Increased risk of cancer for patients with ankylosing spondylitis: a nationwide population-based retrospective cohort study.

OBJECTIVES: Few studies have investigated the relationship between ankylosing spondylitis (AS) and other inflammatory spondyloarthritis and subsequent cancer. The aim of this study was to determine whether AS is associated with cancer risk. METHOD: We used data from the National Health Insurance (NHI) system of Taiwan to investigate this association. The AS cohort included 4133 patients, and each patient was randomly frequency matched with four persons without AS based on sex, age, and entry year (control cohort). We conducted a Cox proportional hazards regression analysis to estimate the influence of AS on cancer risk. RESULTS: Among patients with AS, the overall risk of developing cancer was 38% higher than that of people without AS, and the difference was significant [adjusted hazard ratio (HR) 1.38, 95% confidence interval (CI) 1.18-1.60]. This phenomenon held true even when we analysed males and females separately. The risk of developing lung or head and neck cancer among patients with AS was significantly higher; and risks for liver, bladder, and uterus cancers were marginally significantly higher. CONCLUSIONS: This nationwide population-based cohort study shows that Taiwanese patients with AS have a higher risk of developing cancer, particularly lung or head and neck cancer.