Although immunosuppressive drugs such as azathio-prine (AZA) have been shown to be effective in preventing relapse after medically induced remission, there remains little data available for prevention of postoperative recurrence . Recent studies have suggested possible benefits from immunomodulation. Hanauer et al. assessed 131 postoperative patients randomized to either placebo, mesalamine 3 g/day, or 6-MP 50 mg/day and followed for 2 years. Rates of endoscopic and clinical recurrence at multiple time-points were assessed and generally showed non-significant trends favouring 6-MP. For example, clinical recurrence rates at 2 years were 77% for placebo, 58% for mesalamine, and 50% for 6-MP. The 95% confidence intervals overlapped for all groups, but further analysis showed a difference between 6-MP and placebo (P=0.045). The authors felt the study showed the efficacy of 6-MP compared with placebo. It should also be noted that the dose of 6-MP they used was relatively low compared with doses known to be effective in other clinical settings .
The second study, by Ardizzone et al. compared AZA at a dose of 2 mg/kg per day to mesalamine or placebo in an unblinded, prospective randomized study of 142 patients lasting 2 years. Two-year clinical recurrence rates were 28% for mesalamine and 17% for AZA, a difference that did not reach statistical significance but showed a beneficial trend towards immunomodulation .
A retrospective analysis published in 2001 in France examined 38 patients who were treated with azathioprine between 1987 and 1996 to prevent postoperative CD . The median duration of postoperative follow-up was 29 months. Probabilities of clinical recurrence were 9,16 and 28% at 1, 2 and 3 years, respectively. The authors concluded that in patients treated with AZA, the rate of postoperative endo-scopic recurrence was lower than that previously reported in untreated patients.
In summary, the few trials conducted on the role of immunomodulation tend to support the maintenance efficacy of AZA or 6-MP in the postoperative setting. Because of the stronger evidence supporting the use of AZA or 6-MP in the setting of medically induced remission, even authors highly critical of the existing data acknowledge that the use of thiopurines is likely warranted in high-risk postoperative patients .
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