Circulating tumour DNA (ctDNA) is a promising tool when monitoring the residual disease in colorectal cancer (CRC). Current staging procedures are insufficient to identify the patient cohort at high risk, who might benefit from additional adjuvant therapy.

We will show that the assessment of ctDNA is a non-invasive approach and easily taken at different time points via simple blood draw to monitor residual disease from the colorectal cancer patients after primary surgery. Minimal residual disease could be used in the future for individualized treatment decisions after primary surgery.

Inclusion Criteria:

• planned colorectal primary surgery

Exclusion Criteria:

• unfit patients with dementia