A new analysis published in the American Journal of Roentgenology suggests that follow-up imaging protocols for lung nodules identified via CT may need to be revisited. 

The study retrospectively examined the cases of 76 patients who had positive findings (Lung-RADS category ≥3) on their CT lung cancer screening and were eventually diagnosed with cancer. Current Lung-RADS protocols recommend downgrading category 3 or 4 nodules to category 2 if they remain unchanged on imaging for 3 months, citing that a lack of changes indicates the nodules are likely benign. These specific recommendations, however, have many in the radiology community concerned. 

“This guidance may be problematic considering potential slow-growing cancers, such that lack of nodule growth, particularly at short follow-up intervals, may provide false reassurance,” explained study co-authors Suzanne C. Byrne, MD, and Mark M. Hammer, MD, both from the Department of Radiology at Brigham and Women's Hospital in Boston. 
 
During their analysis of the efficacy of completing additional imaging 3 months after LDCT scans uncovered lung nodules, the experts found the protocol to be unreliable. The median time to growth was recorded at 13 and 11 months by linear and volumetric measurements, with a frequency of growth at the 3-month mark of 5% and 7%. 

The authors shared that as the follow-up interval increased, so did nodule growth in many cases, with linear measurements taken at 6 months revealing another 11% of nodules had grown, followed by an additional 10% at 12 months and 6% at 18 months.