Radiotherapy plays an important role in multidisciplinary treatment of esophageal cancer. However, about half patients received radiotherapy occurred relapse. Once relapse occurred, there is no better treatment strategy. Genomic study of relapsed esophageal cancer is seldom. So the investigators attempt to collect relapsed tissue to conduct with whole exome sequencing in order to investigate the genome landscape of recurrence esophageal cancer.

Tumor tissue of patients received radiotherapy with diagnosis of recurrence between Jan 1, 2010 and Dec 1, 2020 were collected retrospectively. Recurrence tumor tissue is collected between Dec 31, 2020 and Dec 31, 2022 prospectively. Blood and preradiotherapy tumor tissue were also collected to be as contrast. A total of 100 paired blood, preradiotherapy tumor tissue and relapse tumor tissue were collected. What is more, a total of 100 paired blood and preradiotherapy tumor tissue with diagnosis of no recurrence were collected. All samples were conducted with whole exome sequencing.

Here the investigators define recurrence period as within 2 years and no recurrence period as more than 3 years after radiotherapy.

Criteria of relapse: (1) pathologic diagnosis is squamous carcinoma before radiotherapy;(2) received radiotherapy; (3)pathologic diagnosis is also squamous carcinoma after radiotherapy; (4) clinical symptoms including feeding obstruction etc; (5) imaging evidence showed disease progression.

Inclusion Criteria:

1. pathologic diagnosis is squamous cell carcinoma before radiotherapy;
2. pathologic diagnosis is squamous cell carcinoma after radiotherapy;
3. received radiotherapy
4. clinical symptoms including dysphagia, feeding obstruction, etc
5. image evidence showed disease progression
6. the period of recurrence was within 2 years after radiotherapy

Exclusion Criteria:

1. pathologic diagnosis is not squamous cell carcinoma before radiotherapy;
2. pathologic diagnosis is not squamous cell carcinoma after radiotherapy
3. not received radiotherapy
4. the period of recurrence was more than 2 years after radiotherapy
5. the period of no recurrence was within 3 years after radiotherapy

Recurrence group: 100 paired relapsed tumor tissue,blood and preradiotherapy tumor tissue within 2 years after radiotherapy were collected.

No recurrence group:100 paired blood and preradiotherapy tumor tissue with more than 3 years after radiotherapy were collected