Leukaemia relapse after allogeneic transplants for acute myeloid leukaemia: predictive role of WT1 expression

We assessed WT1 expression (expressed as messenger copies/104 ABL1) from marrow cells of 122 patients with acute myeloid leukaemia (AML), before and after an unmanipulated allogeneic haemopoietic stem cell transplant (HSCT). The median age was 44 years (1569), 59% were in first remission, 74% received a myeloablative conditioning regimen and the median follow up was 865 d (342833). Relapse was higher in 67 patients with WT1 expression, at any time post-HSCT, exceeding 100 copies (54%), as compared to 16%, for 55 patients with post-HSCT WT1 expression <100 copies (P < 0.0001). Similarly, actuarial 5-year survival (OS) was 40% vs. 63%, respectively (P = 0.03). In multivariate Cox analysis, WT1 expression post-HSCT was the strongest predictor of relapse (Hazard Ratio [HR] 4.5, P = 0.0001), independent of disease phase (HR 2.3, P = 0.002). Donor lymphocyte infusions (DLI) were given to 17 patients because of increasing WT1 levels: their OS was 44%, vs. 14% for 21 patients with increasing WT1 expression who did not receive DLI (P = 0.004). In conclusion, WT1 expression post-HSCT is a strong predictor of leukaemia relapse and survival in AML; WT1 may be used as a marker for early interventional therapy.