Restricted overexpression of p53 immunohistochemistry (p53IHC RO) as prognostic after colorectal cancer (CRC) resection.

e14602 Background: p53IHC RO was previously described as a distinct pattern from the negative or diffuse p53 IHC expression. p53IHC RO is characterized by a limited number of homogenously scattered strongly positive CRC cells and is associated with some clinico-pathologic CRC feature. The prognostic impact of p53IHC RO remains unknown. Methods: p53 and MMR (MLH1, MSH2, MSH6 and PMS2) proteins IHC expression were performed on CRC primary tumors from an unselected cohort of patients who underwent surgery at the Cliniques St-Luc between 1995 and 2000. p53 IHC results were defined as negative, diffuse or restricted expression. Clinico-pathologic CRC characteristics and patients follow-up were available for this analysis. Comparisons of numerical and categorical clinico-pathological data were evaluated respectively by ANOVA and Fisher exact tests between p53 expression groups. Progression-Free Survival (PFS) and Overall Survival (OS) analyses were performed using Kaplan-Meier method and compared with the log-r...