AIM: To study the apoptosis induced by preoperative oral 5'-DFUR administration in gastric adenocarcinoma and its mechanism of action.METHODS: Sixty gastric cancer patients were divided randomly into three groups (20 each group) before operation: group one: 5'-DFUR oral administration at the dose of 800-1200mg/d for 3 - 5 d, group two: 500mg 5-FU + 200 mg/d CF by venous drip for 3 - 5 d, group three (control group). One or two days after chemotherapy, the patients were operated. Fas/FasL, PD-ECGF and PCNA were examined by immunohistochemistry and apoptotic tumor cells were detected by in situ TUNEL method. Fifty-four patients received gastrectomy, including 12 palliative resections and 42 radical resections.Six patients were excluded. Finally 18 cases in 5'-DFUR group, 16 cases in CF+5-FU group, and 20 cases in control group were analyzed.RESULTS: There was no significant difference in patient mean age, gender, white blood cell count, haematoglobin (HB), thromboplastin, perioperative complication incidence, radical or palliation resection, invasion depth (T),lymphonode involvement (N), metastasis (M) and TNM staging among the three groups. However, the PCNA index (PI) in 5'-DFUR group (40.51 ± 12.62) and 5-FU +CF group (41.12± 15.26) was significantly lower than that in control group (58.33 ± 15.69) (F= 9.083, P= 0.000).The apoptotic index (AI) in 5'-DFUR group (14.39 ± 9.49)and 5-FU+CF group (14.11±9.68) was significantly higher than that in control group (6.88 ± 7.37) (F= 4.409,P=0.017). The expression rates of Fas and FasL in group one and group three were 66.7% (12/18) and 50% (9/18), 43.8% (7/16) and 81.3% (13/16), 45.0%(9/20) and 85% (17/20), respectively. The expression rate of FasL in 5'-DFUR group was significantly lower than that in the other two groups (x2=6.708, P= 0.035).Meanwhile, the expression rate of PD-ECGF was significantly lower in 5'-DFUR group (4/18, 28.6%) than in CF+5-FU group (9/16, 56.3%) and control group (13/20, 65.0%) (x2 = 7.542, P= 0.023). The frequency of Fas expression was significantly correlated with palliative or radical resection (x2 = 7.651, P= 0.006), invasion depth (x2= 8.927, P= 0.003), lymphatic spread (x2=4.488,P= 0.034) and UICC stages (x2= 8.063, P= 0.045) respectively. By the end of March 2005, 45 patients were followed up. The 0.5-, 1-, 2-, 3-year survival rates were 96%, 73%, 60%, 48%, respectively, which were related with T, N, M and Fas expression, but not with PDECGF and FasL expression.CONCLUSION: Preoperative oral 5'-DFUR administration may induce apoptosis of gastric carcinoma cells and decrease tumor cell proliferation index, but cannot improve the prognosis of patients with gastric cancer. Downregulation of FasL and PD-ECGF expression mediated by 5'-DFUR may be one of its anti-cancer mechanisms. Fas expression correlates with the progression of gastric carcinoma and may be an effective prognostic factor.