C-Reactive Protein, Interleukin 6 and Lung Cancer Risk: A Meta-Analysis

Purpose: Epidemiologic findings are inconsistent concerning the associations between C-reactive protein (CRP), interleukin 6 (IL-6) and lung cancer risk. We conducted a meta-analysis of epidemiologic studies to examine these associations. Methods: A systematic literature search up to October 2011 was performed in MEDLINE and EMBASE. Study-specific risk estimates were pooled using a random-effects model. Results: The 10 studies on CRP involved a total of 1918 lung cancer cases. The pooled RR of lung cancer for one unit change in natural logarithm (ln) CRP was 1.28 (95% CI 1.17-1.41). There was no statistically significant heterogeneity among studies (P = 0.116; I-2 = 36.6%). We also found that CRP was significantly associated with increased risk of lung cancer among men (RR 1.18, 95% CI 1.09-1.28) but not among women. The 5 studies on IL-6 involved a total of 924 lung cancer cases. The pooled RR of lung cancer for one unit change in ln IL-6 was 1.28 (95% CI 0.92-1.79), however, statistically significant heterogeneity was found. After excluding the study contributing most to the heterogeneity, the summary estimate was essentially unchanged. Conclusion: CRP was associated with increased risk of lung cancer, especially among men. There was no significant association between IL-6 and lung cancer risk.