CIrculating TUmor CELls (CTCs), circulating tumor DNA (ctDNA) and exosomes (Ex) in breast cancer patients: a prospective study

Background The translational study CITUCEL aims to correlate the presence of CTCs and ctDNA at different time points with the clinical outcome of BC patients in neo-adjuvant, adjuvant or advanced setting and to compare the mutational profiles of the primary tumor, CTCs and ctDNA in the different settings. Methods CTCs have been characterized and isolated single or in pool with the DEPArray system, after immunologic negative enrichment with antibodies coupled to magnetic beads against common leukocytes and red blood cells antigens, followed by cells labelling with specific antibody for epithelial, mesenchymal and pan-leukocyte markers. CTCs mutational analyses have been performed by NGS on the Ion Torrent™ platform using the Oncomine Breast cfDNA V2.0 Kit and an in house developed approach based on the molecular tagging. The same kit and the same panel was used to analyse ctDNA, extracted from plasma using ccfDNA LV kit (Promega). Primary tumor mutational profile has been evaluated in NGS with a custom panel. Results A total of 60 patients have been enrolled in the study (32 in neo-adjuvant, 22 in adjuvant and 6 in advanced settings). CTCs have been recovered and morphologically/phenotypically re-evaluated; ctDNA has been extracted, quantified and analysed by NGS. Preliminary analysis shown a significative difference in CTCs baseline counts between the early settings and the advanced one (P=0.038). No significative change has been detected before and after treatment in the (neo)-adiuvant setting, but remarcably a lower CTCs baseline count correlates with pCR (P=0.0399). Similar results have been obtained in regards of ctDNA, definitely higher in the blood of MTS patients (P=0.0127); no significative differences were detected before and after treatment, and no correlation has been found with pCR. The mutational analysis is in progress. Conclusions The results of the study will provide information on the applicability of liquid biopsy in clinical practice.