Abstract
Background. Hyponatremia in patients with lung cancer during treatment may be caused by syndrome of inappropriate secretion of antidiuretic hormone (SIADH), which is rarely produced by anticancer drugs. Case. A 71-year-old man was referred to our hospital for detected examinations of an abnormal shadow on chest X-ray films and edema of the face and the upper extremities. The tumor in the upper lobe of the right lung with mediastinal lymphadenopathy on chest CT was diagnosed as poorly differentiated adenocarcinoma based on the transbronchial lung biopsy findings. Furthermore, this tumor was thought to be a granulocyte colony-stimulating factor (G-CSF) producing lung cancer because of the remarkable leukocytosis and the high levels of plasma G-CSF shown by laboratory data on admission. Two weeks after initiation of radiation therapy, the patient received combination chemotherapy with nedaplatin and docetaxel, resulting in delirium at 9 days after the start of chemotherapy. The diagnosis of SIADH was confirmed based on laboratory findings such as hyponatremia with decreased plasma osmolality and elevation of plasma ADH levels. After treatment by sodium supplement together with intravenous diuretics, fluid restriction improved the patient's clinical condition and hyponatremia did not appear again. Conclusion. Although emergency treatments may be required for patients with symptomatic hyponatremia, it is important to differentiate the cause of the SIADH by considering the possibility of drug-induced SIADH.
