Conversion surgery for gastric remnant cancer with liver metastasis after nivolumab combination chemotherapy achieving pathological complete response: a case report and literature review

Nivolumab combination chemotherapy has recently emerged as a potential first-line treatment for patients with unresectable or metastatic gastric cancer (GC). Further research has indicated that R0 resection by conversion surgery could be an effective treatment strategy to improve overall survival. However, there have been limited reports on the successful application of conversion surgery following combination chemotherapy achieving pathological complete response (pCR) in cases of advanced gastric remnant cancer with liver metastasis. Here, we present a case of long-term survival in a patient who underwent this treatment. A 54-year-old man was initially referred to our department for treatment of stage III (cT3N1M0) gastric cancer where he underwent laparoscopic distal gastrectomy and D2 lymph node dissection. After a year of uneventful follow-up, the patient was diagnosed with a tumor in the gastric remnant combined with liver metastasis, resulting in a diagnosis of stage IV (cT3N0M1) gastric remnant cancer. Subsequently, the patient was treated with four cycles of TS-1, Oxaliplatin, and Nivolumab as the first-line regimen. Remarkably, both the remnant tumor and liver metastasis exhibited significant shrinkage, and no new lesions were found. Given this response, conversion surgery was performed to achieve complete resection of the remnant gastric cancer and liver metastasis, followed by laparoscopic remnant gastrectomy and partial hepatectomy. Pathological examination revealed the absence of residual carcinoma cells and lymph node metastases. Postoperatively, the patient was treated with adjuvant chemotherapy with S-1 for 1 year, and survived without recurrence for 18 months after conversion surgery. Nivolumab combination chemotherapy shows promise as a clinically beneficial treatment approach for gastric remnant cancer with liver metastasis, particularly when pCR can be achieved following conversion surgery.