Prognostic value of tumor-infiltrating lymphocytes in colon cancer.

[BACKGROUND] Several clinico-pathological prognostic factors are essential to guide therapeutic management for colon cancer (CC). The benefit of adjuvant chemotherapy remains controversial for patients with stage II CC and is currently not systematically applied. This leads to define two subgroups of patients, "low" and "high risk" of recurrence. In this setting, tumor-infiltrating lymphocytes (TILs) may represent a promising marker.

[AIMS] Our study aimed to assess the prognostic value of TILs in stage II CC.

[MATERIALS AND METHODS] We conducted a retrospective study involving the patients who underwent curative surgery for primary stage II colonic adenocarcinoma. The data were collected over a period of 15 years.

[RESULTS] Seventy patients were included. The mean age of the patients was 60 years. The most frequent circumstances of discovery were abdominal pain (48%), followed by digestive transit disorders (26%) and digestive bleeding (20%). All patients at "high risk" of recurrence had received adjuvant chemotherapy except for seven patients. The mean overall survival and recurrence-free survival rates were 51 and 56 months, respectively. TILs rate varied between 3% and 80% with a median of 50%. TIL rates < 50% significantly decreased recurrence-free survival in univariate analysis (P = 0.001). In multivariate analysis, it was identified as an independent factor for the recurrence-free survival. We found a correlation between the rate of TILs < 50% and the lymphatic invasion (P = 0.022), the high grade of the tumor (P = 0.02) and the tumor size >3 cm (P = 0.009).

[CONCLUSION] TILs represent an important prognostic and predictive factor for stage II CC. It should be introduced in clinical practice to identify patients with "high-risk" stage II CC.