COVID & Flu: Increased Lung Cancer Risk – New Research Reveals Link

A severe bout of influenza or COVID-19 may carry a longer-term health risk than previously understood, potentially increasing the likelihood of developing lung cancer months or even years after the initial infection. Recent research suggests a link between hospitalization for these respiratory illnesses and a heightened risk of lung cancer, regardless of smoking history or other known risk factors.

The findings, while preliminary, add to a growing body of evidence indicating that respiratory viruses can have lasting effects beyond the acute phase of infection. “What we have is further evidence that respiratory viruses can be associated with more than just the infection itself,” explains James DeGregori, PhD, a professor of biochemistry and molecular genetics at the University of Colorado Anschutz School of Medicine and the interim director of the University of Colorado Cancer Center in Aurora, Colorado. Dr. DeGregori, who has researched the impact of respiratory viral infections on dormant cancer cells, was not directly involved in this latest study.

How Viral Infections May Influence Lung Cancer Development

Researchers investigated the potential connection between severe respiratory illnesses and cancer risk by examining data from both animal models and human populations. In mice, those who experienced severe lung infections from influenza or COVID-19 were more prone to developing lung cancer and experiencing poorer outcomes.

To explore this link in humans, the team analyzed health data from over 76 million adults across the United States, Lebanon, and Saudi Arabia who had been hospitalized with COVID-19 before January 2022, and had no prior cancer diagnoses. The study tracked these individuals to identify any new cancer diagnoses following their hospitalization. The results revealed a 24 percent increase in lung cancer diagnoses among those hospitalized with COVID-19, a statistically significant finding even when accounting for factors like smoking status and pre-existing health conditions.

“That is considered a pretty significant increase in lung cancer, particularly considering the relatively short time window,” says Jie Sun, PhD, a professor of medicine and the codirector of the Beirne B. Carter Center for Immunology Research at the University of Virginia School of Medicine in Charlottesville, Virginia, and the study’s lead author. Dr. Sun notes that the widespread nature of the COVID-19 pandemic provided a unique opportunity to study this phenomenon, as a large number of people experienced the same viral illness simultaneously.

The underlying mechanism appears to involve inflammation. Severe viral infections can trigger changes in immune system cells that normally protect lung tissue, leading to a state of chronic inflammation. This inflammatory environment may create conditions that are more conducive to cancer development or progression. “The findings basically show a ‘memory’ function within the lung environment. So the environment of the lung seems to be switched given that of this infection, and that switch within the lung is more conducive to cancer initiation or progression,” explains DeGregori.

This isn’t the first time a viral infection has been linked to cancer. Hepatitis B infection is known to increase the risk of liver cancer, and human papillomavirus (HPV) can cause cervical cancer. Recent research has also suggested that viral respiratory infections can awaken dormant cancer cells in the lungs and accelerate the growth of existing lung tumors. Dr. DeGregori’s previous work has explored this very phenomenon.

Understanding the Study’s Nuances and Limitations

While this study establishes a correlation between prior viral infection and lung cancer development, it’s important to acknowledge its limitations. Researchers emphasize that this is the first study to demonstrate a causal link, and further investigation is needed to confirm these findings.

One potential factor influencing the results is the increased medical scrutiny received by individuals hospitalized with COVID-19 before January 2022. Charlotte Kuperwasser, PhD, a professor at Tufts University School of Medicine, points out that these patients were more likely to undergo imaging and follow-up care, which could have led to the incidental detection of existing, undiagnosed lung cancer or premalignant lesions. “This would have increased the likelihood of imaging and incidental findings,” she explains. It’s also possible that individuals who developed severe COVID-19 already had underlying lung conditions or immune dysfunction that predisposed them to both severe infection and cancer.

Another limitation is the lack of information regarding COVID-19 vaccination status. Wafik S. El-Deiry, MD, PhD, director of the Legorreta Cancer Center at Brown University, highlights the importance of understanding the role of vaccination in mitigating this risk. “The lack of information about prior COVID vaccination or why if patients received COVID vaccination they still developed severe pneumonia is important to understand better and reconcile with the mouse data,” he says. However, the mouse data suggests that the virus itself, rather than a specific strain, may be the primary driver of the increased cancer risk, as similar results were observed with other severe viral pneumonias.

Protecting Yourself and What to Expect Moving Forward

The researchers emphasize the importance of vaccination against both influenza and COVID-19 as a key preventative measure. They also recommend that healthcare providers consider close monitoring for lung cancer in individuals with a history of severe respiratory infections. “Severe viral infections are not only harmful in the acute phase, but may also contribute to the development of chronic diseases, including cancer. It is important to protect ourselves from severe infections whenever possible,” says Dr. Sun.

For individuals at high risk of severe illness from viral infections, medications like Tamiflu (for influenza) or Paxlovid (for COVID-19) can facilitate prevent a mild infection from progressing to a more serious stage. The University of Colorado Anschutz Medical Campus provides ongoing updates and resources related to COVID-19 and other respiratory viruses, including guidance from the Centers for Disease Control and Prevention.

Personal precautions, such as vaccination and avoiding crowded settings during peak infection periods, remain important. As Dr. DeGregori notes, “If I was a cancer survivor, I would definitely not only make sure I’m vaccinated, but I’d probably avoid a context where I thought there was a really high risk of getting infected. But everyone’s always got to make their own choices about risk.”

Ongoing Surveillance and Research: Public health agencies are continually monitoring for potential long-term effects of COVID-19 and other respiratory viruses. Further research is needed to fully understand the mechanisms linking viral infections to lung cancer, to identify individuals at highest risk, and to develop targeted prevention and screening strategies. Expect to spot continued investigation into the role of vaccination, the impact of viral variants, and the potential for early detection through enhanced lung cancer screening programs.