Influence of p53 status on prognosis in preoperatively irradiated rectal carcinoma

Even when they are analogous in microscopic and macroscopic appearance, 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 rectal carcinoma patients.

The p53 status of rectal adenocarcinomas was examined immunohistochemically (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).

p53 protein expression was detected in 55 of 100 biopsy samples (> or = 5% nuclear staining). There was essentially no difference in p53 expression between biopsy samples and corresponding resected specimens (54 of 97 vs. 55 of 97). In univariate analysis, p53 immunoreactivity of biopsy samples did not correlate with age, gender, tumor location, TNM stage, pT category, pN category, or histologic grade. Unlike clinicopathologic variables, p53 expression did not have a statistically significant association with local recurrence free, disease free, or overall survival in either univariate (P = 0.91, 0.18, and 0.17, respectively) or multivariate analysis.

In contrast to cell line studies, this immunohistochemical study demonstrates that p53 status is not useful as a prognostic marker in preoperatively irradiated rectal carcinoma.