- A new study found that people with asthma may be 36% more likely to develop cancer than people without asthma.
- While a correlation is possible, both the research team and outside experts agree that more research is needed to make a conclusive decision.
- Experts advise asthmatic patients to quit smoking and maintain an up-to-date vaccination record to lower their risk of cancer.
New research shows that people with asthma are 36% more likely to develop cancer compared to people who do not suffer from respiratory disease. Asthma was linked to a higher risk of five types of cancer: lung, blood, melanoma, kidney, and ovarian.
“The rationale is that asthma patients experience chronic inflammation in their body, whereas chronic inflammation is heavily indicated in cancer etiology. There is very little evidence in the literature on this potential association, and it has not been examined in large-scale, real-world medical datasets,” Yi Guo, PhD, assistant professor in the College of Medicine at the University of Florida and first author of the study, told Health.
Guo and colleagues examined the potential association between asthma and subsequent cancer risk by analyzing electronic health records and claims data from 2012–2020. The information was taken from a large electronic health records database, called OneFlorida+ clinical research network.
By looking at more than 90,000 adult patients with asthma and more than 270,000 adult patients without asthma, the researchers built Cox proportional hazards models to examine the association
between asthma diagnosis and subsequent cancer risk.
“Our study is the first to report an association between asthma and subsequent cancer risk in real-world medical data. As an association study, our study does not imply any causal relationships (e.g., asthma causes lung cancer), but it opens a door for more studies to examine causal relationships and risk mechanisms,” explained Guo, “We are not impacting clinical care yet.”
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The Impact of Inhaled Steroids
While the study results show that cancer risk is elevated in asthma patients overall, Guo noted the results show that asthma patients using inhaled steroids have relatively lower cancer risk compared to asthma patients not using inhaled steroids.
In their analyses of specific cancer types, cancer risk was elevated for nine of 13 cancers in asthma patients without inhaled steroid use, but only for two of 13 cancers in asthma patients with inhaled steroid use, suggesting a protective effect of inhaled steroid use on cancer.
However, he pointed out that researchers did not have a perfect measure of “managed asthma.”
“This finding suggests a potential mechanism for cancer risk control, but more research is needed to further examine if there is a causal relationship,” he said. “There are many cancer risk factors that could mediate this asthma cancer association…The finding on inhaled steroids seems to support chronic inflammation as a highly plausible reason.”
Scott Evans, MD, professor and interim chair of pulmonary medicine at the University of Texas MD Anderson Cancer Center, noted prior studies have also suggested that inhaled steroid use may lower the risk of some lung cancers.
“These data are promising, but inconclusive. The current study suggests that inhaled corticosteroids are associated with a lower risk of non-lung cancers, as well. This result seems less plausible, as the amount of inhaled corticosteroid that is detected in organs outside the lungs is extremely small,” he clarified. “Being far-fetched does not mean the results are wrong, but it does require focused study to determine whether it might be right.”
Dr. Evans added that chronic lung inflammation is a hallmark of asthma and that it is well-established that persistent inflammation and dysregulated immune responses can drive the development of many kinds of cancer.
“[The] kind of inflammation associated with asthma (Type 2) is not the kind most often associated with cancer development and progression,” he noted. “If there is a true link between asthma and lung cancer, this would seem to be the most likely mechanism.”
Because inhaled corticosteroids are essential controller therapies for people with persistent asthma, he advised that people with asthma not modify their use of inhaled corticosteroids based on the results of this study.
“The positive benefit of inhaled steroids on reducing annual rates of asthma exacerbation, hospitalization, and death is much, much greater than the modest effect noted on cancer risk in this study,” said Dr. Evans.
But Additional Research Is Needed
Dr. Evans pointed out that several prior studies have investigated whether asthma confers an increased risk of lung cancer.
“Most—but, importantly, not all—of those studies have suggested there may be a small increased risk of some kinds of lung cancer in people with asthma,” he said. “So, it is important to recognize the limitations of each study’s ability to provide definitive answers.”
For instance, he noted there are features of the University of Florida study that limit its ability to draw firm conclusions, such as the analysis was performed retrospectively, meaning the authors looked back at already collected data to make their assessments.
“This introduces many issues in terms of missing data and risk factors that cannot be assessed,” he explained.
Further, the patients with asthma in this study differed in critical ways from the non-asthma group.
“For example, the asthmatic patients were more likely to have other clear risk factors for cancer, such as smoking or being diagnosed with chronic obstructive pulmonary disease (COPD),” Dr. Evans said. “These issues do not mean the conclusions are wrong, but they mean that more investigation is needed to know whether the results are verifiable.”
Lowering Your Risk of Cancer
Nearly 26 million people in the United States have asthma—about 1 in 13 people.
While studies have not fully answered the connection between asthma and cancer, Dr. Evans is hopeful existing and continued research will help inform the development of future definitive studies.
For now, he recommends asthmatic patients quit smoking and maintain up-to-date vaccinations to prevent asthma exacerbations and reduce their risk of cancer.
Dr. Evans concluded, “Since asthma affects such a large portion of the population, and since many cancers are devastating diseases, the question of whether asthma impacts cancer development is important to answer.”
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