New and growing nodules are strongly associated with malignancy in follow-up screens for lung cancer: a cohort study.

Abstract

Pulmonary nodules are frequently detected on low dose computed tomography (LDCT) screening for lung cancer, though the majority are benign. Nodules detected on follow-up scans may be new or show interval growth since baseline. What is the risk of malignancy among new or growing nodules detected on follow up screening CT scans? Subjects in the LDCT screening arm of the National Lung Cancer Screening Trial (NLST) with a baseline screen and at least one follow-up screen were included. The primary exposure of interest was nodules that were new or growing on the first (T1) follow-up LDCT. Other covariates included age, sex, family history of lung cancer, presence of emphysema, nodule size, attenuation, lobe location and spiculation. The primary outcome was lung cancer diagnosis within 2 years of T1. Among 24,604 participants with baseline and T1 follow-up LDCT, 6,952 had nodules present during the first round of follow-up screening from which lung cancer was diagnosed within 2 years in 208 participants. Compared to pre-existing nodules with no growth, new nodules were associated with nearly 4-fold greater odds of lung cancer within 2 years (OR: 3.9, 95% CI: 2.51, 6.05, p<0.0001); pre-existing nodules with growth were associated with nearly 20-fold increased odds (OR: 19.7, 95% CI: 13.6, 28.4, p<0.0001). New and growing nodules detected on follow-up LDCT are strongly associated with the risk of malignancy. The magnitude of these risks is substantially greater than for most other well-established risk factors.