Drug: Aspirin;Drug: Placebo

Inclusion Criteria:

- Written informed consent according to ICH/GCP regulations before inclusion and prior
to any trial-related investigations.

- Histologically confirmed diagnosis of adenocarcinoma of the colon.

- Stage II (pT3/T4 N0 cM0) or stage III (pTx pN+ cM0) colon cancer.

- Availability of cancer tissue for central molecular testing.

- Presence of predefined, activating PIK3CA mutation in exons 9 or 20 (centrally
assessed).

- Complete resection of the primary tumor (R0) within 14 weeks maximum before
registration.

- WHO performance status 0-2.

- Age between 18-80 years.

- Adequate hematological values: hemoglobin = 80 g/L, platelets = 50 x 109/L.

- Adequate hepatic function: total bilirubin =1.5xULN, AST =2.5xULN, ALT =2.5xULN, AP
=2.5xULN.

- Calculated creatinine clearance > 30 mL/min, according to the formula of
Cockcroft-Gault.

- Women with child-bearing potential are using effective contraception, are not pregnant
or lactating and agree not to become pregnant during trial treatment. A negative
pregnancy test before inclusion (within 7 days) into the trial is required for all
women with child-bearing potential.

Exclusion Criteria:

- Previous or concomitant malignancy within 3 years of registration, except for
adequately treated cervical carcinoma in situ or localized non-melanoma skin cancer.

- Multiple adenocarcinomas of the colon.

- Rectal cancer (defined as distance from anal verge to proximal/oral tumor edge =15
cm).

- Severe or uncontrolled cardiovascular disease (congestive heart failure NYHA III or
IV, unstable angina pectoris, history of myocardial infarction) within three months
prior to registration.

- Systemic rheumatic diseases or degenerative disorders affecting the musculoskeletal
system with a relevant risk of requiring treatment with NSAIDs in the future.

- Comorbidities that require regular (i.e. more than 3x per month, any dose) intake of
acetylsalicylic acid or other NSAIDs or COX-2 inhibitors.

- Clinically relevant upper gastro-intestinal bleeding within 12 months prior to
registration.

- Presence of any bleeding disorder that is an absolute contraindication to the use of
aspirin.

- General tendency to hypersensitivity and history of asthma triggered by salicylates or
substances with a similar mechanism of action, and non-steroidal anti-inflammatory
drugs in particular

- Any serious underlying medical condition, at the judgment of the investigator, which
could impair the ability of the patient to participate in the trial (e.g. uncontrolled
infection, active autoimmune disease, uncontrolled diabetes).

- Concurrent treatment with other experimental drugs or treatment in an interventional
clinical trial within 30 days prior to trial entry. Concomitant use of adjuvant
chemotherapy for stage III and high risk stage II colon cancer according to
international treatment guidelines is allowed (chemotherapy regimens include
intravenous 5-fluorouracil or oral capecitabine either alone or in combination with
intravenous oxaliplatin).

- Psychiatric disorder precluding understanding of trial information, giving informed
consent or interfering with compliance for oral drug intake.

- Any familial, sociological or geographical condition potentially hampering proper
staging and compliance with the trial protocol.

- Known or suspected hypersensitivity to any component of the trial drug or any agent
given in association with this trial.

- Known galactose-1-phosphate uridyl transferase deficiency, UDP galactose 4 epimerase
deficiency, galactokinase deficiency, orFanconi-Bickel syndrome, congenital lactase
deficiency,or glucose-galactose malabsorption (due to the lactose-containing placebo).

- Any concomitant drugs contraindicated for use with the trial drug according to the
approved product information.