Is treatment with 6-mercaptopurine for colitis associated with the development of colorectal cancer?

Patients with ulcerative colitis and Crohn's colitis have an increased risk of colon cancer influenced by the duration, extent, and severity of disease. Surveillance colonoscopy serves to detect cancer and precancerous dysplasia at the earliest possible time. Reduction of inflammation should theoretically reduce the development of cancer. Immunosuppressives should do so, but there is a fear that indeed the risk of cancer might be increased with their use. Our study was conducted to determine whether a relationship exists between receiving treatment with 6-MP for ulcerative and Crohn's colitis and increasing or decreasing the incidence of colorectal cancer (CRC).

We conducted a single-center, retrospective cohort study of patients with long standing colitis (ulcerative and Crohn's) using the database of the senior investigator (B.I.K.). Two groups were matched based on their propensity to receive treatment with 6-MP; one group received 6-MP treatment, the other did not. Both groups were compared on the incidence of colon cancer.

No significant differences existed between the two cohorts with regard to type of disease, duration, extent, age, and sex. Six out of 27 patients not on 6-MP and seven out of 27 patients on 6-MP developed CRC (P= 1).

We conclude that there is neither sufficient evidence currently to state that 6-MP is associated with an increased development of CRC, nor that it has a chemopreventive effect.