Association of ankylosing spondylitis with the risk of cancer: a meta-analysis of cohort studies

Objectives: The potential impact of ankylosing spondylitis (AS) on cancer risk remains unclear. This study seeks to investigate the relationship between AS and different types of cancers. Methods: A literature search on PubMed, EMBASE and Cochrane Library up to 10 July 2023 was conducted. Two investigators selected eligible studies and extracted relevant data. The study used the random-effects model to explore the causality between AS and cancer, utilizing relative risk (RR) as a measure for the study. Results: A total of 20 cohorts with >330 000 participants were included. The pooling analysis shows AS being associated with a higher risk of cancers (RR = 1.16, 95% CI: 1.07-1.26, P = 0.001, I-2 = 70.60%). In the subgroup analysis, AS has a higher cancer risk in Asia, but this association is not significant in Europe. Individual investigations indicate that AS is associated with an increased risk of bone cancer (RR = 3.41, 95% CI: 1.45-7.99, P = 0.005, I-2 = 0.00%), thyroid gland cancer (RR = 1.76, 95% CI: 1.29-2.40, P < 0.001, I-2 = 13.70%), multiple myeloma (RR = 1.74, 95% CI: 1.42-2.15, P < 0.001, I-2 = 27.20%), leukaemia (RR = 1.52, 95% CI: 1.27-1.82, P < 0.001, I-2 = 0.00%), kidney cancer (RR = 1.45, 95% CI: 1.08-1.94, P = 0.014, I-2 = 0.00%), prostate cancer (RR = 1.43, 95% CI: 1.17-1.74, P < 0.001, I-2 = 82.80%) and non-Hodgkin's lymphoma (RR = 1.42, 95% CI: 1.17-1.73, P < 0.001, I-2 = 0.00%). However, there is no significant correlation with connective tissue cancer, brain cancer, testicular and other male cancers, bladder cancer, female cancers, skin cancer, and cancers of the digestive system and respiratory system. Conclusion: AS appears to be related to cancer development. The results highlighted the necessity for large-scale studies, considering influencing factors such as AS course, medication histories and potential biases when examining cancer risk.