The study discussant, Giulia Veronesi, MD, of the Division of Thoracic Surgery, European Institute of Oncology, Milan, Italy, said that diagnostic algorithms aim to strike a balance between a too-invasive workup that exposes screened persons to useless invasive procedures and overtreatment, and insufficient surveillance that increases the risks of delayed diagnosis and false-negatives.
Many screening programs have adopted 5 mm as the cutoff between positive and negative nodules on CT, she noted. The Fleischner Society guidelines suggested 4 mm as the threshold below which no follow-up was needed.1 This cutoff was used by the National Lung Screening Trial (NLST) and resulted in a very high rate of baseline positivity. Other investigators consider nodule volumes instead of nodule diameter to obtain more reliable assessments of nodule growth.
Dr. Veronesi noted that NELSON is the largest randomized controlled trial with low-dose CT screening in Europe and the first study to incorporate software-calculated volume-doubling time of nodules into a management algorithm to distinguish between positive and negative.
According to Dr. Veronesi, remaining questions for the authors to address include the recall rate after baseline and after consecutive screening rounds. The NELSON recall rate is lower than that of the NLST study, even when considering positive and indeterminate nodules together. She asked if the higher rate of recalls in the NLST was due only to the lower size cutoff or if there might be other causes. Dr. Veronesi speculated that when the multidisciplinary staff decides how to consider nodules, the rate of recalls is reduced.
Dr. Veronesi also asked the NELSON study authors about the standard treatment of positive cases. Should that entail CT/positron-emission tomography or routine fine-needle aspiration biopsy in every positive case? She then asked about slow-growing nodules suspicious for malignancy—should they be managed with a wait-and-see strategy or surgical resection. In the case of surgery, would a limited resection, as opposed to lobectomy, be adequate?
The results from NELSON and other ongoing screening studies are expected to answer these questions, she said. ■
Disclosure: Dr. Veronesi reported no potential conflicts of interest.
1. MacMahon H, Austin JH, Gamsu G, et al: Guidelines for management of small pulmonary nodules detected on CT scans: a statement from the Fleischner Society. Radiology 237:395-400, 2005.