Cancer is the second leading cause of death in Switzerland. Patients who have been diagnosed with colorectal carcinoma and received curative surgical R0-Resection frequently relapse or develop metastases in the first 2–3 years postoperatively. With timely detection through appropriate aftercare, some of these patients could potentially be cured. In order to optimize follow-up adherence, we implemented a study environment based on an app, which reminds patients to schedule their follow-up appointments timely with their GP or specialist. In addition, the study environment comprises a central server to collect pseudonomized study data regarding follow-up compliance. The next step will be a study to evaluate the potential impact of such an app. We present the outline of the planned study.