癌症的早期发现对于增加患者的生存机会至关重要。用于诊断癌症的三大技术是仪器检查、组织活检和肿瘤生物标志物检测。循环肿瘤DNA（ctDNA）由于相对于传统技术的高灵敏度、高特异性、非侵入性等优势，近年来受到广泛关注。通过肿瘤细胞凋亡、坏死和循环外泌体释放的机制，ctDNA可以扩散到整个循环系统，并携带甲基化、突变、基因重排和微卫星不稳定性等修饰。传统的基因检测技术难以实现实时、低成本和便携式 ctDNA 测量，而电化学生物传感器为 ctDNA 检测提供低成本、高特异性、灵敏度和便携性。因此，本综述重点描述各种癌症类型的 ctDNA 生物标志物的最新进展以及用于实时、无创和快速 ctDNA 检测的生物传感器的开发。在进一步的评论中，还讨论了 ctDNA 传感器基于电极表面识别元件选择受体探针的问题。

Early detection of cancer is vital for increasing patient survivability chances. The three major techniques used to diagnose cancers are instrumental examination, tissue biopsy, and tumor biomarker detection. Circulating tumor DNA (ctDNA) has gained much attention in recent years due to advantages over traditional technology, such as high sensitivity, high specificity, and noninvasive nature. Through the mechanism of apoptosis, necrosis, and circulating exosome release in tumor cells, ctDNA can spread throughout the circulatory system and carry modifications such as methylations, mutations, gene rearrangements, and microsatellite instability. Traditional gene-detection technology struggles to achieve real-time, low-cost, and portable ctDNA measurement, whereas electrochemical biosensors offer low cost, high specificity alongside sensitivity, and portability for the detection of ctDNA. Therefore, this review focuses on describing the recent advancements in ctDNA biomarkers for various cancer types and biosensor developments for real-time, noninvasive, and rapid ctDNA detection. Further in the review, ctDNA sensors are also discussed in regards to their selections of probes for receptors based on the electrode surface recognition elements.