This is a multicenter, randomized, parallel group, prospective, double blind, placebo controlled clinical trial of chemoprevention in patients at increased risk of developing colorectal cancer (CRC). The Colotech combination treatment (acetylsalicylic acid, 1α 25-dihydroxy cholecalciferol, and calcium carbonate) will be compared to placebo with regards to safety and efficacy during 3 years of treatment. The randomized treatment period will be preceded by a 3-week single blind placebo run-in period, which will assess patient's compliance to treatment. In order to collect data on the durability of treatment effect, follow-up data from a surveillance colonoscopy will be collected two years after the 3-year colonoscopy.
