Management of the syndrome of inappropriate antidiuretic hormone secretion in small cell lung cancer.

From 1976 to 1980, 18 of the 250 patients (7%) seen with small cell carcinoma of the lung had clinically evident inappropriate secretion of antidiuretic hormone (ADH). Hyponatremia was usually severe (116 +/- 7 meq/l), and eight patients showed symptoms of water intoxication at the time of diagnosis. Of the eight patients who had plasma ADH measured at diagnosis, seven had elevated values (mean 52.0, range 16.1 - greater than 250 pg/ml). Intensive combination chemotherapy produced objective tumor responses in all patients, and syndrome of inappropriate ADH secretion (SIADH) resolved in 16 of 17 evaluable patients within three weeks of initiation of treatment. ADH values after therapy were normal, and all patients maintained a normal serum sodium during the period of tumor remission in spite of unrestricted fluid intake. All 17 evaluable patients have developed progressive cancer, but only 10 have manifested recurrent SIADH. Patient survival was similar to the overall population of small cell carcinoma patients without SIADH. The indirect methods of treatment for SIADH (fluid restriction, demeclocycline, lithium, urea) are frequently of transient value while awaiting a response to chemotherapy or in patients with resistant tumors. However, the initial treatment of choice for SIADH associated with small cell carcinoma of the lung is combination chemotherapy.