Abstract P2-04-15: Diagnostic potential of disseminated and circulating cancer cells: A case study of a 34-years-old patient with rapidly progressing breast cancer

Abstract Presenting the case of a 34-year-old patient diagnosed with early breast cancer NST stage cT2, cN+, G3, M0, ER IRS4, PR IRS3, Her2neu 1+, Ki67 75% in July 2022 with rapidly progressing disease, we are exploring the diagnostic potential of disseminated and circulating cancer cells. Before and during the treatment of the patient, disseminated cancer cells (DCCs) were isolated using cytokeratin staining of bone marrow aspirates. Furthermore, the number of circulating cancer cells (CTCs) in 7,5 ml of blood was measured at different timepoints using the CellSearch® CTC-Assay. Single DCCs and CTCs were isolated using a micromanipulator. By comparing the number of CTCs with clinical data, we noted a correlation between the number of CTCs with treatment response, but also disease progression. As not only enumeration of CTC but also their molecular profiling may provide important information, we analyzed the mutational landscape of CTCs using the newly developed single cell IMPACT-Assay. This panel sequencing approach captures around 470 actionably or therapeutically relevant genetic changes. Based on the sequencing results we are currently performing an in vitro drug screen using 35 single drugs and drug combinations on cancer cells isolated from a pleural effusion of the patient. We will ask whether the mutational or the functional assays allow predicting the clinical response of the patient and provide a novel rational that could support decision making of the molecular tumor board. The results will be presented on the poster. Citation Format: Jonas Roth, Clara Chaiban, Lukas Wöhrl, Kirsten Utpatel, Valeria Gerthofer, Julian Schornbaum, Christian Werno, Olaf Ortmann, Stephan Seitz, Zbigniew Czyz, Christoph A. Klein. Diagnostic potential of disseminated and circulating cancer cells: A case study of a 34-years-old patient with rapidly progressing breast cancer [abstract]. In: Proceedings of the San Antonio Breast Cancer Symposium 2024; 2024 Dec 10-13; San Antonio, TX. Philadelphia (PA): AACR; Clin Cancer Res 2025;31(12 Suppl):Abstract nr P2-04-15.