Graft-vs-host disease (GVHD) causes substantial mortality, morbidity and poor quality of life
after blood or marrow transplantation (BMT). In Alberta, we use antithymocyte globulin (ATG,
given on days -2, -1 and 0) in addition to methotrexate and cyclosporine for GVHD
prophylaxis. In spite of that, ~40% patients develop significant GVHD (grade 2-4 acute GVHD
or chronic GVHD needing systemic immunosuppressive therapy). ATG at the dose we typically use
(4.5 mg/kg) is relatively non-toxic. At higher doses, ATG could increase the likelihood of
posttransplant infections or relapse. Thus an extra dose of ATG (on top of the routine 4.5
mg/kg) might be justified only for patients at high risk of developing significant GVHD. In
our experience, low serum level of interleukin-15 (IL15) and high serum level of
interleukin-2 receptor alpha (IL2Ra) on day 7 predict development of significant GVHD. Here
we will test whether, compared to historical/concurrent controls, an extra dose of ATG (3
mg/kg on day 8) given to patients with low IL15 or high IL2Ra on day 7 reduces the incidence
of significant GVHD, and improves survival free of relapse and GVHD, and quality of life.