Benefits and Risks of Redefining a Positive CT Result for Lung Cancer

Using a threshold of 7 or 8 mm to define a positive lung cancer result in a baseline round of computed tomography (CT) could decrease false positive screening results. However, prospective research is needed to determine whether increasing the threshold may delay diagnosis of cancer in some patients.

In CT screening for lung cancer, the positive result of the initial low-dose CT indicates whether further diagnostic work-up is needed before the first scheduled repeated screening. A definition that is too inclusive may cause excessive diagnostic work-up and unnecessary treatment, while a definition that is too restrictive may delay diagnosis.

In the past decade, the frequency of identifying a noncalcified nodule (NCN) of any size on the initial baseline CT scan has almost tripled. This is mostly due to technological advances in CT scanners and the use of large computer monitors to display the CT images. Changing the size threshold for a positive screening could help reduce the harms associated with unnecessary, invasive work-up of false positive screening tests.

Researchers reviewed medical records for a cohort of 21,136 patients who had a baseline CT performed between 2006 and 2010 to assess how using a more restrictive threshold in the baseline round of screening would affect the number of positive results and delayed diagnoses. Of the participants undergoing baseline screenings, 57 percent had at least one NCN discovered.

By using the current definition of 5 mm, 16 percent (3,396 of the 21,136 patients) had a positive result. Of those, 8 were diagnosed with lung cancer within 12 months of baseline enrollment. Increasing the threshold to 6, 7, 8, and 9 mm would have lowered the frequency to 10, 7, 5, and 4 percent respectively, thus decreasing further work-up by 36, 56, 68, and 75 percent respectively.

The authors of an accompanying editorial in Annals of Internal Medicine express concern that nodule size may not be the best indicator of cancer risk. Other variables, such as presence of emphysema or nodule spiculation could predict which nodules are likely to be cancerous.

The editorialists call for development of a comprehensive computer-based risk calculator that integrates nodule and demographic information.

Source: http://www.sciencecodex.com/benefits_and_risks_of_redefining_a_positive_ct_result_for_lung_cancer-107411

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