This study aims to explore whether pre-operative or post-operative percentages of circulating myeloid-derived suppressor cells (MDSC) have any correlations with clinicopathological parameters in patients with rectal cancer and have any predictive values for local recurrence and disease free survival. Lin-/HLADR-/CD11b+/CD33+ MDSCs were analyzed in the study. Blood samples before and after surgery were measured by flow cytometry to determine the MDSC percentages. Plasma arginase I levels were analyzed using an enzyme-linked immunosorbent assay. Digital rectal examination, abdominal ultrasonography, or computed tomography was performed every three months after surgery to monitor local recurrence. Prior to surgery, cancer patients presented with higher levels of circulating MDSC compared to healthy controls (medians of 3.89% and 0.57%, respectively). Seven days after operation, we observed an immediate increase in MDSC followed by a downtrend. Local recurrence was observed in 11 of 41 patients (26.8%) with stage I/II cancer and 11 of 23 patients (47.8%) with stage III cancer. Significantly higher percentages of MDSC were observed in patients who had local recurrence versus patients without local recurrence. Multivariate analysis further verified that the pre-operative level of MDSC was significantly associated with local recurrence (P=0.038). Therefore, our results indicate that pre-operative percentage of MDSC appears to be a reliable prognostic marker for local recurrence and poor disease free survival in rectal cancer patients with curative resection.
Keywords: myeloid-derived suppressor cells, rectal cancer, plasma arginase I, local recurrence, disease free survival.