Esophageal cancer is one of the common malignant tumors in the world. In 2020, the number of new cases of esophageal cancer in the world will reach 604000, and the number of deaths will reach 544000. As a high incidence area of esophageal cancer in China, esophageal squamous cell carcinoma (ESCC) is the most common, with about 324000 cases of morbidity and 301000 deaths each year, posing a serious threat to people's lives and health. With the continuous development of digestive endoscopy technology, endoscopic submucosal dissection (ESD) and other minimally invasive endoscopic techniques have become the first line of treatment for early esophageal cancer. However, studies have shown that there is a risk of local recurrence within one year after ESD for early esophageal cancer, with a recurrence rate of 0-17%. Therefore, surveillance detection after ESD has become an important link in the diagnosis and treatment of esophageal cancer.

At present, there is no uniform standard at home and abroad for surveillance after ESD for esophageal squamous cell carcinoma, no matter the frequency or method of surveillance. For example, the guidelines issued by Japan suggest that the surveillance should be conducted every 6 to 12 months after ESD, at least once a year. In the guidelines issued by the European Society of Gastroenterology, it is recommended to review endoscopy 3 to 6 months after ESD. If there is no recurrence, it can be changed to review endoscopy once a year. The Guidelines for the Diagnosis and Treatment of Esophageal Cancer issued by the National Health Commission in April 2022 suggests that patients should be rechecked 3 months, 6 months and 12 months after ESD, and if there is no recurrence, they should be rechecked once a year. Recheck once every three months within two years after surgery, once every six months within two to five years, and once every year after five years. Although the above guidelines and specific strategies for surveillance after esophageal cancer surgery have not yet been unified, the use of upper gastrointestinal endoscopy (hereinafter referred to as "gastroscope") as the main means of review and close surveillance are more consistent.

However, due to the invasiveness, cost and availability of gastroscope, frequent endoscopic surveillance of patients with esophageal cancer after ESD may bring significant economic and health burden to patients, and lead to a decline in patients' subjective surveillance enthusiasm. Therefore, it is of great significance to find a more safe, economical and comfortable surveillance method that is equivalent to the diagnostic performance of gastroscope for standardizing the surveillance after ESD for esophageal cancer.

cytosponge is a new non-invasive examination method, which can diagnose esophageal lesions by collecting esophageal cells and carrying out cytological examination and p53 staining. Its diagnostic efficacy for esophageal cancer has been confirmed in various studies at home and abroad. Esophageal cytology has been proved to have a good application prospect in the identification and screening of high-risk groups of esophageal cancer. In the 20th century, our country widely carried out esophageal mesh cytology for screening esophageal cancer in high incidence areas, but this method has low sensitivity (39%\~47%), is easy to miss diagnosis, and has poor inspection comfort, and has been eliminated at present. The improved new esophageal cell collectors (such as CytospongeTM, EsophaCapTM, Shikang No. 1 TM, etc.) adopt the expanded sponge capsule design, which increases the contact area with esophageal mucosa, and has a higher success rate than the original dragnet cytology sampling. Cytological examination is relatively simple. Combining with the high-risk factor scoring scale can improve the screening effect and improve the positive rate and screening efficiency of surveillance endoscopic intensive examination. Foreign studies on Barrett's esophagus showed that the sensitivity of cytology combined with different biomarkers of the new cell collector of the esophagus was 73.3% - 93.1%, and the specificity was 92.4-95.7%; It can play a good risk stratification role in Barrett's esophageal related dysplasia and early esophageal adenocarcinoma (0% in low-risk group, 14% in medium risk group, and 87% in high-risk group). The diagnostic and management guidelines for Barrett's esophagus formulated by the British Gastroenterological Association and the American Gastroenterological Society both point out that: Cytosponge can be used as a screening method for Barrett's esophagus, and it is more in line with the principles of health economics. As early as 2010, a prospective cohort study in the UK showed that the sensitivity and specificity of cytosponges in diagnosing Barrett's esophagus with a circumference of 1cm or more were 73.3% and 93.8%, respectively. Similarly, a multicenter randomized controlled trial in the UK in recent years also confirmed the diagnostic efficacy of cellular sponge capsule in Barrett's esophagus. In addition, for areas with high incidence of ESCC, a study based on the Golestan cohort in Iran pointed out that the accuracy of cytological examination combined with p53 staining in detecting high-grade esophageal squamous hyperplasia could reach 100%. In a previous study conducted by our team, 1844 subjects from high-risk areas of ESCC were recruited, and the effectiveness, safety and comfort of the two in esophageal cancer screening were compared through cytosponge examination and gastroscopy. The results showed that the sensitivity and specificity of cellular sponge capsule in the diagnosis of high-grade esophageal lesions (including esophageal squamous cell carcinoma and high-grade intraepithelial neoplasia) were 90% and 93.7% respectively. However, no serious adverse events were recorded during cell collection, which fully demonstrates the feasibility and safety of AI helper cytosponge in community screening of ESCC.

To sum up, the cellular sponge capsule has good diagnostic efficacy in the diagnosis of esophageal cancer, and is more safe, economical and comfortable. It is expected to replace gastroscope in the surveillance after ESD to a certain extent. At present, there is no relevant research at home and abroad. This study plans to establish a large sample cohort based on the collaborative research network established earlier, prospectively include 1000 patients who received ESD resection treatment for early esophageal cancer and compare the effectiveness and safety of cytosponge and gastroscope in the surveillance of early esophageal cancer after ESD through self-comparison.