Abstract
BACKGROUND: We conducted two independent nested case-control studies to identify circulating inflammation markers reproducibly associated with lung cancer risk and to investigate the utility of replicated markers for lung cancer risk stratification. METHODS: Nested within the Prostate, Lung, Colorectal, and Ovarian Cancer Screening Trial, the previously published discovery study included 526 lung cancer patients and 592 control subjects and the replication study included 526 lung cancer case patients and 625 control subjects. Control subjects were matched by sex, age, smoking, study visit, and years of blood draw and exit. Serum levels of 51 inflammation markers were measured. Odds ratios (ORs) were estimated with conditional logistic regression. All statistical tests were two-sided. RESULTS: Of 11 markers identified in the discovery study, C-reactive protein (CRP) (odds ratio [OR] [highest vs. lowest category] = 1.77, 95% confidence interval [CI] = 1.23 to 2.54), serum amyloid A (SAA) (OR = 1.88, 95% CI = 1.28 to 2.76), soluble tumor necrosis factor receptor-2 (sTNFRII) (OR = 1.70, 95% CI = 1.18 to 2.45), and monokine induced by gamma interferon (CXCL9/MIG) (OR = 2.09, 95% CI = 1.41 to 3.00) were associated with lung cancer risk in the replication study (P trend < .01). In pooled analyses, CRP, SAA, and CXCL9/MIG remained associated with lung cancer more than six years before diagnosis (P trend < .05). The incorporation of an inflammation score combining these four markers did not improve the sensitivity (77.6% vs 75.8%, P = .33) or specificity (56.1% vs 56.1%, P = .98) of risk-based lung cancer models. CONCLUSIONS: Circulating levels of CRP, SAA, sTNFRII, and CXCL9/MIG were reproducibly associated with lung cancer risk in two independent studies within the Prostate, Lung, Colorectal, and Ovarian Cancer Screening Trial, underscoring an etiologic role for inflammation in lung carcinogenesis, though replication is needed in other populations. Markers did not improve lung cancer risk stratification beyond standard demographic and behavioral characteristics.