Conversion Surgery for Alpha-Fetoprotein–Producing Esophagogastric Junction Cancer with Multiple Liver Metastases and Portal Vein Tumor Thrombus after Nivolumab Combination Chemotherapy: A Case Report and Literature Review

INTRODUCTION: Alpha-fetoprotein-producing gastric cancer (AFPGC) is a rare subtype of gastric cancer associated with poor prognosis due to early liver metastasis. There have been limited reports on conversion surgery following nivolumab combination chemotherapy in cases of AFPGC with liver metastasis. Here, we present a case of alpha-fetoprotein-producing esophagogastric junction cancer (AFP-EGJC) successfully treated with this treatment. CASE PRESENTATION: The patient was a 31-year-old man. After liver tumors were incidentally detected, he was diagnosed with esophagogastric junction cancer (cT3N1M1) with multiple liver metastases and portal vein tumor thrombus. Combination therapy with S-1 (tegafur/gimeracil/oteracil), oxaliplatin, and nivolumab was initiated. The response was remarkable, with the rapid disappearance of liver metastases. Serum AFP was also abnormally high at 691.9 ng/mL, but it quickly normalized after the start of treatment. Fifteen months later, the patient was diagnosed with progressive disease, and the regimen was switched to nab-paclitaxel and ramucirumab therapy. However, there was no recurrence of liver metastases, and only the primary tumor was poorly controlled. Therefore, a laparoscopic proximal gastrectomy was performed 22 months after the initial treatment. The postoperative diagnosis was ypT2 (MP) N0M0, ypStage IB. The patient remains alive and recurrence-free 12 months after surgery, without adjuvant chemotherapy. CONCLUSIONS: Conversion surgery after nivolumab combination chemotherapy may be feasible in selected patients with AFP-EGJC with liver metastasis.