Abstract
The potential of cell-free DNA (cfDNA) methylation profiling in oncology is increasingly recognized for its ability to offer a comprehensive assessment of tumor biology. In this report, we explore the plasma methylome dynamics in patients with early breast cancer (BC) undergoing neoadjuvant chemotherapy (NACT) using an agnostic genome-wide approach with cell-free DNA immunoprecipitation and sequencing (cfMeDIP-seq). Our cohort comprised seven women with triple-positive BC, assessed for cfDNA methylation changes at multiple time points during their treatment course. Genome-wide analysis revealed distinctive patterns of differential methylation in patients achieving pathological complete response (pCR), with no significant epigenomic modifications in patients with residual disease (RD). Gene set enrichment analysis highlighted dynamic variations in functional pathways associated with therapy response, including metabolism, immune response, and response to xenobiotics, with a notable reversibility post-treatment. Principal component analysis of the differentially methylated regions demonstrated a clear distinction between pCR and RD patients, indicating the potential of cfMeDIP-seq for the non-invasive assessment of therapy response. Such findings suggest that cfMeDIP-seq could complement ctDNA offering broader insights into the global modifications induced by chemotherapy. Although future research is needed to validate and expand on our findings, we offer a proof-of-principle of the potential utility of cfMeDIP-seq in the personalized management of BC.