Association of serum tumor markers with interstitial lung disease in patients with or without connective tissue disease: A cross-sectional study

Background: Serum markers, such as Krebs von den Lungen-6 (KL-6), are reported to reflect the severity, progression and prognosis of idiopathic pulmonary fibrosis (IPF). We aimed to evaluate whether tumor markers could improve the diagnosis of connective tissue diseases (CTDs) and predict CTD-related interstitial lung diseases (ILDs) (CTD–ILD); and whether there was a significant difference between ILD patients with CTD and without CTD (non-CTD–ILD). Methods: In this study, 146 patients with ILD only, 61 with CTD–ILD, 102 with lung cancer (LC), 111 with COPD, and 46 with CTD were enrolled. Serum levels of several tumor markers were collected. Results: Compared with COPD, the serum levels of CEA, NSE, CYFRA21-1, CA19-9 and CA125 were higher, but the level of SCC was lower; meanwhile, there were significant differences in NSE, SCC, CYFRA21-1 and CA125 between CTD–ILD and non-CTD–ILD groups. Conclusions: It appears that tumor-associated antigens may be the predictive factors for CTD–ILD that could be used to identify CTD from ILD before it is detected on autoimmune symptoms or auto-antibodies. However, further studies are needed to validate our findings and determine whether serum tumor markers have prognostic value or predict progressive CTD–ILD.