Background and purpose: This study aimed to evaluate the efficacy of radical radiotherapy and assess prognostic factors in metachronous oligometastatic esophageal cancer (MOEC) patients after initial treatment with curative-intent surgery and/or chemoradiotherapy. Materials and methods: MOEC Patients during 2009-2018 in ÂÂÂ Central Hospital were retrospectively analyzed. Each patient had 5 oligometastatic lesions, and the primary lesions were controlled in this study. Patients were devided into radiotherapy (RT) and non-radiotherapy (NRT) groups. The study endpoints were overall survival (OS) and treatment toxicities. Results: This study included 82 patients who underwent intensity-modulated radiotherapy for MOEC. Median OS were 14 (95% confidence interval [CI], 11.0-17.0) and 7 (95% CI, 4.5-9.5) months for the RT and NRT groups, respectively (P = 0.016). Median OS were 18 (95% CI, 13.6-22.4) and 10 (95% CI, 5.1-14.9) months for lung and bone metastases, respectively (P = 0.010). Median OS were 15 (95% CI, 12.4-17.6) and 10 (95% CI, 7.6-12.4) months for interval time from initial diagnosis to metastasis !12 and <12 months, respectively (P = 0.026). Median OS were 16 (95% CI, 12.2-19.8) and 10 (95% CI, 5.0-15.0) months for biological effective dose (BED 10) ! 60 Gy and BED 10 < 60 Gy, respectively (P = 0.033). Cox multivariate regression analysis showed that treatment modality (RT vs. NRT) was an independent prognostic factor for MOEC patients (hazard ratio: 1.8, 95% CI: 1.1-3.0; P = 0.022). No toxic side effects greater than grade 3 were observed in all patients. Conclusions: Radiotherapy is a feasible and positive treatment for MOEC patients after initial treatment, a radical radiation dose with BED 10 ! 60 Gy has benefits in extending survival. Radical radiotherapy should thus be considered for MOEC patients.

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. Trial registration: Clinical trial number: ChiCTR1900020609.

To our knowledge, this study protocol is the first to identify the sensitivity and specificity of oral meglumine diatrizoate in an esophagogram for screening esophageal fistula during radiotherapy. If oral meglumine diatrizoate can be used to screening esophageal fistula, more patients will benefit from early detection and treatment.