Researchers challenge the definition of a positive result in first-round lung cancer screening with low-dose computed tomography (CT) in the Annals of Internal Medicine.
The International Early Lung Cancer Action Program investigators say that increasing the parenchymal, solid, or part-solid noncalcified nodule size threshold for a positive screen from 5 mm or larger to 7 or 8 mm would significantly reduce the number of positive screens from 16.1% to 7.1% and 5.1%, respectively.
This would result in a 56% and 68% reduction in the burden of work-up with 7- and 8-mm thresholds, respectively, compared with the 5-mm definition.
However, the study, based on findings from 21,136 participants undergoing screening between 2006 and 2010, shows that increasing the nodule size threshold to 7 mm or 8 mm would also result in an estimated 5.0% and 5.9% reduction, respectively, in the number of patients diagnosed with stage I disease within the first year.
Claudia Henschke (Mount Sinai School of Medicine, New York, New York, USA) and co-authors explain that the study's retrospective analysis cannot determine whether this delay would result in stage progression and a reduced likelihood of cure in affected patients.
However, they note that previous research has shown that the majority of tumors detected in first-round screening are stage I adenocarcinomas with a volume doubling time of around 121 days. A 7-mm diameter nodule would be expected to be less than 14 mm in diameter a year later and typically still be highly curable stage I disease.
Recommending further research to determine the optimal screening threshold, the researchers emphasize: "The key point of this article is that the definition of positive result needs to be continually prospectively evaluated and updated in light of emerging evidence from ongoing screening programs to reduce unnecessary surgery for nonmalignant pulmonary nodules and reduce potential harms of the diagnostic work-up, while maximizing the diagnosis and treatment of curable cases of lung cancer."
In an accompanying editorial, Stephen Lam (British Columbia Cancer Agency, Vancouver, Canada) and co-authors write that nodule size is not the only significant factor.
"A comprehensive computer-based risk calculator (prediction model) that integrates demographic characteristics and multiple CT image features (nodule size, type, and spiculation and emphysema status) would help to estimate risk for lung cancer for different types of lung nodules to guide clinical decisions on the basis of cancer probability," they write.
Lam et al add: "Work to develop an accurate risk calculator for lung nodules is already under way by our team."
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