Understanding risk factors, progression of interstitial lung abnormalities

Key takeaways:

• Aging and tobacco smoke exposure increased the chances for interstitial lung abnormalities.
• These abnormalities may progress to become interstitial lung disease, so follow-up is important.

Knowing that interstitial lung abnormalities heighten interstitial lung disease and all-cause mortality risk, it is important that pulmonologists know how to recognize and distinguish these abnormalities.

“The prevalence of interstitial lung abnormalities (ILAs) is reported to range from 4% to 9% in lung cancer screening cohorts and lower (2% to 5%) in other asymptomatic non-smoker cohorts,” Charles A. Powell, MD, MBA, Florette and Ernst Rosenfeld and Joseph Solomon Professor of Medicine and system division chief of pulmonary, critical care and sleep medicine at the Icahn School of Medicine at Mount Sinai, told Healio.

Powell recently spoke on the importance of ILAs detected incidentally on CT at the Mount Sinai Respiratory Institute Symposium, and Healio caught up with him after his presentation to find out more about diagnosing ILAs, who is at risk for these abnormalities and future research on this condition.

Diagnosis, risk factors

To make an adequate diagnosis of ILA or interstitial lung disease, Powell told Healio high-resolution chest CT imaging is a necessity, and pulmonologists should look for thin sections less than 1.5 mm.

Patients of older age and patients with tobacco smoke exposure are at an increased risk for ILAs and idiopathic pulmonary fibrosis, Powell told Healio.

“ILA can be considered to represent a biomarker of lung injury in response to common exposures,” he said, “A common theme for many lung diseases is that disease manifests in individuals with susceptibility amongst all who are exposed to agents such as cigarette smoke, asbestos and tuberculosis, to name a few. The susceptibility factors may be unclear, but the manifestation is clearly demonstrated in this case by the incidence of ILA.”

Another risk factor for ILA involves genetics.

“There is evidence of a genetic risk for ILA in individuals with variants of the gene MUC5B, which is also associated with familial interstitial pneumonia,” Powell told Healio.

When diagnosing a patient with ILA, it is important to determine the radiologic subcategory of ILA, as this impacts progression and mortality.

During his presentation, Powell highlighted that there are three radiologic subcategories of ILA, including nonemphysematous cysts, nonfibrotic ILA and fibrotic ILA, with the highest risk for progression and mortality in patients with the subpleural fibrotic ILA subtype.

“Fibrosis is characterized by the presence of architectural distortion with traction bronchiectasis or honeycombing, or both,” he told Healio.

Powell also noted that progression tends to occur more quickly in patients who are older, cigarette smokers, chemotherapy or immune checkpoint inhibitor recipients, radiation therapy recipients, thoracic surgery recipients and those with lower limits of normal physiologic or gas exchange findings.

Progression, long-term follow-up

Since ILAs may develop over time, a good practice to adopt is long-term follow-up with patients.

“Overall, the rate of imaging progression of ILA ranges from 20% over 2 years to 50% in 5 years,” Powell told Healio.

“Long term follow-up is recommended because of the substantial rate of progression to ILD and the appreciation that there may be opportunities to intervene and mitigate progression of lung fibrosis,” Powell added.

Notably, Powell said pulmonologists should keep a close eye on patients with both ILA and cancer since ILA in these patients is linked to decreased survival and with acute lung injury after surgery, radiation pneumonitis and drug toxicity.

“In cancer, patients with ILA are at a higher risk of drug-induced lung injury after treatment with chemotherapy or immunotherapy,” he said. “This important information can be used to tailor approaches to monitor and enhance early diagnosis of drug induced lung injury in patients identified by imaging as higher risk.”

Future research

Despite everything outlined above, Powell told Healio there are still topics that need to be addressed in future research to aid the current understanding of ILAs.

“A key topic is to develop approaches to facilitate diagnosis using automated analysis of chest CT imaging data since this can reduce the variability in ILA detection,” Powell said. “Clinical trials to evaluate therapies to prevent or reduce progression of ILA to clinical ILD are also critically important.”

As the risk for death from any cause was elevated among those with vs. without ILA in large study cohorts, Powell further emphasized the need for more research on this condition.

References:

• Hatabu H, et al. Lancet Respir Med. 2020;doi:10.1016/S2213-2600(20)30168-5.
• Powell CA. Interstitial lung abnormalities detected on CT: A Fleischner Society position paper. Presented at: Mount Sinai Respiratory Institute Symposium; Oct. 20-21, 2023; New York.

For more information:

Charles A. Powell, MD, MBA, can be reached at charles.powell@mssm.edu.