Abstract PS5-07-18: Advancing personalized treatment of patients with metastatic breast cancer by functional drug screening and IMC profiling

Abstract Background: Worldwide, nearly 2.6 million women are diagnosed annually with breast cancer and 685 000 lives are lost to the disease, the vast majority due to drug-resistant metastases. Although new therapies significantly increased cure rates for early-stage breast cancer, the situation for metastatic disease has hardly changed. Cutting-edge technologies may help characterize the cancer better and tailor therapy decision. Testing drugs on ex-vivo avatar models of patients’ tumors (i.e., personalized treatment) coupled with their in-depth characterization raises the hope of identifying more efficacious treatments. This should also spare the patients the side effects of ineffective treatments. Methodes: We have initiated the nation-wide Swiss Personalized Oncology National Data Stream (SPO-NDS) study that uses a variety of OMICs to inform clinical decision making for patients with advanced breast cancer. We have been using high-resolution image-based functional drug screening on patient-derived organoids (PDO). We pre-emptively tested drug’s efficacy, alone or in combination, on tissue biopsies taken upon disease progression on standard-of-care treatment (any line). Freshly isolated tumour cells were grown in 3D-culture, which retain the patient’s molecular and cellular characteristics. This has been combined with high-resolution imaging mass cytometry (IMC) which enables the analysis of dozens of markers at single-cell resolution while preserving spatial tumor architecture, and informing about tumor content, immune cell infiltration, presence of a specific target, or activation of specific pathways. The results of our studies were integrated into a molecular summary report, discussed at a Swisswide interdisciplinary molecular tumour board, yielding patient-specific cancer vulnerabilities and informing highly-personalized treatment recommendations. The future development of these technologies as a routine tool in the clinics could be of paramount importance to provide tailored therapies to the unique genomic, molecular, and clinical characteristics of each patient’s disease. Conclusion: This trial-in-progress supports the feasibility of using functional drug screening and multi-OMIC profiling to inform personalized treatment in advanced breast cancer. Citation Format: M. Vetter, C. Jehanno, S. Foo, A. Rouchon, Y. Blum, A. Mock, M. Diepenbruck, E. Bartoszek, L. Toniato, M. Kloc, J. Gomez-Miragaya, G. Boot, S. Muenst-Soysal, K. Mertz, V. Kölzer, R. Bill, A. Ring, B. Kasenda, C. Zech, A. Oseledchyk, C. Kurzeder, W. Weber, B. Bodenmiller, A. Wicki, M. Bentires-Alj, National Data Stream Consortium Switzerland. Advancing personalized treatment of patients with metastatic breast cancer by functional drug screening and IMC profiling [abstract]. In: Proceedings of the San Antonio Breast Cancer Symposium 2025; 2025 Dec 9-12; San Antonio, TX. Philadelphia (PA): AACR; Clin Cancer Res 2026;32(4 Suppl):Abstract nr PS5-07-18.