Introduction/Background Currently available imaging techniques are often inadequate for early breast cancer detection, hence the interest for novel non-invasive biologic markers. Liquid biopsies, e.g. the analysis of circulating tumor DNA (ct-DNA), represent an alternative to tissue biopsies and characterize tumor genetic features in a non-invasive manner. ct-DNA is a promising prognostic and predictive biomarker, but in the case of early breast cancer, its role is still unclear.

Methodology We conducted a prospective analysis of plasma ct-DNA of patients with histologically confirmed breast cancer undergoing surgical treatment. The patients were enrolled between January 2018 and March 2019 at a university based medical center. Prior to surgical treatment patients provided a blood sample and mFAST-SeqS method was used for analysis. The data about tumour size, histological type, lymph node status, hormone receptors, Ki67 were collected and correlation with ct-DNA was analysed. For correlation analysis, non-parametric Spearman’s coefficient was used. Non-parametric tests were used for comparison of continous variables.

Results We have included 69 patients to the study. The median age of the patients was 64 years (range 31–92 years). The median size of the tumours was 18 mm (range 4–94 mm). In all but one patient, the detected ct-DNA fractions were less then 10% of total cell free DNA (z-score <5). There was no statistically significant correlation between the size of the tumour and ct-DNA (Spearman’s correlation coefficient -0.31, p>0.05). When comparing the tumours <1 cm in size to the larger tumours, the median z-score was 2.04 vs. 2.59 (p>0.05). Patients with negative lymph nodes had comparable median z-score to patiens with positive lymph nodes (2.34 vs 2.41, p>0.05). There was no statistically significant correlation between ct-DNA z-score and Ki67 expression and tumour marker CA 15-3.

Conclusion Our results do not support ct-DNA detection as a feasible biomarker for early breast cancer detection.

Disclosure Nothing to disclose.