Inspite of curative treatment 30-50% patients with ColoRectal Cancer (CRC) develop tumor relapse during the first 3 years after treatment of the primary tumor. Treatment of relapses is based on surgical resection, when possible, chemotherapy and targeted therapies. To detect recurrences or metastases, a surveillance strategy is recommended for patients able to withstand complementary treatment during a five-year period. Over this period, the probability of one false-positive result is 87%. Considering that less than 10% of recurrent patients are suitable for potentially curative treatment and that more intensive programs enable an increase of the overall rate of curative resection but do not result in reduced mortality, less time and cost-consuming, tailored follow-up is necessary. The level of circulating ccfDNA, defined as extra cellular DNA, increases in CRC patients. The Inplex® method could validate the use of ccfDNA as a cancer biomarker in terms of prognosis and surveillance.

Tubes for ccfDNA analysis will be taken during medical examination at the same time of the CEA dosage (if it was not made before the consultation). Cryotubes of plasma will be sent for analysis in the laboratory INSERM (National Health Institute) of Montpellier and the remaining plasma will be kept in biological collection.

Patients will have a consultation of follow-up every 3-4 months during which the dosage of CEA and ccfDNA will be realized as well as a medical examination, a general examination (weight, size, and blood pressure), an evaluation of the indices of performance status and a nutritional evaluation in case of loss of weight.

Inclusion Criteria:

• Age ≥ 18 years
• Primary diagnosis of stages II and III CRC:
• is already operated and histological proven (biopsy at least)
• is patient that must be operated: curative treatment for stages II and III CRC
• Patient benefiting from a program personalized by care
• Written informed consent

Exclusion Criteria:

• Patient already treated for stages II and III CRC and in surveillance
• Patient with indication or with palliative treatment
• Pregnant or nursing patients
• Known pregnancy
• Difficulties to understand the protocol
• Patients under protection measure (guardianship, curatorship, protection of justice)

the data are anonymized