Precolectomy thiopurine use was not independently correlated with risk for primary neoplasia after total proctocolectomy (TPC) with ileal pouch anal anastomosis (IPAA), according to a study published in the International Journal of Colorectal Disease.

The retrospective cohort analysis included patients with ulcerative colitis (UC) or indeterminate colitis who underwent TPC with IPAA and had at least 2 pouchoscopies with biopsies postprocedure. Patients who were taking any thiopurine (azathioprine, 6-mercaptopurine) for at least 12 weeks immediately prior to the procedure (n=97) were matched with patients in a control group, who had not been exposed to thiopurines, based on demographic characteristics.

The primary outcome of the study was the rate of primary neoplasia following TPC with IPAA. Primary neoplasia included indefinite, low-grade, and high-grade dysplasia.


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The final cohort for analysis included 284 patients; 57.4% were men and median age was 35.6 years. In total, 95.4% of patients were diagnosed with UC and the rest with indeterminate colitis.

Patients with thiopurine exposure were less likely to have dysplasia (7.2% vs 23.0%) compared with those having no exposure, respectively. Thiopurine exposure was also associated with lower grades of dysplasia.

Of the 9 patients who developed neoplasia postprocedure, only 1 patient was in the thiopurine exposure group. This difference was not statistically significant, however, and multivariate analysis did not show an independent correlation. Patients with postprocedure neoplasia were likely to be of more advanced age and have had preprocedure neoplasia.

This study is greatly limited by its small sample size and may include unaccounted confounders. Additionally, there may have been selection bias due to the inclusion of a high-risk study cohort with precolectomy dysplasia.

Limitations aside, investigators are confident these study results add another piece to solving the ongoing puzzle of risk factors and potential protection for the development of primary neoplasia.

Reference

Kayal M, Riggs A, Plietz M, et al. The association between pre‐colectomy thiopurine use and risk of neoplasia after ileal pouch anal anastomosis in patients with ulcerative colitis or indeterminate colitis: a propensity score analysis. Int J Colorectal Dis. Published online September 27, 2021. doi: 10.1007/s00384-021-04033-2