In Denmark, approximately 3,600 persons are diagnosed with colorectal cancer every year. Of these patients, 75-80% may undergo intended curative resection, but within a few years the disease recurs in about half of the curatively resected patients. Less than half of the total number of patients will survive the subsequent five years. Radiotherapy and adjuvant systemic chemotherapy have a limited effect on overall survival. It is therefore imperative to optimise the overall treatment of patients with colorectal cancer. One substantial option might be the development, validation and implementation of biological markers that could be used for early detection/screening, prognosis evaluation, surveillance, selection of patients for adjuvant therapy independent of stage of the disease, and monitoring of the given treatment.