Clinical Outcomes of Adult Patients With Newly Diagnosed Mixed Phenotype Acute Leukemia.

[PURPOSE] Mixed phenotype acute leukemia (MPAL) is a rare clinical entity with historically poor outcomes.

[METHODS] We conducted a retrospective analysis of adults 18 years and older with newly diagnosed B-cell (B/M) or T-cell/myeloid (T/M) MPAL treated at our institution between 2017 and 2024.

[RESULTS] We identified 42 patients (median age 70 years); 20 (48%) had B/M MPAL, and 22 (52%) had T/M MPAL; 57% of patients had adverse risk cytogenetics, and 41% had a mutation. Sixty-two percent of patients were treated with a hybrid regimen, and 45% of patients received intensive therapy. A composite complete remission (CRc; CR + CRi) was achieved in 57% of patients (86% measurable residual disease [MRD]-negative). After a median follow-up of 27.9 months, the median relapse-free survival in patients achieving an overall response (CRc + morphological leukemia-free state) was 10.1 months, 17.8 months in those who achieved a CRc, and not reached (NR) in patients with MRD-negative CRc. The median overall survival (OS) for all patients was 9.5 months and NR for patients achieving a CRc. Although patients with T/M MPAL had a trend toward improved survival compared with those with B/M MPAL (median OS of 9.1 25 months = .28), this difference abrogated when comparison was stratified by treatment intensity. Twelve patients (29%) underwent allogeneic hematopoietic stem-cell transplantation (HSCT); on landmark analysis, HSCT trended to improve OS (NR 22.8, = .12). Multivariate Cox analysis demonstrated that mutation was associated with increased hazards for death (hazard ratio [HR], 3.5, = .01), whereas the use of intensive chemotherapy trended to be favorable (HR, 0.45, = .11).

[CONCLUSION] Overall, these data demonstrate the need for treatment intensification in MPAL with HSCT in first remission for best outcomes.