Abstract
Introduction: The MLL gene on located on 11q23 plays an essential role in positive regulation of gene expression in early embryonic development and hematopoiesis. Fusion genes, such as MLL-AF4 resulting from t(4:11)(q21;q23), alter normal cellular proliferation and differentiation, favoring leukemogenesis. The DOT1L histone methyltransferase associated with MLL appears to be required for maintenance of ALL. MLL-AF4 is detected in about 10% of de novo B-lymphoblastic leukemia or 30=40% of pro-B ALL subtypes. The 11q23/MLL subtype of ALL has been associated with extremely poor outcomes. We conducted a retrospective analysis of de novo adult ALL with 11q23/MLL gene rearrangements.
Methods: Overall the database included 74 pts with 11q23/MLL gene rearrangements referred to our institution between 1980 and 2014. Of these, 20 (27%) pts were relapsed/refractory, 4 (5%) were minimally pretreated, 5 (7%) were inevaluable for response, 3 (4%) had concomitant Philadelphia chromosome, 2 (3%) were T-lineage, 2 (3%) were mature B-ALL. The remaining 38 cases comprised the study cohort evaluated with respect to pretreatment characteristics and outcome measures such as response to therapy, remission duration (CRD), and survival (OS).
Results: Baseline characteristics of the cohort included median age 44 yrs (range, 20-75); 26% were older than 60 yrs. Ten (26%) pts had a prior malignancy and were designated secondary ALL. Five (13%) pts had CNS disease at presentation. Median WBC count was 69.8 K/uL (range, 0.5-612); 24 (63%) pts had WBC > 30 K/uL. Nineteen (50%) pts had serum LDH > 1400 U/L. Co-expression of myeloid markers (CD13, CD33 +/- CD117) was noted in 6 (16%) pts. Distribution of the 11q23/MLL gene aberrancies were: t(4;11) (q21; q23) in 25 (66%) pts, 11q23 without translocation partner in 10 (26%) pts, and t(11;19)(q23;p13.1) in 3 (8%) pts. Thirty two (84%) pts were treated per the hyper-CVAD (cyclophosphamide, vincristine, doxorubicin, dexamethasone alternating with high dose methotrexate and cytarabine) regimen (3 [10%] received concurrent rituximab) and 6 (16%) pts were treated per the augmented BFM regimen. Overall response rate was 95%; complete remission (CR) in 92% and CR without platelet recovery (CRp) in 3%. Overall median CRD was 26.3 mos (range 0.2-93+ mos); median OS was 24.2 mos. Overall, the 5-yr CRD and OS rates were 19% and 26%, respectively, with a median follow-up of 60 mos (range, 4.8-173+ mos). Median OS in pts with 11q23 without chromosomal translocation was 48.5 mos, compared with 24 mos for t(11; 19) and 13.3 mos for t(4; 11) (p= 0.07) (Fig. 1). There were no differences in outcomes by older age or designation as secondary ALL.
Conclusion: The 11q23/MLL positive B-lymphoblastic subsets are associated with differentially inferior outcomes, although MLL-AF4 remains the ALL subset associated with highest risk of disease recurrence particularly in the absence of allogeneic stem cell transplantation; the relatively rarity of these subsets poses challenges in establishing the optimal treatment strategies. Therapeutic approaches incorporating hypomethylating agents, histone deacetylase inhibitors, and CAR-T cells could improve these dismal outcomes; targeted agents such as DOT1L inhibitors are under investigation in clinical trials.
No relevant conflicts of interest to declare.
This feature is available to Subscribers Only
Sign In or Create an Account Close Modal