We performed univariate and multivariate logistic regression analysis to explore independent factors for lung cancer in CPFE patients, which demonstrated that pack-years ≥ 20 (OR: 3.672, 95% CI: 1.165–11.579), family history of cancer (OR: 8.353, 95% CI: 2.368–10.417), fibrinogen > 4.81 g/L (OR: 3.628, 95% CI: 1.403–9.385) and serum C3 > 1.00 g/L (OR: 5.299, 95% CI: 1.727–16.263) were independently associated with lung cancer in patients with CPFE (Table 3). This evidence concerns the gene C3 and cancer.