Neither the presence nor the severity of hyponatremia affected the outcome of the patients with small cell lung cancer

Abstract

Background: Hyponatremia is the most common electrolyte disorder in lung cancer, and it particularly occurs in small cell lung cancer (SCLC) patients. The prognostic significance of hyponatremia has been reported in several studies with controversial results. Aims: We aimed in this study to investigate hyponatremia and evaluate its prognostic value in SCLC patients. Methods: The data of 373 SCLC patients were analyzed retrospectively. Serum sodium concentrations were measured from blood samples taken from all patients before treatment. Hyponatremia was defined as a serum sodium concentration below 135 mmol/L and then assigned into two groups: mild (130 to 134 mmol/L) and severe (below ≤ 129 mmol/L) hyponatremia. Results: Hyponatremia was detected in 85 (22.8%) patients (mild hyponatremia in 51 (13.7%) and severe hyponatremia in 34 (9.1%) patients). Furthermore, 26% (63 of 242) of ED-SCLC patients and 16.8% (22 of 131) of LD-SCLC patients had hyponatremia. While no clinical parameter was statistically associated with serum sodium concentrations in LD-SCLC patients, hyponatremic ED-SCLC patients were more frequently associated with weight loss (p = 0.04) and liver metastasis (p = 0.04). In LD-SCLC, the overall survival (OS) rates of patients with hyponatremia were similar to those with normonatremia (p = 0.6). Likewise, hyponatremic and normonatremic ED-SCLC patients had similar life expectancies (p = 0.1). Moreover, the severity of hyponatremia did not affect OS in either LD-SCLC (p = 0.3) or ED-SCLC (p = 0.1). Conclusion: Serum sodium concentration did not have an impact on survival in SCLC patients; thus, we concluded that neither the presence nor the severity of hyponatremia affected the outcome of these patients.