The prognostic value of elevated KL-6 for OS was significant for patients with lung cancer without ILD (HR 1.85, 95% CI: 1.21–2.83; P = 0.005) but not for those with ILD (HR 1.27, 95% CI: 0.59–2.75; P = 0.539). This evidence concerns the gene MUC1 and interstitial lung disease.