Tumor-associated macrophages as predictive biomarkers for postoperative adjuvant chemotherapy in patients with stage II colon cancer.

Abstract

620 Background: For stage II colon cancer, the effect of postoperative adjuvant chemotherapy is still controversial. It is well known that tumor-associated macrophages (TAMs) play an important role in tumor progression. The aim of this study is to determine the effect of TAMs as predictor for adjuvant chemotherapy for stage II colon cancer. Methods: From July 2009 to June 2012, 521 patients with pathological stage II colon cancer were included. TAMs were detected using tissue microarray and immunohistochemistry (all TAMs detected by CD68; M2 subtype detected by CD206). The density of CD68+ TAMs, CD206+ TAMs and the ratio of CD206+ TAMs / CD68+ TAMs (CD206 / CD68 ratio) were calculated. The cut-off values were defined using X-Tile software. Results: High CD206+ TAMs density and high CD206 / CD68 ratio were significantly associated with reduced disease-free survival (DFS, P < 0.001 and P < 0.001, respectively) and overall survival (OS, P < 0.001 and P < 0.001, respectively). And CD206 / CD68 ratio had a better prognostic power. Furthermore, for patients with low CD206 / CD68 ratio, adjuvant chemotherapy made no benefit. But for high CD206 / CD68 ratio, adjuvant chemotherapy significantly improved DFS and OS (as shown in Table 1). In subgroup analysis, for T3 with high-risk factors or T4 tumors, CD206 / CD68 ratio was also a significant predictor for adjuvant chemotherapy (interaction P = 0.024 in DFS). Conclusions: For stage II colon cancer, CD206 / CD68 ratio was a good prognostic and predictive biomarker for adjuvant chemotherapy. Together with clinicopathological high-risk factors, it might facilitate patient counselling and individualise management. [Table: see text]