Pretreatment p53 immunoreactivity does not infer radioresistance in prostate cancer patients

Purpose: To test, in a clinical context, the hypothesis that p53 aberrations, assessed by immunoreactivity, are related to radioresistance as suggested by several experimental studies. Methods and Materials: Sixty patients with prostate cancer who underwent transurethral resection of the prostate or biopsy prior to definitive external beam therapy were retrospectively identified. The endpoint in the study was cancer specific survival. The nuclear accumulation of the aberrant p53 protein was evaluated by immunohistochemistry with the pantropic, monoclonal Ab-6 anti-p53 antibody (clone DO-1) on pretreatment biopsies. Immunoreactivity was related to stage, grade, and cancer-specific survival. Results: There was a correlation between p53 immunoreactivity and low tumor stage (p < 0.001), but no relation between p53 status and grade was found. Moreover, no significant difference was found in cancer-specific survival between the p53 positive tumors (109 months) and the p53 negative tumors (99 months). Conclusions: No disadvantage regarding survival was seen for patients with p53 immunoreactive tumors, implicating that p53 immunoreactivity does not infer radioresistance in prostate cancer. This suggests that the p53 inactivation may be a less important determinant of tumor response to radiotherapy in some human cancers than in the previously studied experimental situations. Thus, other mechanisms may be more important in determining outcome after radiation. However, the series is small and data should be interpreted with caution.