Long-term graft outcome with mycophenolate mofetil and azathioprine: A paired kidney analysis

Background. Randomized controlled trials and U.S. Registry data have demonstrated that mycophenolate mofetil (MMF) reduces acute rejection rates and improves graft survival. We undertook the first paired kidney analysis comparing the effects of MMF and azathioprine on graft outcome in the United Kingdom. Methods. In all, 238 deceased donors from 1999 to 2002 who donated one kidney to a patient treated with MMF and the other kidney to a patient treated with azathioprine were identified from the national transplant database held by U.K. Transplant. Graft function and rates of change of graft function were compared using multiple linear regression analyses adjusting for covariates on an intention-to-treat basis. Incidence of acute rejection and delayed graft function were studied using logistic regression. Patient and graft survival censored for death were evaluated with Cox regression analyses. Results. The MMF-treated patients exhibited a nonsignificant trend towards improved graft function but with increased rejection rates (44% versus 31%, P < 0.01). Treatment with MMF did not reduce delayed graft function rates. Univariate analysis showed that graft survival was inferior in MMF-treated patients (90% versus 95%, log-rank, P=0.02) but in multivariate Cox regression models, MMF treatment was not a significant factor. Surprisingly, in the first year 32% of patients achieved daily doses of less than 2 g of MMF compared to 18% of patients who received less than 100 mg of azathioprine (P < 0.01). Conclusion. In this real-life study, there was no difference in patient or graft outcome between MMF and azathioprine treated groups despite increased rejection rates in patients receiving MMF therapy.