Increased Infiltration of Natural Killer and T Cells in Colorectal Liver Metastases Improves Patient Overall Survival.

Introduction: Cancer heterogeneity and degree of intra-tumoral immune cells represent variables affecting overall survival (OS). The present study investigated the impact of natural killer (NK) and T cells infiltrating colorectal liver metastases (CLM) in patients undergoing hepatectomy after neoadjuvant chemotherapy.

Methods: The frequencies of intra-tumoral, marginal, and peritumoral CD3+ T and NKp46+ NK cells were determined for 121 patients. OS was assessed in relation to prognostic factors.

Results: At univariate analysis, several variables, including T and N of the primary tumor, metachronous CLM, radiological response, and higher density of intra-tumoral CD3+ T cell (>1%/mm) and of NKp46+ NK cells (>1 cell/mm), were associated with OS. Only increased frequencies of intra-tumoral CD3+ T cells (p = 0.005) and NKp46+ NK cells (p = 0.004) correlated with OS at multivariate analysis. The logistic regression revealed that metachronous CLM (OR = 2.781; p = 0.002), the use of an epidermal growth factor receptor inhibitor (OR = 3.891; p = 0.001), and radiological response (OR = 3.219; p = 0.001) were associated with higher infiltration of these cells.

Conclusions: High frequencies of NK and T cells in response to chemotherapy predict OS in CLM patients. These findings provide important insights that can help physicians to choose the best treatment option and adopt more predictive follow-up strategies for patients with CLM.