Circulating tumor DNA (ctDNA) analysis has emerged as a pivotal tool in cancer diagnostics and monitoring, particularly in understanding tumor heterogeneity and treatment resistance. One significant study developed a DNA methylation-based classifier, SCLC-DMC, which accurately distinguishes subtypes of small cell lung cancer (SCLC) using genomic-wide reduced-representation bisulfite sequencing in a cohort of 179 patients (ref: Heeke doi.org/10.1016/j.ccell.2024.01.001/). This classifier's ability to utilize ctDNA for subtype identification addresses the challenge of limited tissue availability in clinical settings. In breast cancer, longitudinal profiling of ctDNA revealed co-occurring mutations associated with PARP inhibitor resistance, highlighting the dynamic nature of tumor evolution and the need for adaptive therapeutic strategies (ref: Harvey-Jones doi.org/10.1016/j.annonc.2024.01.003/). Furthermore, the integration of ctDNA and tumor tissue analysis in gastric cancer has been shown to enhance prognostic accuracy, establishing a strong correlation between mutation concordance and cancer recurrence (ref: Yun doi.org/10.14216/kjco.23008/). These findings underscore the potential of ctDNA as a non-invasive biomarker for real-time monitoring of tumor dynamics and treatment efficacy. Methodological advancements have also been pivotal in enhancing ctDNA analysis. The introduction of ultrafast bisulfite sequencing (UBS-seq) significantly reduces reaction times and DNA damage, allowing for more accurate detection of 5-methylcytosine in small DNA samples (ref: Dai doi.org/10.1038/s41587-023-02034-w/). Additionally, a novel approach to transiently reduce the clearance of cell-free DNA in vivo has been proposed to improve the sensitivity of liquid biopsies, thereby facilitating earlier detection of cancer (ref: Martin-Alonso doi.org/10.1126/science.adf2341/). The exploration of methylation patterns in circulating cell-free DNA for colorectal cancer detection has also shown promising results, with over 85% of cases exhibiting significant methylation changes (ref: Yasui doi.org/10.1186/s12943-023-01910-y/). Collectively, these studies illustrate the transformative potential of ctDNA analysis in precision oncology, providing insights into tumor biology and paving the way for personalized treatment approaches.