475 Background: The prognostic importance of the local antitumor immune response in colorectal carcinoma (CRC) is well established. Recent studies suggest that systemic antitumor immunity may also impact on survival. This study aimed to determine the relationship between peripheral blood lymphocyte counts (PBLCs), reactive features in regional lymph nodes, local tumoral/peri-tumoral lymphocytic inflammation and survival in stage II CRC. Methods: Resection specimens from 185 patients with stage II CRC were assessed for peri-tumoral lymphocytic inflammation, tumor-infiltrating lymphocytes, lymph node yield, lymph node size, and reactive changes in individual lymph nodes. Reactive changes were scored semi-quantitatively and given a reactivity [R] score of 1-4 based on the presence and size of germinal centers. Pre-operative PBLCs and neutrophil counts were recorded. Results: Lower peripheral lymphocyte counts were associated with advanced age (p = 0.016), T4 disease (p = 0.006), venous invasion (p = 0.006), lymph node yields <12 (p = 0.024), smaller mean nodal diameters (p = 0.021), absence of tumor-infiltrating lymphocytes (p = 0.002) and fewer highly-reactive lymph nodes (R score 4) per case (p = 0.032). Cox regression analysis revealed that advanced age (Hazard Ratio, 1.03 per year [95% confidence interval, 1.01-1.05]; p = 0.015) and higher peripheral lymphocyte counts (HR, 0.52 per 1x109cells/L [95% CI, 0.31-0.86]; p = 0.011) were independently predictive of disease-free survival. Neutrophil counts were not associated with outcome. A higher neutrophil to lymphocyte ratio was associated with worse survival on univariate, but not multivariable analysis. Conclusions: The PBLC is an independent predictor of survival in stage II CRC, and is significantly associated with the immune status of regional lymph nodes and the local lymphocytic immune response.
Tumor-infiltrating lymphocytes are a marker for microsatellite instability in colorectal carcinoma
