Abstract 6456: The utility of clinical sequencing in the diagnosis and treatment of soft tissue sarcomas; Real world data based on nation-wide database

Abstract Purpose: Soft tissue sarcomas (STS) are rare and heterogeneous tumors arising from mesenchymal connective tissue, accounting for approximately 1%-2% of all malignancies. Due to their rarity and heterogeneity, it is challenging for accurate diagnosis, prognosis, and treatment of sarcoma. Recently, next-generation sequencing (NGS)-based comprehensive cancer genome profiling (CGP) has increasingly become a routine practice for patients with solid cancers worldwide. To collect genomic information and clinical characteristics of patients who underwent CGP, the Center for Cancer Genomics and Advanced Therapeutics (C-CAT) has also been established since 2018 in Japan. Almost all the clinical and genomic data of patients who received CGP tests the had been collected in C-CAT. Here, we examined the utility of CGP test in the diagnosis and treatment of STS using this nation-wide database. Patients and Methods: We retrospectively evaluated the records of patients with STS who received F1CDx between 2019 and 2022 and registered in C-CAT. This assay carries 324 genes and determines nucleotide substitutions, insertions/deletions, and copy number (CN) alterations of 309 genes, fusions of 36 genes, tumor mutation burden (TMB) and microsatellite instability (MSI). High TMB (TMB-H) was defined as a TMB value >10 muts/Mb. Ranges of the MSI score were assigned MSI-High (MSI-H) or microsatellite stable (MSS). Results: From 2019 to 2022, 1387 patients with STS were registered in C-CAT. The histological types included leiomyosarcoma in 357 patients, dedifferentiated liposarcoma in 178 patients, and undifferentiated pleomorphic sarcoma in 82 patients, and the others. The most commonly altered genes included TP53, CDKN2A, Rb1, and CDKN2B. Among the 1387 cases, we observed 110 fusion events in 108 cases (7.7%), and 2 cases showed 2 types of fusion transcripts. Fifteen (2.8%) patients were re-classified based on the detection of highly histology-specific translocations. Among them, an initial diagnosis of sarcoma NOS was classified as Ewing Sarcoma (EWSR1-FLI1 in 2 patients), NTRK-rearranged spindle cell neoplasm (NTRK fusion in 3 patients), CIC-rearranged sarcoma (CIC-DUX4 in 3 patients), and sarcoma with BCOR genetic alterations (BCOR-ZC3H7B in 1 patient) as these gene fusions were identified. Druggable gene alterations was detected in 347 patients (25%) and 55 patients (4%) who received genotype-matched therapy. In 38 patients for whom the effect of treatment could be evaluated, complete response and partial response were achieved in 2 (5%) and 10 (26%) patients, respectively. Discussion: In conclusion, the comprehensive genomic profiling test appears to be an important tool in the diagnosis and treatment of sarcomas. Citation Format: Eiji Nakada, Tomohiro Fujiwara, Toshi Kunisada, Shota Takihira, Daisuke Ennishi, Hideki Yamamoto, Kiichiro Ninomiya, Shuta Tomida, Mashu Futagawa, Akira Hirasawa, Shinichi Toyooka, Toshifumi Ozaki. The utility of clinical sequencing in the diagnosis and treatment of soft tissue sarcomas; Real world data based on nation-wide database [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 6456.