Renal Transplantation in the Setting of Early Steroid Withdrawal: A Comparison of Rabbit Antithymocyte Globulin Induction Dosing in Two Eras

Background: Modern immunosuppression and rabbit antithymocyte globulin (rATG) have facilitated the success of early steroid withdrawal (ESW) protocols. Little data exist on optimal rATG dosing in ESW protocols. Methods: Rejection at 12 months in era 1 (four doses of rATG, 1.25 mg/kg) vs. era 2 (three doses of rATG, 1.25 mg/kg) was the primary endpoint. Secondary endpoints included patient and graft survival, renal function and infectious complications. Factors associated with rejection at 1 year were identified. Results: 199 patients received rATG induction and ESW: 102 in era 1 and 97 in era 2. Compared to era 1, era 2 was not associated with worse outcomes, including rejection, renal function, infection or graft survival. Rejection at 1 year and uncensored graft survival differed between the dosing groups. Rejection rates were significantly higher in the <4 mg/kg group compared to the 4-5.9-mg/kg and the ≥6-mg/kg groups, whereas uncensored graft survival was the lowest in the ≥6-mg/kg group. Factors associated with rejection at 12 months included: rATG dose received of 4-5.9 versus <4 mg/kg (OR 0.20, 95% CI 0.036-0.85, p = 0.026); recipient age (per year, OR 0.94, 95% CI 0.89-1.0, p = 0.038); panel reactive antibody 10-79.9 versus <10% (OR 5.4, 95% CI 1.2-25, p = 0.030) and rATG dose held (OR 4.0, 95% CI 1.0-15, p = 0.049). Conclusions: A comparison of rATG dosing based on era did not result in a significant difference in rejection, renal function, infection or graft survival. However, when evaluating the study population based on actual dose received there were notable differences in both rejection rates and uncensored graft survival.