According to findings from a study published in Arthritis and Rheumatology, individuals with rheumatoid arthritis (RA) have over 50% augmented risk of developing lung cancer. Additionally, patients diagnosed with rheumatoid arthritis–associated interstitial lung disease (RA-ILD) are especially susceptible to an increased risk of lung cancer, with an estimated threefold greater risk.

The retrospective matched cohort study included patients with RA and non-RA patients from the Veterans Health Administration from January 2000 to December 2019. The objective of the retrospective matched cohort study was to assess the risk of lung cancer in RA and RA-ILD.

The authors wrote, “Understanding whether RA predisposes to the development of lung cancer independent of other risk factors and whether people with RA-ILD represent a uniquely high-risk group could inform cancer screening strategies. We hypothesized that people with RA would have a higher risk of lung cancer than matched non-RA controls and that this risk would be further increased among those with RA-ILD.”

A total of 72,795 participants with RA were matched with 633,937 participants without RA based on birth year, gender, and Veterans Affairs (VA) enrollment year. Among patients with RA, 757 had prevalent RA-ILD and were matched with 5,931 participants without RA-ILD. The primary outcome was incident lung cancer, assessed using the VA Oncology Raw Domain and the National Death Index.

The authors wrote, “Conditional Cox regression models assessed lung cancer risk adjusting for race, ethnicity, smoking status, Agent Orange exposure, and comorbidity burden among matched individuals.”

The results revealed that over 4,481,323 patient-years (mean follow-up 6.3 years), 17,099 incident lung cancers occurred (n = 2,974 in RA; n = 14,125 in non-RA). Moreover, RA was independently associated with an augmented lung cancer risk (adjusted hazard ratio [aHR], 1.58 [1.52, 1.64]), which continued in never-smokers (aHR, 1.65 [1.22, 2.24]) and incident RA (aHR, 1.54 [1.44, 1.65]).

Compared with non-RA controls, prevalent RA-ILD (n = 757) was more robustly linked with lung cancer risk (aHR, 3.25 [2.13, 4.95]) than RA without ILD (aHR, 1.57 (1.51, 1.64]), and analyses of both prevalent and incident RA-ILD generated comparable results (RA-ILD vs. non-RA aHR, 2.88 [2.45, 3.40]).

The authors concluded that RA was linked with a >50% augmented risk of lung cancer, and RA-ILD represented an especially high-risk group with an estimated threefold expanded risk; therefore, expanded surveillance for lung cancer in patients with RA, and especially RA-ILD, may be a beneficial strategy for diminishing the burden posed by the leading cause of mortality from cancer death.

“In summary, both RA and RA-ILD were associated with an increased risk of lung cancer independent of other lung cancer risk factors. Smoking status, a shared risk factor for RA/RA-ILD and lung cancer, did not fully explain the heightened risk of lung cancer observed in RA/RA-ILD. Because RA and RA-ILD represent high-risk populations for developing lung cancer, enhanced screening may be warranted to achieve earlier diagnoses and reduce mortality in RA and RA-ILD-associated lung cancer,” the authors concluded.

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