OBJECTIVETo observe the efficacy and safety of chemotherapy regimens oxaliplatin combined with capecitabine (CAPOX) or oxaliplatin combined with tegafur, gimeracil and oteracil potassium capsules (S-1)(SOX), and to investigate the value of expression of thymidine phosphorylase (TP) and dihydropyrimidine dehydrogenase (DPD) proteins in tumor tissue for predicting the efficacy of CAPOX and SOX regimens in advanced gastric cancer patients.

METHODSA total of 107 newly-diagnosed, stage Ⅲc/Ⅳ gastric cancer patients (no surgical indication, ECOG performance scores 0-2 and expected survival time ≥3 months) were recruited with 101 patients evaluated. The patients were randomly divided into two groups. One was study group in which the patients received CAPOX regimen. The other was control group received SOX regimen. Each patient received four cycles, at least two cycles chemotherapy every three weeks and followed up until death or lost. Tumor biopsies were obtained by gastroscopy for immunohistochemical examination of the expression of TP and DPD proteins before chemotherapy. Response rate (ORR), overall survival (OS) and time to tumor progression (TTP) of the patients were assessed.

RESULTSThe objective response rate (ORR) of the study and control groups was 49.0% (5/51) vs. 46.0% (23/50), respectively (P>0.05). The overall survival (OS) was 357.36±24.69 days in the study group and 349.87±22.63 days in the control group, and the time-to-progression (TTP) was 216.75±19.32 days in the study group and 220.54±18.47 days in the control group (P>0.05 for both). Stratified analysis showed that the ORR of TP-positive patients in the study group was significantly higher than that in the control group (72.0 % vs. 41.7 %, P=0.032). There was no significant difference in ORR between the TP-negative patients in the study and control groups (26.9% vs. 50.0%, P=0.087), while the ORR of DPD-positive patients in the control group was significantly higher than that of the study group (51.9% vs. 34.6%, P=0.046). There was no significant difference in the ORR between DPD-negative patients in the study and control groups (64.0% vs. 39.1%, P=0.084). The follow-up showed that the OS (378.42±22.56 days) and TTP (271.77±24.92 days) in the TP-positive patients of the study group were significantly longer than those of the control group (OS: 326.57±19.84 days, and TTP: 229.13±22.68 days)( P<0.05). The OS was 371.25±23.97 days and TTP was 264.66±21.36 days in the DPD-positive patients of control group, significantly longer than those of the study group (OS: 334.73±21.47days, and TTP: 208.58±20.70 days) (P<0.05). But there was no significant difference in the OS and TTP between the TP- and DPD-negative patients in the two groups (P>0.05). In respect of adverse events, both the rates of hematological and non-hematological toxicities were low and similar between the two groups (P>0.05), and well-tolerated by the patients.

CONCLUSIONSBoth CAPOX and SOX regimens are effective chemotherapeutic protocols in treatment of patients with advanced gastric cancer. The expression levels of TP and DPD in tumor tissue can be used as a predictive factor for the efficacy of capecitabine or tegafur, gimeracil and oteracil potassium capsules combined with oxaliplatin regimens. CAPOX chemotherapy regimen is more suitable for the TP-positive gastric cancer patients, and SOX regimen is more suitable for the DPS-positive gastric cancer patients.