Smoothly Marginated or Attached Pulmonary Nodules Are Benign

Smoothly Marginated or Attached Pulmonary Nodules Are Benign

A recent study set out to evaluate whether there are any features of solid noncalcified nodules (NCNs) seen on baseline CT that predict lung cancer.

The study was part of the Dutch-Belgian randomized lung cancer screening trial (NELSON study) and the results were published in a recent issue of Radiology.

The results seem to indicate that noncalcified pulmonary nodules with a volume between 50 and 500 mm3 (diameter between 4.6 and 9.8 mm) that have smooth margins and/or are attached to the pleura, fissures, or vessels are not malignant, based on a 1-year CT follow-up study.

The Study
658 patients with 891 solid NCNs were evaluated. Only nodules with a volume between 50 and 500 mm3 (corresponding to a diameter between 4.6 and 9.8 mm) were evaluated.

Methodology
All CTs were performed with a 16-section multi-detector CT. Images were reconstructed with 1.0-mm section thickness and 0.7-mm reconstruction increment.

All nodules had their volumes calculated with the aid of a 3-dimensional volumetric computer software program. All nodules were classified as spherical or nonspherical. A spherical nodule’s maximum diameter was less than twice its minimum diameter.

Margins of all nodules were characterized as smooth, lobulated, spiculated, or irregular.

Nodules were characterized as being intraparenchymal or attached.

An attached nodule was one whose contact surface with the pleura, a fissure, or a vessel, was >50% of the diameter of the nodule at volume-rendered reconstruction or axial image.

All patients had CTs generally repeated at 3 months and 1 year to assess any interim growth.

Results of the Study
86% of nodules were spherical, and 14% were nonspherical. 73% of nodules were smooth, 19% were lobulated, and 8% were spiculated or irregular. Also, 46% of nodules were intraparenchymal and 54% were attached.
Sixteen of 891 nodules (1.8%) were malignant.

At 3-month follow-up and at 1-year follow-up, 8% and 1% of nodules, respectively, had grown, of which 15% and 50% were malignant, respectively.

All nodules that were cancer had non-smooth margins and were intraparenchymal in location without attachment to the pleura, fissures, or vessels.

For non-smooth intraparenchymal nodules, a baseline volume ≥130 mm3 was a significant predictor of malignancy (odds ratio [OR], 6.3; 95% CI, 1.7 to 23.0).

After including the 3-month and 1-year follow-up CT data, a greater volume doubling time also helped predict malignancy (OR, 15.6; 95% CI, 4.5 to 53.5 and OR, 213.3; 95% CI, 18.7 to 2430.9, respectively).

Conclusions
NCNs that were smooth and/or were attached to the pleura, fissures, or vessels were not found to be malignant on 1-year follow-up CT.

Reviewer’s Comments
One of the limitations of this study, which the authors acknowledge, is the relatively short follow-up period of only 1 year. We hope there will be a continuation of this study with a more lengthy follow-up period.

Author: Vineet R. Jain, MD
Reference:

Xu DM, van der Zaag-Loonen HJ, et al. Smooth or Attached Solid Indeterminate Nodules Detected at Baseline CT Screening in the NELSON Study: Cancer Risk During 1 Year of Follow-Up. Radiology; 2009;250 (January): 264-272