Sarcomas, including bone sarcomas and soft tissue sarcomas (STSs), are a heterogeneous group of mesenchymal malignancies. Recent advancements in next-generation sequencing (NGS) have enabled the identification of novel chromosomal translocations and fusion genes, which play a critical role in sarcoma subtypes. Our study focuses on gene fusions in sarcomas among Chinese patients, comparing their genomic profiles to those of Western populations. We analyzed 1048 sarcoma samples from Chinese patients using a panel of over 500 genes, identifying 481 gene fusions in 329 patients. The most common fusions included EWSR1, HMGA2, and SS18, with notable subtype-specific fusions such as EWSR1-FLI1 in Ewing sarcoma and NAB2-STAT6 in solitary fibrous tumors. In comparison to Chinese and Western populations, variations in fusion spectrum exist, potentially necessitating distinct treatment strategies; however, further validation of these fusions is warranted. Our findings highlight the importance of gene fusions as diagnostic markers and potential therapeutic targets. Actionable fusions, including kinase-related fusions like ALK, NTRK3, and BRAF, were detected in 67 patients (6.4%) and may guide precision therapies. Additionally, we observed the frequent co-occurrence of genomic alterations, particularly in cell cycle regulators such as CDK4 and MDM2. Genomic profiling of sarcomas offers valuable insights into their molecular drivers and can support personalized therapeutic approaches. Further research is needed to validate these findings and optimize treatment strategies for sarcoma patients.

Sequential regimens in patients with epidermal growth factor receptor (EGFR) mutation-positive non-small cell lung cancer (NSCLC) can overcome tyrosine kinase inhibitor (TKI) resistance and maximize clinical benefit. Patients with advanced NSCLC can achieve excellent tumor control after a period of EGFR-TKI treatment. Patients may benefit from additional local treatment, such as surgery or radiation therapy, once the tumor is under control. Here, we present a case of a patient with advanced oligometastatic NSCLC with EGFR mutations who achieved downstaging through sequential EGFR-TKI-based precision medicine allowing resection of residual disease. This case report describes a patient with advanced oligometastatic non-small cell lung cancer with EGFR mutations who achieved downstaging through sequential EGFR-TKI-based precision medicine allowing resection of residual disease.

e23573 Background: Generally sarcomas are categorized as soft tissue and bone sarcomas and represent heterogenous group of malignancies with more than 70 distinct histologic subtypes. Due to their rarity and heterogeneity, sarcomas present particular challenges for accurate diagnosis, prognosis, and treatment. The presence and persistence of circulating tumor cells (CTCs) in the peripheral blood are believed to be associated with poor prognosis and distant metastases. A blood-based CTCs test is thus greatly needed for monitoring disease progression and predicting clinical outcomes. Methods: In this study, we developed a CTCs test for the detection and surveillance of sarcoma patients’ CTCs, and subsequently explored its clinical value. 123 patients with sarcomas were enrolled as the cohort for serial CTCs tests. Dynamic CTCs counting, in combination with therapy evaluation and post-treatment follow-up, was used to explore predicting pre- and post-chemotherapy evaluation and prognosis. Results: Quantification of CTCs demonstrated a significant increase in sarcoma patients compared to healthy individuals. Furthermore, patients in stage III-IV had a higher CTC count than those in stage I-II (p<0.01), suggesting a correlation between CTCs and disease development. Remarkably, there was variation in the quantity of CTCs among different types of sarcomas. The highest number of CTCs was observed in undifferentiated small round cell sarcoma, followed by soft tissue tumor, while bone tumors had the lowest number. In addition, the number of CTCs in patients with positive PD-L1 expression was considerably greater than in those with negative expression (p<0.01). The count of CTCs shown a substantial decrease following neoadjuvant chemotherapy treatment. There was a decline in the number of CTCs both before and after postoperative adjuvant chemotherapy treatment, however, there was no significant statistical discrepancy. The number of CTCs at the baseline was shown to be considerably larger in the group of patients with progressive disease or stable disease (PD+SD) compared to the group with partial response or complete response (PR+CR) (p<0.05). This difference was particularly pronounced for interstitial-type CTCs (p<0.01). Conclusions: The rate of presence of CTCs in the peripheral blood of sarcoma patients is high, and patients with an increased percentage of CTCs after treatment have a poor treatment effect. The dynamic monitoring of changes in CTCs counts after treatment has clinical significance for the timely detection of recurrence or metastasis. CTCs also showed a clinical value in prediction of therapy efficiency or prognosis, and may be clinically valuable for the whole course management of patients.

Cholangiocarcinoma (CCA) is a primary malignancy which is often diagnosed when it is advanced and inoperable due to the lack of effective biomarkers and poor sensitivity of clinical diagnosis. Molecular profiling may provide information for improved clinical management, particularly targeted therapy. The study aimed to improve the understanding of molecular characteristics and its association with prognosis in Chinese CCA. We enrolled 41 Chinese patients with CCA, including 6 intrahepatic CCA (iCCA), 14 perihilar CCA (pCCA), and 21 distal CCA (dCCA) cases, all patients underwent radical operations and tumor samples underwent next-generation sequencing (NGS) by Foundation One Dx, which analyzed 324 genes. The patients’ genetic characteristics, clinical management, and prognosis were analyzed. The most mutated genes were TP53 (68%, 28/41), CDKN2A (37%, 15/41), and SMAD4 (29%, 12/41). The genetic mutations in dCCA, pCCA, and iCCA were significantly different. For example, NOTCH3 mutations were not found in dCCA. The gene mutations of AXL were specifically associated with lymph node metastasis in patients with CCA, whereas gene mutations of SMAD4 were specifically associated with lymphovascular invasion. Furthermore, mutations in APC , DAXX , FANCA , LTK , MAP2K4 , and NOTCH1 were associated with a poor prognosis ( P < 0.05). This study provides an overview of genetic alterations in Chinese patients with CCA, which will provide novel potential biomarkers for the diagnosis of CCA and may guide targeted therapeutic strategies for Chinese patients with CCA.

Introduction:Sarcomas are classified into two types, bone sarcoma and soft tissue sarcoma (STS), which account for approximately 1% of adult solid malignancies and 20% of pediatric solid malignancies. There exist more than 50 subtypes within the two types of sarcoma. Each subtype is highly diverse and characterized by significant variations in morphology and phenotypes. Understanding tumor molecular genetics is helpful in improving the diagnostic accuracy of tumors that have been difficult to classify based on morphology alone or that have overlapping morphological features. The different molecular characteristics of bone sarcoma and STS in China remain poorly understood. Therefore, this study aimed to analyze genomic landscapes and actionable genomic alterations (GAs) as well as tumor mutational burden (TMB), microsatellite instability (MSI), and programmed death ligand-1 (PD-L1) expression among Chinese individuals diagnosed with primary bone sarcomas and STS.Methods:This retrospective study included 145 patients with primary bone sarcomas (n = 75) and STS (n = 70), who were categorized based on the 2020 World Health Organization classification system.Results:Patients diagnosed with bone sarcomas were significantly younger than those diagnosed with STS (p < 0.01). The top 10 frequently altered genes in bone sarcoma and STS were TP53, CDKN2A, CDKN2B, MAP3K1, LRP1B, MDM2, RB1, PTEN, MYC, and CDK4.The EWSR1 fusions exhibited statistically significant differences (p < 0.01) between primary bone sarcoma and STS in terms of their altered genes. Based on the actionable genes defined by OncoKB, actionable GAs was found in 30.7% (23/75) of the patients with bone sarcomas and 35.7% (25/70) of those with STS. There were 4.0% (3/75) patients with bone sarcoma and 4.3% (3/70) patients with STS exhibited high tumor mutational burden (TMB-H) (TMB ≥ 10). There was only one patient with STS exhibited MSI-L, while the remaining cases were microsatellite stable. The positive rate of PD-L1 expression was slightly higher in STS (35.2%) than in bone sarcoma (33.3%), however, this difference did not reach statistical significance. The expression of PD-L1 in STS patients was associated with a poorer prognosis (p = 0.007). Patients with STS had a better prognosis than those with bone sarcoma, but the observed difference did not attain statistical significance (p = 0.21). Amplification of MET and MYC genes were negatively correlated with clinical prognosis in bone tumors (p<0.01).Discussion:In conclusion, bone sarcoma and STS have significantly different clinical and molecular characteristics, suggesting that it is vital to diagnose accurately for clinical treatment. Additionally, comprehensive genetic landscape can provide novel treatment perspectives for primary bone sarcoma and STS. Taking TMB, MSI, PD-L1 expression, and OncoKB definition together into consideration, there are still many patients who have the potential to respond to targeted therapy or immunotherapy.

Undifferentiated high-grade pleomorphic sarcoma (UHPS) is a rare soft tissue sarcoma (STS) originated from mesenchyme. UHPS is mostly advanced, aggressive and has poor prognosis. Patients with UHPS tend to have a lower 5-year survival rate than patients with other types of STS. NTRK fusions are commonly found in rare histological tumor types. Among sarcomas, 90% of infantile fibrosarcomas have NTRK fusions. Many other types of sarcomas have also been studied for NTRK fusions. Targeted therapy with NTRK inhibitors, such as Larotrectinib and Entrectinib, leads to response in most patients with NTRK1/2/3 gene fusion-positive tumors. Herein, we present a 68-years old man with UHPS by pathological diagnosis. Next-generation sequencing (NGS) revealed a novel TMTC2-NTRK3 fusion, which was also detected by immunohistochemistry (IHC) and fluorescence in situ hybridization (FISH). This report broadens the spectrum of NTRK fusions in UHPS and highlights a new target for treatment.

Abstract Background: DICER1 plays a significantly important role in short dsRNA-mediated post-transcriptional gene silencing that is deeply embedded in the network of cancer genes. Aberrant expression and mutation of DICER1 have been studied and reported to be closely associated with tumorigenesis and development, while lower levels of DICER1 mRNA or protein are associated with poorer prognosis in some cancers. However, there is little research about the effect and mechanism of mutated DICER1. Materials and Methods: In our study, DICER1 mutation in the TCGA database from the top 10 cancers were analyzed to explore the effect of DICER1 mutants in cancer prognosis and the possible potential mechanisms. Results: We found that DICER1 mutation was closely related to better clinical outcomes in pan-cancer and uterine corpus endometrial carcinoma (UCEC) treatment, which meant that DICER1 could be served as a prognosis factor for pan-cancer, especially UCEC. And mechanism research indicated that DICER1-mut facilitated antitumor immunity, which could be the potential mechanism for DICER1-mut prognosis value. Moreover, tumor microenvironment (TME) features and higher TMB of DICER1-mut manifested that DICER1 may be a potential biomarker of immunotherapy, which needed more clinical and basic research to validate.Conclusions: In summary, our finding suggested that DICER1 may be a potential prognostic biomarker and was associated with TME in UCEC. In addition, it might be a marker of immunotherapy.

Angiosarcoma (AS) is a rare, clinically aggressive tumor with limited treatment options and a poor prognosis. Mutations involving the angiogenesis-related genesTP53, PTPRB, PLCG1, KDR as well as FLT4 amplification have been observed in AS. There is a potential therapeutic value of inhibition of the VEGF pathway against angiosarcoma. Our case first described a patient with two sites of cutaneous angiosarcomas (cASs) that responded differently to anlotinib. And genetic analysis revealed that those two sites had different FLT4 variants, suggesting that FLT4 amplification could be the cause of anlotinib non-response.

We presented a 67-year-old nonsmoking female lung adenocarcinoma patient with novel epidermal growth factor receptor (EGFR) A289G/F287_G288insHA cis mutations who responded positively to sintilimab combined with regorafenib and albumin paclitaxel, and sequential treatment of icotinib. Gene mutations in patients were detected by next-generation sequencing (NGS) technology, and changes in gene mutations before and after treatments were observed by ctDNA monitoring. We observed the efficacy of the patient through chest computed tomography (CT) imaging and carcinoembryonic antigen (CEA) level and found that the patient benefited from immunotherapy in combination with antiangiogenesis and chemotherapy for more than 1 year, CEA levels initially fell sharply and then rebounded during the treatment period. After changing to EGFR-TKI therapy, the CEA level of the patient does not only decreased sharply at the initial stage of treatment but also rebounded and increased at the later stage of treatment. The patient was tested for genetic mutations after 4 months of sequential EGFR-TKI therapy and was found to have lost all previous EGFR mutations, which may be the cause of resistance to targeted drug icotinib. We believe that our findings have enriched the EGFR mutation spectrum in NSCLC and highlighted the possible choice for patients harboring this mutation by immunotherapy combined with chemotherapy and antivascular therapy, and EGFR-TKI-targeted therapy.

More than half of new cases of hepatocellular carcinoma (HCC) and associated deaths occurring annually worldwide are recorded in China. Chinese patients with HCC exhibit special characteristics in terms of etiology, leading to differences in prognosis versus Western patients. In recent years, several angiogenesis inhibitors were approved, and immune checkpoint blockers (ICBs) were recommended as second-line therapy for advanced HCC. In addition, the recent success of a combination of atezolizumab with bevacizumab signals resulted in an essential change in the first-line treatment of HCC. We investigated the characteristics of patients with HCC in China and summarized the rapidly emerging relevant clinical data, which relate to the prospects and challenges associated with the use of ICBs in this setting. We further evaluated the efficacy of ICBs in Chinese patients with HCC based on data obtained from global trials, and discussed possible factors influencing the effectiveness of ICBs in patients with HCC in China. Immunotherapy offers new options for the treatment of advanced HCC, though responses varied between patients. Currently, there is a need to discover specific biomarkers for the accurate identification of patients who would more likely benefit from immunotherapy. Furthermore, investigation of patient characteristics in different countries is necessary to provide a clinical practice basis and reference value for the diagnosis and treatment of HCC.

Dermatofibrosarcoma protuberans (DFSP) is a kind of soft tissue sarcoma, mostly occurs in the trunk, followed by proximal extremities and head and neck. Surgical resection is the most important treatment for DFSP, but the local recurrence rate of DFSP is high. Except reported specific chromosomal tran7slocations occurred in DFSP, the association between DNA repair gene mutations and DFSP still unknown. In this report we found a 19-year-old boy with DFSP carries a novel heterozygous germline ERCC2 mutation, which belongs to the nucleotide excision repair (NER) pathway and genetic defects in ERCC2 may contribute to the cancer susceptibility xeroderma pigmentosum (XP), Cocaine syndrome (CS), and trichothiodystrophy (TTD). Different mutations of the ERCC2 gene can lead to diverse diseases, but there are no targeted therapies. In summary, our results enlarged the mutation spectrum of the DFSP patients. It also provides new insights into genetic counseling and targeted therapeutic strategies for patients with DFSP.

e15583 Background: The peritoneal metastasis (PM) in patients with colorectal cancer (CRC) is associated with poor survival, especially in those with Ras mutations. However, knowledge on the mechanism of molecular biology in CRC peritoneal metastasis (CRCPM) is limited, and the impact of tumor immune microenvironment (TME) on PM pathogenesis and the prognosis of CRCPM remain unclear. Therefore, we characterized the TME of CRCPM and evaluated its potential diagnostic and prognostic values. Methods: This study involved 21 patients with metastatic CRC (mCRC), of whom 11 with CRCPM were classified into the experimental group and 10 with mCRC without PM (noCRCPM) were classified into the control group. Formalin-fixed and paraffin-embedded tissue of primary tumors from all patients was examined using the NanoString RNA sequencing system. The clinicopathological variables and TME biomarkers were compared using the chi-square test and Cox regression analysis. According to the results of multivariate analysis, a prognostic nomogram was generated, and its prediction ability was measured using the concordance index (C-index). Survival curves were generated using the Kaplan–Meier method, and survival comparison between groups was conducted using the log-rank test. Results: The TME in the CRCPM and noCRCPM groups was different, especially the expression of NOS2, TNSF9, KIR3DL2, MAGEA12, MRC1, KIR3DL1, and CD244 and the content of DC cells, macrophages, exhausted CD8+T cells, NK CD56dim cells, and M2 macrophages. Univariate analysis revealed that the expression of PTPN11, TIE1, MAGEA4, PDGFB, and PMS2 was significantly correlated with progression-free survival (PFS) time. These genes were subjected to the least absolute shrinkage and selection operator regression analysis and established a risk score model. Multiple Cox regression analysis showed that the risk score was a significant independent prognostic factor. However, considering the particularity of serum carcinoembryonic antigen (CEA), we built a combined model that included the CEA level and risk score. It could perform well in predicting the PFS time in patients with CRCPM (C-index 0.77). Conclusions: The TME of the primary lesion was significantly different between the CRCPM and noCRCPM groups. The model that combined the risk score and CEA level was a better outcome predictor among patients with CRCPM.

ERBB2 amplification is one of the most important and mature targets for HER2-targeted drug therapy. Somatic mutations of ERBB2 in the tyrosine kinase domain have been studied extensively, and play a role in response to anti-HER2 therapy among different cancer types. However, ERBB2 fusion has not been got attention and its relevance to HER2-targeted therapy is unclear. We comprehensively characterized ERBB2 fusions from next-generation sequencing (NGS) data between May 2018 and October 2021 in 32,131 various solid tumors. Among the tumors, 0.28% harbored ERBB2 fusions, which occurred more commonly in gastroesophageal junction cancer (3.12%; 3/96), breast cancer (1.89%; 8/422), urothelial carcinoma (1.72%; 1/58), and gastric cancer (1.60%; 23/1,437). Our population presented with a median age of 65 years (range 28 to 88 years), a high proportion of men (55 men vs 34 women; 61.80%). Among the patients with ERBB2 fusions, TP53 (82%), APC (18%), and CDK4 (15%) were the top3 co-mutant genes. What's more, most patients with ERBB2 fusion also had ERBB2 amplification (75.28%; 67/89), which was similar to the data in the TCGA database (88.00%; 44/50). Furthermore, TCGA database shows that patients with ERBB2 fusions in pan-cancer had a worse prognosis than those without ERBB2 fusions, as well as in breast cancer. Besides, ERBB2 amplification combined with ERBB2 fusion had worse prognosis than those with only ERBB2 amplification. ERBB2 fusion may interfere the effect of anti-HER2-targeted antibody drugs and influence the prognosis of patients with ERBB2 amplification. Prospective clinical trials are warranted to confirm the results in the future.

2603 Background: Dicer1 functions as a tumor suppressor in mouse models. In humans, somatic mutations are associated with many cancers in adults, and patients with DICER1 syndrome with DICER1 germline mutations are susceptible to childhood cancers. DICER1 is the core caner-intrinsic CTL-evasion gene, especially positive correlate with innate anti-PD-1 resistance signature or IPRES signature and hERV expression which involved in sensitivity and resistance to ICIs. Nevertheless, the association between mutations in DICER1 and the Chinese patients, the relationship between DICER1 mutations with immunotherapy biomarkers are unknown. Methods: NGS and clinical data were collected from 10953 Western pan-cancer patients (TCGA cohort). A 539-gene panel targeted sequencing assay was performed on FFPE tumor samples from 3514 Chinese pan-cancer patients (Chinese cohort). Both DICER1 mutation ratio and TMB were calculated on the two cohorts following the same criteria.DNA NGS testing (MSI-high vs low/stable (MSS)) in Chinese cohort were included. NGS data of 3514 patients who also detected PD-L1 expression from Chinese clinical dataset were analyzed to explore the association with mutation and PD-L1. The survival information was collected from 1661 pan-cancer patients to analyze the association between DICER1 mutation and efficacy of immunotherapy (MSKCC cohort). Results: In total, 2.91% (319/10953) patients in TCGA harbored DICER1 mutation; in the Chinese cohort, the DICER1 mutation ratio (2.67%, 94/3514) was similar to TCGA. The top 5 mutant DICER1-associated cancer types in Chinese cohort were lung cancer, colon adenocarcinoma, liver cancer, uterine corpus endometrial carcinoma, melanoma. In both cohorts, TMB level of mutation group was significantly higher than wild-type group (p < 0.001). The ration of mutation group in MSI-H (50%) and MSI-L (23.53%) was significantly higher than wild-type group in Chinese cohort (2.17%) (p < 0.001). In addition, the ratio of PD-L1 positive expression (≥1%) in mutation group (48.94%, 46/48) was significantly higher than wild-type in Chinese cohort (38.48%,1316/2104) (p < 0.05). The survival probability of mutation group was significantly longer than wild-type group in immunotherapy. Conclusions: The results indicated that DICER1 mutation was associated with a higher TMB, MSI-H and PD-L1 expression level in Chinese patients. Patients with DICER1 mutations may benefit more from ICIs.

e21060 Background: LRP1B (low-density lipoprotein receptor-related protein 1B) is frequently mutated in non-small cell lung cancer (NSCLC). Previous studies showed LRP1B mutations were associated with prolonged survival in melanoma and NSCLC immunotherapy cohort. Higher tumor mutation burden was found in LRP1B mutated patients, suggesting potential benefit of immunotherapy. Herein, we investigate the relationship of LRP1B and immunotherapy biomarker in lager cohort of Chinese and Western NSCLC patients. Methods: Next-generation sequencing data and clinical data were collected from 1053 TCGA NSCLC patients (Western cohort). A 539-gene panel targeted sequencing assay was performed on FFPE tumor samples from 1056 Chinese pan-cancer patients (Chinese cohort). Both LRP1B mutation ratio and TMB were calculated on the two cohorts following the same criteria. TMB-H was defined as the top quartile of all TMB values. Results: In total, 208 (20%) of the 1056 Chinese patients and 385 (37%) of the 1053 Western patients had at least one mutation of LRP1B genes (LRP1B mutant group). The frequency of LRP1B mutation between Western cohort and Chinese cohort had significant difference (20% vs. 37%, p＜0.001). In both cohorts, TMB was higher in the LRP1B mutant group compared to non-LRP1B mutant group. In Chinese cohort, PD-L1 positive was not associated with LRP1B mutation. Patients with LRP1B mutation were associated with prolonged survival in Western immunotherapy cohort. Conclusions: Our study provided a landscape of LRP1B mutations in a much larger Chinese NSCLC group, which could be a valuable complement to TCGA dataset and previous study. Results of our study was consistent with previous studies. Both in Chinese and Western cohorts, the higher TMB in LRP1B mutant patients suggested potential efficacy from immunotherapy of LRP1B mutant group. This result and the potential predictive value of LRP1B in immunotherapy should be validation in a larger Chinese LRP1B mutant cohort in the further.

e15074 Background: CDK4/6 kinases associate with cyclin D proteins during transition from G1 to S phase of the cell cycle. Amplification of CDK4/6 may elicit the activity of cyclin D, which hyperphosphorylates RB, ultimately leading to uncontrolled cell proliferation. Currently, three CDK4/6 inhibitors are used in breast cancer, ovarian cancer and sarcoma. Herein, we investigate the prevalence of CDK4/6 amplification in Chinese and Western cancer patients, hope to find more cancer subtypes with CDK4/6 amplification. Methods: Next-generation sequencing data and clinical data were collected from 10828 TCGA pan-cancer patients (Western cohort). A 539-gene panel targeted sequencing assay was performed on FFPE tumor samples from 4181 Chinese pan-cancer patients (Chinese cohort). CDK4 and CDK6 amplification were calculated on the two cohorts following the same criteria. Results: In total, 182 (4.4%) of the 4181 Chinese patients and 529 (4.9%) of the 10828 Western patients had CDK4 amplification, 133 (3.2%) of the 4181 Chinese patients and 475 (4.4%) of the 10828 Western patients had CDK6 amplification. In Western cohort, the top 5 CDK4 amplification-associated cancer types were sarcoma, glioblastoma multiforme, lung adenocarcinoma, ovarian carcinoma, and adrenocortical carcinoma, and the top 5 CDK6 amplification-associated cancer types were esophageal carcinoma, ovarian carcinoma, lung squamous cell carcinoma, stomach adenocarcinoma, sarcoma. In Chinese cohort, the top 5 CDK4 amplification-associated cancer types were lung adenocarcinoma, melanoma, sarcoma, stomach carcinoma, liver cancer, and the top 5 CDK6 amplification-associated cancer types were lung adenocarcinoma, stomach carcinoma, liver cancer, melanoma, glioma. In addition, CDK4 amplification in Chinese cohort, 22 (11%) of the 203 Chinese bone and soft tissue sarcoma patients had CDK4 amplification, and 4 (2%) of the 203 had CDK6 amplification. Bone and soft tissue sarcoma types with CDK4 / 6 amplification including soft tissue sarcoma, bone cancer, fibrosarcoma, chondrosarcoma, rhabdomyosarcoma, liposarcoma, synovial sarcoma. Conclusions: Our study provided a characteristic of CDK4/6 amplification in Chinese and Western pan-cancer patients. Analysis revealed frequent CDK4 / 6 amplification in lung cancer, sarcoma, stomach carcinoma, ovarian carcinoma and liver cancer. It is suggested patient with these cancer types may potentially benefit from CDK4/6 inhibitor.

e23532 Background: Sarcomas are a broad family of mesenchymal malignancies exhibiting remarkable histologic diversity. The clinical presentation and gene mutations in different subtypes are often atypical, and the profile of gene mutations vary widely. Meanwhile there are many genetic mutations difference between West countries patients and Chinese patients in many cancer types, however little is known about soft tissue tumors' difference. Methods: Next-generation sequencing data and clinical data were collected from 255 Western soft-tissue sarcoma patients (TCGA cohort). A 539-gene panel targeted sequencing assay was performed on FFPE tumor samples from 271 Chinese soft-tissue sarcoma patients (Chinese cohort). Both somatic mutations and germline mutations were detected on the Chinese cohort, then we compared the somatic mutations between TCGA and Chinese cohort. Results: In Chinese cohort, top 5 mutant genes were TP53(35.69%), ATRX(14.12%), MUC16(12.94%), RB1(10.98%), CSMD1(8.24%); while in TCGA cohort were TP53(22.88%), MUC16(8.12%), RB1(6.27%), TERT(5.17%), NF1(4.80%). The mutation frequency of 7 genes were higher in TCGA cohort than in Chinese cohort: TP53(35.69% vs 22.88%, p = 0.0015), ATRX(14.12% vs 4.06%, p < 0.001), CSMD1(8.24% vs 1.85%, p < 0.001), LRP1B(6.27% vs 2.21%, p < 0.05), CSMD3(3.92% vs 1.11%, p < 0.05), EPHA7(3.92% vs 0.74%, p < 0.05) and PIK3C2G(3.53% vs 0.37%, p = 0.009). However, TERT showed the opposite, which in TCGA cohort(1.57%) was lower than Chinese cohort(5.17%)(p < 0.05). Meanwhile, we detected the germline mutations in Chinese cohort. There are three patients had BRCA1 mutations, the SLX4, TP53, MUTYH, ATM, ERCC3 and NBN were all only happened once. There were 21 patients from Chinese cohort had EWSR1-X fusions, including EWSR1-ERG(6/21, 28%), EWSR1-FLI1(6/21,28%), EWSR1-ATF1(4/21,19%), EWSR1-CREB1(1/21,5%), EWSR1-DCTN2 (1/21, 5%), EWSR1-POU5F1(1/21, 5%), EWSR1-WT1(1/21, 5%).Besides, we discovered a novel fusion gene EWSR1-DDIT3(1/21, 5%) in Chinese cohort. Conclusions: We described the general landscape and differences of genetic variation in Chinese and Western populations, we also discovered some new mutations such as novel fusion.In conclusion, comprehensive genomic profiling in a large cohort highlights the promise of targeted therapies.

e15524 Background: Efforts by previous study had provided molecular profile of MSS & TMB-H gastrointestinal (GI) cancers, however, Asian patients were underrepresented in this study. We aim to investigate specific molecular features of Chinese MSS & TMB-H colorectal cancer patients. Methods: FFPE tumor samples from 249 Chinese colorectal cancer patients with MSS & TMB-H (Chinese cohort) were sequencing using a panel targeting 539 cancer-related genes of the human genome. Genomic data from our cohort was compared with publicly available data from 508 MSS & TMB-H colorectal cancer patients from the TCGA dataset (TCGA cohort). TMB was calculated on the two cohorts following the same criteria. TMB-H was defined as the top quartile of all TMB values. Results: In total, 48 (19%) MSS & TMB-H patients were found in Chinese cohort, and 55 (10%) were found in TCGA cohort. Based on the analysis of the genetic alteration profile from our cohort, in MSS & TMB-H colorectal cancer patients, APC (85%), TP53 (81%), KRAS (44%), and LRP1B (378%) as the most commonly altered genes. In TCGA cohort, TTN (84%), APC (80%), TP53 (64%), SYNE1 (51%), and MUC16 (51%) as the most commonly altered genes. On the other hand, the most difference genes between MSS & TMB-H group and MSS/TMB-L group in TCGA cohort were TNN (84% vs. 52%; p = 0.000008), SYNE1 (56% vs. 24%; p = 0.000003), MUC16 (51% vs. 23%; p = 0.00006), FAT4 (47% vs. 16%; p = 0.000002), RYR2 (44%vs. 16%; p = 0.00001). Compared with TCGA cohort, LRP1B (38% vs. 13%; p = 0.0005), TCF7L2 (33% vs. 8%; p = 0.00003), SPTA1 (29% vs. 6%; p = 0.00005), PREX2 (19% vs. 3%; p = 0.0006) were the most difference genes between MSS & TMB-H group and MSS/TMB-L group in Chinese cohort. Conclusions: Our study contributes to the understanding of specific genetic alterations harbored by MSS & TMB-H colorectal cancer patients that could potentially be developed as markers of precision medicine.

e21061 Background: MUC16 is frequently mutated in non-small cell lung cancer (NSCLC). Previous studies showed MUC16 mutation were associated with TMB and prognostic outcome in gastric cancer patients and may benefits for patients with immunotherapy. Herein, we aimed to characterize the association of MUC16 with immunotherapy biomarkers in Chinese and Western NSCLC patients. Methods: Next-generation sequencing data and clinical data were collected from 1053 TCGA NSCLC patients (Western cohort). A 539-gene panel targeted sequencing assay was performed on FFPE tumor samples from 1056 Chinese pan-cancer patients (Chinese cohort). Both MUC16 mutation ratio and TMB were calculated on the two cohorts following the same criteria. Results: In total, 269 (25%) of the 1056 Chinese patients and 494 (47%) of the 1053 Western patients had at least one mutation of MUC16 genes ( MUC16 mutant group). The Chinese cohort had a higher mutation frequency of MUC16 gene than the Western cohort (25% vs. 47%, p＜0.001). In both cohorts, TMB was higher in the MUC16 mutant group compared to non- MUC16 mutant group. In Chinese cohort, PD-L1 positive was not associated with MUC16 mutation. However, patients with MUC16 mutation were not associated with prolonged survival in Western immunotherapy cohort. Conclusions: Our study provided a landscape of MUC16 mutations in a much larger Chinese NSCLC group, which could be a valuable complement to TCGA dataset. Both in Chinese and Western cohorts, the higher TMB in MUC16 mutant patients suggested potential efficacy from immunotherapy of MUC16 mutant group. A larger validation cohort of MUC16 mutant is required to confirm these findings in the further.

Undifferentiated high-grade pleomorphic sarcoma (UPS) is a rare soft tissue sarcoma (STS) of mesenchymal origin, particularly the extremities and retroperitoneum, meanwhile it has been reported in almost all parts of the body. UPS is highly invasive and has a poor prognosis due to its clinical manifestations of painless mass and deep tumor site, which are usually found at an advanced stage. Patients with UPS tend to have a lower 5-year survival rate than patients with other types of STS. Recently, NTRK fusions were detected in many cancer types, such as thyroid cancer, colorectal cancer, non-small cell lung cancer, soft tissue tumors, uterine sarcomas, and melanomas. However, the mutation frequency of NTRK fusion in all cancers is only 0.1-1%. Targeted therapy with NTRK inhibitors, such as Larotrectinib and Entrectinib, leads to a response in most patients with NTRK1/2/3 gene fusion-positive tumors. Herein, we present a 68-years old man diagnosed with stage IIIA (T2N0M0G3) UPS. Next-generation sequencing (NGS) revealed a novel TMTC2-NTRK3 fusion. The NTRK3 positivity was also detected by immunohistochemistry (IHC) and fluorescence in situ hybridization (FISH). He had a response to Larotrectinib. This report broadens the spectrum of NTRK fusions in UPS and highlights a new target for treatment.