[A Case in Which Trastuzumab Combined Chemotherapy Was Effective for Recurrence of Post-Operative Gastric Cancer with Partial HER2 Overexpression].

We report a case in which recurrent partial HER2-positive gastric cancer showed complete clinical response to capecitabine (Cape)/oxaliplatin(L-OHP/OX)(CapeOX)plus trastuzumab(Tmab)combined chemotherapy for 32months. A 65-yearold man underwent distal gastrectomy, D2 lymph node dissection, and Roux-en-Y reconstruction for type 2 gastric cancer of the prepyloric anterior wall in December 2014. Pathological stage was as follows: L, ant, Type 2, 32×22 mm, tub1>tub2> por1, pT2(MP), int>med, INF c>a, Ly1a, V0, pN0, cM0, cH0, cP0, pCY0, pStage I B, pPM0(60mm), pDM0(75mm), pR0. Immunostaining of the tumor indicated overexpression of the HER2 gene in more than 10% of the well differentiated tubular adenocarcinoma(tub1). Nineteen months post-surgery, pancreatic head lymph node metastasis was diagnosed, and we started CapeOX plus Tmab combined chemotherapy. After 19 courses, the metastatic lymph node reduced its size until we could not detect it on CT. We continued treatment for 45 courses(about 32 months). During the courses, there were adverse events such as peripheral neuropathy(Grade 3, CTCAE v5.0), which required interruption of L-OHP, and oral mucosal ulcer (Grade 2).