Safety and efficacy of pulsed low-dose rate radiotherapy for local recurrent esophageal squamous cell carcinoma after radiotherapy Study protocol for a prospective multi-center phase II trial

Introduction: Re-irradiation after radiotherapy is a common treatment for locally recurrent esophageal cancer. However, the side effects of re-irradiation are serious. The most serious adverse reactions of re-irradiation include esophageal perforation and hemorrhage caused by esophageal perforation. Studies have shown that pulsed low-dose rate radiotherapy (PLDR) induces a hypersensitivity effect on tumor tissue and a hyper-repair effect on normal tissue, which can simultaneously reduce damage on the normal tissue and increase the therapeutic effect on the tumor. The objective of this study is to explore whether PLDR can reduce rate of esophageal perforation and improve efficacy in patients with recurrent esophageal squamous cell carcinoma (ESCC) after radiotherapy. Methods and analysis: This study is a prospective, multi-center, open, single-arm clinical trial designed to enroll 27 patients with locally recurrent ESCC after radiotherapy with or without chemotherapy. Re-irradiation will be performed using intensity modulated radiation therapy in 50 Gy/25 fractions. The strategy of PLDR includes dividing 2 Gy into 10 fractions, and administering each irradiating dose of 20 cGy at an interval of 3 minutes before the next low-dose irradiation. The actual dose rate of administration each time will be 16.67 cGy/minute. The primary endpoint in this study is the rate of esophageal perforation. The secondary endpoints are the objective remission rate, the palliative effect on quality of life and pain, and the time of disease progression. The observation time is 2 years after the end of the study.