Prognostic Significance of Wilms’ Tumor 1 Gene Mutations in Acute Myeloid Leukemia: Risk Stratification and Survival Outcomes

Introduction: Acute myeloid leukemia (AML) is a heterogeneous hematologic malignancy characterized by diverse cytogenetics and molecular profiles. This underlying biological heterogeneity results in heterogeneous clinical outcomes. The European LeukemiaNet risk stratification scheme (ELN22) incorporates mutations and cytogenetic data to risk stratify AML. However, additional heterogeneity remains in ELN22 defined subgroups. Wilms’ tumor 1 (WT1) gene mutations account for nearly 10-15% of mutations in AML and have differing outcomes, according to various reports. This mutation is not included in ELN22 for risk stratification. Here, we describe the outcome of WT1 mutations in a cohort of adult AML risk stratified as per ELN22.

Methods: A total of 506 adult de novo AML patients (≥18 years) were accrued over 10 years (2012-2023) who were treated with ‘3+7’ induction therapy. The median follow-up was 29.5 months. Diagnostic samples were sequenced using a 50 gene myeloid panel (till 2020) based on single molecule molecular inversion probes and subsequently using a 135 gene hybrid capture-based panel. All cases (n=506) were stratified in accordance with ELN22 guidelines. As per WT1 gene mutation (WT1^{wild type} or WT1^mut) status, ELN22 risk category was further stratified into six groups: Group1 (49.40%, n=250): ELN22 Favorable/WT1^{wild type}, Group2 (5.1%, n=26): ELN22 Favorable/WT1^mut, Group3 (24.15%, n=122): ELN22 Intermediate/WT1^{wild type}, Group4 (5.5%, n=28): ELN22 Intermediate/WT1^mut, Group5 (13%, n=66): ELN22 Adverse/WT1^{wild type} and Group6 (2.7%, n=14): ELN22 Adverse/WT1^mut. At the post-induction (PI) time period, measurable residual disease (MRD) was assessed using a 10 or 16 color flow cytometry (MFC MRD). The prognostic impact on overall survival (OS) and relapse-free survival (RFS) was computed using the Kaplan-Meier method and compared using log-rank test. Multivariable Cox proportional hazard models were used for survival endpoints.

Results: Of the 506 patients, 13.4% (n=68) were WT1^mut at the diagnostic time point and the remaining 86.6% (n=438) were WT1^{wild type}. No significant difference in age and WBC count was observed between WT1^mut and WT1^{wild type}. The median OS of WT1^mut patients was shorter compared to WT1^{wild type} (29.3 vs 85.9 months; p = 0.01). Similarly, median RFS of WT1^mut patients was shorter compared to WT1^{wild type} (24.60 vs 63.81 months; p = 0.0013). WT1^mut were more likely to harbor MFC-MRD as compared to WT1^{wild type} AML (p = 0.05). WT1^mut AML was most commonly associated with FLT3-ITD (32.3%) followed by in-frame bzip CEBPA (19.1%), NPM1 (16.1%), NRAS (16.1%), GATA2 (13.2%), RUNX1 (11.7%), FLT3-TKD (10.2%), RAD21 (10.2%), TET2 (8.8%), CSF3R (7.3%). No survival difference was found amongst WT1^mut cases, with or without FLT3-ITD mutation (OS; p= 0.29, RFS; p = 0.66). Of the total cases (n=506), the majority of patients were stratified as ELN22 favorable (54.5%) and the rest as intermediate (29.4%) and adverse risk (15.8%). ELN22 adverse risk patients had inferior OS [HR: 3.2; 95% CI: 2.0 - 5.0; p <0.0001] and RFS [HR: 2.7; 95% CI: 1.4 - 5.5; p = 0.0002] compared to favorable risk. Similarly, patients classified as ELN22 intermediate risk had inferior OS [HR: 1.7; 95% CI: 1.2 - 2.4] and RFS [(HR: 1.3; 95% CI: 0.9 - 1.9] as compared to favorable risk. On further stratification of ELN22 risk groups based on WT1 gene mutation status, Group 4 had significantly inferior OS compared to Group 3 (HR: 2.1%, 95% CI: 1.0 to 4.3, p = 0.01). Group 4 (ELN22-Intermediate/WT1^mut) had a similar median OS compared to ELN22 adverse risk (p = 0.90). Shorter RFS was observed in Group 4 compared to Group 3 (HR: 2.6%, 95% CI: 0.73 to 9.3, p = 0.02) and also in Group 2 compared to Group 1 (HR: 2.1%, 95% CI: 1.0 to 4.5, p =0.02). On multivariate analysis, ELN22 adverse risk [HR: 2.9; 95% CI: 1.73 to 5.05; p = 0.0001], intermediate risk [HR: 1.6; 95% CI: 1.06 to 2.5; p = 1.6] and PI MFC MRD [HR: 1.5; 95% CI: 1.1 to 2.1; p = 0.005] were significantly associated with shorter OS; while WT1 mutation status had no impact (p= 0.15). For RFS, WT1 mutation status (HR: 2.15; 95% CI: 1.36 to 3.40; p = 0.001) and ELN22 adverse risk (HR: 2.75; 95% CI: 1.66 to 4.5; p = 0.0001) were independent poor prognostic factor.

Conclusion: WT1 gene mutation had a significant prognostic impact on de novo adult AML patients treated with ‘3+7’ therapy. Incorporation of WT1 gene mutation in ELN22 may aid in better risk stratification of these patients.