Chemotherapy is not necessary after surgery for gastric cancer.
Currently, the Chinese Society of Clinical Oncology (CSCO) guidelines recommend that postoperative adjuvant chemotherapy should be given to patients with T2 or higher and/or lymph node metastases who have undergone D2 surgery (lymph node dissection to the second station lymph nodes around the stomach) R0 resection (no cancer cells were found to remain under microscopy) and have not received preoperative treatment, while postoperative adjuvant chemotherapy is not recommended for patients with stage I pathological staging.
However, it is important to note that patients usually need regular postoperative review for early detection of possible recurrence or metastasis.