The density of macrophages in the invasive front is inversely correlated to liver metastasis in colon cancer

Background: Although an abundance of evidence has indicated that tumor-associated macrophages (TAMs) are associated with a favorable prognosis in patients with colon cancer, it is still unknown how TAMs exert a protective effect. This study examined whether TAMs are involved in hepatic metastasis of colon cancer. Materials and methods: One hundred and sixty cases of pathologically-confirmed specimens were obtained from colon carcinoma patients with TNM stage IIIB and IV between January 1997 and July 2004 at the Cancer Center of Sun Yat-Sen University. The density of macrophages in the invasive front (CD68TF(Hotspot)) was scored with an immunohistochemical assay. The relationship between the CD68TF(Hotspot) and the clinicopathologic parameters, the potential of hepatic metastasis, and the 5-year survival rate were analyzed. Results: TAMs were associated with the incidence of hepatic metastasis and the 5-year survival rate in patients with colon cancers. Both univariate and multivariate analyses revealed that the CD68TF(Hotspot) was independently prognostic of survival. A higher 5-year survival rate among patients with stage IIIB after radical resection occurred in patients with a higher macrophage infiltration in the invasive front (81.0%) than in those with a lower macrophage infiltration (48.6%). Most importantly, the CD68TF(Hotspot) was associated with both the potential of hepatic metastasis and the interval between colon resection and the occurrence of hepatic metastasis. Conclusion: This study showed evidence that TAMs infiltrated in the invasive front are associated with improvement in both hepatic metastasis and overall survival in colon cancer, implying that TAMs have protective potential in colon cancers and might serve as a novel therapeutic target.