Syndrome of Inappropriate Antidiuretic Hormone Secretion: A Poor Prognosis in Small-cell Lung Cancer

Small cell lung cancer (SCLC) is frequently associated with syndrome of inappropriate antidiuretic hormone (SIADH) secretion. In this study we investigated the prognostic value of SIADH in Chinese patients with SCLC. We prospectively studied a total of 385 patients with SCLC diagnosed in our institution. The relationship between the SIADH and treatment outcomes including progression-free survival (PFS) and overall survival (OS) were analyzed. Univariate analysis and Cox multivariate analyses were used for statistical analyses. PFS and OS curves were drawn using Kaplan-Meier method. The median PFS and OS in patients with SIADH was 6.7 months (95% confidence interval [CI]: 4.3–9.1) and 11.6 months (95% CI: 7.4–15.7), respectively. The corresponding PFS and OS in SCLC without SIADH was 9.2 months (95% CI: 8.6–9.8) and 19.2 months (95% CI: 16.5–21.9), respectively; the difference between groups was statistically significant (p = 0.007 and p = 0.000, respectively). The association of SIADH with poor PFS (p = 0.000) and OS (p = 0.002) retained its statistical significance after adjusting for potential confounding variables. In addition, PFS (p = 0.000) and OS (p = 0.000) of SIAHD patients with plasma sodium <125 mmol/L or without plasma sodium recovery to normal level are both shorter than in patients without SIADH. OS in SIAHD patients with plasma sodium recovery time to normal level is also shorter than patients without SIADH (p = 0.03). SIADH is a common occurrence in patients with SCLC and is associated with poor prognosis for SCLC in Chinese patients.