OBJECTIVETo observe the change of myeloid-derived suppressor cells (MDSCs) percentage in peripheral blood after operation in rectal cancer patients and to examine its association with the prognosis.

METHODSBlood samples of pre-operation and postoperative 21-day from 64 stage I(-III( rectal cancer patients who underwent surgery in Department of General Surgery, The Affiliated Cancer Hospital, Zhengzhou University between January and December 2009 were collected. MDSCs percentage was detected by flow cytometry. Its association with the prognosis of patients was analyzed.

RESULTSMDSCs percentage of postoperative 21-day decreased significantly compared with pre-operation (P<0.01). When local recurrence or distant metastasis presented, MDSCs percentage increased again (all P<0.01) and reached the preoperative level(P>0.05). All the patients were further divided into two groups based on median MDSCs percentage. Patients with higher MDSCs percentage before operation (>3.78%) and after operation (>2.11%) had significantly lower 5-year overall survival(OS) (58.1% and 62.1%) and 5-year disease-free survival (DFS)(54.8% and 58.6%) as compared to those with lower MDSCs percentage(5-year OS 87.9% and 84.8%; 5-year DFS 82.8% and 80.0%, all P<0.05). Multivariate analysis showed that preoperative MDSCs percentage was an independent prognostic factor of rectal cancer(HR:4.065, 95% CI:1.026 to 16.108, P=0.04).

CONCLUSIONSPreoperative increased MDSCs percentage may be an important predictor of poor OS in rectal cancer patients. Dynamic change of MDSCs percentage can reflect the disease development.