Minimal residual disease (MRD) was monitored in 80 patients with acute lymphoid (ALL, n=44) or myeloid (AML, n=36) leukemia, undergoing allogeneic haemopoietic stem cell transplantations. MRD markers were IgH-VDJ and TCR gene re-arrangement for ALL, and Wilm's Tumor (WT1) expression for AML. The overall cumulative incidence (CI) of MRD was positive in 45% and the CI of hematologic relapse was 24% (36% in MRD+ vs. 16% in MRD patients, p=0.03). The median interval from transplant to first MRD positivity was 120 days and to hematologic relapse 203 days. Patients were divided in 3 MRD groups: MRD (n=44), MRD+ given donor lymphocyte infusions (DLI) (n=17) and MRD+ not given DLI (n=19): leukemia relapse rates in these 3 groups were 16%, 6% and 63%, respectively (p<0.0001); the actuarial 3-year survival rates were 78%, 80% and 26% (p=0.001). In multivariate COX analysis, the MRD group was predictor of relapse (p<0.0001) and survival (p=0.01), together with disease phase and chronic graft versus host disease. In MRD+ patients, DLI protected against relapse (p=0.003) and improved survival (p=0.01). In conclusion, MRD positivity post-transplant predicts leukemia relapse: however, when MRD+ patients are given DLI, their outcomes are comparable to MRD- patients.
Minimal residual disease; acute myeloid leukemia; acute lymphoid leukemia; donor lymphocyte infusion; allogeneic hematopoietic stem cell transplantation