OBJECTIVETo observe the proportion change of immune cells in the peripheral blood of patients with rectal cancer after neoadjuvant therapy and to explore the relationship between tumor regression and CD4⁺CD25(High)CD127(low) regularly T cells(Treg cells).

METHODSPatients with rectal cancer who underwent the neoadjuvant therapy before surgery at the Shanxi Cancer Hospital Colorectal Surgery Department from January to December 2013 were prospectively enrolled. These patients were divided into down-staging group and non-down-staging group according to the change of staging in accordance with TNM classification for rectal cancer after neoadjuvant therapy. Flow cytometry was used to analyze the proportions of Treg cells, CD4+T cells, CD8+T cells, NK cells, B cells, and CD4+/CD8+ ratio in the peripheral blood from these patients before and after neoadjuvant therapy.

RESULTSA total of 108 patients were enrolled, including 76 cases in the down staging group and 32 cases in the non-down-staging group. Differences of immune cells proportions between two groups before neoadjuvant therapy were not statistically significant(all P>0.05). In the down-staging group, the proportions of Treg cells, B cells and CD4+/CD8+ ratio were decreased while the proportion of NK cells did not change obviously after the neoadjuvant therapy. Interestingly, in the non-down-staging group, the proportions of B cells and CD4+/CD8+ ratio were decreased while the proportions of Treg cells and NK cells did not change obviously after the neoadjuvant therapy. In addition, after neoadjunvat therapy, the proportion of Treg cells in down-staging group was significantly lower than that in non-down-staging group [(4.4 ± 1.7)% vs. (6.2 ± 1.9)%, P=0.001].

CONCLUSIONFor patients in the down-staging group after neoadjuvant therapy, the proportion of Treg cells in peripheral blood decreases, suggesting that Treg cells may be a valuable biomarker for assessing tumor regression.