Intrinsic radiosensitivity by metallothionein expression has no great influence on clinical radiosensitivity in esophageal carcinoma

Several studies have shown that macroscopically infiltrative type of esophageal carcinoma generally has a poorer local response to radiation therapy than that of localized type. The aim of this study was to determine the role of metallothionein (MT) as a radioprotective agent in the difference of clinical radiosensitivities in esophageal carcinoma. A total of 45 surgically resected esophageal carcinoma tissues [20 macroscopically localized type without preoperative treatment (PT), 20 macroscopically infiltrative type without PT and 5 macroscopically infiltrative type with PT] were stained for MT by immunohistochemistry and were analyzed. MT expression level of macroscopically localized type of esophageal carcinoma was significantly higher than that of infiltrative type without PT (P=0.026) and was significantly higher than that of infiltrative type with PT (P=0.024). No significant difference was found between MT expression levels in infiltrative type of esophageal carcinoma without PT and that with PT. The results of this study suggest that there is less possibility that clinical radioresistance of the tumor is due to MT expression in esophageal carcinoma and also suggest that there is less possibility that MT synthesis is induced by fractionated irradiation of a moderate dose or by an anti-cancer agent during a course of treatment.