The impact of early and late acute rejection on graft survival in renal transplantation

BACKGROUND: Advances in immunosuppression after kidney transplantation have decreased the influence of early acute rejection (EAR) on graft survival. Several studies have suggested that late acute rejection (LAR) has a poorer effect on long-term graft survival than EAR. We investigated whether the timing of acute rejection (AR) influences graft survival, and analyzed the risk factors for EAR and LAR. METHODS: We performed a retrospective cohort study involving 709 patients who underwent kidney transplantation between 2000 and 2009 at the Samsung Medical Center, Seoul, Korea. Patients were divided into three groups: no AR, EAR, and LAR. EAR and LAR were defined as rejection before 1 year and after 1 year, respectively. Differences in graft survival between the three groups and risk factors of graft failure were analyzed. RESULTS: Of the 709 patients, 198 (30%) had biopsy-proven AR [EAR=152 patients (77%); LAR=46 patients (23%)]. A total of 65 transplants were lost. The 5-year graft survival rates were 97%, 89%, and 85% for patients with no AR, EAR, and LAR, respectively. These differences were significant (P<0.001 for both by log-rank test). In time-dependent Cox regression analysis, EAR (hazards ratio, 3.37; 95% confidence interval, 1.90–5.99) and LAR (hazards ratio, 5.32; 95% confidence interval, 2.65–10.69) were significantly related to graft failure. When we set LAR as standard and compared it with EAR, there was no statistical difference between EAR and LAR (P=0.21). CONCLUSION: AR, regardless of its timing, significantly worsened graft survival. Treatments to reduce the incidence of AR and improve prognosis are needed.