Chen Yen-Nien1, Hsu Wen-Fen2, Chang Li-Chun2, Tu Chia-Hung2, Wu Ming-Shiang2, Chiu Han-Mo2

1Department of Medicine, National Taiwan University Cancer Center, Taipei, Taiwan, 2Department of Internal Medicine, National Taiwan University Hospital, Taipei, Taiwan.

Background/Aims: In western countries, inflammatory bowel disease (IBD) patients treated with thiopurines were reported to have higher incidences of certain malignancies, such as lymphoma and non-melanoma skin cancers. However, a lack of increased risk of lymphoma in Japan was reported. We conducted a study to explore whether the cancer risk increased or not in IBD patients treated with thiopurines in Taiwan.

Methods: A retrospective study was conducted to analyze data recorded from January 2002 through December 2016 in the registered database compiled by the National Health Insurance and provided by the Ministry of Health and Welfare, Taiwan. We linked files of catastrophic diagnoses, medication prescriptions, and cancer diagnoses and then compared incidence rates of cancer subgroups between users and non-users of thiopurines.

Results: A total of 4,528 patients with catastrophic IBD illness were registered from 2002 to 2016 in Taiwan (CD, 1059; UC, 3,469). 1,007 patients received azathioprine treatment, and 65 patients received 6-mercaptopurine(6-MP) treatment. The total dosage of the azathioprine was divided into 4 scales (0-Q1, Q1-Q2, Q2-Q3, >Q3); each subgroup contained around 250 patients. However, there were no notable differences in cancer incidence than those who did not receive thiopurine in any dosage subgroup. The aHR (adjusted hazard ratio) of these 4 scales (0-Q1, Q1-Q2, Q2-Q3, >Q3) were 1.48 (95% confidence interval (CI): 0.67-3.26), 0.90 (95% CI: 0.27-3.06), 0.45 (95% CI: 0.05-3.89) and 2.52 (95% CI: 0.30-20.99), respectively.

Conclusion: There is no evidence for an increased incidence of any specific cancer in IBD patients receiving thiopurine in Taiwan.

Keywords: Inflammatory bowel disease, Thiopurine, Azathioprine, Malignancy, Lymphoma