Prediction of tumor radiosensitivity in rectal carcinoma based on p53 and Ku70 expression.

The identification of predictive indicators of radiosensitivity is extremely useful in selecting patients suited for preoperative radiotherapy and avoiding unnecessary preoperative treatment. In this study, we evaluated the possible role of the immunohistochemical expression pattern of p53 and Ku70 protein in determining tumor radiosensitivity in rectal cancer before preoperative irradiation. We examined pretreatment biopsy materials from 111 patients by immunohistochemistry. The expression pattern of p53 and Ku70 was evaluated for association with tumor radiosensitivity, which was defined according to the criteria of the Japanese Research Society for Cancer of the Colon and Rectum. There was a significant correlation between the expression pattern of p53 and tumor radiosensitivity (P = 0.045); Ku70 and tumor radiosensitivity (P < 0.001); and the combination of p53 and Ku70, and tumor radiosensitivity (P < 0.001). The sensitivity, specificity, positive predictive value, negative predictive value, and accuracy in both p53 and Ku70-positive cases for radioresistance were all superior to those of the group positive for p53 alone. In conclusion the examination of the combination of p53 and Ku70 may predict the radiosensitivity of rectal cancer before preoperative irradiation.