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

We assessed WT1 expression (expressed as messenger copies/10(4) 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 (15-69), 59% were in first remission, 74% received a myeloablative conditioning regimen and the median follow up was 865 d (34-2833). 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.