Circulating tumor DNA (ctDNA) has emerged as a pivotal biomarker in oncology, offering insights into tumor dynamics and treatment responses. Cohen et al. provide practical recommendations for the clinical utility of ctDNA, emphasizing its strengths and limitations in various treatment settings, particularly for solid tumors (ref: Cohen doi.org/10.1038/s41586-023-06225-y/). In a comprehensive analysis of whole-genome sequencing data from the Pan-Cancer Analysis of Whole Genomes (PCAWG) study, Bruhm et al. identified distinct mutation profiles in cell-free DNA, demonstrating a machine-learning model that achieved over 90% detection accuracy for early-stage lung cancer (ref: Bruhm doi.org/10.1038/s41588-023-01446-3/). The IMvigor010 trial by Powles et al. highlighted that ctDNA positivity correlates with overall survival (OS) outcomes in muscle-invasive urothelial carcinoma, showcasing that ctDNA clearance after treatment with atezolizumab is associated with improved OS (ref: Powles doi.org/10.1016/j.eururo.2023.06.007/). Furthermore, García-Pardo et al. demonstrated that ctDNA testing prior to tissue diagnosis can significantly reduce time to treatment in advanced non-small cell lung cancer (NSCLC) patients (ref: García-Pardo doi.org/10.1001/jamanetworkopen.2023.25332/). Brenne et al. reported that ctDNA markers could detect colorectal cancer up to two years before clinical diagnosis, suggesting a potential role in early screening programs (ref: Brenne doi.org/10.1038/s41416-023-02337-4/). Tsai et al. explored the emergence of RAS mutations during cetuximab treatment, finding a 9.3% detection rate of RAS mutations in patients initially classified as RAS wild-type (ref: Tsai doi.org/10.1038/s41416-023-02366-z/). Collectively, these studies underscore the transformative potential of ctDNA in cancer diagnosis, monitoring, and treatment decision-making.