Abstract:Malignant tumors remain a major global public health challenge owing to their high incidence and mortality. Detection technologies constitute the foundation of precision oncology. Although tissue biopsy is regarded as the gold standard for tumor diagnosis, its invasiveness and limited feasibility for longitudinal monitoring restrict its clinical utility in certain scenarios. In recent years, circulating tumor DNA (ctDNA)–based liquid biopsy has rapidly emerged as a promising analytical approach, offering advantages such as minimal invasiveness, repeatability, and real-time reflection of tumor molecular characteristics. Accumulating evidence indicates that ctDNA plays an important role in early tumor monitoring, auxiliary diagnosis, prognostic evaluation, detection of minimal residual disease and recurrence, prediction of neoadjuvant therapy response, assessment of metastatic disease, therapeutic decision-making, and monitoring of treatment efficacy and drug resistance. This review systematically summarizes the biological characteristics of ctDNA and its current clinical applications throughout the entire continuum of cancer management, and discusses existing challenges and future perspectives, aiming to provide insights for the standardized clinical implementation of ctDNA testing.