Retrospective analysis of the clinical features and prognosis of idiopathic pulmonary fibrosis combined with lung cancer

Idiopathic pulmonary fibrosis (IPF) is an interstitial lung disease with a markedly poor prognosis, imposing a heavy burden on society and being prone to various comorbidities, with lung cancer (LC) being one of the most common. Although IPF and LC have not been characterized as overlapping syndromes, a high incidence and unfavorable prognosis have been revealed for IPF combined with LC (IPF-LC). Therefore, the clinical characteristics of patients with IPF-LC vs. those with IPF alone were further investigated, the risk factors for IPF-LC were analyzed, and the risk factors for poor prognosis were identified. The aim of the present study was to raise clinical awareness and provide a reference for early identification and management of LC in patients with IPF. A total of 20 patients with IPF-LC admitted to Yueyang Hospital Affiliated to Hunan Normal University (Yueyang, China) between January 2020 and October 2023 were recruited as the observational group, and 105 patients with IPF alone hospitalized during the same period were selected as the control group. The basic data, clinical manifestations, serum biomarkers, blood gas analysis and tumor markers of the two groups were compared and the risk factors affecting the prognosis of IPF-LC were analyzed. Comparison of the general information (sex, age and smoking) of the two groups revealed that the differences were not statistically significant (P > 0.999, P = 0.316 and P > 0.999, respectively). The percentage of phlegm in the observation group (15%) was lower than that of the control group (41.90%), and the difference was statistically significant (χ2 = 5.183 and P = 0.025). In addition, comparison of the tumor markers between the observation and control groups revealed that the differences in cytokeratin-19 fragment (CYFRA21-1) and squamous cell carcinoma antigen were statistically significant (t = 5.915 and t = 3.274; P = 0.005 and P = 0.001, respectively). The differences in carcinoembryonic antigen and neuron-specific enolase were not statistically significant (P > 0.05). The serum procalcitonin levels of patients with IPF-LC were higher than those of patients with IPF alone (t = 2.291 and P = 0.001), and the difference was statistically significant. There were no statistically significant differences in C-reactive protein and lactate dehydrogenase levels (P > 0.05). Oxygen partial pressure and carbon dioxide partial pressure of arterial blood gas analysis were not statistically significant (P > 0.05). Cox regression analysis for risk factors of patients with IPF-LC revealed that age (HR = 1.147; 95% CI, 1.011-1.300; P = 0.033) and CYFRA21-1 (HR = 1.434; 95% CI, 1.110-1.853; P = 0.006) were statistically significant risk factors. Receiver operating characteristic (ROC) curve analysis further confirmed the prognostic significance of CYFRA21-1, yielding an area under the curve (AUC) of 0.839 with an optimal cut-off value of 5.585 ng/mL. Serum CYFRA21-1 was revealed to be independent risk factors for poor prognosis in patients with IPF-LC. Regular monitoring of CYFRA21-1 and close follow-up are recommended for patients with IPF to reduce the rate of missed diagnosis of combined LC, and to slow the disease progression.