Blood samples (8ml) from patients (n=142) who underwent work-up for lower gastrointestinal malignancy during the time period 2003-2006. Colonoscopy was performed, and no malignancy or premalignant lesions found. Blood samples were collected before/after colonoscopy. These blood samples were collected during a previous PhD-study: "Pre- and postoperative Venous Thromboembolism in Patients with Colorectal Cancer - implications of Radiotherapy" (ID-number VN 2003/102). The plasma samples will be analysed at the Section of Molecular Diagnostics, Clinical Biochemistry, Aalborg University Hospital, and the methylation profile of the cell-free DNA in plasma will be analysed, using methylation specific PCR based on the accelerated bisulfite treatment protocol.