[Complete Response of Liver Metastases from a HER2-Positive Gastric Cancer Treated with Combined S-1/Trastuzumab Chemotherapy].

: A 74-year-old man with upper abdominal pain and anorexia was referred to our hospital in December 2013. Based on computed tomography(CT)and gastroendoscopy findings, the patient was diagnosed as having advanced gastric cancer with multiple liver metastases(S3, S5, and S6 lesions). Because of high pyloric stenosis, distal gastrectomy Roux-en-Y reconstruction was performed in mid-December 2013. Histopathological findings of the patient were L, Ant-Gre, 35×60 mm, type 2, pT4a(SE), tub2>tub1, int, INF b, ly2, v1(VB), pPM0(95mm), pDM0(15mm), pN0(0/2), HER2(IHC 3+). Postop- eratively, the patient received combined S-1/trastuzumab chemotherapy toward the end of January 2014. The clinical response was PR after 2 courses and clinical CR(cCR)after 4 courses. Because hand-foot syndrome caused by S-1 was prolonged, the dosage was completed in 11 courses. He remains alive 4.5 years after surgery without recurrence. Although ToGA examination showed that trastuzumab was effective for HER 2-positive unresectable gastric cancer, few reported cases showed progression to cCR after the treatment followed by a regimen of trastuzumab without CDDP, and they had good prognosis. Furthermore, in this case, the liver metastases showed complete response without CDDP. Thus, trastuzumab might be a chemotherapy option for patients who have difficulty using platinum analogs, including the elderly patients.