Prognostic role of hyponatremia in 564 small cell lung cancer patients treated with topotecan

Objectives: Hyponatremia is reported in about 15% of small cell lung cancer (SCLC). Variable results of the prognostic significance of low plasmatic sodium (Napl) have been reported. Our study was performed to investigate the prognostic role of hyponatremia in SCLC patients treated in second-line with topotecan chemotherapy. Materials and methods: Data were retrospectively collected from a database including clinical data from 631 patients enrolled in 6 prospective topotecan iv studies. Final data were obtained from 564 patients in which data on baseline Napl were available. Univariate and multivariate analysis were carried out to study the possible correlation between Napl and second-line clinical outcomes. Results: Hyponatremia (Napl<135mequiv./l) was present in 101 cases (17.9%). Napl was <125mequiv./l in 16 patients (2.8%), 126-130mequiv./l in 11 (2%), 130-134mequiv./l in 74 (13.1%), while 463 patients (82.1%) showed normal values. The median survival was 28.7 weeks in patients with normal Napl, and 21.1 weeks in patients with hyponatremia (p<0.0001, HR=1.67, 95%CI=1.32-2.10). By Cox multivariate analysis, hyponatremia was associated with poorer prognosis (p=0.0024, HR=1.44, 95%CI=1.13-1.82). A not statistically significant trend of correlation between hyponatremia and progression-free survival (p=0.085, HR=1.23, 95%CI 0.97-1.55) and response rate (p=0.5037, OR=0.81, 95%CI 0.44-1.49) was observed. Conclusion: Hyponatremia is an independent prognostic factor for patients with SCLC treated with topotecan in second-line setting. Further studies are needed to prospectically confirm these results and to develop an optimal therapy for hyponatremic patients.