Abstract PO5-16-05: Integrating Circulating Tumor Cells (CTCs) and Cell-free DNA (cfDNA) Signatures for Monitoring Treatment Response in Stage III/IV Inflammatory Breast Cancer

Abstract Background: Inflammatory breast cancer (IBC) is a rare and aggressive form of breast cancer, comprising only between 1-5% of all breast cancer cases in the United States. Despite its low incidence, IBC accounts for 10% of breast cancer-related deaths and is often diagnosed with metastasis, resulting in shorter survival compared to non-IBC cases. The 5-year relative survival rate for all stages of IBC is 39%, dropping to 19% for patients with distant metastasis. Liquid biopsy-based biomarkers have emerged as potential analytes for predicting prognosis and monitoring response to therapies in IBC patients. We explored the prognostic role of liquid biopsy encompassing both CTCs and cfDNA in the blood of patients with stage III/IV IBC and their clinical outcomes. Methods: CTC and cfDNA analysis was performed on 90 blood samples from 47 patients with stage III and IV IBC. Samples were collected before (pre-treatment, n=43) initiation and after (post-treatment, n=47) completion of neoadjuvant chemotherapy. CTCs were enriched and enumerated using the CellSearch® platform (Menarini-Silicon Biosystems). CfDNA was extracted from plasma using MagMax™ Cell-Free Total Nucleic Acid Isolation Kit (Applied Biosystems™) and quantified using the Qubit™ dsDNA High Sensitivity kit (Invitrogen™). Differences in cfDNA concentrations were used to plot a receiver operating characteristic (ROC) curve which was then used to determine Area Under the Curve (AUC) and a cfDNA cut-off point. ROC cut-off was calculated based on Youden Index J. Survival analysis was performed by the Kaplan-Meier estimator and Cox regression models. P-values were measured using the Student t-test. Results: Prior to neoadjuvant treatment, CTC was detected in 51% of patient samples, and the median cfDNA concentration was 5.87 ng/mL (range 0.95-24.11 ng/mL). After completion of neoadjuvant treatment, CTC was detected in 25% of patient samples, and the median cfDNA concentration was 11.19 ng/mL (range 3.41-88.13 ng/mL). The cut-off points determined for pre-treatment and post-treatment cfDNA concentration was 4.2 ng/mL and 9.5 ng/mL respectively. At pre-treatment, CTC detection and cfDNA concentration 4.2 ng/mL were independently associated with disease relapse (P=0.007, 0.016, respectively). The combination of CTC detection and cfDNA concentration 4.2 ng/mL was significantly associated with disease relapse (P=0.0004), decreased relapse free survival (RFS, P=0.005) and overall survival (OS, P=0.007). At the post-neoadjuvant treatment time point, the combination of CTC detection and cfDNA concentration 9.5 ng/mL was significantly associated with relapse regardless of pCR status (P=0.02). Conclusion: The combined presence of CTCs and elevated cfDNA concentrations in patients with stage III/IV IBC after completion of neoadjuvant chemotherapy was associated with disease relapse regardless of pCR status. A combination of elevated cfDNA and CTC detection signatures after completion of neoadjuvant chemotherapy may be useful for risk stratification and adjuvant systemic therapy planning. Citation Format: Sridevi Addanki, Salyna Meas, Vanessa Sarli, Abdulkader Almosa, Wendy Woodward, Dhruvajyoti Roy, Anthony Lucci. Integrating Circulating Tumor Cells (CTCs) and Cell-free DNA (cfDNA) Signatures for Monitoring Treatment Response in Stage III/IV Inflammatory Breast Cancer abstract. In: Proceedings of the 2023 San Antonio Breast Cancer Symposium; 2023 Dec 5-9; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2024;84(9 Suppl):Abstract nr PO5-16-05.