The possibility of that ctDNA could be used to detect micrometastatic disease in patients received surgical resection was suggested in several studies. UsingNext Generation Sequencing (NGS),Newman et al. have shown that the serum level of ctDNA was correlated withtumor progress and prognosis in NSCLC. Isaac et al. demonstrated the postoperativectDNA level was associated with breast cancer progression, and it was more sensitive compared to CT scan for predicting the early relapse. Tie et al. examined the postoperative ctDNA level of 1046 plasma samples from a prospective cohort of 230 patients with resected stage II CRC by NGS, and their results demonstrated that recurrence happened in 79% of the patients with positive postoperative ctDNA at median follow-up of 27 months, versus 9.8% in the negative postoperative ctDNA group.