Analysis of a single-center experience with mycophenolate mofetil based immunosuppression in renal transplantation.

PURPOSE: Acute rejection continues to be a major clinical issue in renal transplantation. Three large multicenter trials have demonstrated a 50% decline in biopsy-proven rejection when mycophenolate mofetil (MMF) was given to renal transplant recipients with corticosteroids and cyclosporine. The purpose of this study was to compare the 6-month outcome of renal transplant recipients using MMF and non-MMF based immunosuppression protocols over a 4-year period at a single center.

METHODS: This retrospective study analyzed three patient groups defined by their immunosuppression protocol. The first group included patients who received a quadruple immunosuppression regimen of anti-lymphocyte induction (ATG), cyclosporine (CYA), azathioprine (AZA), and corticosteroids (CCS), and were transplanted between October 1993 and May 1995 (AZA group). The second group included patients who received a triple immunosuppression regimen of CYA, MMF, and CCS, and were transplanted between June 1995 and May 1996 (MMF group). The third group included patients who were transplanted between January 1997 and December 1997, and received an immunosuppression regimen of CYA and MMF with a reduced CCS dosing schema (reduced steroid group (RST)). Data were collected from a retrospective review of inpatient and outpatient clinical records.

RESULTS: A total of 325 patients were included in the study (106 AZA, 106 MMF, 113 RST). The demographic characteristics of the three groups were similar; however, the mean donor age for the AZA group was 40+/-15.1 years versus 33+/-14.1 years and 34+/-13.1 years for the MMF and RST groups, respectively (p<0.043). The incidence of acute, biopsy-proven rejection at 6 months was significantly less in the MMF group when compared with the AZA group [16 (15.1%) versus 35 (33%) patients, p = 0.002]. However, the incidence of acute, biopsy-proven rejection in the RST group (35 patients, 31%) was similar to that of the AZA group. Kaplan-Meier estimates for the cumulative incidence of acute rejection demonstrated a significant difference between the MMF group and the other two groups (p = 0.0059). The AZA group had more severe rejection as demonstrated by the more frequent use of antilymphocyte therapy for rejection treatment (68.4% episodes) compared with the MMF (38.9%) and RST (47.6%) groups. After 6 months of follow-up, 11 patients had lost their grafts (8, AZA; 1, MMF; 2, RST). One patient died in each of the AZA and RST groups due to hemorrhage and a pulmonary embolus, respectively. Four AZA patients were diagnosed with a malignancy (three post-transplant lymphoproliferative disorder, one squamous skin cell carcinoma) compared with 2 MMF patients (prostate cancer, basal skin cell carcinoma) and no RST patients. Herpes zoster was the only infection that occurred more frequently in the MMF group (p = 0.03). No other differences in infection rates were noted among the three groups. The initial length of hospital stay declined significantly over the 4-year study period [11+/-4.3 d (AZA), 7.0+/-4.0 d (MMF), 6.2+/-3.3 d (RST), p<0.001]. Total number of hospital days for the first 6 months also followed a similar declining pattern. Despite using intravenous cyclosporine immediately post-transplant in the MMF and RST groups, the incidence of delayed graft function was similar among the three groups. Average serum creatinine at 1 month was significantly lower in the MMF group (p = 0.008), but no difference was noted at 3 and 6 months when compared with the AZA and RST groups.

CONCLUSION: This retrospective analysis indicates that MMF is an effective immunosuppressant. Decreased length of stay and less steroid resistant rejections with MMF is favorable for decreased hospital costs. However, the rebound in rejection rate with the RST group suggests that further study is needed to define the optimal use of this agent in combination with others to maximize effectiveness and minimize negative side effects.