Significant incidental findings on low-dose CT (LDCT) lung exams are tied to a higher risk of an extrapulmonary cancer diagnosis in the year following scanning, according to research published March 31 in JAMA Network Open. 

The association was clearest for findings linked to the urinary system and other cancers, including lymphoma and leukemia, wrote a team led by Ilana Gareen, PhD, from Brown University in Providence, RI. 

“[Our study suggests] that certain [incidental LDCT results] should be evaluated as potential indicators of undiagnosed cancers,” the Gareen team wrote. 

LDCT for lung cancer screening often detects incidental findings that are unrelated to lung cancer, but which may have clinical significance to the point where radiologists inform the referring physicians. 

However, the researchers noted a lack of data on whether these incidental findings are associated with extrapulmonary cancer diagnoses. 

Gareen and colleagues recently classified text comments from case report forms in the National Lung Screening Trial (NLST). These described significant incidental findings detected on LDCT exams, with the researchers using criteria described in American College of Radiology (ACR) white papers. 

For their current study, the researchers studied potential ties between concerning significant incidental findings found on lung LDCT exams and diagnosis of extrapulmonary cancer within one year of screening. Using NLST data, they included 75,104 LDCT exams performed in three screening rounds for 26,445 trial participants with an average age of 61.4 years. 

The team reported significant incidental findings for 2,265 screening rounds (3%) in 1,807 participants (6.8%) across the screening rounds. Doctors diagnosed extrapulmonary cancer in 67 participants (3%) who had a concerning significant incidental finding during a screening round (n = 2,265). 

After adjusting for covariates and participants, the researchers found a marginal risk difference of 13.89 per 1,000 participants. The marginal risk differences were significantly higher for urinary cancers (17 per 1,000 participants) and other cancer categories in the Surveillance, Epidemiology, and End Results (SEER) Program. These included lymphoma and leukemia (14 per 1,000 participants). 

Early detection of these cancers may lead to early treatment and reduce associated morbidity and mortality, the study authors highlighted. 

“Identification of [incidental findings] associated with extrapulmonary cancers in NLST participants could be used to plan appropriate diagnostic evaluations for patients undergoing lung cancer screening,” they wrote. 

The findings could help researchers design protocols to deal with significant incidental findings across multiple organ sites, according to an accompanying editorial written by Patrick Senior from Gloucestershire Hospitals NHS Foundation Trust and Andrew Creamer, PhD, from University College London, both in the U.K. 

“They also underscore the importance of both a robust health economics analysis of how screening programs manage such incidental findings and patient-centered research to understand the impact that such unexpected results may have on the individual,” Senior and Creamer wrote. 

The two called for more research to make sure that screening programs are confident “when faced with information they did not ask for.” 

Read the full study here.