When doctors review CT scans for lung cancer, they often spot things that have nothing to do with the lungs. New research now shows that some of those incidental findings could be early warning signs of other cancers growing elsewhere in the body.
The study, led by researchers at the Brown University School of Public Health, analysed lung screening data from more than 26,000 participants in the National Lung Screening Trial — a large federal study that helped establish CT scanning as a standard screening tool for people at high risk of lung cancer, particularly long-term smokers.
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Because CT scans capture a wider field than just the lungs, doctors frequently encounter abnormalities in surrounding areas — including the kidneys, liver, and lymph nodes.
The Brown University team focused on a specific subset of these findings: abnormalities that physicians flagged as potentially cancer-related. Across more than 75,000 scans conducted over three rounds of screening, such findings appeared in roughly 3 percent of screening rounds and in 6.8 percent of participants overall.
People with these abnormalities were significantly more likely to be diagnosed with a cancer outside the lungs within a year of their scan.
The most notable associations were found with urinary system cancers — particularly kidney and bladder cancer — as well as blood cancers such as lymphoma and leukaemia.
The findings, published in JAMA Network Open, offer clinicians clearer guidance on which types of incidental abnormalities are more likely to represent a genuine cancer signal and which may not require immediate follow-up.
Balancing early detection with unnecessary procedures
The research addresses a long-standing tension in modern medicine: the challenge of catching cancer early without subjecting patients to unnecessary and potentially harmful tests and procedures.
"The goal is to give physicians and patients better data so that they can make more informed choices about those abnormalities that should be considered for follow-up and those that most likely can be ignored," said study author Ilana F. Gareen, a professor of epidemiology at Brown.
As lung cancer screening becomes more widespread across the United States, doctors will increasingly encounter these kinds of incidental findings. Earlier research by the same team found that roughly one in three participants in the national trial had a clinically significant finding unrelated to lung cancer show up on their scan.
Gareen said the next step is to examine whether findings from the trial hold up in real-world community screening settings — and whether the rates of abnormalities and associated cancers are consistent outside of a controlled clinical environment.
The research team
The study involved researchers from Brown University, the Providence V.A. Medical Center, Duke Health, Massachusetts General Hospital, Atrium Health Wake Forest Baptist, and the University of Iowa. Funding was provided by the National Cancer Institute.