［Abstract］ Background and purpose: Immunity function is one of the most profound factors in affecting the prognosis of breast cancer patients. Cytotoxic T lymphocytes counts in the peripheral blood and focal tumor tissue could indicate the overall survival time of these patients. On the other hand

adjuvant chemotherapy is also an important part in improving both the disease free survival and overall survival time of breast cancer patients. Selecting chemotherapy regime which is both able to kill all the tumor cells and reserve the immunity function to the greatest extent is of great importance in improving the survival rate of breast cancer patients. The aim of this study was to compare the effect of two chemotherapy regimens CEF (cyclophosphamide

epirubicin and fluorouracil) and EC followed by P (paclitaxel) on the peripheral blood lymphocytes in early stage breast cancer. Methods: The clinicopathological characteristics and  peripheral blood lymphocyte parameters before and after chemotherapy of CEF or EC-P regimen were retrospectively analyzed in post-operate patients with early stage breast cancer during the period from Nov. 2012 to May 2013. The lymphocyte parameters included: total blood lymphocytes count

percentages of T lymphocytes

cytotoxic T lymphocytes

helper T lymphocytes

active T lymphocytes and nature killer (NK) cells. Results: Patients undertook EC-P regimen were those at comparably high risk (significant differences of clinical stage

tumor size

axillary lymph node status

estrogen/progestogen receptor and histological subtype were observed). There was no difference of lymphocyte parameters between these two groups before adjuvant chemotherapy. However

during the process of chemotherapy

peripheral blood lymphocytes counts decreased significantly after 4 and 5 cycles of chemotherapy of CEF regime (1 077±359/μL; 1 181±271/μL) compared with the level before chemotherapy (1 607±322/μL

P0.05). On the contrary

there was no significant difference of peripheral blood lymphocytes count before (1 746±576 /μL) and after 4 and 5 cycles of chemotherapy (1 500±312/μL; 1 623±468/μL) in EC-P group (P0.05). Percentage of active T lymphocyte increased significantly along with the chemotherapy in both groups (CEF group: 11.8±7.1 vs 23±9.3

P0.05; EC-P group: 11.8±5.8 vs 17.6±8.2

P0.05) (pre-chemotherapy vs after 5 cycles of chemotherapy). In EC-P group

the percentage of helper T lymphocyte (37.8±5.7) decreased significantly compared with the levels before chemotherapy (41.3±4.3) and before paclitaxel was undertaken (41.9±5.6

P0.05) and the percentage of NK cells (21.5±5.2) increased significantly compared with the levels before chemotherapy (15.3±7.6) and before paclitaxel was undertaken (14.9±5.9

P0.01) after one cycle of paclitaxel therapy. Conclusion:The effect of chemotherapy on peripheral blood lymphocyte is less profound in EC-P group compared to CEF group. Furthermore

paclitaxel can increase the NK cells without any effect to the levels of T lymphocytes and cytotoxic T lymphocyte. It is superior over other drug in conserving immune function in early stage breast cancer.