Here is the design of a clinical trial:

Official Title: Prophylactic Surgery Plus Hyperthermic Intraperitoneal Chemotherapy (HIPEC CO2) Versus Standard Surgery in Colorectal Carcinoma at High Risk Peritoneal Carcinomatosis. Short and Long-term Outcomes. CHECK STUDY

Included conditions:
- Colorectal Neoplasms

Study Armgroups:
- {'label': 'Experimental', 'type': 'EXPERIMENTAL', 'description': 'ARM A: Prophylactic surgery plus HIPEC CO2 performed with mitomycin', 'interventionNames': ['Procedure: HIPEC CO2 surgery', 'Drug: Mitomycin']}
- {'label': 'Comparator', 'type': 'ACTIVE_COMPARATOR', 'description': 'ARM B: Standard surgey without HIPEC CO2 The arm B is with standard surgery without HIPEC CO2', 'interventionNames': ['Procedure: Standard surgery']}

Interventions:
- {'type': 'PROCEDURE', 'name': 'HIPEC CO2 surgery', 'description': 'Prophylactic surgery plus HIPEC CO2 performed with mitomycin', 'armGroupLabels': ['Experimental']}
- {'type': 'PROCEDURE', 'name': 'Standard surgery', 'description': 'Standard surgery without HIPEC CO2', 'armGroupLabels': ['Comparator']}
- {'type': 'DRUG', 'name': 'Mitomycin', 'description': 'Prophylactic surgery plus HIPEC CO2 performed with mitomycin', 'armGroupLabels': ['Experimental'], 'otherNames': ['HIPEC CO2 surgery with mitomycin']}

Primary Outcomes:
- {'measure': 'Local recurrence free survival (LRFS)', 'description': 'The primary efficacy endpoint is LRFS defined as the time from randomization to the date of first local relapse, peritoneal carcinomatosis or death for any cause, whichever comes first.', 'timeFrame': 'This outcome measure will be assess approximately 3 years after the last patient enrolled'}

Please estimate the sample size based on the assumption: 
Two-sided type I error of 4.9%, power of 80%, 15% of randomised patients not eligible, 5% level of significance for secondary endpoint, 80% power to detect a relative reduction in the risk of recurrence/death of at least 33%.
Sample size
        Setting a two-sided type I error of 4.9% and a power of 80%, to detect a relative reduction of 50% in the incidence of LRFS events in the experimental group compared with the control group, 72 events are required. Assuming 36 months of accrual and 36 months of follow-up, it will be necessary to include approximately 330 patients (165 per arm). Assuming a 15% of randomised patients not eligible because of the presence of PC undetected by CT scan and discovered only during the surgical procedure, it will be necessary to randomise a total of 388 patients (194 per arm) in order to reach approximately 330 patients evaluable for the analysis of the primary endpoint.
        In this setting considering all types of recurrences (local and distant), we expect a incidence of local recurrence as primary site in 30%â40% of patients.
        Reaching the target number of events of local recurrences (72 events), about 200 recurrences of any type (local or distant) will be observed. Therefore, the trial will have adequate power to analyse the secondary endpoint DFS: 80% power to detect a relative reduction in the risk of recurrence/death of at least 33%, with a 5% level of significance at two sides.