial availability for AYAs with cancer: A time-trend analysis.

1534 Background: Low participation of adolescents and young adults (AYAs, age 15-39 yrs at diagnosis) in cancer clinical trials (CCT) limits their access to novel therapies and hinders the ability to study disease biology and age-specific toxicities. Patient age may be an important barrier as younger and older AYAs may be excluded depending on the trial’s focus. In 2017, the American Society of Clinical Oncology and Friends of Cancer Research issued a joint statement encouraging removal of age as a CCT eligibility criterion unless there is specific biological rationale. To evaluate the impact of this statement, we undertook this analysis of CCT availability for AYAs. Our primary objective was to compare the number of CCT available for AYAs, overall and by tumor types, from 2019-2023 vs previously published data from 2007-2018. The availability of early phase trials and study sponsor was also assessed. Methods: We identified CCT registered on ClinicalTrials.gov from January 2019 to July 2023 enrolling patients with 10 malignancies relevant for AYAs (Hodgkin lymphoma, anaplastic large cell lymphoma, melanoma, extracranial germ cell tumors [GCT], medulloblastoma, thyroid cancer, Ewing sarcoma, osteosarcoma, rhabdomyosarcoma [RMS], and synovial sarcoma). Trials were categorized as adult (≥18 yrs), transitional (patients < or ≥18 yrs), or pediatric (<18 yrs). Transitional trials with an age range 12-18 to <40 yrs were defined as AYA specific trials. Early phase included phase 1 and 1/2 trials; late phase included phase 2/3 and 3 trials. Trial availability from 2007-2018 was identified from a prior analysis by deRojas et al in 2019 (PMID:32337483). The proportion of trials in each category was compared between 2007-2018 and 2019-2023 using z-tests. Results: There were 1071 eligible trials registered on Clinicaltrials.gov: 840 (78%) adult, 226 (21%) transitional, and 5 (0.5%) pediatric. Four trials were AYA-specific. Compared to the prior 10 years, the proportion of transitional trials did not change overall (19% vs 21%, p=0.24) or within any disease. Whereas the proportion of trials available at age 17 has not significantly changed overall (20% vs 21%; p=0.48) or within any disease, the proportion of trials available at age 18 significantly increased (95% vs 98%; p<0.001) in aggregate and specifically for Ewing sarcoma (93% vs 100%; p=0.003), GCT (96% vs 99%; p=0.002), medulloblastoma (86% vs 98%; p=0.006), RMS (87% vs 98%; p=0.007) and thyroid cancer (92% vs 98%; p=0.01). Time trends for transitional trials by phase and sponsor are summarized (Table). Conclusions: Availability of transitional trials for AYAs has not increased, particularly for those <18 yrs. The 18-yr-old age limit continues to be an obstacle in CCT availability and enrollment. [Table: see text]

Eribulin and irinotecan for refractory or recurrent Ewing sarcoma: A retrospective study.

e23502 Background: The effectiveness of eribulin and irinotecan in treatment of xenograft models of Ewing sarcoma is well-established but little clinical data has been reported. Encouraging results from preclinical models and a shortage of temozolomide in our hospital have prompted the administration of the eribulin as substitute for temozolomide and vincristine in combination of irinotecan at our institution from 2022 to 2023 in an off-label way. Methods: We retrospectively reviewed the medical records of patients treated for refractory or recurrent Ewing sarcoma with 1.4mg/m2 D1,8 eribulin and 20mg/m2/d D1-5,8-12 irinotecan at 21 day intervals (ERII) at Peking University People’s Hospital. Results: Finally, a total of 17 patients with median age 18.6 years were treated with a total of 77 courses of ERII between February 2022 and February 2023. The objective response rate was 35.3%, the disease control rate 58.9% and the median event-free survival (EFS) 2.07 months. 35.3% patients had 6 months EFS and overall survival was 66.9%. Grade 3 or 4 toxicities were observed in 37.6% courses and in 64.7% of the patients, with myelosuppression, especially neutropenia, being the most common and diarrhea / abdominal pain the second most common. In the dx5x2 VIT protocol the later portion was given two days after the end of early portion. However, in this substitute regimen of eribulin, the median time interval between the end of the early portion to the start of later portion was 5 days. The dose intensity of the regimen was reduced by 21% per cycle. The later portion was delayed mostly because of unrecovered myelosuppression. Conclusions: The efficacy and safety of eribulin and irinotecan as a second-line regimen was inferior to historical reports of temozolomide and irinotecan in the same institute. There was no need for further prospective trials on this combination unless mechanisms of synergy and biomarkers are identified. [Table: see text]

Feasibility of tumor-informed circulating tumor DNA (ctDNA) for molecular residual disease (MRD) assessment in pediatric patients with solid tumors.

10058 Background: Circulating Tumor DNA (ctDNA) is a noninvasive biomarker which has been validated as a prognostic tool in multiple adult cancers. There is evolving evidence that ctDNA may be prognostic in pediatric solid tumors, but experience with commercially available assays in pediatric patients is scarce. Signatera is a ctDNA assay which utilizes whole exome sequencing of tumor and whole blood to identify 16 tumor-specific, clonal, somatic variants. These variants are then monitored in plasma as a molecular residual disease (MRD) assessment. Methods: From November 2021 through August 2023, 30 patients were enrolled on a single center study evaluating the feasibility and utility of Signatera MRD monitoring in pediatric patients with solid tumors. Patients 6 months to 25 years of age with any malignant extracranial solid tumor including lymphoma were eligible. Peripheral blood has been collected every 3 weeks to 3 months while on therapy and every 3 to 6 months while off therapy for up to 2 years. A minimum of 22mL of blood was required for the first draw, and 16mL for subsequent draws. Timing of blood draws was aligned with standard of care blood draws when possible. Results of ctDNA MRD were compared with imaging obtained for disease response and surveillance as standard of care. Results: The cohort consisted of 6 cases of neuroblastoma, 6 osteosarcomas, 4 Wilms tumors, 4 carcinomas, 3 soft tissue sarcomas, 2 Ewing sarcomas, 2 germ cell tumors, 2 lymphomas, and one hepatoblastoma. Of 30 patients enrolled, a tumor-informed ctDNA assay was successfully created for 27 (90%). Of 25 patients who had radiographic evidence of disease at any time of monitoring, 23 (92%) had simultaneous detectable ctDNA. Seven patients have had disease recurrence, of whom all seven had detectable ctDNA at or preceding time of recurrence. Conclusions: Signatera tumor-informed ctDNA assay is a feasible noninvasive tool which may be utilized in parallel with standard of care imaging to monitor for disease recurrence in pediatric patients with extracranial solid tumors. Additional analysis of a larger patient cohort is needed to identify tumor types and clinical scenarios for which its application is most useful.

SARC037: Phase II results of trabectedin given as a 1-hour (h) infusion in combination with low dose irinotecan in patients (pts) with relapsed/refractory Ewing sarcoma (ES).

SARC037: Phase II results of trabectedin given as a 1-hour (h) infusion in combination with low dose irinotecan in patients (pts) with relapsed/refractory Ewing sarcoma (ES).

Results of a randomized phase II trial of 2nd-line treatment for advanced soft tissue sarcoma comparing trabectedin, eribulin and pazopanib: Japan Clinical Oncology Group study JCOG1802 (2ND-STEP).

11551 Background: Trabectedin, eribulin, pazopanib, and gemcitabine plus docetaxel (GD) are the candidates of second-line chemotherapy for advanced soft tissue sarcomas (STS), although there is no clear evidence showing which is better among those agents. This clinical trial aims to determine the most promising regimen among trabectedin, eribulin, and pazopanib as the test arm regimen in the future phase III trial of the second-line treatment for patients with advanced STS. Methods: This study, JCOG1802, is a multicenter randomized phase II selection design trial comparing trabectedin (1.2 mg/m2 IV, every 3 weeks), eribulin (1.4 mg/m2 IV, days 1 and 8, every 3 weeks) and pazopanib (800 mg PO, everyday) for patients with unresectable or metastatic STS refractory to doxorubicin-based first-line chemotherapy. Eligibility criteria include 16 years old or older, ECOG performance status of 0–2, unresectable and/or metastatic STS, an exacerbation within 6 months prior to registration, histological diagnosis of STS other than Ewing sarcoma, well-differentiated liposarcoma and myxoid liposarcoma, a history of chemotherapy of doxorubicin-based regimen for STS, and sufficient organ function. Primary endpoint is progression-free survival (PFS), and secondary endpoints include overall survival (OS), disease-control rate (DCR), response rate (RR), and adverse events. The planned total sample size was set at 120 patients to select the most promising regimen with a probability of at least 80%, assuming a median PFS of 3 months in the worst regimen and 4 months in the best regimen. The regimen demonstrating the most favorable point estimate of hazard ratio for PFS is chosen for the subsequent phase III trial. Results: From December 2019 to March 2023, 120 patients with advanced STS were enrolled (31 with leiomyosarcomas, 26 with liposarcomas, 18 with translocation-related sarcomas, and 45 with others) and randomized. Median PFS for trabectedin was 2.9 months (95% CI 1.3-5.3), for eribulin was 2.2 months (1.5-3.8), and for pazopanib was 3.7 months (2.6-5.2), respectively. The hazard ratios for eribulin and pazopanib compared to trabectedin were 1.22 (0.77-1.94) and 0.99 (0.63-1.56), respectively. Median OS for trabectedin was 14.8 months (10.8-29.1), for eribulin was 13.3 months (7.6-20.1), and for pazopanib was 15.7 months (9.8-not estimable). DCR for trabectedin was 50.0% (32.4-67.6), for eribulin was 34.3% (19.1-52.2), and for pazopanib was 64.9% (47.5-79.8). Conclusions: Pazopanib showed the best PFS and OS as the second-line treatment for patients with advanced STS among trabectedin, eribulin, and pazopanib. A phase III trial comparing GD with pazopanib is planned as the next step. Clinical trial information: jRCTs031190152 .

Prevalence of neurotrophic tropomyosin receptor kinase (NTRK) fusion gene positivity in patients with solid tumors in Japan.

Members of the neurotrophic tropomyosin receptor kinase (NTRK) gene family, NTRK1, NTRK2, and NTRK3 encode TRK receptor tyrosine kinases. Intra- or inter-chromosomal gene rearrangements produce NTRK gene fusions encoding fusion proteins which are oncogenic drivers in various solid tumors. This study investigated the prevalence of NTRK fusion genes and identified fusion partners in Japanese patients with solid tumors recorded in the Center for Cancer Genomics and Advanced Therapeutics database of comprehensive genomic profiling test. In the analysis population (n = 46,621), NTRK fusion genes were detected in 91 patients (0.20%). The rate was higher in pediatric cases (<18 years; 1.69%) than in adults (0.16%). NTRK gene fusions were identified in 21 different solid tumor types involving 38 different partner genes including 22 (57.9%) previously unreported NTRK gene fusions. The highest frequency of NTRK gene fusions was head and neck cancer (1.31%) and thyroid cancer (1.31%), followed by soft tissue sarcoma (STS; 0.91%). A total of 97 NTRK fusion gene partners were analyzed involving mainly NTRK1 (49.5%) or NTRK3 (44.2%) gene fusions. The only fusion gene detected in head and neck cancer was ETV6::NTRK3 (n = 22); in STS, ETV6::NTRK3 (n = 7) and LMNA::NTRK1 (n = 5) were common. Statistically significant mutual exclusivity of NTRK fusions with alterations was confirmed in TP53, KRAS, and APC. NTRK gene fusion was detected from 11 STS cases: seven unclassified sarcoma, three sarcoma NOS, and one Ewing sarcoma. NTRK gene fusion identification in solid tumors enables accurate diagnosis and potential TRK inhibitor therapy.

Posterior fossa primary intracranial extraosseous Ewing’s sarcoma: case report

BackgroundPrimary intracranial Ewing’s sarcoma (ES) is a type of primitive neuroectodermal tumour and is a rare malignant tumour in children and adolescents. The imaging features of ES overlap with other central nervous system embryonal tumours, making it difficult to pinpoint a specific diagnosis. We aim to explore the clinical, neuroimaging and differential diagnoses of this entity.Case presentationWe describe a 6-month-old infant who presented with complaints of enlarging the head size and poor feeding. Imaging revealed a contrast-enhancing large solid-cystic mass lesion with internal calcification, focal bone erosion and haemorrhage in the posterior fossa. Histopathological examinations, immunohistochemistry, and molecular analysis confirmed ES.ConclusionsThe confirmative diagnosis of primary intracranial ES requires histological examination, immunohistochemical analysis, and genetic detection, along with radiological findings. Surgical excision followed by combined radiotherapy and chemotherapy is the treatment of choice.

Non-Wilms renal tumors: Twenty years experience in a referral center

BackgroundNon-Wilms Renal Tumors (NWRT) constitute less than 10% of all renal tumors diagnosed in childhood. We studied our experience in the diagnosis and management of these tumors to compare our results with the current literature. Study designThis is a retrospective observational study which includes all patients aged 0-18 years with histopathological diagnosis of NWRT treated in our center during the period 2000-2022. ResultsWe identified 10 patients with diagnosis of: cystic nephroma(3), congenital mesoblastic nephroma(1), renal cell carcinoma(2), clear cell sarcoma of the kidney (2), renal Ewing's sarcoma(1) and malignant rhabdoid tumor of the kidney(1). Sixty percent (60%) were female. The median age at diagnosis was 3.25 years (IQR 1.5-10). Median age at diagnosis excluding CN was 6 years old (IQR 2.62-10.75). Molecular alterations were detected in 60% of the cases. Hematuria (40%) and palpable abdominal mass (40%) were the most frequent presenting symptoms. In total, 62.5% patients were misdiagnosed during the preoperative period as Wilms' tumor (WT), based on imaging data. A Radical nephroureterectomy was performed in all cases and staging lymphadenectomy in 70%. We recorded a major complication in one patient, who suffered a contralateral lower renal pole infarction due to section of a polar vessel during surgery. This patient had no preoperative vascular study. The recurrence-free survival rate was 90% with a median follow-up of 6.4 years (IQR 2-13.9). DiscussionRadiological imaging has fundamental importance in the diagnosis of renal tumors, especially to identify children who might benefit from initial surgical treatment or the indication of biopsy for preoperative histopathological confirmation before initiating cytotoxic treatment. However, there are no pathognomonic imaging findings that clearly differentiate between WT and other renal tumors, nor among the heterogeneous group of NWRT[3]. In our series, 62.5% of patients were misdiagnosed as WT based on imaging features.We found different molecular alterations in 60% of our patients (Table 1). None of them predispose to the development of bilateral tumors nor correlates with predisposing syndromes of metachronous tumors.Apart from its retrospective design, this study is limited by small number of cases and a long study period. ConclusionsCorrect differential diagnosis of NWRT is necessary for an adequate therapeutic approach. The molecular-genetic profile is an important step in the diagnosis of NWRT that allows for the use of targeted therapies in refractory patients. Detailed anatomical study by vascular mapping minimizes the risk of iatrogenic damage during tumor resection.

PULMONARY EWING SARCOMA/PRIMITIVE NEUROECTODERMAL TUMOR : A CASE REPORT

Extraosseous Ewings sarcoma is an extremely rare neuroectodermal tumor,Although thoracic Ewing sarcoma/primitive neuroectodermal tumor (PNET) usually developson the chest wall, there have been reports of primary Ewing sarcoma/PNET of the lung Wereport the case of a 30-year-old manwho presented with right-sided pulmonary mass.Radiology, histopathology, and immunohistochemistry confirmed the diagnosis of primarypulmonary Ewings sarcoma, the patient wastreated by chemotherapy ( regimen ofvincristine, doxorubicin, cyclophosphamide alternating with ifosfamide, etoposide ) andradiotherapy.

Lumbar functional evaluation of pelvic bone sarcomas after surgical resection and spinal pelvic fixation: A clinical study of 304 cases.

We endeavored to introduce a novel scoring system (Lumbar Functional Index, LFI) capable of evaluating lumbar function in pelvic bone sarcoma patients who underwent surgical resection and spinal pelvic fixation, while simultaneously identifying the incidence, outcomes, and risk factors of lumbar function impairment among these populations. A cohort of 304 primary bone sarcoma patients were recruited. The LFI was created based on the Oswestry Dysfunction Index (ODI) and Japanese Orthopaedic Association (JOA) scores. Lumbar function impairment was defined as LFI score ≥ 18 points, which was identified as high LFI. Demographic data, clinical characteristics, and oncological outcomes were analyzed. The cohort included chondrosarcoma (39.8%), osteosarcoma (29.9%), Ewing sarcoma (8.6%), bone-derived undifferentiated pleomorphic sarcoma (7.2%), giant cell tumor of bone (7.2%), chordoma (2.3%), and other bone sarcomas (5.0%). The LFI score exhibited significant negative correlation with common scoring systems of bone sarcoma. The incidence of high LFI was 23.0%. Patients with high LFI demonstrated a higher prevalence of type I + II + III + IV pelvic tumor, more sacrificed nerve roots and bilateral lumbar spine fixation during surgery, while lower percentage of R0 resection and local control of pelvic tumor. Decreased median overall survival (30 vs. 52 months, p < 0.001) and recurrence-free survival (14 vs. 24 months, p < 0.001) time were observed in these patients. Type I + II + III + IV pelvic tumor and sacrificed nerve roots≥2 were identified as risk factors for high LFI, while R0 resection and local control were identified as protective factors. The LFI scoring system exhibited a significant negative correlation to current scoring systems. High LFI patients had worse prognosis and distinct characteristics. The risk factors of high LFI included type I + II + III + IV pelvic tumor and sacrificed nerve roots≥2, and the protective factors included R0 resection and local control.

Disease Control and Toxicity Outcomes after Stereotactic Ablative Radiation Therapy for Recurrent and/or Metastatic Cancers in Young-Adult and Pediatric Patients.

Pediatric patients with metastatic and/or recurrent solid tumors have poor survival outcomes despite standard-of-care systemic therapy. Stereotactic ablative radiation therapy (SABR) may improve tumor control. We report the outcomes with the use of SABR in our pediatric solid tumor population. This was a single-institutional study in patients < 30 years treated with SABR. The primary endpoint was local control (LC), while the secondary endpoints were progression-free survival (PFS), overall survival (OS), and toxicity. The survival analysis was performed using Kaplan-Meier estimates in R v4.2.3. In total, 48 patients receiving 135 SABR courses were included. The median age was 15.6 years (interquartile range, IQR 14-23 y) and the median follow-up was 18.1 months (IQR: 7.7-29.1). The median SABR dose was 30 Gy (IQR 25-35 Gy). The most common primary histologies were Ewing sarcoma (25%), rhabdomyosarcoma (17%), osteosarcoma (13%), and central nervous system (CNS) gliomas (13%). Furthermore, 57% of patients had oligometastatic disease (≤5 lesions) at the time of SABR. The one-year LC, PFS, and OS rates were 94%, 22%, and 70%, respectively. No grade 4 or higher toxicities were observed, while the rates of any grade 1, 2, and 3 toxicities were 11.8%, 3.7%, and 4.4%, respectively. Patients with oligometastatic disease, lung, or brain metastases and those who underwent surgery for a metastatic site had a significantly longer PFS. LC at 1-year was significantly higher for patients with a sarcoma histology (95.7% vs. 86.5%, p = 0.01) and for those who received a biological equivalent dose (BED10) > 48 Gy (100% vs. 91.2%, p = 0.001). SABR is well tolerated in pediatric patients with 1-year local failure and OS rates of <10% and 70%, respectively. Future studies evaluating SABR in combination with systemic therapy are needed to address progression outside of the irradiated field.

Ganglioside SSEA-4 in Ewing sarcoma marks a tumor cell population with aggressive features and is a potential cell-surface immune target

Carbohydrate markers of immature cells during prenatal human development can be aberrantly expressed in cancers and deserve evaluation as immune targets. A candidate target in Ewing sarcoma is the globo-series ganglioside stage-specific embryonic antigen-4 (SSEA-4). We detected SSEA-4 expression on the cell surface of all of 14 EwS cell lines and in 21 of 31 (68%) primary EwS tumor biopsies. Among paired subpopulations of tumor cells with low versus high SSEA-4 expression, SSEA-4high expression was significantly and consistently associated with functional characteristics of tumor aggressiveness, including higher cell proliferation, colony formation, chemoresistance and propensity to migrate. SSEA-4low versus SSEA-4high expression was not related to expression levels of the EWSR1-FLI1 fusion transcript or markers of epithelial/mesenchymal plasticity. SSEA-4low cells selected from bulk populations regained higher SSEA-4 expression in vitro and during in vivo tumor growth in a murine xenograft model. T cells engineered to express SSEA-4-specific chimeric antigen receptors (CARs) specifically interacted with SSEA-4 positive EwS cells and exerted effective antigen-specific tumor cell lysis in vitro. In conclusion, with its stable expression and functional significance in EwS, SSEA-4 is an attractive therapeutic immune target in this cancer that deserves further evaluation for clinical translation.