Lymphocytic Infiltration as a Prognostic Factor in Patients with Colon Cancer

Host-defense mechanisms may have an important role in predicting the outcome of colorectal cancer patients. We designed our study to evaluate the possible prognostic significance of the presence of lymphocytic infiltration (LI) and subgroups of lymphocytes (CD3 and CD20) in the primary tumors. We randomly selected 195 patients operated for colorectal carcinoma from a larger cohort of 1527 patients with colorectal cancer. Histological slides were blindly reevaluated for the presence of LI that was graded 0 to 3. Immunohistochemical phenotyping of the lymphocytes was performed only for tumors with LI score 3 and included antibodies CD3 and CD20. CD3 and CD20 immunostaining were graded in the same manner as LI. The mean duration of follow-up was 63.8 months. The distribution of patients with colorectal cancer according to LI scores was as follows: score 0, 20/195 (10.2%); score 1, 61/195 (31.3%); score 2, 78/195 (40%); and score 3, 36/195 (18.5%). There was no correlation between any clinicopathological pattern and LI. Score 3 staining for CD3 was more common than for CD20 (64.7% vs 8.8%, P <.0001). Prominent lymphocytic infiltration (score 3) was associated with better disease-free survival (P =.062). Recurrence was diagnosed among 2/22 (9.1%) patients with prominent CD3 staining versus 62/171 (36.2%) of all other patient groups (P =.054) and they correspondingly had better disease-free survival (P =.018). It seems we can identify a group of patients with colorectal cancer who have an excellent prognosis according to a single immunological test unrelated to other known prognostic factors.