Severe COVID or flu may raise lung cancer risk years later

 Serious cases of COVID-19 and influenza may do more than cause short term illness. New research from UVA Health's Beirne B. Carter Center for Immunology Research and the UVA Comprehensive Cancer Center suggests that severe viral infections can create conditions in the lungs that help cancer develop and progress more quickly. The study also found that vaccination can prevent many of these harmful effects.

Researchers led by UVA School of Medicine scientist Jie Sun, PhD, discovered that severe respiratory infections can alter immune cells in the lungs in ways that support tumor growth months or even years later. Based on these findings, the scientists recommend that doctors closely watch patients who recover from severe COVID, flu, or pneumonia so lung cancer can be detected early, when treatment is most effective.

"A bad case of COVID or flu can leave the lungs in a long-lasting 'inflamed' state that makes it easier for cancer to take hold later," said Sun, co-director of UVA's Carter Center and a member of UVA's Division of Infectious Diseases and International Health. "The encouraging news is that vaccination largely prevents those harmful changes for cancer growth in the lung."

Severe Respiratory Infections and Long Term Lung Damage

Respiratory illnesses such as influenza and COVID are among the most common sources of lung injury. However, scientists have not fully understood how this type of damage might influence cancer risk years later. To explore this question, Sun and his team studied the effects of severe lung infections in both laboratory mice and human patients.

The findings were striking. Mice that experienced severe lung infections were more likely to develop lung cancer later and were also more likely to die from the disease. When the researchers analyzed patient data, they found a similar pattern. People who had previously been hospitalized with COVID-19 showed a higher rate of lung cancer diagnoses.

The analysis revealed a 1.24-fold increase in lung cancer incidence among patients who had been hospitalized for COVID-19. This elevated risk was seen regardless of whether the individuals smoked or had other medical conditions, which doctors refer to as "comorbidities."

"These findings have important immediate implications for how we monitor patients after severe respiratory viral infection," said Jeffrey Sturek, MD, PhD, a UVA physician-scientist who collaborated on the study. "We've known for a long time that things like smoking increase the risk for lung cancer. The results from this study suggest that we may need to think about severe respiratory viral infection similarly. For example, in some patients who are at high risk for lung cancer based on smoking history, we recommend close monitoring with routine screening CT scans of the lungs to catch cancer early. In future studies, we may want to consider a similar approach after severe respiratory viral infection."

Immune Changes That Create a Pro Tumor Environment

Experiments in mice helped the researchers uncover why severe infections may increase cancer risk. The team observed major changes in immune cells known as neutrophils and macrophages, which normally help defend the lungs.

After severe infection, some neutrophils began behaving abnormally and contributed to a persistent inflammatory environment described as "pro-tumor," meaning it supports cancer growth. The scientists also found significant changes in epithelial cells that line the lungs and the tiny air sacs responsible for breathing.

Vaccination May Protect the Lungs

The study also produced encouraging findings about prevention. Prior vaccination appeared to block many of the lung changes linked to cancer development. Vaccines help the immune system respond more effectively to infections, which reduces how severe the illness becomes.

The researchers observed the increased cancer risk mainly in people who had severe COVID-19. Individuals who experienced only mild infections did not show this elevated risk and actually had a slight decrease in lung cancer incidence.

Even so, the scientists warn that many people who survived severe COVID-19 or other serious respiratory infections could face a higher risk of lung cancer in the future.

"With tens of millions of people globally experiencing long-term pulmonary [COVID-19] sequelae, these findings carry significant implications for clinical care," the researchers wrote in their scientific paper. "Individuals recovering from severe viral pneumonia, particularly those with smoking history, may benefit from enhanced lung cancer surveillance, and preventing severe infection through vaccination may confer indirect cancer protection benefits."

Source: ScienceDaily