Neuropeptide production by small cell carcinoma: vasopressin and oxytocin as plasma markers of disease.

Vasopressin (VP) and oxytocin (OT) were evaluated as tumor markers for small cell carcinoma of the lung by measuring the concentrations of these hormones in plasma samples obtained from patients at the onset of therapy and during treatment. Patient levels of VP before treatment ranged from 0.9-116 pmol/L, and this hormone was elevated (greater than 2.4 times) in 37 of 80 patients (46%) when values were compared to those of 25 healthy volunteers (normal mean, 2.13 +/- 0.15 pmol/L). Seventeen patients with elevated arginine VP displayed symptoms of the syndrome of inappropriate secretion of antidiuretic hormone. Patient levels of OT ranged from 0.3-124 pmol/L, and OT was elevated (greater than 2.4 times) in 14 of 72 patients (19%) compared with values in normal subjects (normal mean, 2.23 +/- 0.34 pmol/L). Both hormones were elevated in 6 patients. A positive response to treatment (partial or complete remission) was associated with reductions of elevated VP to 34.6 +/- 4.0% and of elevated OT to 34.7 +/- 7.5%, of values before treatment. Relapse was associated with an increase to 334 +/- 93% of remission values for VP (6 patients) and to 307% for OT (1 patient). These results indicate that VP and OT may be suitable plasma markers for a majority of small cell tumors. In most cases, an elevated concentration of hormone was associated with an elevation of the biosynthetically related neurophysin and vice versa. However, there were a number of exceptions, so that an elevated plasma concentration of VP, OT, or a neurophysin was found for 88% of patients with extensive disease and 70% of patients with limited disease.