However, there was no significant difference in survival according to high and low serum KL-6 levels in patients with severe TR-ILD (5.7 months, 95% CI 3.4–8.0 vs. 12.6 months, 95% CI 2.9–22.3; p = 0.478) (Fig. 5c), whereas a high serum KL-6 level was associated with worse OS in patients without severe TR-ILD (8.4 months, 95% CI 4.9–11.9 vs. not reached; p = 0.002) (Fig. 5d). Here, MUC1 is linked to interstitial lung disease.