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Failure to undergo activation-induced cell death due to global dysregulation of apoptosis is the pathogenic hallmark of large granular lymphocyte (LGL) leukemia. Consequently, immunosuppressive agents are rational choices for treatment. This first prospective trial in LGL leukemia was a multicenter, phase 2 clinical trial evaluating methotrexate at 10 mg/m2 orally weekly as initial therapy (Step 1). Patients failing methotrexate were eligible for treatment with cyclophosphamide at 100 mg orally daily (Step 2). The overall response in Step 1 was 38% with 95% confidence interval (CI): 26%, 53%. The overall response in Step 2 was 64% with 95% CI: 35%, 87%. The median overall survival for patients with anemia was 69 months with a 95% CI lower bound of 46 months and an upper bound not yet reached. The median overall survival for patients with neutropenia has not been reached 13 years from study activation. Serum biomarker studies confirmed the inflammatory milieu of LGL but were not a priori predictive of response. We identify a gene expression signature that correlates with response and may be STAT3 mutation driven. Immunosuppressive therapies have efficacy in LGL leukemia. Gene signature and mutational profiling may be an effective tool in determining whether methotrexate is appropriate therapy.

We examined 1229 younger patients with acute myeloid leukemia who achieved CR1 on Eastern Cooperative Oncology Group trials. We defined late relapse as occurring after ≥ 3 years of CR1. With median follow-up of 11.3 years, there were 14 late relapses (1.1% of CR1 patients; 3.3% of 3-year CR1 patients). Eight achieved second CR and median overall survival after late relapse was 3.2 years. Most patients tested (9/11) had a normal karyotype at diagnosis; none had new cytogenetic abnormalities at relapse. Late relapse is rare and nearly all 3-year CR1 patients are cured. If late relapse occurs, outcomes are relatively favorable.

We report a long-term follow-up (median 11.8 years) of the First North American Intergroup Study. 379 patients were randomized to induction with ATRA or to chemotherapy. All complete responders (CR) received consolidation chemotherapy, then randomized to 1 year ATRA or observation. 245 patients received ATRA sometime during the study: 195 (80%) achieved a CR. Nine (4.6%) relapsed late (>3 years from CR), the last occurred after 4.6 years; 7 of them were still alive after 5.5–15 years. In APL patients, late relapses are uncommon, and those who sustain CR >5 years can be considered cured.

Genetic lesions such as BCR–ABL1, E2A–PBX1, and MLL rearrangements (MLLr) are associated with unfavorable outcomes in adult B-cell precursor acute lymphoblastic leukemia (B-ALL). Leukemia oncoproteins may directly or indirectly disrupt cytosine methylation patterning to mediate the malignant phenotype. We postulated that DNA methylation signatures in these aggressive B-ALLs would point toward disease mechanisms and useful biomarkers and therapeutic targets. We therefore conducted DNA methylation and gene expression profiling on a cohort of 215 adult patients with B-ALL enrolled in a single phase III clinical trial (ECOG E2993) and normal control B cells. In BCR–ABL1-positive B-ALLs, aberrant cytosine methylation patterning centered around a cytokine network defined by hypomethylation and overexpression of IL2RA(CD25). The E2993 trial clinical data showed that CD25 expression was strongly associated with a poor outcome in patients with ALL regardless of BCR–ABL1 status, suggesting CD25 as a novel prognostic biomarker for risk stratification in B-ALLs. In E2A–PBX1-positive B-ALLs, aberrant DNA methylation patterning was strongly associated with direct fusion protein binding as shown by the E2A–PBX1 chromatin immunoprecipitation (ChIP) sequencing (ChIP-seq), suggesting that E2A–PBX1 fusion protein directly remodels the epigenome to impose an aggressive B-ALL phenotype. MLLr B-ALL featured prominent cytosine hypomethylation, which was linked with MLL fusion protein binding, H3K79 dimethylation, and transcriptional upregulation, affecting a set of known and newly identified MLL fusion direct targets with oncogenic activity such as FLT3 and BCL6. Notably, BCL6 blockade or loss of function suppressed proliferation and survival of MLLr leukemia cells, suggesting BCL6-targeted therapy as a new therapeutic strategy for MLLr B-ALLs. Significance: We conducted the first integrative epigenomic study in adult B-ALLs, as a correlative study to the ECOG E2993 phase III clinical trial. This study links for the first time the direct actions of oncogenic fusion proteins with disruption of epigenetic regulation mediated by cytosine methylation. We identify a novel clinically actionable biomarker in B-ALLs: IL2RA(CD25), which is linked with BCR–ABL1 and an inflammatory signaling network associated with chemotherapy resistance. We show that BCL6 is a novel MLL fusion protein target that is required to maintain the proliferation and survival of primary human adult MLLr cells and provide the basis for a clinical trial with BCL6 inhibitors for patients with MLLr. Cancer Discov; 2(11); 1004–23. ©2012 AACR. Read the Commentary on this article by Cimmino and Aifantis, p. 976. This article is highlighted in the In This Issue feature, p. 961

Previous small series have suggested that acute myeloid leukemia with t(8;16) is a distinct morphologic and clinical entity associated with poor prognosis. We describe 18 patients with t(8;16) AML, including their clinical, cytomorphologic, immunophenotypic and cytogenetic features. Half of the patients had extramedullary disease, most commonly leukemia cutis, which often preceded bone marrow involvement and six had therapy-related AML. Patients with t(8;16) AML commonly present with clinical and pathological features that mimic APL, with promyelocytes and promyeloblast-like cells and coagulopathy in most patients. Several patients also presented with marrow histiocytes with hemophagocytosis and erythrophagocytosis. Comprehensive molecular analysis for co-occurring genetic alterations revealed a somatic mutation in RUNX1 in 1 of 6 t(8;16) patients with no known AML mutation in the remaining five t(8;16) patients. This suggests that the t(8;16) translocation could be sufficient to induce hematopoietic cell transformation to AML without acquiring other genetic alteration. These data further support classifying t(8;16) AML as a clinically and molecularly defined subtype of AML marked by characteristic clinical and cytomorphologic features that mimic APL, and is associated with very poor survival.

Abstract 132 Late relapse in acute myeloid leukemia (AML) has been infrequently studied and variably defined in the literature. Two series have shown that late relapse of AML ≥5 years after first complete remission (CR1) is uncommon, with rates of 1.19–3% (Medeiros et al, Leuk Lymphoma 2007; Verma et al, Leuk Lymphoma 2010). We searched the long-term data available on 784 adults ( Outcomes We found that 11 patients (1.4%) relapsed late; of these, 2 were treated on E3483, 1 on PC486, 5 on E3489, and 3 on E1900. Seven patients with late relapse died from their disease and 4 were living at last known follow-up. Only 1 patient (0.13%) had recurrence of AML ≥5 years after achieving CR1. It is possible that more late relapses will occur on E1900 (a more recent study with ongoing follow-up). All of these trials except E3483 treated some patients with autologous hematopoietic cell transplantation (autoHCT) as part of post remission therapy. On PC486, no post remission consolidation chemotherapy was administered before autoHCT. Ninety-eight total patients on E3489 and PC486 received autoHCT, and there were no late relapses; on E1900, 2 of the 141 patients treated with autoHCT developed late relapse. No patients who underwent allogeneic (allo) HCT in CR1 experienced late relapse on any of the 4 clinical trials. Nine of the 11 patients with late relapse did not undergo HCT; of these, 5 were consolidated with high-dose cytarabine, 2 received maintenance with low-dose cytarabine and 6-thioguanine, and 2 received unknown post remission therapy. Of the 3 patients with late relapse on E1900, 2 received standard-dose and 1 high-dose daunorubicin with induction. Conclusions Across all 4 trials, only 2 of the 239 patients (0.8%) treated with post remission autoHCT experienced late relapse of AML (≥3 years after CR1), which reinforces previously published data that late relapse after autoHCT is uncommon (Cassileth et al, J Clin Oncol 1993). Furthermore, of the 35 patients treated with autoHCT on PC486, 11 relapsed early and no patients relapsed late, suggesting that post remission chemotherapy may not be necessary before autoHCT. Based on this large AML cohort of nearly 800 patients with long-term follow-up, patients who remain in CCR for at least 3 years have a very low risk of relapse and can be considered cured of their disease. Moreover, given that recurrent AML was extremely rare after 5 years or more of CCR ( Disclosures: No relevant conflicts of interest to declare.

Abstract 83 The European APL91 and the North American Intergroup study I0129 reported in the 1990s that ATRA combined with chemotherapy markedly improves the outcome of APL. Large randomized and single arm studies from around the world with both short and relatively long-term follow-up, confirm this impact of ATRA, while optimizing their mode of administration. However, the incidence and outcome of late relapses have not been well established. Furthermore, as strategies to minimize or eliminate chemotherapy by combining ATRA and arsenic trioxide are being adopted, the long-term durability of ATRA and chemotherapy regimens is even more relevant. We now report on late relapses among the APL patients enrolled in the North American Intergroup study I0129 conducted between 4/92 -2/95. Methods: 380 patients (excluding 14 who had never received ATRA, and 3 ineligible) from 6 cooperative oncology groups, were randomized to induction with either ATRA or chemotherapy with daunorubicin and ara-C (DA). Patients then received two cycles of anthracycline-containing consolidation chemotherapy and then irrespective of their induction arm, patients were randomized to receive 1 year of maintenance with ATRA or observation (Obs) (Tallman et al NEJM 1997). Late relapse was defined as relapse 3 years or later from CR. Data analysis as of March 25, 2011 with a median follow-up of 11.8 (ranges 0.4–14.5) years. Results: Of 191 pts on DA and 189 pts on ATRA induction arms, 85 vs. 116 (total 201) were last known to be alive, median OS 3.6 years (95% CI: 2.0, 8.7) vs. not yet reached (p=0.0007), respectively. CR was achieved in 272 (72%) pts, and 113 are known to have relapsed. In addition, 70 relapsed pts. had received ATRA at any time, of them 60 pts relapsed early and 10 pts. relapsed late; 43 pts relapsed patients did not receive any ATRA and all relapsed early (P=0.01). Follow up information is known so far on 5 late relapses. Relapse sites: BM -4 Pts, CNS – 1pt. Late relapse salvage: chemotherapy-5 pts., alloBMT-2 pts., Auto BMT -1pt., arsenic trioxide –none. Of the 10 late relapses, 3 died, all from disease progression. Median duration in CR1 prior to late relapse: survivors vs. died 3.9 and 4.1yrs, respectively. Only 35 (34%) of the early relapses are alive. Two second malignancies in the breast were identified, all in no known relapse pts. Conclusions: This is among the largest studies with very long follow-up to report that, in newly diagnosed APL patients receiving consolidation chemotherapy, the significantly higher OS rate after induction with ATRA compared to chemotherapy, is sustained. Most relapses in APL occur early, including in patients who had received ATRA at any time. Late relapses after 3 years: 1) are uncommon (4%) and are very rare after 4 years (1); at that time CR1 patients are most likely cured; 2) survive longer than early relapses, independent of CR1 duration, implicating the effectiveness of salvage therapy; 3) do not differ from early relapses in WBC and age at diagnosis; 4) were slightly more likely to be on ATRA maintenance. As the number of long-term APL survivors increases, future studies should address survivorship, late treatment-related complications, and determine whether some late relapses represent new therapy-related AML. Finally, if the high rate of early death (Park et al Blood, 2011) can be reduced, more patients will benefit from the high cure rate reported by this and other studies. Disclosures: No relevant conflicts of interest to declare.