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

Background: For stage II colon cancer, the efficacy of postoperative adjuvant chemotherapy remains controversial. It is well known that tumor-associated macrophages (TAMs) are important in tumor progression. In this study, TAMs were investigated as prognostic and predictive biomarkers for the efficacy of adjuvant chemotherapy for stage II colon cancer after radical resection. Methods: This study enrolled two independent cohorts of consecutive patients from one medical center with pathological stage II colon cancer after radical resections. Macrophages were detected using immunohistochemical staining of CD68 and CD206. Infiltration densities of CD68+ TAMs, CD206+ TAMs and ratio of CD206+ TAMs / CD68+ TAMs (CD206/CD68 ratio) were calculated as prognostic and predictive biomarkers. Results: The primary and validation cohorts consisted of 521 and 314 patients, respectively. In both cohorts, high CD206/CD68 ratio was significantly associated with poor disease-free survival (DFS) and overall survival (OS). As an independent risk factor, CD206/CD68 ratio also had significantly better prognostic efficacy than CD68+ TAM density, CD206+ TAM density and traditional clinicopathological high-risk factors. Moreover, adjuvant chemotherapy significantly improved DFS and OS for patients with high CD206/CD68 ratio but not for those with low CD206/CD68 ratio. The interaction analyses were also significant for DFS. In subgroup analysis, CD206/CD68 ratio was still a significant predictor for adjuvant chemotherapy for patients in traditional high-risk group of recurrence (significant interaction for DFS). Conclusions: For stage II colon cancer, CD206/CD68 ratio is a better prognostic and predictive biomarker for postoperative adjuvant chemotherapy. Together with clinicopathological high-risk factors, it will aid in precision treatment.