Prognostic value of the density of tumor-infiltrating lymphocytes in colorectal cancer liver metastases.

Tumor-infiltrating lymphocytes (TILs) have been reported to reflect the anti-tumor immune status of patients and to be correlated with their prognosis and therapeutic outcomes. However, the characteristics of the local immune status in metastatic tumors is poorly understood, as primary tumors have been the focus in most previous studies. In addition, the local immune status may be influenced by preoperative chemotherapy. The present study aimed therefore to investigate the relationship between the degree of TIL infiltration and the prognosis in patients with curative resection of colorectal cancer liver metastases and to examine the effects of preoperative chemotherapy on the function of immune cells. A total of 108 patients who underwent curative resection of colorectal cancer liver metastases in our department between May 1996 and January 2017 were enrolled in the present study. Peripheral blood samples were obtained within two weeks before surgery. TIL infiltration was evaluated by immunohistochemical staining of surgically resected specimens of liver metastases using anti-CD8/CD3 antibodies. The mean number of TILs in five different fields was calculated, and patients were classified into a high-TIL group and a low-TIL group. Furthermore, patients were divided into three groups as follows: i) A group of patients who did not receive preoperative chemotherapy; ii) a group of patients who received short-term preoperative chemotherapy for <6 months; and iii) a group of patients who received long-term preoperative chemotherapy for ≥6 months. The results demonstrated that the density of TILs in colorectal liver metastases was not correlated with the absolute peripheral lymphocyte count in all patients. Furthermore, the degree of CD8