Detection of Gene Fusions in Soft Tissue Sarcoma Using Next-Generation Sequencing

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Introduction: Soft tissue sarcomas (STS) exhibit profound molecular heterogeneity. While recurrent gene fusions hold significant diagnostic and therapeutic value—guiding treatment selection and identifying novel molecular targets—our understanding of their broader clinical implications remains limited. Materials and Methods: We performed next-generation sequencing (NGS; FusionPlex Sarcoma v2, Archer™) and bioinformatic analysis (STAR v.2.7, Arriba) on formalin-fixed paraffin-embedded (FFPE) core needle biopsy specimens. The cohort consisted of patients enrolled in a phase II clinical trial (NCT03651375) who received preoperative chemoradiotherapy according to the UNRESARC protocol. Results: The analysed cohort comprised nine adult patients (median age 66 years; range 44–73) diagnosed with undifferentiated pleomorphic sarcoma (UPS; n = 3), malignant peripheral nerve sheath tumour (MPNST; n = 3), myxofibrosarcoma (MFS; n = 2), and leiomyosarcoma (LMS; n = 1), predominantly high-grade (G3; 5/9) and extremity-localised (6/9). Gene fusions were detected in one-third of patients (3/9), exclusively in G3 tumours. Specifically, we identified an SGSH-PRKCA fusion in MFS (thigh), a LINC01133-OGA fusion in MPNST (thorax), and a concurrent JAZF1-MYH7B (chr7:27995037 intronic-chr20:33563203 exon/splice-site, out-of-frame but preserving myosin domains) with a PRKCA-associated intergenic rearrangement (chr1, retaining C1/kinase domains) in UPS (upper back). Notably, the SGSH-PRKCA and JAZF1-MYH7B pairs have not been previously described in the literature for these STS subtypes. Fusion-positive (F1) cases showed stable radiological disease (RECIST 1.1 SD) and EORTC C/D pathological responses with 5–20% residual viable tumour, whereas fusion-negative (F0) cases showed a wider range of radiological and pathological outcomes, including partial response, progression, and stable disease. Conclusions: Our analysis suggests that broad genomic profiling may provide complementary molecular information in diagnostically challenging cases managed at specialised sarcoma centres, particularly when morphology and immunohistochemistry are insufficient. In the present series, however, the detected rearrangements did not alter systemic treatment, and the data do not support claims of prognostic, predictive, or therapeutic actionability.

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