Wilms' tumor gene 1 (WT1) expression is a well-known predictor for relapse in acute myeloid leukemia. We monitored WT1 decrement along the treatment course to identify its significant role as a marker for residual disease in acute promyelocytic leukemia (APL) and tried to suggest its significance for relapse prediction. In this single center retrospective study, we serially measured PML-RARa and WT1 expression from 117 APL patients at diagnosis, at post-induction and post-consolidation chemotherapies, and at every 3 months after starting maintenance therapy. All 117 patients were in molecular remission after treatment of at least 2 consolidation chemotherapies. We used WT1 ProfileQuant™ kit (Ipsogen) for WT1 monitoring. High WT1 expression (>120 copies/104 ABL1) after consolidation and at early period (3 months) after maintenance therapy significantly predicted subsequent relapse. All paired PML-RARa RQ-PCR were not detected except for one sample with early relapse. Patients with high WT1 expression at 3 months after maintenance therapy (n = 40) showed a significantly higher relapse rate (30.5 vs. 6.9%, P < 0.001) and inferior disease free survival (62.8 vs. 91.4%, P < 0.001). Multivariate analysis revealed that high peak leukocyte counts at diagnosis (HR = 6.4, P < 0.001) and high WT1 expression at 3 months after maintenance therapy (HR = 7.1, P < 0.001) were significant factors for prediction of relapse. Our data showed high post-remission WT1 expression was a reliable marker for prediction of subsequent molecular relapse in APL. In this high-risk group, early intervention with ATRA ± ATO, anti-CD33 antibody therapy, and WT1-specific therapy may be used for relapse prevention.
Trial registration: Clinical Research Information Service (CRIS), KCT0002079.
Keywords: Acute promyelocytic leukemia; FLT3 mutation; Minimal residual disease; WT1.