Compared with the non-relapse group, the relapse group had a significantly higher proportion of non-smokers (30.8 vs. 3.3%, <i>p</i> = 0.035), a greater frequency of Common Terminology Criteria for Adverse Events (CTCAE) Grade 2 pneumonitis (92.3 vs. 53.8%, <i>p</i> = 0.029), and lower serum KL-6 levels (288 vs. 704 U/mL, <i>p</i> = 0.014). Here, MUC1 is linked to pneumonitis.