High WT1 expression is an early predictor for relapse in patients with acute promyelocytic leukemia in first remission with negative PML-RARa after anthracycline-based chemotherapy: a single-center cohort study
© The Author(s). 2017
Received: 17 November 2016
Accepted: 18 January 2017
Published: 23 January 2017
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.
Clinical Research Information Service (CRIS), KCT0002079
In acute promyelocytic leukemia (APL), PML-RARa transcript is used as a marker for minimal residual disease (MRD), but the marker is not useful for pre-emptive management since its positivity directly indicates relapse. High Wilms’ tumor gene 1 (WT1) expression was related with subsequent relapse in acute myeloid leukemia, and Hecht et al. recently reported that high initial WT1 expression was associated with more relapse in APL [1–3].
We confirmed APL by chromosome analysis and PML-RARα reverse transcriptase polymerase chain reaction (RT-PCR) method. All were treated with idarubicin (12 mg/m2, days 1, 3, 5, and 7) and all-trans retinoic acid (ATRA; 45 mg/m2/day) [4, 5]. After achievement of hematological complete remission (CR), all received three courses of consolidation—first, idarubicin (7 mg/m2, days 1–4); second, mitoxantrone (10 mg/m2, days 1–4); and third, idarubicin (12 mg/m2, day 1–2)—followed by 2-year maintenance using 6-mercaptopurine (50 mg/m2/day) plus ATRA [5–7]. The molecular studies were performed at diagnosis and 1 month after chemotherapy, and every 3 months after maintenance. Quantification of PML-RARα and WT1 were performed using the real-time quantitative (RQ)-PCR methods (Real-Q PML-RARα quantification kit, Biosewoom, Korea, and WT1 ProfileQuant™ kit, Ipsogen, France) presenting a similar sensitivity of 4.5 log.
Baseline characteristics of enrolled patients
Total n = 117
Number or median value
Age, median (range)
Laboratory findings at diagnosis
Leukocyte count (×109/L)
Leukocytes count at peak (×109/L)
Lactate dehydrogenase (LDH, U/L)
Prothrombin time (PT, %)
Partial thromboplastin time (aPTT, s)
Antithrombin III (%)
t(15;17) with 1 additional karyotype
t(15;17) with ≥2 additional karyotype
No FLT3 mutation
WT1 (copies/104 ABL), median (range)
At diagnosis (n = 117)
Post-induction (n = 117)
Post 1st consolidation (n = 117)
Post 2nd consolidation (n = 117)
Post 3rd consolidation (n = 117)
aPost-maintenance 3 months (n = 117)
aPost-maintenance 1 year (n = 87)
aPost-maintenance 2 year (n = 62)
At relapse (n = 16)
Leukapheresis at initial treatment
Hematological complete response
After 2nd induction
Complete molecular response (CMR)
After 2nd induction
After 1st consolidation
After 2nd consolidation
We compared the level of WT1 between relapsed and non-relapsed group during the course of treatment (Additional file 1: Figure S2) and identified that median WT1 was significantly different at post 2nd consolidation (171.5 vs. 76.3, P = 0.049), at post 3rd consolidation (156.0 vs. 67.6, P = 0.013) and at 3 months post-maintenance (162.0 vs. 59.1, P = 0.002). We found that WT1 post-maintenance 3 months was the most significant parameter for relapse prediction at the cutoff of ≥120.0 copies/104 ABL.
Multivariate analysis (Additional file 1: Table S1) revealed that 4-year CIR was significantly higher in patients with high peak leukocyte count (HR = 6.414; 95% CI, 2.1–19.3, P < 0.001) and high WT1 post-maintenance 3 month (HR = 7.533; 95% CI, 2.3–24.8, P < 0.001), and 4-year DFS was significantly inferior in patients with high peak leukocyte count (HR = 5.275; 95% CI, 1.9–14.7, P = 0.001) and high WT1 post-maintenance 3 month (HR = 8.241; 95% CI, 2.3–29.1, P = 0.001).
Unfortunately, our chemotherapy regimen was not differently specified for high-risk APL and the standard treatment of APL is now changed to a combination therapy using ATO. Therefore, current results may not be applicable in the treatment course using ATO and another validation is needed. Conclusively, high post-remission WT1 expression is a reliable marker for prediction of subsequent relapse in APL patients treated with conventional chemotherapy. For patients with high-risk of relapse, early intervention using WT1-specific therapy may prevent relapse and improve survival outcomes [8, 9].
This study was supported by the Research Fund of Seoul St. Mary’s Hospital, The Catholic University of Korea, and also supported by a grant from the Basic Science Research Program through the National Research Foundation of Korea (NRF) funded by the Ministry of Education (2015R1D1A1A01059819).
Availability of data and materials
The data of the current study are available from the corresponding author on a reasonable request.
J-HY performed the molecular research, collected and analyzed data, and wrote the manuscript. D-HK, S-SP, B-SC, Y-WJ, S-EL, K-SE, Y-JK, SL, C-KM, S-GC, D-WK, JWL, and W-SM provided patients and materials and reviewed the manuscript. H-JK designed and conducted the study, provided patients and materials, analyzed data, and wrote the manuscript. All authors read and approved the final manuscript.
The authors declare that they have no competing interests.
Consent for publication
The consent for publication is not applicable for this study and is permitted by the Institutional Review Board and Ethics Committee guidelines of the Catholic Medical Center (KC15RISI0862).
Ethics approval and consent to participate
This research was conducted in accordance with the Institutional Review Board and Ethics Committee guidelines of the Catholic Medical Center (KC15RISI0862). Additionally, this research is also permitted and registered in Clinical Research Information Service (CRIS) which is connected to WHO ICTRP; Korea Centers for Disease Control and Prevention, Ministry of Health and Welfare (Republic of Korea); KCT0002079.
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