Influence of p53 status on prognosis in preoperatively irradiated rectal carcinoma

BACKGROUND. Even when they are analogous in microscopic and macroscopic app earance, tumors vary in their response rates to radiotherapy. Cell culture and xenograft experiments with colorectal cell lines have demonstrated that wild-type p53 increases radiosensitivity. Hence, the authors investigated, in a well-defined population of patients treated at the same institution, whether p53 status was a prognostic factor in preoperatively irradiated rec tal carcinoma patients. METHODS. The p53 status of rectal adenocarcinomas was examined immunohistoc hemically (with monoclonal antibody DO-1) in preirradiated biopsy samples ( n = 100) and corresponding postirradiated resected specimens (n = 97). The mean follow-up was 73.2 months (median, 71.3 months; range, 4.3-157 months) . Statistical analysis was performed using the SPSS program (SPSS, Chicago, IL). RESULTS. p53 protein expression was detected in 55 of 100 biopsy samples (g reater than or equal to 5% nuclear staining). There was essentially no diff erence in p53 expression between biopsy samples and corresponding resected specimens (54 of 97 vs. 55 of 97). In univariate analysis, p53 immunoreacti vity of biopsy samples did not correlate with age, gender, tumor location, TNM stage, pT category, pN category, or histologic grade. Unlike clinicopat hologic variables, p53 expression did not have a statistically significant association with local recurrence free, disease free, or overall survival i n either univariate (P = 0.91, 0.18, and 0.17, respectively) or multivariat e analysis. CONCLUSIONS. In contrast to cell line studies, this immunohistochemical stu dy demonstrates that p53 status is not useful as a prognostic marker in pre operatively irradiated rectal carcinoma. Cancer 1999;85:2541-8. (C) 1999 Am erican Cancer Society.