A systematic review and meta-analysis to evaluate blood levels of interleukin-6 in lung cancer patients

Introduction
The exact mechanism responsible for inflammation in malignancy is not completely understood, but it is possible that interleukin-6 (IL-6) plays a major role in triggering and maintaining an inflammatory response.

Aim
To conduct a systematic review and meta-analysis of the levels of IL-6 in the serum/plasma of lung cancer (LC) patients.

Material and methods
The researchers searched four databases up to September 11, 2022, to find studies that reported on IL-6 levels in LC patients compared to healthy controls (HCs). They calculated effect sizes using standardized mean difference (SMD) with a 95% confidence interval (CI). To evaluate the quality of each study, they used the Newcastle-Ottawa Scale (NOS). They performed subgroup analysis, sensitivity analysis, meta-regression analysis, heterogeneity analyses, trial sequential analysis, and publication bias with the trim-and-fill method.

Results
The meta-analysis included 28 studies, and the results showed that the pooled SMD was 1.71 (95% CI: 1.22, 2.19; p < 0.00001; I2 = 98%), indicating that LC patients had significantly higher levels of IL-6 in their serum/plasma than HCs.

Conclusions
The study found that the publication year and quality score of the studies were positively associated with the level of IL-6, while the sample size was inversely related. The research suggests that measuring IL-6 levels in the blood could be useful for detecting and monitoring LC as it appears to be a reliable biomarker.