Association between hyponatremia and prognosis of patients with small cell lung cancer

Objective To investigate the association between hyponatremia and the prognosis of patients with small cell lung cancer (SCLC). Methods The clinical data of 489 patients with SCLC who were treated in Zhejiang Cancer Hospital from January 1, 2010 to December 31, 2012 were retrospectively analyzed.110 patients have hyponatremia in all patients.Hyponatremia incidence was compared with χ2 test. Survival rates were calculated by the Kaplan-Meier method and compared by the log-rank test. The Cox proportional hazards model was applied to analyze the prognostic factors including hyponatremia. Results Before initial treatment, after 2 cycles of chemotherapy, after radiotherapy, and after the end of the last treatment, the incidence of hyponatremia was 17.9%, 13.3%, 12.5%, and 18.9%, respectively; the 3-years survival rate were 10.1% vs. 21.1%(P=0.000), 14.7% vs. 20.5%(P=0.022), 12.1% vs. 28.3%(P=0.000), 7.0% vs. 21.8%(P=0.000) with hyponatremia than normal blood sodium, respectively. The Cox regression analysis showed that the relative risk of death in patients with hyponatremia was elevated 1.297 times (95% CI=1.160-1.449, P=0.000), 1.366 times (95% CI=1.023-1.825, P=0.035), 1.770 times (95% CI=1.168-2.682, P=0.007), and 1.507 times (95% CI=1.167-1.944, P=0.002) in before initial treatment, after 2 cycles of chemotherapy, after radiotherapy, and after the end of the last treatment. Conclusion Hyponatremia is an independent prognostic factor for patients with SCLC. Key words: Hyponatremia; Carcinoma, small cell lung/chemotherapy; Carcinoma, small cell lung/radiotherapy; Prognosis