XRCC5 and lung adenocarcinoma: 27 demonstrated Ku80 was related to survival of patients with lung adenocarcinoma. But study of Soderlund et al. 32 did not support that Ku80 could predict outcomes of breast cancer. Even in same malignant tumor, the findings were controversial 33, 34. There is no available information about the relationship between Ku80 and prognosis of superficial ESCC patients to our knowledge. Here, our data indicated long OS and DFS of midthoracic superficial ESCC patients were related to Ku80 low expression (Table 2 and 3).