Prevalence and Epidemiological Characteristics of Incidental Pulmonary Nodules in China: A Prospective Multicenter Trial of 10,560 Cases

Background: A clinical trial (NCT03651986) is conducted to assess the performance of our previously established model based on cfDNA methylation sequencing (Liang, W. et al. J Clin Invest 2021;131(10): e145973) for early diagnosis of lung cancer. Aims and Objective: To report the prevalence and epidemiological characteristics of subjects in this trial at baseline. Methods: A prospective cohort of 10,560 subjects with incidental pulmonary nodules (IPNs) sized in 5-30 mm indicated by CT/LDCT were enrolled at 23 centers. The demographic, clinical, and CT imaging features of all cases at baseline were analyzed. Results: Totally 13,310 pulmonary nodules (PNs) were identified in 10,560 cases (mean [SD], 53.12 [11.88] years; 56.6% female; 71.3% never-smokers), including 4,997 (37.54%) solid nodules (SNs), 5,111 (38.40%) pure ground-glass nodules (pGGNs) and 3,202 (24.06%) mixed ground-glass nodules (mGGNs). 2,246 (1,814 malignant, 332 benign) PNs from 1,981 patients (53.9 [11.21] years; 60.6% female; 77.3% never-smokers) at high risk underwent surgical resection with definitive diagnosis at baseline. Up to 98.15% of female patients with malignant PNs were never-smoker. 76.7% of malignant PNs were GGNs and 58.8% of benign PNs were SNs. 92.78% of malignant PNs were lung adenocarcinoma and 87.54% (1,588) were at early stages (0-I). 46.99% (156) of benign PNs were inflammation. Gender, age, nodule size, location, types, lobulation, pleural traction, and vacuole signs were significant lung cancer risk factors (p<0.05). Conclusions: These findings describe a typical profile of IPN patients in China that form a foundation for future clinical management of IPN patients.