Higher Cancer Risk Found in Asthma Patients, Not Limited to Lung Cancer

New research reveals that individuals with asthma have a 36% higher chance of developing cancer in comparison to those without respiratory illness. Asthma is linked to a greater risk of five types of cancer: lung, blood, melanoma, kidney, and ovarian, according to the study.

The authors of the study, including Yi Guo, PhD, assistant professor in the College of Medicine at the University of Florida, analyzed electronic health records and claims data from 2012 to 2020 to examine the correlation between asthma and subsequent cancer risk. "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," said Guo, emphasizing that the study does not affect clinical care yet.

The study discovered that cancer risk was heightened in asthma patients in general, but patients using inhaled steroids had a lower risk of cancer than those who were not. The team of experts found that asthma patients without inhaled steroid use had a greater risk of nine out of 13 cancers, whereas those with the treatment had an elevated cancer risk for only 2 out of 13 cancer types, indicating a possible preventive effect of inhaled steroid usage on cancer.

"These results are promising but inconclusive," commented Scott Evans, MD, Interim Chair of Pulmonary Medicine at the University of Texas MD Anderson Cancer Center, who added that inhaled corticosteroids, which are prescribed to people suffering from persistent asthma as a controller therapy, are associated with lower risk of lung cancer.

"Being far-fetched does not mean the results are wrong, but it does require focused study to determine whether it might be right," he said, warning people with asthma not to alter their use of inhaled corticosteroids based on this study's findings, emphasizing their positive impact on reducing the rates of asthma exacerbation, hospitalization, and death.

Dr. Evans noted that previous studies have suggested that asthma may pose a small increased risk of some lung cancer types. However, he cautioned that the University of Florida's retrospective data analysis has limitations and that each study has its restrictions in providing definitive answers.

“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.”

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.”