How dangerous are ground glass nodules over time?
image: Radiology Assistant
Ground-Glass Nodules: If Growing, Assume Cancer
The more CT scans that are performed, the more ground-glass opacities (GGO’s) are seen and what to do with these abnormalities can be difficult to ascertain for clinicians. With the National Lung Cancer Screening Trial showing a mortality benefit from low dose CT scan in lung cancer, it's not likely that the number CT scans will decrease anytime soon. So what happens to these pure ground-glass nodules are discovered on screening CT scanning? This is the question Chang and colleagues tried to answer in their recent publication.
What They Did
Single-center, retrospective cohort of patients over nearly ten years undergoing low-dose CT scanning for screening purposes. Patients were included if they had pure GGO lung nodules and were followed for more than two years after the initial scan. Patients with transient or diffuse GGO's were excluded, as were those with a previous history of primary lung cancer or other malignancy. GGO'S were defined by tumor shadow disappearance rate. A change in size was defined as an increase or decrease in the GGO by 2 mm.
What They Found
What started as a very large sample size (40,006 scans on 19,919 patients with 857 patients with GGO) finished with only 89 patients and 122 pure GGO nodules.
82% of patients were men in the median nodule size was 5.5 mm
13.5% of patients had growth during follow-up (12 of 89); 9.8% of all nodules grew (12/122)
Increased baseline size (p=0.003) and development of an internal solid portion of GGO (p=0.009) were predictive of growth
11 of 12 patients who had increased nodule size underwent biopsy (one refused) and all 11 had primary lung cancer (early stage)
Adenocarcinoma was found in 73% (8 of 11)
Median postoperative follow-up was 51 months and all patient survived.
Median volume doubling time was 769 days. 11 of 12 pure GGO nodules had volume doubling time greater than 400 days.
Age, sex, smoking history, or lesion multiplicity were not predictive of growth.
What It Means
In this study of patients without a previous history of cancer, larger pure ground glass opacity nodules, and those that developed a solid component over time, both had increased likelihood of growth; this growth was associated with malignancy. However, we cannot know the true incidence of lung cancer in this cohort because not all patients underwent biopsy (only those whose nodules were clearly growing). Lung cancer screening guidelines from RSNA recommend consideration of surgical resection of pure GGO greater than 10 mm, and this study seems to support that recommendation. While 90% of GGOs found on screening did not grow during follow-up, more specific predictive information from the study is limited by its retrospective design, heterogenous follow-up and probably outdated technology.
Clinical Takeaway: GGO’s in high risk patients that grow on serial exams are concerning for cancer and available data seem to support recent guidelines of surgical resection of those GGO’s greater than 10 mm. Larger, prospective studies are needed in patients without previous cancer to further delineate predictive features of GGO’s that warrant aggressive intervention. Natural history of pure ground-glass opacity lung modules detected by low-dose CT scans. Chang B et al. Chest 2013; 143(1): 172-8.