Here is the design of a clinical trial:

Official Title: Preventive HIPEC in Combination With Perioperative FLOT Versus FLOT Alone for Resectable Diffuse Type Gastric and Gastroesophageal Junction Type II/III Adenocarcinoma - The Phase III "PREVENT" Trial of the AIO /CAOGI /ACO

Included conditions:
- Gastric Cancer
- Gastroesophageal Junction Adenocarcinoma

Study Armgroups:
- {'label': 'Arm A - FLOT', 'type': 'ACTIVE_COMPARATOR', 'description': 'Patients randomized to treatment Arm A already received 3-6 cycles of FLOT in 2-week treatment cycles prior to undergoing surgery. Following surgery, patients will receive four further 2-week cycles FLOT. FLOT can be deescalated to FLO, FLT or FL in case of chemorelated toxicity at any time and at the discretion of investigator.\n\nFLOT = Docetaxel 50 mg/m², Oxaliplatin 85 mg/m², Leucovorin 200 mg/m², 5-FU 2600 mg/m².', 'interventionNames': ['Drug: 5-Fluorouracil', 'Drug: Leucovorin', 'Drug: Oxaliplatin', 'Drug: Docetaxel']}
- {'label': 'Arm B - FLOT/HIPEC', 'type': 'EXPERIMENTAL', 'description': 'Patients randomized to treatment Arm B already received 3-6 cycles of FLOT in 2-week treatment cycles prior to undergoing surgery including Intraoperative Hyperthermic IntraPEritoneal Chemoperfusion (HIPEC) during gastric-/ esophagogastric resection using Cisplatin 75mg/m². Following surgery, patients will receive four further 2-week cycles FLOT. FLOT can be deescalated to FLO, FLT or FL in case of chemorelated toxicity at any time and at the discretion of investigator.\n\nFLOT = Docetaxel 50 mg/m², Oxaliplatin 85 mg/m², Leucovorin 200 mg/m², 5-FU 2600 mg/m².', 'interventionNames': ['Drug: 5-Fluorouracil', 'Drug: Leucovorin', 'Drug: Oxaliplatin', 'Drug: Docetaxel', 'Drug: Cisplatin']}

Interventions:
- {'type': 'DRUG', 'name': '5-Fluorouracil', 'description': 'Day 1 q2w: 2600 mg/m² IV over 24 hours', 'armGroupLabels': ['Arm A - FLOT', 'Arm B - FLOT/HIPEC'], 'otherNames': ['5-FU']}
- {'type': 'DRUG', 'name': 'Leucovorin', 'description': 'Day 1 q2w: 200 mg/m² IV over 30 minutes', 'armGroupLabels': ['Arm A - FLOT', 'Arm B - FLOT/HIPEC'], 'otherNames': ['Calciumfolinat']}
- {'type': 'DRUG', 'name': 'Oxaliplatin', 'description': 'Day 1 q2w: 85 mg/m² IV over 2 hours', 'armGroupLabels': ['Arm A - FLOT', 'Arm B - FLOT/HIPEC']}
- {'type': 'DRUG', 'name': 'Docetaxel', 'description': 'Day 1 q2w: 50 mg/m² IV over 1 hour', 'armGroupLabels': ['Arm A - FLOT', 'Arm B - FLOT/HIPEC']}
- {'type': 'DRUG', 'name': 'Cisplatin', 'description': 'intraoperative: 75mg/m² intraabdominal solution over 1 hour and 30 minutes', 'armGroupLabels': ['Arm B - FLOT/HIPEC']}

Primary Outcomes:
- {'measure': 'Comparison of progression-/disease-free survival (PFS/DFS) between arms', 'description': 'To compare PFS/DFS in patients with localized and advanced diffuse or mixed type adenocarcinoma of the stomach and Type II/III GEJ (i.e. ≥cT3 any N or any T N-positive) with exclusion of distant metastases and after receiving neoadjuvant FLOT- therapy will be included in this trial after a central review, receiving 3-6 cycles perioperative FLOT versus FLOT alone in the intent to treat population (ITT) and where PFS/DFS is defined as the time from randomization to disease progression or relapse after surgery or death from any cause.', 'timeFrame': 'from randomization up to 5 years'}

Please estimate the sample size based on the assumption: 
Type I error is 5% and one-sided Log rank test is used. Statistical power is 80%. Dropouts prior to randomization are set at 35%. Dropouts after randomization are set at 5%. Accrual time is 42 months followed by 2 years follow up period.
Sample size calculation
          The primary efficacy analysis will compare randomized surgical resection combined with HIPEC to randomized surgical resection only on the time to the primary efficacy endpoint using the intent-to-treat population. The hypothesis test will use the log rank test to compare the investigational arms. The study assumes a Hazard ratio of 0.65 favoring the HIPEC group. The PFS/DFS in the reference arm is set as 20.19âmonths (calculation on complete data from study FLOT4) for signet ring cell containing gastric cancers. Accrual time is 42âmonths followed by 2âyears follow up period. Dropouts prior to randomization are set at 35%. Dropouts after randomization are set 5%. Type I error is 5% and one-sided Log rank test is used. Two hundred patients are to be randomized to provide a statistical power of 80%. These 200 patients will be recruited in 20 German sites with already proven experience in conducting HIPEC procedure.