The purpose of this study is to determine whether acetylsalicylic acid is effective on the recurrence and survival of colon cancer patients.

The purpose of this study is to determine the effect of 80mg acetylsalicylic acid (given orally once daily for 5 years) on 5 year overall survival (OS) for stage II and III colon cancer patients of 45 years of age and older. Preclinical, epidemiologic and clinical evidence suggest that acetylsalicylic acid use may reduce overall cancer risk and mortality in colon cancer patients. It is a phase III double blind placebo controlled, randomized trial of adjuvant low-dose acetylsalicylic acid in colon cancer patients. Patients will be stratified at randomization by centre, age (<70 and ≥70 years) chemotherapy use (any versus none) and disease stage.

Inclusion Criteria:

• Patients 45 years and older with histologically confirmed adenocarcinoma of the colon
• Patients must have TNM stage that is one of the following: pT3-4; N0-2 and M0, or pT1-2 and N1-2 (Union for International Cancer Control (UICC) stage II and III) (in case of >1 tumour: more advanced tumour is stage II or III)
• Patients must have completed surgical resection (R0) (both laparoscopic and open surgery) within 12 weeks of randomization

Exclusion Criteria:

• Patients with rectal cancer (defined as tumour within 15 cm from the anal verge)
• Patients currently taking oral anti-coagulants or use of LMWH or use of DOACs
• Patients currently taking (low-dose) acetylsalicylic acid or other anti-aggregantia for any reason
• Patients with a history of bleeding disorders or active gastric or duodenal ulcers
• Patients currently taking high dose systemic glucocorticoids (≥ 30 mg predniso(lo)n or equivalent)
• Patients with (suspected) (non-) polyposis syndrome (FAP/AFAP, MAP, Lynch syndrome)
• Patients with >100 polyps of the colon or a known hereditary syndrome of the colon in a first degree family member
• Allergy or intolerance to salicylates
• Patients with local or distant recurrent disease
• Previous malignancies other than CIN or SCC with a disease free survival less than 5 years
• Presence of any psychological, familial, sociological or geographical condition potentially hampering compliance with the study protocol and follow-up schedule; those conditions should be discussed with the patient before registration in the trial