Japan colorectal tumor prevention study: randomized controlled trial by low-dose aspirin

INTERVENTION: Aspirin (100 mg/day) enteric‐coated tablet Placebo tablet / day CONDITION: colorectal tumor PRIMARY OUTCOME: Only the occurrence of a colorectal tumor (adenoma or cancer) is selected as the primary endpoint. INCLUSION CRITERIA: Candidate patients have to meet all the following inclusion criteria to participate in the study. # Patients with at least one colorectal tumor (intramucosal cancer and adenoma) as confirmed by histological diagnosis, all of which have been removed endoscopically (at any time) # Patients with known history of all endoscopic treatments (including histological diagnosis) of colorectal tumors # Patients who have undergone total colonoscopy at least twice # Patients with clean colon as confirmed by total colonoscopy within 3 months before the study