People with asthma have an elevated risk for a variety of cancers other than lung cancer, including melanoma as well as blood, kidney, and ovarian cancers, new research suggests.
But, the authors found, treatment with an inhaled steroid may lower that risk, perhaps by keeping inflammation in check.
“Using real-world data, our study is the first to provide evidence of a positive association between asthma and cancer risk in United States patients,” Yi Guo, PhD, with the University of Florida, Gainesville, said in a news release.
The study was published online in Cancer Medicine.
The relationship between chronic inflammation and cancer remains a key area of exploration in cancer etiology. Data show that the risk for developing cancer is higher in patients with chronic inflammatory diseases, and patients with asthma have complex and chronic inflammation. However, prior studies exploring a possible link between asthma and cancer have yielded mixed results.
To investigate further, Dr. Guo and colleagues analyzed electronic health records and claims data in the OneFlorida+ clinical research network for roughly 90,000 adults with asthma and a matched cohort of about 270,000 adults without asthma.
Multivariable analysis revealed that adults with asthma were more likely to develop cancer, compared with peers without asthma (hazard ratio, 1.36), the investigators found.
Adults with asthma had an elevated cancer risk for five of the 13 cancers assessed, including melanoma (HR, 1.98), ovarian cancer (HR, 1.88), lung cancer (HR, 1.56), kidney cancer (HR, 1.48), and blood cancer (HR, 1.26).
Compared with adults without asthma, those with asthma who did not treat it with an inhaled steroid had a more pronounced overall cancer risk, compared with those who were on an inhaled steroid (HR, 1.60 vs. 1.11).
For specific cancer types, the risk was elevated for nine of 13 cancers in patients with asthma not taking an inhaled steroid: prostate (HR, 1.50), lung (HR, 1.74), colorectal (HR, 1.51), blood (HR, 1.44), melanoma (HR, 2.05), corpus uteri (HR, 1.76), kidney (HR, 1.52), ovarian (HR, 2.31), and cervical (HR, 1.46).
In contrast, in patients with asthma who did use an inhaled steroid, an elevated cancer risk was observed for only two cancers, lung cancer (HR, 1.39) and melanoma (HR, 1.92), suggesting a potential protective effect of inhaled steroid use on cancer, the researchers said.
Although prior studies have shown a protective effect of inhaled steroid use on some cancers, potentially by reducing inflammation, the “speculative nature of chronic inflammation (asthma as a common example) as a driver for pan-cancer development requires more investigation,” Dr. Guo and colleagues cautioned.
And because of the observational nature of the current study, Dr. Guo’s team stressed that these findings do not prove a causal relationship between asthma and cancer.
“More in-depth studies using real-word data are needed to further explore the causal mechanisms of asthma on cancer risk,” the researchers concluded.
Funding for the study was provided in part by grants to the researchers from the National Institutes of Health, National Cancer Institute, National Institute on Aging, and the Centers for Disease Control and Prevention. This project was supported by the Cancer Informatics Shared Resource in the University of Florida Health Cancer Center. The authors have disclosed no conflicts of interest.
A version of this article first appeared on Medscape.com.