Pulmonary pure ground-glass opacity lesions: Use of computed tomography attenuation for predicting tumor progression.

Abstract

7548 Background: Cases with pure ground-glass opacity (GGO) are increasing with the use of computed tomography (CT). In some cases, pure GGO on follow-up CT may represent tumor enlargement or the presence of solid components. We evaluated the natural progression of pure GGO lesions during a long-term follow-up period of more than 2 years. Methods: We retrospectively investigated 95 patients with pure GGO lesions detected between February 2003 and December 2010, in whom these lesions were monitored using CT for more than 2 years. Results: The median follow-up period was 64.7 months (range, 24–114 months). During the follow-up period, areas showing GGO increased in size or appeared to have solid components in 49 patients (group 1) and showed no change in 46 patients (group 2). We compared patient characteristics and tumor properties between the 2 groups. Mean CT attenuation values of the tumors differed significantly between groups 1 (-639.9 ± 88.9 HU) and 2 (-709.2 ± 60.9 HU). In contrast, no significant differences were noted with regard to age, gender, smoking history, lung cancer history, tumor size, and total numbers of GGO lesions between the 2 groups. The difference in the time to tumor growth according to the initial mean CT attenuation value was estimated using the Kaplan–Meier method. The growth incidence at 114 months for lesions with a mean CT attenuation value of -650 HU or more (n = 35) and less than -650 HU (n = 60) were estimated to be 96% and 48%, respectively. The difference between the 2 Kaplan–Meier curves was statistically significant (p < 0.0001). The usefulness of the mean CT attenuation value in predicting the growth of GGO lesions was evaluated using receiver operating characteristic analysis. The sensitivity and specificity was 63% and 87%, respectively, for a mean CT attenuation cutoff value of -650 HU. The area under the curve was 0.76. Conclusions: Many pure GGO lesions have potential for growth as seen during long-term follow-up. CT attenuation is useful in predicting the growth of GGO lesions.