Despite concerted efforts that have been made to characterize and understand the genomic landscape of gastric cancer (GC), only HER2 has been validated as a molecular target for GC treatment.Identifying new valid therapeutic targets is important for the treatment of this disease. The present report describes a Chinese male with a history of smoking two packs per day, who did not have a family history of cancer or other hereditary diseases, we discovered a small painless lump in the right groin in February 2018. Histopathology revealed a primary gastric adenocarcinoma. Positron emission tomography-computed tomography (PET-CT) showed multiple hypermetabolic nodules in the right upper lung, greater curvature of the stomach, and muscles. The patient had received treatment included oxaliplatin, docetaxel, and tegafur for two cycles, and second-line therapy of irinotecan and capecitabine, inguinal mass excision followed by concurrent radio-chemotherapy. However, the disease rapidly progressed. Whole exome sequencing (WES) showed uncommon epidermal growth factor receptor (EGFR) mutation of G719S + L861Q. The following EGFR tyrosine kinase inhibitors (TKIs) afatinib demonstrated partial response. Two months after targeted therapy, gastroscopy indicated rapid progression. With subsequent gastric specimen WES analysis, secondary MET amplification was found. The patient received local radiotherapy for gastric lesions as well as oral administration of apatinib. However, the disease rapidly progressed. A month later, he died of hepatic encephalopathy caused by obstructive jaundice combined with pulmonary and biliary tract infection. The present study indicated that afatinib might be a beneficial therapeutic option for a subset of GC patients with rare EGFR mutation in their tumors.

Introduction: Gene rearrangement/fusion play an important role in cancer diagnosis and treatment. Comparing with routine diagnostic methods, Sanger sequencing, fluorescence in situ hybridization (FISH) & immunohistochemistry (IHC), next-generation sequencing (NGS)-based panel can provide genetic information with robust sensitivity and precision. Moreover, panel-based RNAseq can detect novel fusions and only requires a small amount of RNA. We have developed a 450-gene DNA & RNA NGS panel, YuanSu S, for clinical sample detection. In this study, YuanSu S was applied to detect gene rearrangements/fusions and determine its limit of detection (LOD) and concordance with FISH/IHC, and difference between DNAseq & RNAseq. Methods: A total of 184 formalin fixed and paraffin embedded (FFPE) sarcoma samples were detected by YuanSu S at OrigiMed, a laboratory certified by College of American Pathologists (CAP) & Clinical Laboratory Improvement Amendments (CLIA). Gene fusions were analyzed by OriFusion, an OrigiMed's proprietary algorithm. For LOD determination, gradient amounts of RNA or mixed cell line samples were processed for sequencing. To confirm its concordance with FISH/IHC, 36 sarcomas FFPE samples were examined by FISH (33/36) or IHC (3/36). A cohort of 148 tumor samples was used to analyze rearrangement/fusion detection capability. Results: For RNAseq in YuanSu S, LOD was determined as 5 copies/1ng RNA input and was verified by ddPCR. Samples with rearrangement/fusion ≥ 5% detected by DNAseq were confirmed by ddPCR. For the interfering substance validation, results of samples treated with ethanol or necrotic tissue were consistent with untreated samples. Furthermore, two different Illumina platforms, Nextseq 500 & Novaseq 6000, showed no difference in sequencing abilities. 36 sarcoma FFPE samples were assessed by NGS and verified by FISH or IHC. All the 19 samples with FISH or IHC positive were detected the same rearrangements/fusions by YuanSu S, whereas the negative samples had no fusion detected. In the cohort of 148 samples, 426 rearrangements/fusions were detected by YuanSu S. 101 (23.7%) were detected both by DNAseq & RNAseq; 204 (47.9%) were determined by DNAseq only; while 121 (28.4%) were determined by RNAseq only. Rearrangements were detected by DNAseq in 97 (65.5%) samples, and 40 (41.2%) may benefit from FDA-approved drugs. Importantly, 51 (34.5%) samples had fusions detected only by RNAseq, and 33 (64.7%) may benefit from targeted therapies. Conclusion: Our results confirmed the reliability and advantages of YuanSu S, a DNA plus RNA NGS panel. Experience from YuanSu S indicated that integrative DNA & RNA sequencing could increase sensitivity of fusion detection. Therefore, the combination of DNAseq & RNAseq is able to screen more patients carrying fusion targets who could benefit from corresponding inhibitors and play an important role in guiding treatment decisions. Citation Format: Jiacheng Cai, Feng Li, Haiyan Wu, Weifeng Wang, Qiuyue Pan, Lin Zhang, Kai Wang. Validation & application of next-generation sequencing panel YuanSu S for gene rearrangements/fusions detection [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2021; 2021 Apr 10-15 and May 17-21. Philadelphia (PA): AACR; Cancer Res 2021;81(13_Suppl):Abstract nr 2283.

436 Background: Pancreatic carcinoma is one of the most lethal malignancies worldwide and is characterized by extremely poor prognosis. Gemcitabine plus Nab-paclitaxel (GNp) has been recommended by international guidelines for first-line treatment of locally advanced or metastatic pancreatic carcinoma. However, exploration into molecular biomarkers of GNp treatment is still limited. This study aims to observe and evaluate the efficacy and safety of first-line GNp treatment of pancreatic carcinoma, and to explore potential predictive and prognostic biomarkers to screen advantageous population. Methods: From December 20, 2018 to July 6, 2020, patients with metastatic pancreatic carcinoma, who received first-line GNp treatment, were enrolled. The primary endpoint was progression-free survival (PFS), and the secondary endpoints were overall survival (OS), overall response rate (ORR), disease control rate (DCR), and adverse events (AE). Patients were collected formalin fixed paraffin embedded (FFPE) samples and sequenced by a next-generation sequencing (NGS)-based 450 gene panel carried out by OrigiMed, a College of American Pathologists (CAP) accredited and Clinical Laboratory Improvement Amendments (CLIA) certified laboratory. Results: In this study, tissue samples from 101 patients were assessed by NGS, including 58 (57.4%) primary tissues and 43 (42.6%) metastasis tissues. So far, 72 patients were available for efficacy analysis, the ORR and DCR were 38.2% and 77.9%, respectively, and were similar between patients sampled from primary lesions and metastasis lesions. The PFS and OS were 176 days and 308 days, respectively. The most frequently mutated genes were KRAS (91.9%), TP53 (76.8%), CDKN2A (32.3%) and SMAD4 (26.3%). Germline pathogenic BRCA2 mutations were detected in 3 (3.0%) patients, while somatic mutations of BRCA2 were found in 2 (2.0%) patients. For KRAS, missense mutations resulted in single amino acid substitutions primarily at G12 (88.1%), and lower frequencies at Q61 (4.0%) and V14 (1.0%). At G12, five different amino acid substitutions have been identified, with G12D (37.6%) the predominant mutation, G12V (32.7%), G12R (11.9%), G12C (3.0%) and G12A (1.0%). The ORR to AG treatment was significantly higher in TP53-alteration (-alt, 47.1%) than in TP53-wild-type (-WT, 11.1%) subgroups (p=0.01). Median OS times in CDKN2B-alt and CDKN2B-WT patients were 180 days and 323 days (p=0.029), respectively. Conclusions: Current evidence indicates that GNp is a valuable option for the first-line treatment of metastatic pancreatic cancer. TP53 may serve as a novel response-predictive gene for GNp treatment in pancreatic carcinoma. Overall survival was significantly prolonged in CDKN2B-WT patients compared with CDKN2B-alt patients. This study provided insights in identifying patients who might potentially benefit from GNp therapy. Clinical trial information: NCT03768687.

e15566 Background: As a central component of PI3K/AKT pathway, AKT serves as an attractive target of anti-cancer strategy with various AKT inhibitors, which show great promise in phase I/II clinical trials. This study aimed to investigate AKT1/2/3 status in different types of cancers by using next generation sequencing (NGS). Methods: Formalin-fixed, paraffin-embedded (FFPE) tumor samples were collected from 10,010 Chinese patients with solid tumors and subjected to next-generation sequencing (NGS)-based 450 gene panel testing carried out by a College of American Pathologists (CAP) accredited and Clinical Laboratory Improvement Amendments (CLIA) certified laboratory. Genomic alterations, tumor mutational burden (TMB) values, and microsatellite instability (MSI) status were assessed with a mean coverage of 1000X, including single base substitutions, short and long insertion/deletions, copy number variations, gene fusions, and rearrangements. Genomic data and immune checkpoint inhibitors (ICIs) treatment outcome of a cohort of 1610 patients with solid tumors were derived from cBioPortal (MSKCC, Nat Genet. 2019). Results: AKT1/2/3 were found to be mutually exclusive with each other and accounted for 3.4% in this cohort. The frequencies of AKT1/2/3 variations were 1.1%, 1.6%, and 0.8%, respectively. The most common co-altered genes associated with AKT1/2/3 variations were TP53 (69.4%), PIK3CA (19.3%), KRAS (19%), CCNE1 (18.4%), CDKN2A (16.6%), and 11q13 (6.5%). AKT1/2/3 variations were significantly associated with higher TMB, and independent of MSI status. Outcome data from the MSKCC cohort showed that patients with AKT1/2/3 variations had a remarkable clinical benefit to ICIs treatment compared to patients with wild-type AKT1/2/3 in overall survival (OS) (NA vs 18 months, p = 0.009). Furthermore, AKT1/2/3 variations were independent risk factors of OS (HR: 0.55, 95%CI: 0.34-0.87, p = 0.012). Conclusions: The prevalence of AKT1/2/3 somatic alterations across different types of solid tumors in China was 3.4%. AKT1/2/3 variations were associated with an increased TMB and favorable response to ICIs, suggesting that A KT1/2/3 variations may be biomarkers for guiding anti-AKT agents and ICI treatment.