Our study aims to compare the efficacy and safety of 4-month versus 6-month adjuvant chemotherapy with capecitabine and oxaliplatin following D2 gastrectomy in patients with gastric cancer.

Hypothesis: In patients with gastric cancer who have undergone D2 gastrectomy, a 4-month regimen of capecitabine and oxaliplatin demonstrates noninferiority to a 6-month regimen in terms of disease-free survival (DFS) and safety.

Surgical resection is the cornerstone of treatment for patients with localized gastric cancer. In the CLASSIC trial, capecitabine plus oxaliplatin for 6 months following D2 gastrectomy has been established as an effective postoperative adjuvant treatment for patients with operable stage II or III gastric cancer. However, due to adverse events, chemotherapy discontinuations occurred in 50 (10%) patients, primarily due to nausea, neutropenia, decreased appetite, peripheral neuropathy, diarrhea, and vomiting. At the 2017 ASCO Annual Meeting, Grothey et al. reported the results of the IDEA trial. For patients with lymph node-positive colon cancer (stage III), some may benefit from a shorter duration of chemotherapy post-surgery. An analysis of six clinical trials involving over 12,800 patients showed that 3 months of chemotherapy was nearly as effective as 6 months for patients with a lower recurrence risk, while also causing fewer side effects, particularly nerve damage. Based on the findings from the IDEA trial, we hypothesize that a 4-month regimen of capecitabine plus oxaliplatin may also benefit patients following D2 gastrectomy while reducing adverse events compared with the standard 6-month regimen.

Inclusion Criteria:

1. Age between 18 and 80 years.
2. Histologically confirmed primary adenocarcinoma of the stomach, staged as II, IIIA, or IIIB according to pathological findings.
3. R0 resection and D2 gastrectomy performed.
4. No other concurrent malignancies.
5. Eastern Cooperative Oncology Group (ECOG) performance status of 0 or 1
6. No contraindications to chemotherapy.

Exclusion Criteria:

1. Receipt of preoperative treatment, including radiation therapy, chemotherapy, or immunotherapy.
2. Patients with stage I, IIIC, or IV gastric cancer.
3. Presence of severe organ diseases, including heart, lung, brain, liver, or other vital organ dysfunction.
4. Known or suspected drug allergies.
5. Pregnant or lactating women.