Can CT Lung Cancer Screening Also Detect IPF?

Background

The National Lung Screening Trial (NLST) compared 2 methods of detecting lung cancer in high-risk patients (defined as cigarette smoking of ≥30 pack-years): low-dose computed tomography (CT) and standard chest x-ray.1 The study found that participants who received low-dose CT scans had a 20% lower risk of dying from lung cancer than participants who received standard chest x-rays. Because there is a strong relationship between cigarette smoking and several types of interstitial lung diseases, Jin, Lynch, Chawla, Garg, et al sought to determine the frequency of interstitial lung abnormalities (ILAs) in a lung cancer screening population.2

What They Did

The authors examined the CT scans of cigarette smokers (N=884) who had low-dose CT imaging at a single site in the NLST.2 Based on a questionnaire at enrollment, none of the participants had a history of lung fibrosis. CT findings were grouped into 1 of 3 categories: no evidence of ILA, equivocal for ILA, or ILA. Those with ILA were then categorized by type of ILA: nonfibrotic (ground-glass opacity, consolidation, mosaic attenuation) or fibrotic (ground glass with reticular pattern, reticular pattern, honeycombing). Finally, the change in CT findings over 2-year follow-up were classified as no change, improvement, or progression.

What They Found

Evidence of ILA was found in 9.7% of participants. The type of ILA was fibrotic in 2.1%, nonfibrotic in 5.9%, and mixed fibrotic and nonfibrotic in 1.7%.2 Of those with a fibrotic pattern, 90% were men, and the average age was 64. Over 2-year follow-up, nonfibrotic ILA improved in 48.9% and progressed in 10.9%, while fibrotic ILA did not improve in any participants and progressed in 36.8%.

What It Means

Fibrotic findings consistent with idiopathic interstitial pneumonia (nonspecific interstitial pneumonia or idiopathic pulmonary fibrosis) on CT images were found in 2% (19 of 884) of participants without a history of lung fibrosis who were screened for lung cancer.2 Although these individuals may be asymptomatic, they should be monitored closely and potentially referred to an interstitial lung disease center for a definitive diagnosis and early management.

Link to Abstract: http://www.ncbi.nlm.nih.gov/pubmed/?term=jin+and+lynch+and+chawla



References

  1. Aberle DR, Adams AM, Berg CD, et al. Reduced lung-cancer mortality with low-dose computed tomographic screening. N Engl J Med. 2011;365:395-409.
  2. Jin GY, Lynch D, Chawla A, et al. Interstitial lung abnormalities in a CT lung cancer screening population: prevalence and progression rate. Radiology. 2013;268:563-571.