Eppenberger et al. BMC Cancer 2010, 10:93 http://www.biomedcentral.com/1471-2407/10/93 mismatch repair markers, MLH1, MSH2 and MSH6 identified 102 cases of mismatch repair-deficient color- ectal cancers which were excluded from the analysis. The median follow-up time of patients with mismatch repair-proficient tumours was 30 months (range 0 to 144 months), mean time between local recurrence and surgery was 20.1 months. Outcome measure of interest was cancer-specific survival time. Statistical analysis VEGF ligand/receptor ratios and their association with categorical clinico-pathological features was performed using the non-parametric Wilcoxon Rank Sum Test or Kruskal Wallis test, where appropriate. Missing clinico- pathological information was assumed to be missing at random. Survival analysis was carried out using the Kaplan-Meier and log-rank test. The assumption of pro- portional hazards was verified by analyzing the correla- tion of Schoenfeld residuals and the ranks of individual failure times. Subsequently, multivariable Cox propor- tional hazards regression analysis was carried out to determine the independent prognostic effect of each VEGF ligand, receptor or ratio with significant effects in univariate analysis, after adjusting for the effects of pT, pN and vascular invasion. Hazard ratios (HR) and 95% confidence intervals (CI) were used to determine the Page 5 of 10 prognostic effect of each variable. Due to multiple test- ing, a Bonferroni correction for multiple comparisons indicated that only p-values < 0.0012 should be consid- ered statistically significant. All analyses were carried out using SAS (V9, The SAS Institute). Results Comparison of normal mucosa and colorectal cancer Expression of all VEGF ligands and receptors was signif- icantly greater in colorectal cancers compared to normal colorectal mucosa (p < 0.001; Figure 3). VEGF ligand/receptor ratios (Tables 2 and 3) An increased VEGF-A/VEGFR1 ratio was observed in patients with tumours presenting conspicuous peritu- moural lymphocytic inflammation at the invasive front (p = 0.032). When analyzing VEGF-A and VEGFR1 separately, an increase of both VEGF-A (p = 0.005), and VEGFR1 (p = 0.032) was found in tumours with this histological feature in comparison to those with absence of inflammation. In univariate analysis pT, pN and vas- cular invasion all demonstrated a significant effect on outcome (p < 0.001, each). These features were included into multivariable survival analysis to determine the effect of the VEGF-A, VEGFR1 and VEGF-A/VEGFR1 ratio on prognosis after adjusting for these 3 features. Figure 3 Differences in mean VEGF ligand and receptor expression in normal colorectal mucosa in comparison to colorectal cancers. Standard error bars are shown.