Abstract 7509: Evaluation ofHER-2 expression on circulating tumor cells as a real time biomarker in advanced breast cancer

Abstract Introduction: Breast cancer accounts for 12. 5% of all new annual cancer cases worldwide. Cases classified as HER2-positive tend to proliferate, metastasize, and often lead to relapse. HER-2 is the most valid tumor marker, used as a diagnostics and prognostic biomarker in metastatic breast cancer (MBC). Thus, analysis of expression of HER-2 on CTCs can offer a real time dynamic biomarker for treatment options between endocrine therapy versus chemotherapy in advanced breast cancer. Functional assays on CTCs with HER-2 biomarker offer evolving biomarkers especially when the tissue is not accessible and inadequate. Methods: Retrospectively, 179 breast cancer patients' blood was analyzed for the presence of CTCs using the OncoDiscover® platform approved by Drug Controller General of India (CDSCO). Consisting of immunomagnetic multi-components mediated by anti EpCAM antibodies. The isolated cells were immunostained consisting of a nuclear dye DAPI, CK-18, CD45 and HER-2 antibodies. CTCs were identified by the presence of HER-2 + ve, CK 18 + ve, DAPI + ve and CD 45 -ve staining. Validation of HER-2 expression on the CTCs was analyzed based on the linear intensity gradients of the fluorescence signals. CTCs were termed as HER-2 -ve based on weak or no detectable fluorescence signal and termed +ve based on high fluorescence signal. Results: Among the cohort of 179 patient samples, 63. 68 % samples showed the presence of CTC (CTC ranged from 1-7). 47. 84% of these CTCs showed the expression of HER-2 signal. The mean value for fluorescence intensity for expression of HER-2 in CTCs was found to be 3. 23. The observed mean fluorescence intensity for HER-2 expression further emphasizes the robustness of CTCs as a viable source for molecular characterization. Conclusion: Integration of HER-2 analysis on CTCs into the clinical assessment of metastatic breast cancer, may offer a non-invasive, real-time strategy for profiling and possibly paving the way for more precise and tailored therapeutic interventions. Citation Format: Jayant Khandare, Gourishankar Aland, Saloni Andhari, Ganesh Khutale, Prathamesh Patil, Tanvi Deshpande, Meghana Garbhe, Vikas Jadhav, Aravindan Vasudevan, Sreeja Jayant. Evaluation ofHER-2 expression on circulating tumor cells as a real time biomarker in advanced breast cancer 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 (6Suppl): Abstract nr 7509.