P44-9 A case of recurrent gastric cancer with drug-induced immune thrombocytopenia caused by trastuzumab

Abstract

A 57-year-old woman was referred to the gastroenterology department of our hospital for management of chronic hepatitis B. Abdominal ultrasonography was performed and revealed swelling of the para-aortic lymph nodes. She underwent CT-guided needle biopsy and was diagnosed as having adenocarcinoma, which was positive for HER2. She had undergone total gastrectomy for gastric cancer (T1aN2M0, Stage 2A) 13 years earlier, and pathological examination of the resected specimen showed that the gastric cancer was HER2-positive (3+). Thus, she was diagnosed as having recurrence of HER2-positive gastric cancer in the para-aortic lymph nodes. Trastuzumab with S-1 plus oxaliplatin therapy was started. On day 1 of the first course, an infusion reaction due to trastuzumab occurred. Purpura appeared on the whole body from day 2. On the same day, oral administration of S-1 was stopped at her request. Hematuria appeared on day 3, and she visited our hospital on day 7. The platelet count was 1000/μL, so she was urgently hospitalized. Although platelets were transfused, the platelet count did not improve and bone marrow aspiration showed an increase in polynuclear megakaryocytes. We therefore suspected idiopathic thrombocytopenic purpura. Oral administration of prednisolone 1 mg/kg was started and rapidly improved the thrombocytopenia, suggesting a diagnosis of drug-induced immune idiopathic thrombocytopenia (DITP) rather than idiopathic thrombocytopenic purpura. Oxaliplatin was initially considered to be the causative agent of DITP, and S-1 monotherapy was started. No recurrence of thrombocytopenia was observed with S-1 monotherapy. Subsequently, she was started on S-1 plus trastuzumab therapy. On day 2, purpura appeared again, and the platelet count decreased remarkably. It appeared that DITP was caused by trastuzumab. The platelet count again rapidly improved after starting oral prednisolone. Here, we report this rare case of DITP due to trastuzumab with a review of the literature.