The objectives are to evaluate the efficacy and safety of concurrent chemoradiotherapy after endoscopic resection in early stage esophageal squamous cell carcinoma by evaluating the effectiveness, including 3-year OS, DFS, LRFS, DMFS, LCR, DMR and QOF, and analyzing the toxicity and side effects in 3 years follow-up time.

The study preliminarily explored the recurrence patterns of solely ER for early esophageal squamous cell carcinoma with high risk factors, analyzed the rationality of target areas and dose choices in the treatment regimen of concurrent chemoradiotherapy after ER, and proposed modification schemes of the target area and dose of radiotherapy. Prospectively acquired hematological samples and tissue samples during the treatment will be tested for genetic testing, single-cell genome sequencing, transcriptome and epigenomic analysis, to screen the population with high risk of recurrence or the population who will benefit from this treatment combination.

In terms of sample size, The estimates of survival rate at 3 years for operation group is 85.1% (95% CI: 82.0%, 87.7%) based on SEER study. Assuming that the survival rate at 3 years for ER+CRT is about 90.7%. The difference between operation and ER+CRT is marginal and clinically meaningless. In our study, we will target to establish that the ER+CRT is non-inferiority to operation in term of survival rate at 3 years, and further investigate the benefit of ER+CRT in safety profile and quality of life. A non-inferiority margin 10% is applied with respect to 85.1%. A number of 50 subjects is adequate to achieve 80% statistical power under a type one error rate 0.025 one-sided. The power analysis is based on simulation, 10000 iterations are carried out, Greenwood's method is applied.