The syndrome of inappropriate antidiuretic hormone secretion associated with chemotherapy for hypopharyngeal cancer.

The syndrome of inappropriate antidiuretic hormone secretion (SIADH) is characterized by hyponatremia and the plasma hypoosmolality induced by water retention attributable to persistent antidiuretic hormone (ADH) release. It has been reported that SIADH may occur due to various factors in patients with malignant tumor. We report a case of hypopharyngeal cancer complicated by SIADH following chemotherapy. A 72-year-old woman with hypopharyngeal cancer was treated by oral administration of S-1 and intravenous administration of low-dose cisplatin following radiation therapy. General fatigue and coma occurred during the third course of this chemotherapy, using S-1 and low-dose cisplatin. We believed that she had SIADH because of the results of examinations including hyponatremia, serum hypoosmolality and increasing serum ADH level. We treated her by fluid restriction and intravenous administration of hypertonic saline and furosemide, and she recovered. Unfortunately, her hypopharyngeal cancer gradually progressed and she died of acute pneumonia three months later.