A large-scale randomized European trial of low-dose CT lung cancer screening yielded a nodule rate of 18% but a cancer detection rate of 0.8%, according to a presentation at the ECR on Friday. A separate study based on the same group underscored the importance of accurately identifying nodule growth rate.

The trial was conducted by researchers at three institutions (Groningen, Rotterdam, and Utrecht), with a sample of more than 15,000 participants who were current or former smokers. Participants were randomized into two groups: one was scanned with low-dose 16-slice CT and the other served as a control.

Data from April 2004 through December 2005 were included in the screening study, with a total of 5700 patients screened. A total 1026 patients (18%) were found to have nodules. Of these nodules, 912 were deemed significant and 114 were deemed potentially malignant. Forty-six (0.8%) were found to be lung cancer.

The study is continuing and researchers hope to accumulate a screening population of 8000, said presenter Dr. Y. Wang of Groningen.

Another study involving the same group of participants analyzed nodule growth rates of 453 indeterminate solid nodules over three months to identify which were most likely to grow and proceed to cancer. It found that the chance that fissure- and vessel-attached nodules will grow within three months is less than 8%.

Identifying which lung nodules are most likely to grow has become more important as more nodules are identified on multislice CT scans, said Dr. Donming Xu of Groningen.

Using screening scans of 3881 patients obtained between April 2004 and September 2005, researchers identified 453 indeterminate solid nodules in 331 patients. Twenty percent were fissure-attached, 15% were pleural-based, and 18% were vessel-attached. Eighteen percent of the nodules did not show typical morphological features and 29% were solitary pulmonary nodules. Only 3% of the indeterminate nodules found at baseline had grown more than 25% after three months.

The researchers concluded that focal opacity and solitary pulmonary nodules have the highest possibility of growth, but that pleural-based indeterminate nodules usually do not grow within three months.