MUC1 and lung cancer: Furthermore, the median OS was significantly shorter among patients with lung cancer with high serum KL-6 levels (> 436 U/mL; 8.2 months, 95% CI 5.3–11.1) than among those with low serum KL-6 levels (≤ 436 U/mL; 14.7 months, 95% CI 11.0–18.4), with a HR of 1.70 (95% CI 1.27–2.28; p < 0.001) (Fig. 5b).