Inclusion Criteria:  Age 18-80 years;  Histologically proven colorectal cancer  All the lesion (s) has been R0 resected  Have elevated tumor biomarker (CEA or CA19-9) in three consecutive tests  More than 1 CTC has been detected (including 1)  ECOG 0-1  Hematology tests suggest that they can tolerate chemotherapy  Written informed consent for participation in the trial  Exclusion Criteria:  Have any radiological evidence of recurrence  Other previous malignancy within 5 years