High-dose Intensity-modulated proton therapy versus Standard-dose Intensity-modulated RadIation therapy for esophageal squamous cell carcinoma (HI-SIRI): study protocol for a randomized controlled clinical trial

Background Chemoradiotherapy is the standard of care for esophageal cancer as a neoadjuvant treatment before surgery, or as a definitive treatment for unresectable disease. Intensity-modulated radiotherapy (IMRT) has been considered the standard radiation technique. However, patients suffer from treatment-related toxicities, and most die from disease progression or recurrence. With emerging technological advancement, proton therapy has theoretical advantages over IMRT because it offers apparent dosimetric benefits to allow dose escalation to the target while better sparing surrounding tissues such as the lungs, heart, liver, and spinal cord. The purpose of this study protocol is to investigate the survival benefit of proton therapy using modern intensity-modulated proton therapy (IMPT) compared to standard IMRT for esophageal cancer. Methods This is a two-arm open phase II/III multi-institution randomized controlled trial. Eligible patients will have histologically confirmed squamous cell carcinoma of the thoracic esophagus with no evidence of tracheoesophageal/esophagobronchial fistula or distant metastasis. After stratification according to resectability status (resectable vs. borderline resectable/unresectable), a total of 232 patients will be randomized to receive IMPT or IMRT using a 1:1 allocation ratio. In resectable cases, surgical resection following concurrent chemoradiation will be attempted for the patients who are medically fit at the time of surgery. In those with initially borderline resectable/unresectable disease, definitive concurrent chemoradiation will be performed. The phase II study will assess safety (toxicity and postoperative complications) and feasibility (recruitment rate and chemoradiation dose modification) in 40 patients into each arm. The study will then continue into phase III, further recruit 76 patients into each arm, and compare progression-free survival between IMPT vs IMRT groups. The secondary endpoints will be overall survival, local and distant control, toxicities, health-related quality of life, and cost-utility. This protocol describes a detailed radiotherapy and chemotherapy. Discussion This randomized clinical trial will demonstrate the clinical benefit of IMPT in esophageal cancer treatment in terms of survival and toxicity outcomes which will further establish high-level evidence for radiation modality in squamous cell carcinoma of the thoracic esophagus. Trial registration TCTR20200310006. Registered 10 March