Hyponatremia as prognostic factor in small cell lung cancer--a retrospective single institution analysis.

PURPOSE: The aim of this retrospective study is to present data on clinical significance of hyponatremia in an unselected contemporary patient population with small cell lung cancer (SCLC) with limited disease (LD) and extensive disease (ED).

PATIENTS AND METHODS: Our electronic database was searched for patients with newly diagnosed SCLC from June 2004 to December 2008. 395 cases were identified. We collected data on patient characteristics including clinical performance status, serum sodium values, serum LDH values, metastatic sites, chemotherapy regimens and response, radiotherapy and survival.

RESULTS: Hyponatremia (sodium <135 mmol/l) was present in 18.9% of all cases. Severe hyponatremia (sodium <129 mmol/l) was detected in 8.8%. Hyponatremia was present in 58 out of 241 (24%) patients with ED SCLC and 17 of 154 (11%) patients with LD SCLC. Hyponatremia was associated with significantly shorter median survival (SCLC all patients: 9.0 vs. 13.0 months, p < 0.001, LD SCLC: 9.0 vs. 17.0, p = 0.050, ED SCLC 9.0 vs. 10.0, p = 0.135). After adjustment for age, gender, LDH and performance status hyponatremia was an independent predictor of mortality in patients with ED and LD SCLC.

CONCLUSION: According to the extensive statistical analyses in our comprehensive unselected patient population, hyponatremia seems to constitute an independent prognostic factor in patients with SCLC.