极低残余疾病（Minimal Residual Disease，MRD）是指在治疗过程中或之后体内存有极少量残余肿瘤细胞，代表着肿瘤的残留及临床进展的可能性。循环肿瘤DNA（circulating tumor DNA，ctDNA）是肿瘤细胞主动分泌的DNA片段或在肿瘤细胞凋亡或坏死过程中释放到循环系统中的DNA片段，其作为一种无创生物标志物出现，可动态监测治疗效果和预测复发。ctDNA作为MRD检测的可行性以及基于ctDNA的液体活检技术的革命为癌症监测提供了一种潜在方法。本综述总结了ctDNA检测的主要方法（基于PCR的测序和下一代测序），并介绍了它们的优缺点。此外，我们还回顾了ctDNA分析对于指导辅助治疗和预测肺癌、乳腺癌和结肠癌等复发的意义。最后，MRD检测仍面临许多挑战，如缺乏标准化、假阴性或假阳性结果造成误导，以及需使用大规模独立队列进行验证以改善临床结果。版权所有 © 2023 Zhu, Xu, Yang, Shi, Zhang, Liu, Li, Zhou and Bing.

Minimal residual disease (MRD) refers to a very small number of residual tumor cells in the body during or after treatment, representing the persistence of the tumor and the possibility of clinical progress. Circulating tumor DNA (ctDNA) is a DNA fragment actively secreted by tumor cells or released into the circulatory system during the process of apoptosis or necrosis of tumor cells, which emerging as a non-invasive biomarker to dynamically monitor the therapeutic effect and prediction of recurrence. The feasibility of ctDNA as MRD detection and the revolution in ctDNA-based liquid biopsies provides a potential method for cancer monitoring. In this review, we summarized the main methods of ctDNA detection (PCR-based Sequencing and Next-Generation Sequencing) and their advantages and disadvantages. Additionally, we reviewed the significance of ctDNA analysis to guide the adjuvant therapy and predict the relapse of lung, breast and colon cancer et al. Finally, there are still many challenges of MRD detection, such as lack of standardization, false-negatives or false-positives results make misleading, and the requirement of validation using large independent cohorts to improve clinical outcomes.Copyright © 2023 Zhu, Xu, Yang, Shi, Zhang, Liu, Li, Zhou and Bing.