Here is the design of a clinical trial:

Official Title: Comparative Effectiveness Trial of Transoral Head and Neck Surgery Followed by Adjuvant Radio(Chemo)Therapy Versus Primary Radiochemotherapy for Oropharyngeal Cancer

Included conditions:
- Oropharyngeal Cancer

Study Armgroups:
- {'label': 'Resection/adjuvant radio(-chemo)therapy', 'type': 'EXPERIMENTAL', 'description': '* Transoral surgical resection within 4 weeks after randomization\n* Neck dissection can be performed during resection of the primary tumor or within 4 weeks after randomization\n* 6-7 weeks standard risk-adapted adjuvant radio(-chemo)therapy 56-66 Gy (chemotherapy according to arm B if necessary), start within 6 weeks post-surgery', 'interventionNames': ['Procedure: Resection', 'Radiation: Radiotherapy', 'Drug: Chemotherapy']}
- {'label': 'Adjuvant radio(-chemo)therapy/salvage neck dissection', 'type': 'ACTIVE_COMPARATOR', 'description': '* 6-7 weeks standard radiotherapy (IMRT-technique), start within 4 weeks after randomization\n* 70-72 Gy, SIB possible\n* Cisplatin 100 mg/m2 on days 1, 22, 43 or Cisplatin once weekly (30-40 mg/m2) on days 1, 8, 15, 22, 29, 36 or Mitomycin C 10 mg/m2 d1, 29 and 5-FU 600 mg/m2/day iv on days 1-5 or Cisplatin 20 mg/m² + 5-FU 600 mg/m²/day iv d 1-5 and 29-33\n* +/- Salvage neck dissection 12±2 weeks after treatment', 'interventionNames': ['Radiation: Radiotherapy', 'Drug: Chemotherapy', 'Procedure: Salvage neck dissection']}

Interventions:
- {'type': 'PROCEDURE', 'name': 'Resection', 'description': 'Definitive surgery should generally be performed within 2 weeks, but not more than 4 weeks after randomization. The appropriately indicated neck dissection(s) may be performed either prior to, during the same session, or within 2 weeks after the resection of the primary tumor, but not later than 4 weeks following randomization. The primary tumor is to be resected with clear margins (R0) and en bloc in all cases. Frozen section assessment must be routinely and readily available.', 'armGroupLabels': ['Resection/adjuvant radio(-chemo)therapy'], 'otherNames': ['Transoral Surgery']}
- {'type': 'RADIATION', 'name': 'Radiotherapy', 'description': '6-7 weeks standard risk-adapted adjuvant radiotherapy 56-66 Gy, start within 6 weeks post-surgery Arm B: 6-7 weeks standard radiotherapy (IMRT-technique), start within 4 weeks after randomization, 70-72 Gy, SIB possible', 'armGroupLabels': ['Adjuvant radio(-chemo)therapy/salvage neck dissection', 'Resection/adjuvant radio(-chemo)therapy']}
- {'type': 'DRUG', 'name': 'Chemotherapy', 'description': 'The investigational medicinal product (IMP) are the chemotherapeutical drugs Cisplatin, Mitomycin C and 5-FU. According to local routine, chemotherapy protocols as listed in study protocol should be used.', 'armGroupLabels': ['Adjuvant radio(-chemo)therapy/salvage neck dissection', 'Resection/adjuvant radio(-chemo)therapy']}
- {'type': 'PROCEDURE', 'name': 'Salvage neck dissection', 'description': '+/- Salvage neck dissection 12±2 weeks after treatment', 'armGroupLabels': ['Adjuvant radio(-chemo)therapy/salvage neck dissection']}

Primary Outcomes:
- {'measure': 'Time to local or locoregional failure or death from any cause', 'description': 'The primary objective of this study is to evaluate the effectiveness of primary surgical versus non-surgical treatment of patients with locally advanced, but transorally resectable oropharyngeal cancer in terms of time to local or locoregional failure or death from any cause (LRF).', 'timeFrame': 'Defined as time from randomization up to 36 month'}

Please estimate the sample size based on the assumption: 
The trial has a planned observational period of 5 years (2 years recruitment and 3 years follow-up). A 3% lost to follow-up rate is estimated for both arms. Blinded interim analysis will be performed after recruiting 250 patients, and unblinded interim analyses will be conducted after 50% and 75% of observed events. The steering committee will decide on adaptations or early stopping based on these analyses.
Sample size calculations
        The trial is based on an event-driven design with a planned observational period of 5âyears (recruitment time 2âyears and follow-up time 3âyears).
        The event rate in the definitive chemoradiotherapy for oropharyngeal cancer group is assumed to be 50% after 36âmonths. The transoral head and neck surgery followed by adjuvant (chemo) radiotherapy is assumed to reduce the event rate for the primary outcome to 35%. It is assumed that the hazard rate is constant over time. Under these assumptions, 142 events have to be observed during the planned observation period, which will result in a sample size of 280 patients.
        In both arms a 3% lost to follow-up during the study is estimated. After recruiting 250 patients a blinded interim analysis will be performed. The steering committee will decide on adaptation of the sample size/ recruiting time. Additionally, based on results of the planned unblinded interim analysis after 50 and 75% of available observed events, the steering committee will decide on adaptation of the recruiting/follow up time or to allow an early stopping of the trial for success. The recruitment will be stopped immediately if the needed number of events is reached.