Solid Indeterminate Pulmonary Nodules Less Than or Equal to 250 mm3: Application of the Updated Fleischner Society Guidelines in Clinical Practice

Abstract

Background: The latest version of the Fleischner Society guidelines for management of incidental pulmonary nodules was published in 2017. The main purpose of these guidelines is to reduce the number of unnecessary computed tomography (CT) examinations during the follow-up of small indeterminate nodules.

Objective: The present study aimed to evaluate the performance of these guidelines for management of solid indeterminate pulmonary nodules (SIPNs) ≤ 250 mm³.

Materials and methods: During a 7-year period, we retrospectively reviewed the chest CT scans of 672 consecutive patients with SIPNs. The study sample was selected according to the following inclusion criteria: solitary SIPN; diameter ≥ 3 mm; volume ≤ 250 mm³; two or more CT scans performed with the same scanner and same acquisition/reconstruction protocol; thin-section 1-mm images in DICOM format; histologic diagnosis or follow-up ≥ 2 years; and no oncological history. Applying these criteria, a total of 27 patients with single SIPNs ≤ 250 mm³ were enrolled. For each SIPN, the volume and doubling time were calculated using semiautomatic software throughout the follow-up period. For each SIPN, we applied the Fleischner Society guidelines, and the recommended management was compared to what was actually done.

Results: A significant volumetric increase was detected in 5/27 (18.5%) SIPNs; all growing nodules were observed in high-risk patients. In these SIPNs, a histologic diagnosis of malignancy was obtained. Applying the Fleischner Society recommendations, all five malignant nodules would have been identified. None of the SIPNs < 100 mm³ in low-risk patients showed significant growth during the follow-up period. The application of the new guidelines would have led to a significant reduction in follow-up CT examinations (Hodges-Lehmann median difference, -2 CT scans; p = 0.0001).

Conclusion: The application of the updated Fleischner Society guidelines has been shown to be effective in the management of SIPNs ≤ 250 mm³ with a significant reduction in radiation dose.

Figure 1

Solid pulmonary nodule smaller than 100 mm³ with smooth margins located in the right upper lobe in a 71-year-old high-risk male patient. Baseline (left) and follow-up CT scans (right). The interval between the two CT examinations was 184 days. The software calculated significant growth between the baseline and follow-up CT scans with a relative volume variation of 292% (from 55 mm³ to 216 mm³) and a volume doubling time of 93 days. The nodule was surgically removed and proven to be a pulmonary adenocarcinoma. In this case, the new Fleischner Society guidelines would have recommended a follow-up CT examination at 12 months.

Figure 2

Solid pulmonary nodule smaller than 100 mm³ with smooth margins located in the right lower lobe in a 36-year-old low-risk male patient. Baseline (left) and last follow-up CT scans (right). The interval between the two CT examinations was 766 days. The software did not show significant growth of the nodule (relative volume variation of 7% with a volume doubling time of 21 years). The unequivocal nodule stability after more than 2 years indicates the benign nature of the lesion. In this case, the new Fleischner Society guidelines would not have recommended a follow-up CT scan.