AimsThe preoperative serum levels of inflammatory mediators, including C-reactive protein (CRP), procalcitonin (PCT) and interleukin-6 (IL-6), have been demonstrated to be correlated with patient outcomes in colorectal cancer (CRC); however, the prognostic role of these levels has been less well-studied in postoperative settings.Materials and methodsA total of 122 stage I-III CRC patients were retrospectively enrolled. Serum levels of CRP, PCT and IL-6 were measured after surgery, and their prognostic value was evaluated. Kaplan-Meier analysis was used to determine the differences in disease-free survival (DFS) and overall survival (OS) between patients with different levels of these mediators, and the Cox proportional hazards model was used to estimate the risk factors.ResultsIn contrast to CRP and PCT, only the level of IL-6 was significant in predicting DFS (P = 0.01) but not OS (P = 0.07). A total of 66.39% (81/122) of patients were assigned to the low IL-6 group and no significant differences were found in the collected clinicopathological parameters among the low or high IL-6 subgroups. The level of IL-6 was negatively correlated with postoperative (1 w) (R=-0.24, P = 0.02) absolute lymphocyte counts. Patients with low levels of IL-6 had better DFS (log rank = 6.10, P = 0.01) but not OS (log rank = 2.28, P = 0.13). Finally, the level of IL-6 was an independent risk factor for DFS (HR: 1.81, 95% CI: 1.03–3.15, P = 0.04).ConclusionsCompared to CRP and PCT, the level of IL-6 was observed to be the only significant factor in predicting the prognosis of stage I-III CRC patients after surgery, and a low level of IL-6 was associated with good DFS.