Background
Immunosuppression (IS) following transplantation should focus on improving long-term graft and patient survival. The objective of this study was to assess patient and graft survival rates and adverse event (AE) incidence in patients treated with combinations of tacrolimus (TAC) and steroids (ST) with either azathioprine (AZA) or mycophenolate mofetil (MMF).
Material and Methods
Seventy-seven renal transplant recipients (RTRs) treated with TAC/AZA/ST (n=37) or TAC/MMF/ST (n=40) in a single center were studied retrospectively. For 6 months after transplantation, patients were managed according to the COSTAMP study protocol. Afterwards, the follow-up visits were performed yearly for 7 years. Intent-to-treat (ITT) and on randomized therapy (ORT) groups were compared. Primary endpoints were graft function, graft loss, and death. Secondary endpoints included incidence of post-transplant diabetes mellitus (PTDM) and other AEs as estimated by the length of the hospitalization per patient per year.
Results
Demographic characteristics were similar in both groups of patients. Patient and graft survival at 7 years were 89.2% and 70.3% in TAC/AZA ITT; 97.5% and 77.5% in TAC/MMF ITT; and 100% in both ORT groups, respectively (ns). Differences in renal function, PTDM, and other AE incidence were also non-significant.
Conclusions
Our results indicate that TAC-based IS with either MMF or AZA is equally effective with respect to patient and graft survival and AE incidence. Taking into account the costs of both regimens and those of related AE therapies, our results raise the question of whether increasing MMF use in RTRs is justified from the perspective of the long-term results.

Keywords: azathioprine, immunosuppression, long term follow-up, Mycophenolate Mofetil, Tacrolimus