Lung cancer risk and cancer-specific mortality in subjects undergoing routine imaging test when stratified with and without identified lung nodule on imaging study.

OBJECTIVES: To assess the risk of lung cancer and specific mortality rate in patients with and without solitary pulmonary nodules (SPN) on chest radiograph and CT.
METHODS: This prospective study included 16,078 patients ≥35 years old (893 of them had an SPN detected with either chest radiograph or CT) and 15,185 without SPN. Patients were followed up for 18 months or until being diagnosed with lung cancer. Risk and mortality lung cancer were calculated in both groups with Poisson regression.
RESULTS: In patients with SPN, incidence of lung cancer was 8.3 % (95 % CI 6.0-11.2) on radiograph and 12.4 % (95 % CI 9.3-15.9) on CT. A chronic obstructive pulmonary disease in patients with radiographs (odds ratio 2.62; 95 % CI 1.03, 6.67) and smoking habit (odds ratio 20.63; 95 % CI 3.84, 110.77) in patients with CT were associated with a higher probability of lung cancer. Large nodule size and spiculated edge were associated with lung cancer on both CT and radiograph. Lung cancer-specific mortality was lower in patients with SPN than in those without SPN (1.73/1000 person-years, 95 % CI 1.08-2.88 vs. 2.15/1000 person-years, 95 % CI 1.25-3.96).
CONCLUSIONS: The risk of lung cancer for patients with SPN is higher in clinical populations than in screening studies. Moreover, patients with SPN showed lower mortality than those without SPN. KEY POINTS: • Lung cancer risk is 8 % for SPN detected on routine radiographs. • Lung cancer risk is 12.4 % for SPN detected in routine chest CT. • Smoking, COPD, SPN diameter and edge were predictors of malignancy. • Lung cancer risk of SPN in routine practice seems higher than in screening.