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Characteristics of the ground-glass opacity nodules showing growth during follow-up.

7060 Background: The National Lung Screening Trial implemented in the United States demonstrated a significant reduction in lung cancer mortality by screening with computed tomography (CT). These findings will lead to a sharp increase in the use of CT, and consequently an increase in the detection of ground-glass opacity (GGO) nodules. Non-invasive methods, including follow-up with CT, in order to determine which nodules require invasive diagnostic strategies, should rapidly be defined. The aim of this study is to elucidate the characteristics of GGO nodules that show growth during follow-up with CT.


METHODS
Between 2000 and 2008, from our database of over 60,000 CT examinations, we identified 178 GGO nodules, which showed a GGO area greater than 20% and measured less than 2cm in diameter from 172 patients. We investigated the clinical characteristics and CT images of the GGO nodules in relation to changes of the GGO nodules during follow-up period.


RESULTS
The nodule sizes ranged from 4 to 20 mm, with a median of 11 mm. One hundred and fifteen nodules were observed to be pure GGO. Follow-up periods ranged from 1 to 111 months, with a mean of 26 months. During the follow up period, 20 nodules showed fading or shrinkage, 121 showed no change in size, and 37 showed growth of at least 2 mm in diameter. Growth ranged from 2 to 14 mm, with a means of 4 mm. Time to 2mm nodule growth curves were caliculated with Kaplan-Meier methods using nodules excluding those showed fading or shrinkage. The 2- and 5-year cumulative percentages of growth nodule were calculated to be 23% and 31%. According to the nodule size and proportion of GGO, these were 4% and 14% for nodules less than 10 mm, 25% and 34% for 10 to 14 mm, both 60% for greater than 14 mm, 13% and 18% for pure GGO, and 40% and 51% for mixed GGO. No pure GGO nodule smaller or equal to 7mm showed growth. Univariate analysis revealed that nodule size, proportion of GGO, age, gender, history of lung cancer, and smoking history were factors predicting growth. Multivariate analysis disclosed that nodule size is the only predictive factor.


CONCLUSIONS
Follow-up with CT is effective in the selection of patients who require further examination. Size of GGO nodule was strongly associated with the growth of GGO nodule during the follow-up.