Lung cancer is the most frequent cause of cancer deaths in Western countries, and most cases are diagnosed too late for effective intervention, noted Dr. Y. Wang from the University of Groningen in the Netherlands, who presented the study for his research colleague, Dr. Dongming Xu, at this week's European Congress of Radiology (ECR).
"The five-year survival for lung cancer is about 10% in Europe, while the five-year survival for stage 1A cancer is much higher, 83%," Wang said. "Lung cancer screening may improve the survival rate and decrease mortality.... This study is aiming to show a 25% reduction in lung cancer mortality" as a result of screening and follow-up, he said.
To that end, researchers from the ongoing Nelson lung cancer screening trial under way in Groningen and the University of Leuven in Belgium screened 5,700 smokers and former smokers ages 50-75, mostly men, with a smoking history of at least 20 pack years. Participants at four screening centers were enrolled from 30,500 eligible smokers and former smokers who responded to a mail solicitation based on general population registries.
For these preliminary results, 15,530 respondents were randomized to either undergo low-dose multislice CT (Somatom Sensation 16, Siemens Medical Solutions, Erlangen, Germany) lung cancer screening or no screening, with periodic follow-up for those with positive results as determined by two readers working independently, with a third reader deciding in case of disagreement.
The Siemens LungCare CT software package was used to automatically measure solid nodules, while nonsolid and part-solid nodules were measured manually, Wang said. Solid nodules of 50-500 mm3, nonsolid nodules with a diameter greater than 8 mm, and part-solid nodules with these criteria were deemed significant and followed up at three months. Nodules larger than 500 mm3 or those that grew by 25% or more during the three-month follow-up were deemed potentially malignant, and these patients were referred immediately to a pulmonologist.
A total of 5,700 participants were scanned. Of these, 1,026 (18%) had significant nodules according to the criteria, 916 (16%) had stable significant nodules, and 114 (2%) had nodules that were deemed potentially malignant, Wang said. In all, 46 participants were diagnosed with cancer, yielding an overall cancer detection rate of 0.8%.
The 16% positive rate compares to 4% to 36% in Japanese studies; 18% to 43% in studies from Italy, Ireland, and Germany; and 12% to 51% in the U.S. The cancer detection rate of 0.8% compares to 1.9% to 3.4% in U.S. trials, he said.
"The possible explanation about the different cancer detection rates are likely due to several factors," Wang said. "First are the different lung cancer registries in different countries. The second is different participation and selection criteria, different gender composition, different mean age, and different pack years."
Finally, he said, the study was recruited by mail solicitation of the general population, different from studies such as the Early Lung Cancer Action Program (ELCAP) study, which was introduced to the subjects by general practitioners. Cancer detection rates also differ by country, he concluded.
In a companion study, Dr. Dongming Xu presented the results of an analysis of the nodules found in the same trial. Results from the first 3,881 patients scanned showed 453 indeterminate solid nodules in 331 participants, according to an accompanying abstract. Twenty percent (89/453) of the findings were minor or major fissure-attached nodules, 15% (68/43) were pleural-based, and 18% (83/453) were attached to vessels.
Eighteen percent (82/453) did not show typical morphological features, and 29% (131/453) were solitary pulmonary nodules, the group wrote. Just 3% (14/453) grew by more than 25% in the follow-up months. Of these 14, six were solitary pulmonary nodules; five were interpreted as fibrosis, scarring, or nodules missed at baseline; and two were attached to vessels and one to a fissure.
By Eric Barnes
AuntMinnie.com staff writer
March 3, 2006
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