The tumor infiltrating CD8+:FOXP3+ cell ratio may be a predictive marker of disease-free survival in patients with colorectal cancer, according to a recent study.

A team at Kyushu University, Japan analyzed the relationships of intratumoral CD8+ T cells and FOXP3+ cells with traditional pathological measurements for surgically resected specimens from 95 patients with primary colorectal cancer.

The researchers did not detect any correlation between the number of intratumoral CD8+ T cells with any pathological parameter; however, lymph-node metastasis was significantly associated with the number of intratumoral FOXP3+ cells. Furthermore, Suzuki noted that “the ratio of the number of [intratumoral] CD8+ T cells to the number of [intratumoral] FOXP3+ cells (itCD8+:itFOXP3+ cell ratio) was negatively correlated with pathological stages.”

Although the number of CD8+ T cells and FOXP3+ cells was not associated with disease-free survival or overall survival, Suzuki and colleagues found that the “CD8+:FOXP3+ ratio showed a significant positive correlation with disease-free survival (P = 0.023) and overall survival (P = 0.010).”

Importantly, a multivariate analysis revealed that this balance between CD8+ T cells and FOXP3+ cells is an independent indicator for overall survival in patients with colorectal cancer undergoing surgery.

Why this ratio might act as a prognostic marker remains to be elucidated; however, Suzuki suggested that “one possible answer is that antitumor immunity is determined by the immunological balance in the microenvironment of the tumor site.”