This study summary is an excerpt from the book 2 Minute Medicine’s The Classics in Medicine: Summaries of the Landmark Trials
1. In patients with a low clinical risk for lung cancer, incidentally-detected small lung nodules (< 4 mm) found on computed tomography (CT) scans do not require additional longitudinal imaging follow-up; nodules between 4 to 6 mm require a single follow-up CT in 12 months.
2. In patients with high clinical risk for lung cancer, small lung nodules (< 4 mm) require a single follow-up CT at 12 months; nodules between 4 to 6 mm in size require initial follow-up at 6 to 12 months, followed by a repeat follow-up at 18 to 24 months.
Original Date of Publication: November 2005
Study Rundown: Solitary pulmonary nodules are common incidental findings on radiographs or CT scans of the chest, often posing diagnostic difficulties for the radiologist given the wide differential of benign and malignant etiologies. Earlier guidelines recommended up to 5 CT follow-up exams to assess nodules stability, regardless of morphology or size. This often resulted in unnecessary scans and excessive ionizing radiation exposure to patients for nodules with little malignant potential. The purpose of this landmark guideline from the Fleischner Society was to provide expert-consensus guidelines to the follow-up of incidentally found pulmonary nodules on CT.
The guideline article reviewed the results from a number of large international lung cancer screening trials on the outcomes of patients with small pulmonary nodules. The article highlighted the overall low malignancy potential for nodules between 4 and 7 mm in a large lung cancer screening trial as well as the difficulty in accurately measuring small pulmonary nodules to accurately track growth or doubling time. Finally, the article recognized the importance of risk factors (i.e. smoking status, family history, etc.) in assessing small pulmonary nodules. From this data, the Fleischner Society recommended reducing the overall number of CT follow-ups required for small pulmonary nodules.
The Fleischner Society constructed guidelines based on foundational literature demonstrating several key observations:
- Half of all smokers 50 years of age or older have at least one nodule at screening.
- Size is a primary determinant of the malignant potential of nodules.
- Cigarette smoking portends a greater risk of lethal cancers, increasing in proportion to the degree of smoking.
- Nodules in cigarette smokers grow faster than in nonsmokers.
- Nodule morphology correlates with malignant likelihood and growth rate (i.e. nonsolid nodules typically carry a lower malignant potential versus solid nodules).
- Malignant risk of nodules increases with patient age.
Low-risk patients are defined as patients with a minimal or absent smoking history and absence of other known risk factors including a history of lung cancer in a first degree relative and exposure to carcinogenic material (i.e., asbestos, radon, and uranium). Similarly, high-risk patients are defined as patients with a history of smoking or the aforementioned known risk factors. The guidelines do not apply to patient with known or suspected cancers outside of the lungs, patients younger than 35 years of age, or patients with unexplained fever.
The Fleischner Society Guidelines are limited in scope to solitary, solid pulmonary nodules and do not provide follow-up recommendations for subsolid nodules or the presence of multiple nodules. However, the recommendations made by the Fleischner Society have been widely adopted as the imaging follow-up recommendation plan for patients with small, incidentally found pulmonary nodules. A recently published classification system for lung cancer screening, Lung-RADS, by Pinsky et al., was based upon the Fleischner Society criteria. However, this classification system has not yet been prospectively validated.
Click to read the study in Radiology
MacMahon H, Austin JHM, Gamsu G, Herold CJ, Jett JR, Naidich DP, et al. Guidelines for Management of Small Pulmonary Nodules Detected on CT Scans: A Statement from the Fleischner Society. Radiology. 2005 Nov 1;237(2):395–400.
Pinsky PF, Gierada DS, Black W, Munden R, Nath H, Aberle D, et al. Performance of Lung-RADS in the National Lung Screening Trial A Retrospective Assessment Performance of Lung-RADS in the NLST. Ann Intern Med. 2015 Apr 7;162(7):485–91.
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