[A case of recurrent gastric cancer in which liver and lymph node metastases disappeared after third-line treatment with nivolumab monotherapy].

The patient was a 63-year-old man at initial consultation. After pre-operative chemotherapy for advanced gastric cancer, he underwent distal gastrectomy. Eight months later, liver metastases appeared in segments 6 and 7. First-line chemotherapy with capecitabine plus cisplatin was administered, but the liver lesions worsened, and a para-aortic lymph node metastasis was observed. Second-line ramucirumab plus paclitaxel shrank the metastatic lesions without new lesions. Because he could not tolerate further combined chemotherapy, third-line nivolumab monotherapy was started 12 months after chemotherapy initiation. After 6 courses, grade 4 adrenal insufficiency developed, and nivolumab was discontinued. Nevertheless, all metastatic lesions had shrunk and showed peripheral calcification. Ramucirumab monotherapy was resumed (43 courses) based on the patient's clinical status. During this period, the liver metastases continued to decrease and became completely calcified;the para-aortic lymph node resolved. PET-CT showed no FDG accumulation in the liver, consistent with organized, tumor-free lesions. The recurrent disease was judged equivalent to a complete response (CR), and no further treatment was given. Subsequent CT scans showed ongoing shrinkage and gradual decalcification of the organized liver lesions. Thirty-five months after discontinuing ramucirumab, the lesions are cystic and the CR persists. Given the high microsatellite instability status and the timing of lesion shrinkage and calcification, nivolumab likely played the dominant role in achieving CR. Our review of the limited number of reported cases suggests that discontinuing nivolumab after CR in gastric cancer can be a valid option.