Abstract
Background: The prevalence of hyponatremia is highly variable among patients with lung cancer. However, its prevalence and prognostic significance in subgroups of patients with lung cancer have not yet been evaluated in a meta-analysis.Methods: We have registered our meta-analysis and review protocol to the PROSPERO International Prospective Register of Systematic Reviews, with the following registration number: CRD42020167013. A systematic search was done in the following sources: MEDLINE, Embase, CENTRAL, Web of Science, ClinicalTrials.gov, a WHO Global Health Library.Results: We identified a total of 8,962 potentially eligible studies, and we included 31 articles in our evaluation. The prevalence of hyponatremia in patients with lung cancer varied between 3 and 94.8% with an average of 25% without any significant differences between the following subgroups: histotype, gender, age, Eastern Cooperative Oncology Group (ECOG) state, and the extent of disease. The overall survival (OS) was significantly lower in hyponatremic compared to normonatremic patients at 10 months [RR.59 (95% CI.47–0.74), p < 0.001] and at 20 months [RR.44 (95% CI.33–0.59), p < 0.001], with worse survival rates in non-small cell lung cancer (NSCLC) [RR.27 (95% CI.12–0.44), p < 0.001] than in small cell lung cancer (SCLC) [RR.42 (95% CI.27–0.57), p < 0.001]. If hyponatremia was corrected, OS at 10 months was significantly higher than in the uncorrected hyponatremia group [RR 1.83 (95% CI 1.37–2.44), p < 0.001], but, at 20 months, no statistically significant difference could be found between these subgroups [RR 2.65 (95% CI.94–7.50), p = 0.067].Conclusions: Patients with lung cancer diagnosed with hyponatremia, especially patients with NSCLC, seem to have significantly lower survival rates than normonatremic patients. If hyponatremia remains uncorrected, the mortality rates might be even higher.
Highlights
The prevalence of hyponatremia is highly variable among patients with lung cancer
We created a search key based on our PECO, which included search terms related to the group of the patients and the prognostic factor: AND (SIADH OR the sodium level OR the Na level OR hyponatremia OR hyponatremia OR syndrome of inappropriate ADH OR antidiuretic hormone OR hypotonicity)
The prevalence of hyponatremia and/or SIADH was even less: Grohe et al found hyponatremia in 14% of patients with small cell lung cancer (SCLC) and 2.7% of non-small cell lung cancer (NSCLC) [7], while Christoforos Efthymiou et al showed that SIADH was present in 7–16% of patients with SCLC and was rare among patients with NSCLC (1%) [8]
Summary
The prevalence of hyponatremia is highly variable among patients with lung cancer. Lung cancer is one of the most frequent malignancies worldwide in both sexes, and 75% of patients are diagnosed at an advanced stage. According to the reports of the WHO in 2018, it is the leading cause of mortality among cancers [1]. SIADH was diagnosed even less frequently in the general cancer population [4, 13, 14]. This discrepancy may be partially explained by insufficient diagnostic work-up and the presence of other comorbidities that affect the sodium level [15,16,17]
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
