Lung cancer scans can reveal signs of other undiagnosed cancers

When doctors review diagnostic medical scans for lung cancer, they sometimes spot abnormalities unrelated to the lungs. New research shows that some of those abnormalities could be signs of other undiagnosed cancers.

The study, led by researchers at the Brown University School of Public Health, analyzed lung screening data from more than 26,000 people who took part in the landmark National Lung Screening Trial. This large federal study helped establish computerized tomography (CT) scans as a standard way to screen people at high risk for lung cancer - especially longtime smokers.

Because CT scans capture areas of the body beyond the lungs, doctors often see abnormalities that might indicate cancer in other parts of the body, including the kidneys, liver and lymph nodes. For the new study, the researchers focused on certain types of these abnormalities and found that people with these findings were more likely to be diagnosed with a cancer outside of the lungs (extrapulmonary) within a year of screening.

The authors said the study, published in JAMA Network Open, addresses the challenge in modern medicine of balancing early detection with the risk of unnecessary tests and procedures. For both patients and doctors, the results offer clearer guidance on what it means when a scan reveals something unexpected, and which types of abnormalities are more likely to be a sign of an extrapulmonary cancer.

Ultimately, the researchers said, the findings may help clinicians decide when follow-up care is likely to catch cancer early and when it may not be necessary.

In this paper, we provide an evidence base for making decisions on abnormalities outside of the lungs that might be seen at lung screening. 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."

Ilana F. Gareen, study author, professor of epidemiology at Brown

As more people across the United States are screened for lung cancer, doctors will see more of these kinds of abnormalities, the researchers said. In previous research, Gareen and colleagues found that about one in three people in the national trial had a finding of potential clinical importance that was unrelated to lung cancer show up on their scan. In the new study, the researchers narrowed their focus to a subset of those findings - abnormalities that physicians identified as potentially indicative of cancer - to better understand which may warrant follow-up or treatment.

According to the results, cancer-related findings appeared in about 3% of screening rounds and in 6.8% of participants across more than 75,000 scans conducted over three rounds of CT screening. Participants with those abnormalities had a significantly higher risk of being diagnosed with cancers outside the lungs within a year. The strongest links were seen in urinary system cancers, including kidney and bladder cancer, and in other cancers, such as lymphoma and leukemia.

Gareen said she wants to look next at whether the findings are consistent with the experience of patients currently being screened in community settings to determine if the rates of abnormalities and associated cancers seen in the National Lung Screening Trial are replicated outside of a clinical trial.

Other Brown researchers involved in the study included Roee Gutman, Maryanne Thangarajah and Amal N. Trivedi. The study also included researchers from the Providence V.A. Medical Center, Duke Health, Massachusetts General Hospital, Atrium Health Wake Forest Baptist and the University of Iowa. The National Cancer Institute (R01CA204222) provided funding.