Abstract
The syndrome of inappropriate antidiuretic hormone hypersecretion (SIADH) is characterized by hyponatremia induced by a secretion disorder of an antidiuretic hormone and has been recognized in association with various conditions including malignant disease. On the other hand, hyponatremia during treatment of patients with cancer may be caused by SIADH, which is rarely caused by anticancer drugs. SIADH is not commonly associated with the field of oral and maxillofacial surgery and there are few case reports. We report a case of SIADH that developed during chemo-radiotherapy in a patient with oral cancer.
A 55-year-old woman with malignant tumor of the maxilla underwent chemo-radiotherapy. We performed systemic chemotherapy with S-1 at 100 mg/m2 on days 1-21 and cisplatin (CDDP) at 81 mg/m2 on day 11, in addition to radiotherapy followed by a radical dose of 68 Gy/34 fractions of external beam radiation. On day 17, she lapsed into a coma (Japan Coma Scale I-1), and her serum sodium concentration exhibited a sharp decrease to 98 mEq/L. Since the patient presented none of dehydration, a particular history of related disorders, serum hypoosmolality accompanied by urine hyperosmolality, or persistent urinary sodium excretion, we diagnosed that the hyponatremia was due to SIADH induced by the anticancer drug. After treatment with fluid restriction and sodium supplements, she regained consciousness and achieved an appropriate serum sodium level. We consider that a suitable early response is important when hyponatremia occurs, and that serum sodium should be measured frequently for SIADH during and after chemotherapy and chemo-radiotherapy with CDDP.
