Abstract 4551: Increased blood draws for ultrasensitive ctDNA and CTCs detection in early breast cancer patients

Abstract Relapse due to residual disease (RD) is a significant concern for early breast cancer (BC) patients following initial treatment. Liquid biopsy offers a non-invasive approach to detect tumor-derived components in blood; however, detection sensitivity remains limited at early disease stages due to low target concentrations. To improve this, we evaluated 282 high-volume plasma and blood-cell samples for the dual detection of circulating tumor DNA (ctDNA) and circulating tumor cells (CTCs) using droplet-digital PCR. In pre-treatment samples, ctDNA and/or CTCs were detected in all cases. Post-treatment, positive samples achieved enhanced sensitivity, with a minimum variant allele frequency of 0.003% for ctDNA and a minimum CTCs concentration of 0.069 cells/mL, surpassing detection limits of prior studies. Dynamic ctDNA monitoring allowed accurate prediction of pathological response in the tumor, achieving an area under the ROC curve of 0.92. Moreover, blood detection of disease markers preceded clinical relapse by up to 34.6 months in relapsing patients, providing a significant lead time for intervention. This methodology was also applied to a study of 38 additional BC patients treated solely with surgery to further evaluate its capacity for RD detection in a surgically managed cohort. The findings and implications for RD detection are detailed and presented, underscoring the potential of this sensitive, high-volume approach for real-time monitoring in early-stage BC. Citation Format: Inaki Comino-Mendez, María Elena Quirós-Ortega, Jesús Velasco-Suelto, Celia Gaona-Romero, Alfonso Alba-Bernal, Ana Godoy-Ortiz, María Emilia Domínguez-Recio, Begoña Jiménez-Rodríguez, Esperanza López-López, Jesús Peralta-Linero, María Victoria Ortega-Jiménez, Estefanía Bellagarza-García, Laura Troyano-Ramos, Guadalupe Dolores Garrido-Ruiz, Alicia Garrido-Aranda, Rocío Lavado-Valenzuela, Martina Álvarez, Nuria Ribelles-Entrena, Javier Pascual, Emilio Alba. Increased blood draws for ultrasensitive ctDNA and CTCs detection in early breast cancer patients [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2025; Part 1 (Regular Abstracts); 2025 Apr 25-30; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2025;85(8_Suppl_1):Abstract nr 4551.