Prognostic implications of BAX protein expression and microsatellite instability in all non-metastatic stages of primary colon cancer treated by surgery alone

This study examined whether the apoptosis-related protein, BAX, or the microsatellite-instability phenotype provide prognostic information in patients with resected colon cancer. A total of 371 stage I-III patients that previously underwent radical surgery were included (mean follow-up 51.8 months). BAX expression was examined by immunohistochemical staining; high-frequency microsatellite instability (MSI+) was determined by assessing the specific marker, BAT26, using single-strand conformation polymorphism (SSCP)-based analysis. High BAX expression was found in 66.4% of patients. MSI+ tumors were observed in 14.8% of 344 patients. Univariate analysis showed that unlike MSI, low BAX expression was significantly correlated with poor disease-specific overall survival (OS) in stages I-III (p = 0.04). Multivariate subgroup analyses revealed that unlike MSI, low BAX was an independent predictor for OS in stage II (p = 0.009); however, in stages I or III, BAX or MSI were not independent predictors of OS. In stage II colon cancer treated with surgery alone, BAX protein expression may be a predictor for prognosis.