Prognosis remains poor for patients with relapsed or refractory Ewing sarcoma, with limited treatment options after first-line therapy. Oral etoposide has efficacy in the paediatric setting; however, data are limited in adults. A retrospective analysis was conducted on 33 patients with relapsed or refractory Ewing sarcoma who completed at least one cycle of oral etoposide at the Peter MacCallum Cancer Centre from 2005 to 2020. The median age at diagnosis and first relapse was 21 and 23 years, respectively. All patients had prior exposure to intravenous etoposide. Nine patients (27%) had stable disease for at least 6 months, and six patients (18%) had a partial response. The clinical benefit rate was 45%. The median PFS was 3.6 months (95% CI: 1.7-5.5), and OS was 8.5 months (95% CI: 4.1-13.0). Despite prior exposure, oral etoposide demonstrated antitumour activity and durable responses in the relapsed or refractory setting for adult patients with Ewing sarcoma.

The classification of undifferentiated pleomorphic sarcoma (UPS) has been evolving with advances in immunohistochemistry and genomic profiling over the past 20 years. There is a lack of current information on UPS incidence. Due to the lack of designated histology codes for UPS in the Surveillance, Epidemiology, and End Results (SEERs) program, we estimated UPS incidence by three different definitions based on clinical opinions using the 2000-2020 data from 22 registries of the SEER program. The incidence varied widely across the three definitions with 0.06 per 100,000 persons for the least inclusive definition and 0.67 per 100,000 persons for the most inclusive definition in 2016-2020, making it challenging to estimate the exact incidence of UPS. Regardless, all the incidences decreased between 2000 and 2020. Guidelines in UPS diagnosis and classification need to be better implemented in the US.

Desmoplastic small round blue cell tumor (DSRCT) is a highly aggressive fatal sarcoma without evidence-based therapeutic guidelines. We present here seven patients with DSRCT including immunohistochemistry combined with fluorescence in situ hybridization (FISH), next generation sequencing (NGS, n = 6) as well as OncoScan array (n = 3) analyses and show consecutive therapeutic approaches. All seven DSRCT patients presented with an extended abdominal mass; median age at diagnosis was 24.8 years. NGS analyses revealed five class 4 or 5 sequence variants. Remarkably, OncoScan and targeted analyses by FISH identified genomic gains of CCND1 in two cases. Cyclin D1 expression was present in all seven tumors as shown by immunohistochemical staining. Multimodal therapeutic concepts included systemic therapies, resection, and radiation. Six patients were treated as first-line therapy with conventional chemotherapy. All except one patient had a dismal therapy response. Subsequent therapy lines consisted of chemotherapeutic combinations followed by targeted therapies. Due to Cyclin D1 expression, the CDK4/6 inhibitor palbociclib was applied to four patients. The median therapy duration until disease progression in these patients was 4.5 months (range, 1.5-5 months). So, CCND1 genomic gain and Cyclin D1 expression are common features pointing to cell-cycle deregulation as a possible therapeutic target.

Desmoplastic small round cell tumor (DSRCT) is a rare pediatric cancer caused by the EWSR1-WT1 fusion oncogene. Despite initial response to chemotherapy, DSRCT has a recurrence rate of over 80% leading to poor patient prognosis with a 5-year survival rate of only 15-25%. Owing to the rarity of DSRCT, sample scarcity is a barrier in understanding DSRCT biology and developing effective therapies. Utilizing a novel pair of primary and recurrent DSRCTs, we present the first map of DSRCT genomic breakpoints and the first comparison of gene expression alterations between primary and recurrent DSRCT. Our genomic breakpoint map includes the lone previously published DSRCT genomic breakpoint, the breakpoint from our novel primary/recurrent DSRCT pair, as well as the breakpoints of five available DSRCT cell lines and five additional DSRCTs. All mapped breakpoints were unique and most breakpoints included a 1-3 base pair microhomology suggesting microhomology-mediated end-joining as the mechanism of translocation fusion and providing novel insights into the etiology of DSRCT. Through RNA-sequencing analysis, we identified altered genes and pathways between primary and recurrent DSRCTs. Upregulated pathways in the recurrent tumor included several DNA repair and mRNA splicing-related pathways, while downregulated pathways included immune system function and focal adhesion. We further found higher expression of the EWSR1-WT1 upregulated gene set in the recurrent tumor as compared to the primary tumor and lower expression of the EWSR1-WT1 downregulated gene set, suggesting the EWSR1-WT1 fusion continues to play a prominent role in recurrent tumors. The identified pathways including upregulation of DNA repair and downregulation of immune system function may help explain DSRCT's high rate of recurrence and can be utilized to improve the understanding of DSRCT biology and identify novel therapies to both help prevent recurrence and treat recurrent tumors.