MUC1 and retinitis pigmentosa 1: In several studies of patients with lung cancer, KL-6 has been used to predict the development of post-treatment pneumonitis, such as drug-induced ILD18, including ICI-related interstitial pneumonitis19, radiation-induced pneumonitis (RP)20, and exacerbation of underlying idiopathic ILD with lung cancer21, which can be considered treatment-related ILD (TR-ILD).