Syndrome of inappropriate secretion of ADH following chemoradiation therapy

We report a 69-year-old female patient with pulmonary adenocarcinoma complicated by the syndrome of inappropriate secretion of antidiuretic hormone(SIADH)following systemic chemotherapy with cisplatin(CDDP)and vinorelbine(VNR). She was admitted to our hospital for chemo-radiotherapy for advanced lung cancer, and became restless 4 hours after the administration of CDDP and VNR. Symptoms such as restlessness and incontinence were worsening despite the massive infusion that was completed. Laboratory examinations on day 6 after chemotherapy showed severe hyponatremia(107mEq/L)with decreased serum osmolarity(227mOsm/L)and increased urine osmolarity(452mOsm/L). The serum anti-diuretic hormone(ADH)level was elevated to 16. 7 pg/mL despite severe hyponatremia. She was diagnosed with SIADH and was treated with hypertonic saline infusion and fluid restriction. Her restlessness and other psychiatric symptoms were improved. The use of carboplatin and VNR in the subsequent course did not develop SIADH, indicating that the SIADH was induced by CDDP. Although SIADH following CDDP administration is rare, the electrolyte balance should be carefully monitored throughout the clinical course of chemo-radiation therapy, when psychiatric symptoms are found in patients with lung cancer.