Pathological complete response to nivolumab, S1, oxaliplatin, and radiation in a patient with gastric cancer: A case report

BACKGROUND The addition of nivolumab to chemotherapy has proven to be superior as a first-line treatment for unresectable advanced or recurrent gastric cancer, and is currently considered the most effective treatment. The evidence for preoperative therapy is still insufficient. Here, we report the case of a patient with gastric cancer with hepatic invasion who underwent radical surgery after preoperative treatment with nivolumab plus S1 and oxaliplatin (SOX) in combination with radiation, and achieved a pathological complete response. CASE SUMMARY A 73-year-old man was diagnosed with clinical stage IVA (T4bN2M0) gastric cancer and generalized edema due to hypoproteinemia, anemia, and pneumonia. The patient was considered intolerant to gastrectomy with hepatectomy. After five courses of nivolumab plus SOX and radiation therapy, the tumor shrank, and his general condition improved. Distal gastrectomy with D2 lymph node dissection and combined resection of the site of liver invasion were performed. A pathological examination of the resected stomach, liver, and lymph nodes revealed no residual cancer cells. CONCLUSION This is the first report of a pathological complete response to pre-surgical nivolumab plus SOX and radiation in gastric cancer. This therapy is expected to become the first choice for preoperative treatment of gastric cancer in the future.