The growth of screening-detected pure ground-glass nodules after 10 years of stability

Background: It remains uncertain how long pure ground-glass nodules (pGGNs) detected on low dose computed tomography (LDCT) should be followed. Further studies with longer follow-up periods are needed to determine the optimal follow-up duration for pGGNs.

Research question: What is the percentage of enlarging nodules among pGGNs that have remained stable for 10 years?

Study design and methods: This was a retrospective cohort study originating from subjects with pGGNs detected on LDCT scans between 1997 and 2006, whose natural courses were reported in 2013. We re-analyzed all the follow-up data until July 2022. The study subjects were followed by our institutional guidelines until they were no longer a candidate for definitive treatment. The growth of the pGGNs was defined as an increase in the diameter of the entire nodule by 2 mm or more or the appearance of new solid portions within the nodules.

Results: A total of 89 patients with 135 pGGNs were followed for a median of 193 months. Of 135 pGGNs, 23 (17.0%) increased in size, and the median time to the first detection of a size change was 71 months. Of the 23 growing pGGNs, 122 were detected on the first LDCT, and 13 were newly detected on the follow-up CT scan. An increase in size was observed within 5 years in 8 nodules (34.8%), between 5 and 10 years in 12 nodules (52.2%) and after 10 years in 3 nodules (13.0%). Fifteen nodules were histologically confirmed as adenocarcinoma by surgery. Among the 76 pGGNs stable for 10 years, 3 (3.9%) increased in size.

Interpretation: Among pGGNs that remained stable for 10 years, 3.9% eventually grew, indicating that some pGGNs can grow even after a long period of stability. We suggest that pGGNs may need to be followed for more than 10 years to confirm growth.