Thiopurines and the Risk of Cancer in Patients with Inflammatory Bowel Disease and Reference Individuals without Inflammatory Bowel Disease – A Danish Nationwide Cohort Study (1996-2018)

Background 95% CI, 1.05–1.24). Monotherapy (aHR, 1.36; 95% CI, 1.17–1.57) and combination therapy (aHR, 2.49; 95% CI, 1.64–3.78) were associated with an increased risk of cancer compared to unexposed patients with IBD. Among elderly patients (>65 years), the aHR was 2.79 (95% CI, 1.24–6.28) in those receiving combination therapy. In patients discontinuing thiopurines, aHRs returned to the level of unexposed (aHR, 0.89; 95% CI, 0.78–1.01). The aHR was positively associated with cumulative thiopurine exposure and in patients with >5 years of exposure, reaching an aHR of 1.36 (95% CI, 1.15–1.61).ConclusionsThiopurines were associated with increased hazard of cancer, especially when used in combination therapy in the elderly. The hazard increased by 36% when patients were exposed to thiopurines for more than 5 years. Reassuringly, the hazard returned to baseline after discontinuation of thiopurines.