The recently published 5-year follow-up results of the open randomized phase III CLASSIC study suggest that adjuvant therapy with capecitabine in combination with oxaliplatin should be considered for patients with operable stage II or III gastric cancer who have undergone D2 radical gastrectomy. The aim of the study was to compare the impact of adjuvant chemotherapy with capecitabine combined with oxaliplatin after D2 radical gastrectomy for stage II-III gastric cancer compared with surgery alone. The results of the study’s interim analysis (median follow-up of 34 months) suggest that the study has met its primary study endpoint of significantly improved disease-free survival (DFS) with postoperative capecitabine combined with adjuvant chemotherapy with oxaliplatin compared with surgery alone. The study design was a phase III randomized controlled open study with 35 cancer centers from China, Korea and Taiwan. Patients enrolled in the study were stage II-IIIB gastric cancer patients who underwent D2 radical gastrectomy and were randomized in a 1:1 ratio to receive postoperative capecitabine combined with oxaliplatin regimen adjuvant chemotherapy for 6 months (adjuvant treatment group) or long-term observation (observation group). Patients in the treatment group received postoperative adjuvant chemotherapy in a 3-week regimen for 8 cycles, with patients receiving oral capecitabine 1000 mg/m2 twice daily on days 1 to 14 and intravenous oxaliplatin 130 mg/m2 infusion on day 1. Study randomization was stratified by country of enrollment and disease stage, and the method was completed using a size 4 replacement zone group method. Patients enrolled in the study and the investigator were informed of the treatment assignment to the patients. The primary study endpoint was 3-year DFS in the intention-to-treat population, and this article reports the final analysis after 5 years of follow-up. The study was registered with ClinicalTrials.gov under registration number NCT00411229. The results showed that a total of 1035 patients were enrolled, 520 in the adjuvant group and 515 in the observation group, with a median follow-up time of 62.4 months for the intention-to-treat population. 139 patients (27%) in the adjuvant group met the DFS endpoint event, and 203 patients (39%) in the observation group 203 patients (39%) in the observation group had an endpoint event (stratified HR=0.58, P<0.0001). The estimated 5-year dfs was 68% for patients in the adjuvant group and 53% in the observation group. In the study truncated data, 103 (20%) of patients in the adjuvant treatment group and 141 (27%) in the observation group died (stratified hr=0.66, p=0.0015). For overall survival, the estimated 5-year overall survival rate was 78% for patients in the adjuvant treatment group and 69% for the observation group. No further data on treatment side effects were collected after the primary data analysis of the study was completed.