Natural history of pure ground-glass opacity lung nodules detected by low-dose CT scan

Background: Although focal ground-glass opacity (GGO) lung nodules are generally reported to grow slowly, their natural course is unclear. The purpose of this study was to elucidate the natural course of screening-detected pure GGO lung nodules in patients with no history of malignancy. Methods: We retrospectively reviewed the database of subjects who had undergone screenings involving low-dose CT scans. We included patients with pure GGO lung nodules who were followed for >2 years after the initial screening. Results: Between June 1997 and September 2006, 122 pure GGO nodules were found in 89 patients. The median nodule size was 5.5 mm (range, 3-20 mm) in the largest diameter on initial low-dose CT scan. The median follow-up period per patient was 59 months. On a per-person basis, the frequency of growth was 13.5% (12 of 89 patients). On a per-nodule basis, the frequency of growth was 9.8% (12 of 122 nodules). Nodule growth was significantly associated with initial size and new development of an internal solid portion. The median volume doubling time was 769 days for growing pure GGO nodules. A total of 11 growing nodules were surgically validated, and all lesions were confirmed as primary lung cancer. Conclusions: About 90% of the screening-detected pure GGO lung nodules did not grow during long-term follow-up in subjects with no history of malignancy and most growing nodules had an indolent clinical course. A strategy of long-term follow-up and selective surgery for growing nodules should be considered for pure GGO lung nodules.