The positive results of a screening CT scan trial are likely to lead to an increase in the use of CT scanning, and, consequently, an increase in the detection of subsolid nodules. Noninvasive methods including follow-up with CT scanning, to determine which nodules require invasive diagnosis and surgical treatment, should be defined promptly.
Between 2000 and 2008, from our database of > 60,000 examinations with CT scanning, we identified 174 subsolid nodules, which showed a ground-glass opacity area > 20% of the nodule and measured ≤ 2 cm in diameter, in 171 patients. We investigated the clinical characteristics and CT images of the subsolid nodules in relation to changes identified during the follow-up period.
The nodule sizes ranged from 4 mm to 20 mm at the first presentation. Nonsolid nodules numbered 98. During the follow-up period, 18 nodules showed resolution or shrinkage, and 41 showed growth of 2 mm or more in diameter. The time to 2-mm nodule-growth curves calculated by Kaplan-Meier methods indicated that the 2-year and 5-year cumulative percentages of growing nodules were 13% and 23% in patients with nonsolid nodules and 38% and 55% in patients with part-solid nodules, respectively. Multivariate analysis disclosed that a large nodule size (> 10 mm) and history of lung cancer were significant predictive factors of growth in nonsolid nodules.
An effective schedule for follow-up with CT scanning for subsolid nodules should be developed according to the type of subsolid nodule, initial nodule size, and history of lung cancer.