Low infiltration of peritumoral regulatory T cells predicts worse outcome following resection of colorectal liver metastases.

Background: The tumor-infiltrating lymphocyte (TIL) count in several types of cancer, including colorectal cancer and colorectal liver metastases (CRLM), reportedly predicts survival following resection; however, the prognostic significance of the TIL counts remains controversial.
Methods: In total, 162 patients who underwent potentially curative resection for CRLM from 1992 to 2010 were immunohistochemically analyzed retrospectively. CD4, CD8, and FoxP3 were examined as markers for helper T cells, cytotoxic T cells, and regulatory T cells (Tregs), respectively. The correlation between patients' TIL composition and long-term outcome was investigated.
Results: The median follow-up time was 46.6 months for all patients and 46.8 months for survivors. Cancer-specific survival (CSS) at 1, 3, and 5 years was 93.2, 65.6, and 51.0 %, respectively. The 5-year disease-free survival and CSS among patients with high infiltration of peritumoral Tregs was 44.2 and 74.8 %, respectively, while those of patients with low infiltration of peritumoral Tregs was 18.9 and 40.3 %, respectively (p < 0.01 for both). Multivariate analyses indicated that synchronous liver metastases, hypoalbuminemia, and low peritumoral Treg infiltration were significant predictors of unfavorable CSS.
Conclusions: Low peritumoral Treg infiltration proved to be a significant predictor of unfavorable CSS in patients undergoing resection for CRLM.