Here is the design of a clinical trial:

Official Title: Assessment of the Effect of a Daily Chemoprevention by Low-dose Aspirin of New or Recurrent Colorectal Adenomas in Patients With Lynch Syndrome

Included conditions:
- Lynch Syndrome

Study Armgroups:
- {'label': 'Aspirin300', 'type': 'ACTIVE_COMPARATOR', 'description': 'Acetylsalicylic acid 300 mg tablet by mouth, daily dose during 4 years', 'interventionNames': ['Drug: Acetylsalicylic acid lysinate 300 mg']}
- {'label': 'Placebo300', 'type': 'PLACEBO_COMPARATOR', 'description': 'Placebo (like Acetylsalicylic acid 300 mg) tablet by mouth, daily dose during 4 years', 'interventionNames': ['Drug: Placebo (for Aspirin 300)']}
- {'label': 'Aspirin100', 'type': 'ACTIVE_COMPARATOR', 'description': 'Acetylsalicylic acid 100 mg tablet by mouth, daily dose during 4 years', 'interventionNames': ['Drug: Acetylsalicylic acid lysinate 100 mg']}
- {'label': 'Placebo100', 'type': 'PLACEBO_COMPARATOR', 'description': 'Placebo (like Acetylsalicylic acid 100 mg) tablet by mouth, daily dose during 4 years', 'interventionNames': ['Drug: Placebo 100 (for Aspirin 100)']}

Interventions:
- {'type': 'DRUG', 'name': 'Acetylsalicylic acid lysinate 300 mg', 'description': 'Daily dose during 4 years', 'armGroupLabels': ['Aspirin300'], 'otherNames': ['Aspirin300']}
- {'type': 'DRUG', 'name': 'Placebo (for Aspirin 300)', 'description': 'Daily dose during 4 years', 'armGroupLabels': ['Placebo300'], 'otherNames': ['Placebo300']}
- {'type': 'DRUG', 'name': 'Acetylsalicylic acid lysinate 100 mg', 'description': 'Daily dose during 4 years', 'armGroupLabels': ['Aspirin100'], 'otherNames': ['Aspirin100']}
- {'type': 'DRUG', 'name': 'Placebo 100 (for Aspirin 100)', 'description': 'Daily dose during 4 years', 'armGroupLabels': ['Placebo100'], 'otherNames': ['Placebo100']}

Primary Outcomes:
- {'measure': 'Number of patients with at least one adenoma seen on chromo-endoscopy 48 months after complete withdrawal of polyps and initiation of treatment (aspirin or placebo)', 'description': 'To look for a preventive effect of low-dose aspirin (100 or 300 mg/d) compared with placebo on new or recurrent colorectal adenomas in patients with Lynch syndrome', 'timeFrame': '4 years'}

Please estimate the sample size based on the assumption: 
5% alpha risk, 80% power.
Sample size
        The main objective of this trial is to show that adenoma prevalence is less important in the aspirin group (regardless of the dose) than in the placebo group. The initial hypothesis was constructed with a 30% adenoma prevalence in the placebo group and a reduction of 28% expected in the aspirin group, based on our previous RCT on patients without Lynch syndrome but with a history of colorectal adenomas [8]. For a 5% alpha risk and 80% power, according to this hypothesis, 426 patients will be needed in the aspirin group (213 patients for aspirin 100âmg arm and 213 patients for aspirin 300âmg arm) and 426 patients in the placebo group (213 patients for placebo aspirin 100âmg arm and 213 patients for placebo aspirin arm 300âmg). A total of 852 patients will be included.