A case of siadh complicated by a consciousness disorder during ts-1 plus cddp combination chemotherapy for recurrent gastric cancer

Abstract

A 71-year-old man was diagnosed as having a recurrent gastric cancer with peritoneal dissemination and umbilical metastasis. He was started on combination chemotherapy with TS-1 plus cisplatin (CDDP). On the 7th day after the administration of the first course of CDDP chemotherapy, the patient became drowsy ; laboratory studies revealed a serum sodium level of 108 mEq/l, a serum chloride level of 70 mEq/l, a plasma osmolality of 218 mOsm/kgH₂O, a urine sodium level of 127 mEq/l, and a urine osmolality of 533 mOsm/kgH₂O. The syndrome of inappropriate secretion of antidiuretic hormone (SIADH) induced by chemotherapy using CDDP was diagnosed. Fluid restriction and sodium supplementation were started. On the 3rd day after the start of SIADH treatment, the serum sodium concentration rose to within normal limits, and the patient's consciousness disorder had almost fully resolved. The serum sodium concentration has to be frequently checked during S-1 plus CDDP chemotherapy for gastric cancer treatment due to concerns about SIADH.