Small changes in lung CT scans linked to declining lung function

Whether change in fibrosis on high-resolution CT is associated with near- and longer-term outcomes in patients with fibrotic interstitial lung disease (fILD) remains unclear, prompting a new study by researchers led by Matthew Koslow, M.D., of the Center for Interstitial Lung Disease, Division of Pulmonary and Critical Care Medicine at National Jewish Health in Denver, and colleagues.

Their study has discovered that subtle changes in lung scarring over just one year, as measured by quantitative computed tomography imaging, are strongly linked to future lung-function decline and survival in patients with fibrotic interstitial lung disease (fILD).

The findings, which were reported in the American Journal of Respiratory and Critical Care Medicine in September, document that what appear to be small changes in high-resolution CT images of the lung may, in fact, herald more rapid disease progression.

The researchers enrolled a cohort of 407 patients with fILD who underwent high-resolution computed tomography at baseline and again approximately one year later, together with forced vital capacity (FVC) measurements. Then, by utilizing a deep-learning algorithm known as data-driven textural analysis (DTA), the investigators quantified changes in the extent of fibrosis on the CT scans and then related those changes to subsequent lung-function decline and transplant-free survival.

The goal, the authors noted, was to evaluate “the association between 1-year change in quantitative fibrosis scores and subsequent FVC and survival in patients with fILD.”

The findings revealed that an increase in DTA score over one year was independently associated with a steeper decline in FVC and a higher risk of death or lung transplant. For instance, in patients who started with a lower baseline DTA score, a 5% increase in DTA over one year was linked to an FVC decline of -91 mL/year. In contrast, those with stable DTA had an FVC decline of -49 mL/year.

The researchers explained that the hazard ratio for transplant-free survival for a 5% increase in DTA over one year was 1.45 and noted a one-year change in DTA score is associated with future disease trajectory and transplant-free survival in patients with fILD.

This is vital information that could make a difference in the monitoring and treatment of fILD in the future. Koslow and his co-authors explained that in fibrotic lung disease, including conditions such as idiopathic pulmonary fibrosis and other forms of progressive interstitial lung disease, clinicians struggle to identify early which patients will deteriorate rapidly and which will remain stable. Traditional monitoring relies on symptoms, periodic lung-function testing and visual interpretation of CT scans — all of which have limitations.

This new study suggests that an objective, quantitative imaging marker can flag progression earlier than conventional methods. In fact, the authors suggest, DTA “could be a useful trial endpoint, cohort enrichment tool and metric to incorporate into clinical care.”

What’s more, the team validated their findings in an independent cohort drawn from the Pulmonary Fibrosis Foundation Patient Registry, strengthening the generalizability of their results. Therefore, this approach provides a window for identifying patients earlier, especially those whose baseline imaging shows relatively less fibrosis but who nonetheless show meaningful progression over a short interval.

Some caveats remain. The study was observational, so while it shows strong associations and provides a clue to possible causation, it is not definitive proof. Also, implementing DTA-based analysis in everyday clinical practice will require access to the algorithm and standardization of CT acquisition and processing.

Despite these limitations, the study offers compelling evidence that the ability to detect subtle lung-scarring progression within one year can be useful to stratify patient risk and potentially intervene earlier.