Asthmatics have a higher risk of developing cancer, though use of inhaled steroids may have a slight protective effect, according to a US study.
Globally, cancer is the leading cause of mortality, with nearly 10 million recorded deaths in 2020. Data suggests that infection and inflammation contribute to a quarter of all cancers. In fact, the inflammatory milieu within a tumour seems to be an indispensable participant in tumour progression. In asthmatics, the inflammatory nature of their condition increases the risk of lung cancer. Nevertheless, other data either demonstrate a positive association or no association with the risk of other cancers.
In the current study, researchers sought to better understand the relationship between asthma and cancer risk. They analysed electronic health records in a US claims database. The team developed a matching cohort of those with and without asthma which served as the control group. Using regression models, researchers searched for any relationship between asthma and the subsequent development of cancer. The primary outcome was the time to a cancer diagnosis after the date of an asthma diagnosis.
Asthmatics and risk of cancer
The asthma cohort included 90,021 individuals matched to 270,063 without the disease. In multivariable analysis, asthmatics were more likely to develop cancer (hazard ratio, HR = 1.36, 95% CI 1.29 – 1.44). For example, significantly higher risks were observed for melanoma, blood, kidney and lung cancers. However, in contrast, risks were non-significant for bladder, colorectal and prostate cancers.
In a separate analysis examining the effect of inhaled steroid use, the overall cancer risk was slightly lower among steroid users (HR = 1.60 vs 1.11, inhaled steroid vs no steroid). Taken together, cancer risk was higher for nine of 13 cancers in asthmatics not using inhaled steroids but in only two cancers among steroid users. These findings suggest a possible protective effect of inhaled steroid use on cancer risk that requires further evaluation.
