A new analysis of more than 26,000 lung cancer screenings suggests that CT scans can also flag other serious cancers. The findings could help doctors and patients decide which unexpected scan results truly need follow-up.
When doctors order CT scans to check for lung cancer, they are not just getting a look at the lungs. The images also capture nearby organs and tissues — and a new study suggests those “extra” views can sometimes reveal other, previously undiagnosed cancers.
Led by researchers from Brown University School of Public Health, the study analyzed lung screening data from more than 26,000 people and found that certain unexpected abnormalities seen outside the lungs were linked to a higher chance of being diagnosed with another type of cancer within a year.
The work, published in JAMA Network Open, draws on the landmark National Lung Screening Trial, the large federal study that helped establish low-dose CT scans as the standard screening tool for people at high risk of lung cancer, especially longtime smokers.
Because CT scans cover the chest and upper abdomen, radiologists often see incidental findings in organs such as the kidneys and liver, or in lymph nodes. Many of these findings turn out to be harmless. Others can trigger cascades of follow-up tests, biopsies and anxiety, with little benefit.
The Brown-led team set out to clarify which kinds of incidental findings are most likely to signal a real cancer risk.
First author Ilana F. Gareen, a professor of epidemiology at Brown, noted the goal was to turn years of imaging data into practical guidance for clinicians and patients.
“In this paper, we provide an evidence base for making decisions on abnormalities outside of the lungs that might be seen at lung screening,” Gareen said in a news release.
The researchers focused on a subset of incidental findings that radiologists had flagged as potentially related to cancer. They then tracked whether participants with those findings were diagnosed with cancers outside the lungs — known as extrapulmonary cancers — in the year after their screening.
Across more than 75,000 CT scans conducted over three rounds of screening, cancer-related incidental findings appeared in about 3% of screening rounds and in 6.8% of participants.
People with those findings had a significantly higher risk of being diagnosed with an extrapulmonary cancer within a year compared with those whose scans did not show such abnormalities. The strongest links were seen for cancers of the urinary system, including kidney and bladder cancer, as well as for blood-related cancers such as lymphoma and leukemia.
The results highlight both the promise and the complexity of modern imaging. On one hand, a scan ordered for one reason can provide an early warning about a different, serious disease. On the other, not every odd-looking spot is dangerous, and chasing every abnormality can lead to unnecessary procedures and costs.
For years, clinicians have wrestled with how aggressively to pursue incidental findings on lung cancer screening scans. The new analysis offers data to support more nuanced decisions about when follow-up is likely to catch a dangerous cancer early and when it may not be needed.
Gareen emphasized that the study is meant to support shared decision-making between patients and their care teams.
“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,” she said.
The need for clear guidance is growing. As lung cancer screening becomes more widely adopted across the United States, especially among older adults with a history of heavy smoking, the number of incidental findings is expected to rise.
In earlier work using the same national trial data, Gareen and colleagues found that about one in three participants had a potentially important finding unrelated to lung cancer on their scan. The new study narrows in on the smaller group of findings that radiologists specifically viewed as possibly cancer-related, teasing out which of those are most strongly associated with later cancer diagnoses.
The researchers now want to know whether the patterns they observed in the tightly controlled setting of a clinical trial hold up in everyday medical practice. Gareen said her next step is to examine data from patients being screened in community settings, outside of academic medical centers, to see if the rates of incidental abnormalities and related cancers are similar.
If the findings are replicated, they could inform future screening guidelines and radiology reporting standards, helping clinicians prioritize follow-up for the most worrisome abnormalities while sparing patients from unnecessary interventions for low-risk findings.
The study brought together investigators from Brown, the Providence VA Medical Center, Duke Health, Massachusetts General Hospital, Atrium Health Wake Forest Baptist and the University of Iowa, and was funded by the National Cancer Institute.
For patients, the message is not that every unexpected spot on a scan is a cause for alarm, but that these findings deserve thoughtful, evidence-based discussion. As imaging technology continues to improve and screening becomes more common, studies like this one aim to ensure that the extra information CT scans provide is used wisely — catching more cancers early, while avoiding harm from overtesting.
Source: Brown University