Prognostic value of immunohistochemistry for p53 in primary soft-tissue sarcomas: a multivariate analysis of five antibodies

Most changes of tumor suppressor p53 and its pathway involve a protein with prolonged half-life that permits immunohistochemical detection. The goal of this study was to compare the prognostic relevance of five different p53 antibodies in primary soft-tissue sarcomas (STS) with known p53 mutation status, using a multivariate Cox regression model (adjusted to tumor grading, staging, localization, tumor type, and therapy). A group of 198 primary STS of six types were investigated for p53 overexpression, using p53 antibodies DO-1, DO-7, Pab1801, Pab240, and CM-1. A positive marker frequency between 36.2% and 62.6% was detected. Out of 65 patients whose primary tumor reacted positively to all five antibodies, 52 (80%) died within the study period. Only the N-terminal-binding monoclonal antibodies DO-1, DO-7 and Pab1801 showed a multivariate correlation with survival (P = 0.0014, 0.0048 and 0.02). CM-1 and Pab240 had a univariate, but not a multivariate correlation, with a confounding effect of grading. The prognostic relevance for the five p53 antibodies was: DO-1 > Pab1801 > DO-7 > CM-1 > Pab240. This is the first study that investigates multivariately the prognostic relevance of p53 immunostaining in STS. If monoclonal antibodies with an epitope in the N-terminal region of the p53 protein (DO-1, Pab1801, DO-7) are applied, p53 immunohistochemistry provides an independent prognostic marker in STS.