Researchers reported a methylation-based circulating tumor DNA (ctDNA) strategy to track metastatic breast cancer therapy response and disease progression. The approach focuses on methylation ctDNA signals during treatment with CDK4/6 inhibitors, aiming to provide more precise, dynamic readouts than conventional markers. By leveraging methylation patterns in ctDNA—molecular signatures tied to epigenetic regulation—the method is intended to improve monitoring granularity across treatment timepoints. In metastatic disease, earlier detection of response shifts can influence subsequent therapeutic decisions. The work positions methylation ctDNA as a potential companion analytics layer for CDK4/6 regimens, particularly where clinical response may lag behind biological change.