INDUCTION IMMUNOSUPPRESSION IN THE ELDERLY KIDNEY TRANSPLANT RECIPIENT: AN ANALYSIS OF OPTN/UNOS DATA INFORMING A RISK STRATIFIED APPROACH

INDUCTION IMMUNOSUPPRESSION

J. Gill¹, M. Sampaio², Y.W. Cho³, J. Gill⁴, S. Bunnapradist^2
1Nephrology, St. Paul's Hospital, Vancovouver/BC/CANADA, ²Nephrology, UCLA, Los Angeles/CA/UNITED STATES OF AMERICA, ³Research Division, Mendez National Institute of Transplantation, Los Angeles/UNITED STATES OF AMERICA, ⁴Nephrology, Medicine, University of British Columbia, Vancouver/BC/CANADA

Body: Introduction: The choice of induction immunosuppression in the elderly transplant recipient is unclear and has seldom been examined. Lower immunogenicity and an increased risk of infectious complications in the elderly favors less immunosupression, but the preferential allocation of ECD kidneys into the elderly may warrant otherwise. We compared outcomes with the use of interleukin2 receptor antibodies (IL2RA) and rabbit antithymocyte globulin (rATG) among different strata of elderly kidney transplant recipients based on donor and recipient risk factors to inform a risk stratified approach to choice of induction therapy in this population. Methods: Using OPTN/UNOS data, we identified all recipients of deceased donor kidney transplants >60 yrs from 2003-09. The cohort was stratified into 4 groups based on recipient immunologic risk (PRA>20%, prior transplant, black race) and donor risk (ECD, DCD, cold ischemic time>24 hours). Multivariate logistic regression and Cox models were then used to compare post transplant outcomes in each strata by induction agent. Results: 44% of high immunologic risk elderly recipients received a kidney from high risk donors and over 30% of these patients received IL2RA induction. IL2RA use in high immunologic risk recipients was associated with a higher adjusted risk of acute rejection in the 1st year, all-cause graft loss, and death compared to rATG.

	High Risk Recip/High Risk Donor N=2627 rATG, n=1413 IL2RA, n=841	High Risk Recip/Low Risk Donor N=3377 rATG, n=1830 IL2RA, n=1274	Low Risk Recip/High Risk Donor N= 4202 rATG, n=2012 IL2RA, n=1741	Low Risk Recip/Low Risk Donor N=1885 rATG, n=1885 IL2RA, n=2359
AR in 1st year (OR, 95%CI) IL2RA vs rATG	1.71 (1.26-2.32)	1.63 (1.27-2.09)	1.79 (1.43-2.25)	1.24 (0.95-1.62)
All cause graft loss (HR, 95%CI) IL2RA vs rATG	1.21 (1.02-1.42)	1.16 (1.00-1.33)	1.12 (0.99-1.28)	0.98 (0.85-1.11)
Death (HR, 95%CI) IL2RA vs rATG	1.24 (1.02-1.51)	1.17 (0.99-1.38)	1.26 (1.09-1.47)	1.04 (0.90-1.20)

IL2RA use was more common among low immunologic risk elderly recipients who received kidneys from both high (41.4%) and low risk donors (51.1%), but nearly half of the low risk recipients with low risk donors still received rATG induction. In this group, there was no significant difference in the risk of acute rejection, graft loss, or death between IL2RA and rATG. However, IL2RA use was associated with a higher risk of acute rejection and a trend towards all-cause graft loss in low risk recipients with high-risk donor organs. When adjusted for acute rejection, the risk of death and all-cause graft loss was not different between IL2RA and rATG in all strata, suggesting the difference in graft loss and death is mediated by acute rejection. Conclusion: We demonstrated a decreased risk of acute rejection, graft loss, and death with rATG use among elderly patients of high immunologic risk and those with organs from high risk donors, with no difference in low risk patients who received low risk organs. This suggests that in elderly patients who are high immunologic risk or receive high risk donor kidneys, rATG use may be preferable, whereas no benefit exists in low risk scenarios.

Disclosure: All authors have declared no conflicts of interest.