Identifying risk profiles in liver transplant candidates and implications for induction immunosuppression.

Changes in recipient and donor characteristics are redefining the role of induction in liver transplant recipients. Older recipients are more common, with greater concomitant comorbidity. Moderate or severe renal dysfunction is now estimated to affect 40% of liver transplant recipients. Donors are also becoming older, and other factors such as more frequent non-alcoholic fatty liver disease (NAFLD) compromise the quality of some grafts. Rejection rates are now relatively low (~10%) but some patients have a markedly increased risk such as younger recipients and those undergoing re-transplantation. Induction immunosuppression is associated with a significant reduction in rejection risk but due to various factors universal induction is not justified. Steroid-free therapy without induction increases the risk of biopsy-proven acute rejection (BPAR) but randomized trials have shown that induction with an interleukin-2 antagonist receptor (IL-2RA) agent or with rabbit antithymocyte globulin (rATG) maintains immunosuppressive efficacy in steroid-free regimens. Delayed calcineurin inhibitor (CNI) initiation (e.g. to days 4-5 post-transplant) can prevent deterioration of renal function during the first year post-transplant, but requires induction with an IL-2RA agent or rATG to maintain early immunosuppressive efficacy. IL-2RA induction may be inadequate to ensure a low risk of rejection in a steroid-free regimen combined with delayed tacrolimus. Randomized trials of CNI withdrawal at month 1 post-transplant have only achieved an acceptable rate of BPAR when induction is administered. In terms of safety, an increased rate of infection does not seem to be a concern. The most recent large-scale analyses have not indicated any evidence for an increased risk of malignancy, or specifically post-transplant lymphoproliferative disease. In summary, the place of induction in the management of liver transplant patients is becoming established. Selective use in high-risk individuals to avoid graft rejection is still relevant, but the key rationale for induction is to facilitate steroid-sparing and CNI-sparing regimens to reduce long-term complications.