Abstract 1918: Investigation of early dissemination in ductal carcinoma in situ patients using circulating tumor cells

In this study, circulating tumor cells are enriched from blood samples of ductal carcinoma in situ (DCIS) patients and investigated as a potential prognostic biomarker. Raised awareness of the importance of early diagnostics in breast cancer is leading to an increased incidence of DCIS detection through mammographic screening. DCIS is widely defined as a ‘Stage 0’ carcinoma with neoplastic cells still confined to the basement membrane. However, the 20-year breast cancer mortality rate following a DCIS diagnosis, with or without treatment, remains at 3.3%. Ultimately, the goal of the project is to better inform DCIS patient risk stratification via the isolation and analysis of circulating biomarkers. We establish a workflow that targets the gaps in traditional tissue-based diagnostics with liquid biopsies. Our study builds on emerging literature on the early dissemination of breast cancer cells by investigating the value of circulating tumor cells (CTCs) as a biomarker in DCIS. To achieve a more holistic understanding of a patient’s carcinoma, we supplement our study with the Mouse INtraDuctal (MIND) models - an animal model that recapitulates the tumor microenvironment of DCIS in the mammary ducts of mice. Methods: We employed a high throughput, label-free microfluidic platform to enrich CTCs from DCIS patient samples. Enriched CTCs underwent single cell RNA sequencing (scRNA-seq) along with matched tissue samples to understand the clonal origin of these cells. Further, to correlate findings in patient samples to an animal model wherein the timeline of progression to invasive disease can be shortened to 9 to 12 months (vs. 10+ years in patients), we analyzed blood samples from 3 MIND models longitudinally. Results: Applying our workflow to 34 patient samples and 10 healthy controls, we identified CTCs in 76% of the patient samples. The median concentration of CTCs per mL of blood in DCIS patients (6.1 CTCs/mL) was significantly greater than that in healthy controls (0.92 CTCs/mL; p < 0.0001, Mann-Whitney U Test). Via scRNA-seq, inferred CNVs were identified in CTCs. Distinct, dominant subclones were also identified in the tissue epithelial cells as potential contributors to the CTC population. In addition, during the MIND model time course study, CTCs were found in circulation as early as 4 months after formation of the models and while the models were still pre-invasive. Overall, our study enables the assessment of CTCs as a prognostic biomarker for DCIS patients. Not only have we successfully enumerated CTCs in patient samples, but we have also identified distinct subclones in the tissue epithelial cells from which the CTCs could originate, supporting our overarching goal of demystifying early dissemination. Ultimately, we hope to investigate the value of CTCs as a clinical biomarker to inform personalized risk stratification for DCIS patients. Citation Format: Neha Nagpal, Brittany Rupp, Yan Hong, Fariba Behbod, Max Wicha, Sunitha Nagrath. Investigation of early dissemination in ductal carcinoma in situ patients using circulating tumor cells [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 1918.