Achar, Rohan

Background: Hypomethylating agent (HMA) and venetoclax (Ven) frontline therapy for acute myeloid leukemia (AML) is astandard of care for patients (pts) deemed to be poor candidates for intensive induction due to age or fitness. However, given its attractive risk-benefit ratio, there is an increasing interest to extend the preference for HMA + Ven to other pts, including those who are fit for intensive therapy but with adverse risk disease. Unfortunately, most pts treated in this fashion will require future therapies for relapsed/refractory (R/R) disease and intensive therapy is given consideration mostly for pts with a path to allogeneic hematopoietic stem cell transplantation (alloHCT). Little is known about the outcomes of pts who receive intensive induction therapy after use of a frontline less-intensive regimen in the modern era. In this multi-center study, we seek to describe the experience with such a patient population and identify predictors of differential clinical outcomes. Methods: We conducted a multi-center, retrospective study of pts with AML treated with frontline less-intensive chemotherapy, followed by intensive induction chemotherapy for R/R disease. We first described the baseline characteristics of this cohort. Nominal variables were summarized with frequency and percentage while continuous variables were summarized with median and interquartile range (IQR). Overall response rate (ORR) was defined as complete remission (CR), complete remission with incomplete count recovery, or morphologic leukemia free state. Differences in ORR were analyzed with Fisher's exact test for nominal variables and Wilcoxon rank-sum test was used for continuous variables. Kaplan-Meier analysis was used to determine median overall survival (OS) after induction chemotherapy. Log-rank testing and Cox proportional hazard models were used to determine survival differences for nominal and continuous variables, respectively. Statistical significance was determined as p-value <0.05. Results: A total of 23 pts were included in this study. Median age at diagnosis was 64 years (IQR: 62-71). The majority of pts were male (n=12, 52%), white (n=20, 87%), and had an Eastern Cooperative Oncology Group performance status (ECOG PS) of 0 or 1 (n=18, 82%). The majority of pts (61%) at time of frontline therapy had AML arising out of MDS. As expected, the majority of pts had adverse risk ELN cytogenetics (n=16, 70%) with an enrichment for disease harboring TP53 mutation (n=6, 27%) and complex karyotype (n=9, 39%). Fifteen pts (65%) had frontline therapy with azacitidine backbone, 6 pts (26%) with decitabine; some pts received both before intensive therapy. The median number of cycles of frontline therapy was 2 (IQR: 2-5). Median WBC at time of R/R therapy was 1.9 x 10 9/L (IQR: 0.8-6.45), while hemoglobin was 8.4 g/dL (IQR: 7.5-9.45), platelets were 41 x 10 9/L (IQR: 19.5-116.5), and marrow blasts were 25% (IQR: 16.5-30%). The plurality of pts received CPX-351 as intensive R/R therapy (n=9, 39%). Other regimens included 7+3 (n=2, 9%), FLAG-Ida + Ven (n=2, 9%), HiDAC + Mitoxantrone +/- Ven (n=4, 17%) ( Table 1). ORR after intensive R/R therapy was 27% (n=6), with 23% achieving CR. CPX-351 after HMA + Ven was specifically associated with an ORR of 33% (CR rate 22%). Median OS after initiation was 5.8 months. Thirty- and 60-day mortality was 17% and 26%, respectively. Five patients (23%) proceeded to alloHCT ( Table 1). Univariate differences in response rate and median survival were analyzed for each of the aforementioned variables as illustrated in Table 1. While none of the covariates reached statistical significance for impacting ORR or OS, ECOG PS trended towards significantly impacting OS ( p=0.074) and the median OS among patients proceeding to alloHCT was numerically doubled (8.0 vs. 4.0 months, p=0.11) ( Figure 1). Conclusions: Intensive therapy for R/R AML after prior frontline less-intensive therapy was associated with an ORR rate of 27% and median OS of 5.8 months in our cohort. This approach may be an appropriate strategy for a subset of pts, particularly those eligible for alloHCT. The relatively small and heterogeneous nature of this cohort limits strong conclusions regarding efficacy. As the use of frontline HMA + Ven continues to expand, further studies with larger sample size are needed to determine which pts would and would not benefit from intensive induction therapy in the R/R setting.

Background: Core-binding factor acute myeloid leukemia (CBF-AML) is characterized by the presence of inv(16)/t(16;16) or t(8;21), and is classified as favorable risk by the 2022 European LeukemiaNet (ELN) guidelines. High remission rates are observed in the setting of cytarabine- or anthracycline-based induction regimens. The CD33-targeted antibody-drug conjugate gemtuzumab ozogamicin (GO) is FDA-approved for use in newly-diagnosed CD33+ AML; a meta-analysis of 5 prospective randomized studies investigating intensive chemotherapy (IC) +/- GO demonstrated an improved overall survival (OS) with the addition of GO to IC for favorable-risk AML (Hills et al, Lancet Oncol 2014). The trials included in the meta-analysis did not restrict inclusion criteria to CBF-AML alone and there remains variation amongst IC regimens utilized in CBF-AML treatment. In addition, IC combined with the KIT inhibitor dasatinib has shown remission rates and promising overall survival in prospective studies (Paschka et al, Leukemia 2018; Marcucci et al, Blood Adv 2020). We set out to investigate the outcomes of patients (pts) with CBF-AML treated with IC +/- targeted agents (GO or KIT inhibitor) across 5 institutions that are part of the Consortium on Myeloid Malignancies and Neoplastic Diseases (COMMAND). Methods: Retrospective chart review was done to identify pts who were treated with IC with AML harboring inv(16)/t(16;16) or t(8;21) identified on cytogenetics, from January 2010 through April 2023, and were treated across 5 geographically-diverse academic institutions. Pt clinical characteristics, cytogenetics, molecular mutations, treatment, relapse, and OS data were collected. Relapse-free survival (RFS) and OS were both analyzed using Kaplan-Meier analysis. Results: One-hundred forty-nine consecutive pts with CBF-AML were identified, 76 (51%) with inv(16) and 73 (49%) with t(8;21). Median age of pts was 47 years (yrs) (range 18-80yrs), with 64% male pts, and 106 (71%) pts had an ECOG performance status of 0-1. One-hundred seven (72%) pts identified as non-Hispanic White, 22 (15%) identified as non-Hispanic Black, and 12 (8%) identified as Hispanic. Molecular testing via next-generation sequencing was available for 124 pts (83%); 49 (33%) pts had adverse-risk ELN cytogenetics or mutations when excluding CBF status, and 27 (18%) pts harbored KIT mutations. Other baseline pt characteristics are listed in Table 1A. All pts underwent induction with IC; 44 (30%) pts received IC + GO, 21 (14%) received IC + KIT inhibitor (14 received dasatinib, 7 received midostaurin), and the remaining 84 (56%) received IC without a targeted agent. One-hundred fourteen (77%) pts achieved a complete response (CR) to induction therapy, and 1 pt experienced induction-related mortality. Fluorescence in-situ hybridization (FISH) data was available in 82 pts at end of induction with 83% achieving FISH negativity. Measurable residual disease (MRD) testing was done by polymerase chain reaction (PCR) in 62 pts with 76% achieving MRD-negativity. One-hundred forty pts underwent consolidation with a median of 3 cycles of chemotherapy; 21 (15%) pts received GO with consolidation and 17 (12%) received a KIT inhibitor with consolidation. Forty-four (30%) pts underwent allogeneic stem cell transplantation (alloSCT), with 17 in first CR, and 27 after second-line or beyond therapy. With a median follow-up of 22.5 months, the observed 3-yr RFS was 51% (95% CI: 43-61%) and the 3-yr OS was 69% (95% CI: 61-78%). Pts treated with IC + KIT inhibitor had significantly improved 3-yr RFS of 85% (95% CI: 70-100%) compared to other pts, including those who received IC + GO who had a 3-yr RFS of 51% (95% CI: 37-70%) and those who received IC without targeted therapy who had a 3-yr RFS of 45% (95% CI: 35-58%) ( p = 0.02) ( Figure 1). Full survival statistics are shown in Table 1B and Figure 1. Conclusions: In this multi-center retrospective study of pts with CBF-AML undergoing induction with IC regimens with diverse national treatment practices, we find that the addition of GO to IC is not associated with improved outcomes. Pts treated with IC + KIT inhibitor had significantly improved RFS; of note, pts receiving a KIT inhibitor oftentimes continued on maintenance even after consolidation. These data suggest that there may be a role for targeted therapies other than GO to be explored in randomized prospective studies of intensive induction chemotherapy for CBF-AML.

Background: Core-binding factor acute myeloid leukemia (CBF-AML) is characterized by the presence of inv(16)/t(16;16) or t(8;21), and is classified as favorable risk by the 2022 European LeukemiaNet (ELN) guidelines. High remission rates are observed in the setting of cytarabine- or anthracycline-based induction regimens. However, for the subset of patients (pts) who relapse, outcomes after relapse were poor in prior single-center analysis with median survival of less than 1.5 years (Khan et al. Clin Leuk Lymph Myeloma 2017). There remains a need to better understand outcomes of pts who experience relapse after initial complete remission (CR), particularly after diverse intensive chemotherapy (IC) induction regimens, where variable practices show differential induction outcomes. We set out to investigate the outcomes of pts with CBF-AML in first relapse or with disease refractory to initial therapy, across 5 institutions that are part of the Consortium on Myeloid Malignancies and Neoplastic Diseases (COMMAND). Methods: Retrospective chart review was done to identify pts who were treated with intensive IC with inv(16)/t(16;16) or t(8;21) identified on cytogenetics, from January 2010 through April 2023, with disease in first relapse after initial CR or refractory to primary induction. Pts were treated across 5 geographically-diverse, academic institutions. Pt clinical characteristics, cytogenetics, molecular testing via next-generation sequencing (NGS), treatment, relapse, and overall survival (OS) data were collected. OS since time of disease relapse was analyzed using Kaplan-Meier analysis. Results: Fifty-four consecutive pts with relapsed/refractory (R/R) CBF-AML were identified, 24 (44%) with inv(16) and 30 (56%) with t(8;21). Median age of pts at initial diagnosis was 50 years (yrs) (range 20-80yrs), with 61% male pts. Molecular testing and/or NGS was available at initial diagnosis for 41 pts (76%); 12 (22%) pts had adverse-risk ELN cytogenetics or mutations when excluding CBF status, and 8/41 (20%) pts harbored KIT mutations. Other baseline pt characteristics are listed in Table 1. All pts underwent induction with IC; 14 (26%) pts received intensive induction with gemtuzumab ogozamicin (GO), 3 (6%) received intensive induction with a KIT inhibitor (dasatinib or midostaurin), and the remaining 37 (68%) received IC induction without a targeted agent. Forty-one (76%) pts achieved a CR to induction therapy. Measurable residual disease (MRD) testing by polymerase chain reaction (PCR) and/or fluorescence in situ hybridization (FISH) for CBF protein was available in 30 (56%) pts, with 16/21 (76%) achieving MRD-negativity by PCR and 20/26 (77%) by FISH. Forty-six pts underwent consolidation with a median of 4 cycles of chemotherapy (IQR 3-4), with 9 (17%) pts receiving GO with consolidation and 4 (7%) receiving a KIT inhibitor with consolidation. Median time to relapse was 10.1 months (IQR 8.0-13.6 months), and median OS after relapse was 9.2 months (IQR 4.4-22.1 months) for the whole cohort. Second line treatment data was available for 44 pts, with 29 (66%) receiving intensive 2nd line therapy vs 15 (34%) receiving lower intensity 2nd line therapy; 14 (32%) pts received venetoclax as part of their 2nd line therapy. There was no significant difference in 2-yr OS after relapse for those who received IC (50%, 95% CI: 34-72%) vs lower intensity therapy (24%, 95% CI: 8-72%) ( p=0.28) (Figure 1A). Twenty-eight (52%) pts who received 2nd line therapy for R/R disease proceeded to allogeneic stem cell transplantation (alloSCT), with a 2-yr OS of 57% (95%CI: 40-80%) for this group after time of relapse, compared to 15% (95% CI: 5-42%) for those who did not achieve CR after 2ndline therapy and/or proceed to transplant ( p<0.01) (Figure 1B). Conclusions: In this multi-center retrospective study of pts with R/R CBF-AML, we describe patterns of relapse after intensive induction chemotherapy, and do not observe a statistically difference in outcomes based on intensity of 2nd line therapy among pts with available treatment information. Median OS in the entire cohort was 9.2 months from diagnosis of R/R disease. Pts who proceeded to alloSCT after receiving 2nd line therapy had significantly improved long-term outcomes compared to those who did not proceed to alloSCT, highlighting the need for better therapies in the 2nd line and beyond to improve longer term outcomes for pts with CBF-AML.