Association between Androgen Deprivation Therapy and the Risk of Inflammatory Rheumatic Diseases in Men with Prostate Cancer: Nationwide Cohort Study in Lithuania

Background: The aim of this study was to assess the association between androgen deprivation therapy (ADT) and the risk of inflammatory rheumatic diseases in men with prostate cancer. Methods: Patients with prostate cancer between 2012 and 2016 were identified from the Lithuanian Cancer Registry and the National Health Insurance Fund database, on the basis of rheumatic diseases diagnoses and information on prescriptions for androgen deprivation therapy. Cox proportional hazard models were used to estimate hazard ratios (HR) to compare the risks of rheumatic diseases caused by androgen deprivation therapy exposure in groups of prostate cancer patients. Results: A total of 12,505 prostate cancer patients were included in this study, out of whom 3070 were ADT users and 9390 were ADT non-users. We observed a higher risk of rheumatic diseases in the cohort of prostate cancer patients treated with ADT compared with ADT non-users (HR 1.55, 95% confidence interval (CI) 1.01–2.28). Detailed risk by cumulative use of ADT was performed for rheumatoid arthritis, and a statistically significant higher risk was found in the group with longest cumulative ADT exposure (>105 weeks) (HR 3.18, 95% CI 1.39–7.29). Conclusions: Our study suggests that ADT usage could be associated with increased risk of rheumatoid arthritis, adding to the many known side effects of ADT.