Clinical Impact of Tumor-infiltrating Lymphocytes for Survival in Curatively Resected Stage IV Colon Cancer with Isolated Liver or Lung Metastasis

The most reliable prognostic factor to date is tumor, node, metastasis stage. However, prognostic significance of tumor-infiltrating lymphocytes (TILs) in curatively resected stage IV colon cancer with isolated liver or lung lesion has not been clarified. The aim of this study was to assess and compare the prognostic role of TILs in curatively resected stage IV colon cancers. Immunohistochemistry was used to assess the densities of CD8(+), CD45RO(+), and FOXP3(+) according to tumor sites (primary tumor, liver, and lung) from 79 stage IV colon cancers. These were evaluated for association with histopathologic features and patients' overall survival (OS). Higher density of CD45RO(+) at primary and metastatic sites was associated with better patient outcomes (P = 0.009 and 0.027, respectively). The estimated 3-year OS rates for high-density CD45RO(+) at metastatic and primary sites was 82.6 and 62.4 %, respectively, compared to 60.8 and 27.1 % in low-density CD45RO(+). In multivariate analysis, CD45RO(+) at the colon primary site (P = 0.007; relative risk 0.108; 95 % confidence interval 0.021-0.546) was the strongest prognostic factor. High density of CD45RO(+) TILs showed independent prognostic significance for OS. This result may help to improve the prognostication of curatively resected stage IV colon cancer.