The lack of an effective, detailed workup algorithm for positive results in multicenter lung cancer screening trials results in a lower cancer yield from invasive procedures and later diagnoses for participants, according to a new study presented at the RSNA meeting.

During a scientific session on Wednesday afternoon, Dr. David Yankelevitz, investigator in the New York Early Lung Cancer Action Program (NY-ELCAP), compared

workup algorithms and results for the New York trial and the Lung Screening Study (LSS), the pilot study of the National Lung Cancer Screening Study.

In NY-ELCAP, with 6295 participants at risk for lung cancer, a very detailed algorithm was used following diagnosis with CT. In contrast, the LSS, which randomized patients to CT or x-ray, did not specify an algorithm as organizers determined that they could not dictate medical practice. Yankelevitz's study analyzed results for 1586 participants in the LSS's CT-arm.

Participants in the two studies were at similar risk for lung cancer, had the same initial baseline test, and had an annual repeat test.

In the NY-ELCAP, 92% of invasive procedures prompted by the baseline study were positive. Invasive procedures prompted by the annual repeat exam were also positive in 92% of cases. By comparison, in LSS participants, 57% of invasive procedures prompted by the baseline study were positive, and 44% of those prompted by the annual repeat exam were positive.

At baseline in both studies, cancers were detected at larger sizes, as expected.

However, the size of cancers detected at annual repeat differed markedly, as 55% were smaller than 10 mm in the NY-ELCAP study, whereas only 13% were smaller than 10 mm for LSS.

Researchers also noted that the percent of cancers detected at stage 1 was higher in the New York study relative to the LSS.

Outcomes were better in the NY-ELCAP study most likely due to differences in the workup algorithms, according to Yankelevitz, a professor of radiology at Weill Cornell Medical College.

"This study shows the benefit of workup algorithms in screening protocols. Screening is not just about the initial test, it includes the baseline screening test all the way through diagnostics, including pathology," he said in an interview with Diagnostic Imaging after the session.