CT lung screening shows promise in ongoing trial

A CT-based lung cancer screening strategy that combines tumor morphology and tumor doubling times to evaluate cancer risk is producing good results, according to interim data from a Dutch-Belgian screening trial presented at the ECR.

The NELSON study is examining the development of lung cancer in 50- to 75-year-old smokers and ex-smokers, more than four-fifths of them men. Data from the study were presented during a special session. Elements of the material also appear in the January issue of Radiology.

Overall, the data suggest that observations from CT scans can help predict malignancy among indeterminate pulmonary nodules.

"With optimal nodule management based on low-dose CT and 3D volume assessment, no extra workup for additional diagnosis is necessary in new cancer screening," said presenter Dr. Matthijs Oudkerk of the University Medical Center Groningen in the Netherlands.

The protocols used by the NELSON team were keyed to the size of solid nodules at first observation, their doubling times in follow-up scans, and their location and morphology.

If the tumors were less than 50 mm³, they were assigned to one-year follow-up. If they were between 50 and 500 mm³, they were considered indeterminate and assigned to a three to four-month follow-up. Nodules larger than 500 mm³ were considered positive and subject to workup and diagnosis.

The researchers also considered nodule doubling times. If the nodules doubled in volume in less than 400 days, they were considered likely to be malignant. Those with doubling times in the 400 to 600-day range were indeterminate. If they took more than 600 days to double, they were considered negative.

Finally, the researchers looked at morphology and location.

Among the key findings to date:
• Among indeterminate nodules, a volume doubling time of less than 400 days at one year has a positive predictive value of 63%. Volume doubling time has proved to be an extremely powerful tool, Oudkerk said.
• In smooth, solid indeterminate nodules or those attached to fissures, pleura, or vessels, cancer risk is absent at one year. None of the attached nodules had a volume doubling time of less than 400 days. Morphology and localization can suggest whether a nodule is malignant, Oudkerk said.
• Among the solid indeterminate nodules, those that are spherical and smooth have longest volume doubling times and tend to be benign.
• Nonspherical nodules have the largest volumes. Those with spiculated margins are associated with largest volumes. Smooth nodules have smallest volumes.