Feasibility, Reliability, and Satisfaction of CEA Using Home Based (Automated) Capillary Blood Sampling

The goal of this study is to determine the feasibility of CEA assessments at home using (automated) capillary sampling in patients in the follow-up after treatment for colorectal cancer.
The main questions it aims to answer are:
* To determine the success rate of capillary sampling at home by the patient
* To assess reliability and satisfaction of (automated) capillary CEA measurements Participants will be asked to perform automated capillary sampling and lancet capillary sampling at home twice after regular check-up visits in the hospital, with an interval of 3-6 months in between. During this hospital visit, a CEA measurement in blood sampled by venipuncture will be performed to act as a reference for the CEA measurements in (automated) capillary blood to be sampled at home.
Reliability of CEA measurements will be assessed for automated capillary and lancet capillary sampling compared to venipuncture.
Satisfaction in terms of patient reported outcomes (pain, burden, ease of use, and preference) will be evaluated.