New research suggests that significant incidental findings on screening low-dose computed tomography (LDCT) scans for those with a history of heavy smoking may be linked to higher risks for extrapulmonary cancer within one year of screening.
For the retrospective study, recently published in JAMA Network Open, researchers reviewed data from 26,445 participants (mean age of 61.4) from the National Lung Screening Trial (NLST) who had up to three rounds of LDCT screening at one-year intervals and a five to seven-year follow-up period. All patients had at least a 30 pack-year smoking history with a mix of current smokers and those who had quit smoking within a 15-year period prior to the study, according to the study authors.
Overall, the researchers found that patients who had one or more detected cancer SIFs in LDCT screening had a marginal risk difference of 13.89 per 1000 participants in comparison to those with no cancer SIFs for developing extrapulmonary cancer within one year.
In particular, the study authors noted that participants with LCDT-detected cancer SIFs exhibited higher marginal risk differences of 17.03 per 1000 participants for urinary cancers and 13.83 per 1000 participants for an other extrapulmonary cancer category that included leukemia and lymphoma.
“Extrapulmonary cancers are significantly associated with mortality among persons who have smoked cigarettes. … Early detection of these cancers may facilitate early treatment and potentially reduce associated morbidity and mortality,” posited lead study author Ilana F. Gareen, Ph.D., who is affiliated with the Department of Epidemiology at the Brown University School of Public Health in Providence, R.I., and colleagues.
Three Key Takeaways
• Incidental findings may signal near-term cancer risk. Detection of cancer-related significant incidental findings (SIFs) on LDCT was associated with a higher one-year risk of extrapulmonary cancer (absolute risk increase approximately 13.9 per 1,000 vs. no SIFs).
• Risk varies by cancer type. The strongest associations were seen for urinary cancers (approximately 17.0 per 1,000) and other extrapulmonary malignancies (including hematologic cancers) (approximately 13.8 per 1,000), suggesting certain incidental findings may warrant more targeted follow-up.
• Implications for Lung-RADS and reporting. Although the absolute number of extrapulmonary cancers detected was relatively small (approximately 3 percent of those with SIFs), findings support refining the Lung-RADS S modifier to better stratify clinically significant incidental findings and guide downstream evaluation.
While noting the use of the S modifier within the Lung-RADS system to report findings that are clinically significant or demonstrate potential clinical significance, the researchers also acknowledged that extrapulmonary cancer was detected in 67 out of 1,807 participants with a reported cancer SIF (approximately 3 percent).
“Our findings may serve as an impetus for revising the Lung-RADS S modifier to include more specificity on classification of SIFs. Although the number of extrapulmonary cancers potentially associated with SIF detection in the NLST seem relatively small, when considered in context of the nearly 14 million people who now qualify for lung cancer screening in the U.S., the potential impact is large,” added Gareen and colleagues. “Moreover, NLST participants were generally healthier than clinically screened patients, suggesting that the burden of extrapulmonary cancers among clinically screened patients may be higher than reported here.”
(Editor’s note: For related content, see “FDA Clears AI-Powered Software for Assessment of Incidental Lung Nodules on CT,” “Study: AI Assessment of Chest CT May Predict Multiple Mortality Risks” and “Emphysema on Chest CT Linked to Threefold Higher Risk for CPOD Mortality in Next 25 Years.”)
In regard to study limitations, the authors noted the small number of SIFs in each category and a lack of clarity as to whether early detection of extrapulmonary cancers is related to reduced cancer-specific mortality.
