Citations

Abstract The dismal outcome of acute leukemia undergoing immunophenotype-switch, compounded by the increased incidence in the era of immunotherapy, highlights the need for in-depth systemic studies. We investigated the clinicopathological, cytogenetic, and molecular features of 33 patients experiencing switch between acute lymphoblastic leukemia (ALL) and acute myeloid leukemia (AML). The median duration from the primary diagnosis to lineage switch was 7.8 months, with the subsequent median survival being < 3 months. The majority experienced a transition from B-ALL to AML. The AML cases demonstrated a spectrum of differentiation, ranging from minimal to erythroid, with monocytic being the most common. Cytogenetic analysis revealed 11q23/KMT2A fusions as the most recurrent abnormalities (n = 18); also observed were complex karyotype, 7/7q-, 9p-/CDKN2A deletion, t(5;14)/TCLX3::BCL11b, t(8;9)/PCM1::JAK2, t(9;22)/BCR::ABL1, and t(12;19)/TCF3::ZNF384. Remarkably, in 60% of patients lacking KMT2A fusions, a chronic myeloid neoplasm was observed preceding the first leukemia. In contrast, no prior hematological malignancies were observed in KMT2A cases. Deep mutational profiling reinforced the inherent clonal relationship between the initial and subsequent leukemias, evident from the overlapping mutational signatures. The presence of distinct additional mutations across the two phases supports the long-standing theory of lineage switch emerging via divergent evolution of a multipotential progenitor.

Abstract Objectives Fluorescence in situ hybridization (FISH) for plasma cell neoplasms (PCNs) requires plasma cell (PC) identification or purification strategies to optimize results. We compared the efficacy of cytoplasmic immunoglobulin FISH (cIg-FISH) and fluorescence-activated cell sorting FISH (FACS-FISH) in a clinical laboratory setting. Methods The FISH analysis results of 14,855 samples from individuals with a suspected PCN subjected to cytogenetic evaluation between 2019 and 2022 with cIg-FISH (n = 6917) or FACS-FISH (n = 7938) testing were analyzed. Results Fluorescence-activated cell sorting–FISH increased the detection rate of abnormalities in comparison with cIg-FISH, with abnormal results documented in 54% vs 50% of cases, respectively (P &lt; .001). It improved the detection of IGH::CCND1 (P &lt; .001), IGH::MAF (P &lt; .001), IGH::MAFB (P &lt; .001), other IGH rearrangements (P &lt; .001), and gains/amplifications of 1q (P &lt; .001), whereas the detection rates of IGH::FGFR3 fusions (P = .3), loss of 17p (P = .3), and other abnormalities, including hyperdiploidy (P = .5), were similar. Insufficient PC yield for FISH analysis was decreased between cIg-FISH and FACS-FISH (22% and 3% respectively, P &lt; .001). Flow cytometry allowed establishment of ploidy status in 91% of cases. In addition, FACS-FISH decreased analysis times, workload efforts, and operating costs. Conclusions Fluorescence-activated cell sorting–FISH is an efficient PC purification strategy that affords significant improvement in diagnostic yield and decreases workflow requirements in comparison with cIg-FISH.

12057 Background: AlthoughCLL primarily affects older adults (median age 71 years), limited data exists about the outcomes of adults who are ≥80 years old because they are under-enrolled on clinical trials. Methods: The Mayo Clinic CLL Database was used to conduct a retrospective cohort study of adults ≥80 years at the time of frontline CLL treatment. Kaplan-Meier analysis was used to plot OS, and cumulative incidence was used to plot TTNT, accounting for competing risk of death. The Mayo Clinic IRB approved the study. Results: Our study included 216 patients with CLL who were age ≥80 years at the time of frontline CLL therapy between 1/1995 and 11/2022 (Table). The median time from CLL diagnosis to initiation of frontline therapy was 3.1 years. The median OS after start of frontline therapy was 3.9 years. The median OS was 3.3 years (95% CI 2.6–4.2) for patients who received alkylating agents (e.g., chlorambucil, n=96), 3.8 years (95% CI 2.8–not reached [NR]) for purine analogues (e.g., fludarabine, n=11), 3.9 years (95% CI 3.2–4.9) for anti-CD20 monoclonal antibody monotherapy (e.g., obinutuzumab, n=64), and not reached (95% CI 3.3-NR) for novel agents (n=43) (P=0.02). The types of novel agents included ibrutinib (n=19), acalabrutinib (n=16), venetoclax (n=7), and orelabrutinib (n=1). There was no difference in OS between 36 patients who received a BTKi compared to the 7 patients who received venetoclax-based therapy. At a median follow-up time of 6.7 years from the first visit, 143 patients died from the following: progressive CLL (n=63), infections (n=12), other cancer (n=11), non-CLL reasons (n=21). Cause of death was unavailable for 36 patients. On multivariable analyses, older age (i.e., any 5-year increase in age) was associated with a 50% increased risk of death (HR 1.5, 95% CI 1.2-1.9, p=0.001), and treatment with non-novel agents was associated with 3.2 times increased risk of death (HR 3.2, 95% CI 1.2-8.9, p=0.02). Of the 216 patients, 76 patients required second-line therapy; the median TTNT was 4.2 years (95% CI 2.9-NE). The most used second-line agents were monoclonal antibodies alone (20/76, 26%) and single-agent alkylators (18/76, 24%). Conclusions: When compared to all other CLL treatments, novel agents such as BTKi and venetoclax-based treatments are associated with significantly improved OS in patients with CLL ≥80 years old when used in the frontline setting. [Table: see text]

Abstract Tγδ large granular lymphocyte leukemia (LGLL) is a rare variant of T-cell LGLL (T-LGLL) that has been less investigated as compared with the more frequent Tαβ LGLL, particularly in terms of frequency of STAT3 and STAT5b mutations. In this study, we characterized the clinical and biological features of 137 patients affected by Tγδ LGLL; data were retrospectively collected from 1997 to 2020 at 8 referral centers. Neutropenia and anemia were the most relevant clinical features, being present in 54.2% and 49.6% of cases, respectively, including severe neutropenia and anemia in ∼20% of cases each. Among the various treatments, cyclosporine A was shown to provide the best response rates. DNA samples of 97 and 94 cases were available for STAT3 and STAT5b mutation analysis, with 38.1% and 4.2% of cases being mutated, respectively. Clinical and biological features of our series of Tγδ cases were also compared with a recently published Tαβ cohort including 129 cases. Though no differences in STAT3 and STAT5b mutational frequency were found, Tγδ cases more frequently presented with neutropenia (P = .0161), anemia (P &lt; .0001), severe anemia (P = .0065), and thrombocytopenia (P = .0187). Moreover, Vδ2− cases displayed higher frequency of symptomatic disease. Overall, Tγδ cases displayed reduced survival with respect to Tαβ cases (P = .0017). Although there was no difference in STAT3 mutation frequency, our results showed that Tγδ LGLL represents a subset of T-LGLL characterized by more frequent symptoms and reduced survival as compared with Tαβ LGLL.

Anaplastic large cell lymphoma (ALCL) can be classified genetically based on rearrangements (R) of the ALK, TP63, and/or DUSP22 genes. ALK-R defines a specific entity, ALK-positive ALCL, while DUSP22-R and TP63-R define subgroups of ALK-negative ALCLs with distinct clinicopathologic features. ALK-R and TP63-R produce oncogenic fusion proteins that can be detected by immunohistochemistry. ALK immunohistochemistry is an excellent surrogate for ALK-R and screening with p63 immunohistochemistry excludes TP63-R in two third of ALCLs. In contrast, DUSP22-R does not produce a fusion protein and its identification requires fluorescence in situ hybridization. However, DUSP22-R ALCL has a characteristic phenotype including negativity for cytotoxic markers and phospho-STAT3Y705. Recently, we also identified overexpression of the LEF1 transcription factor in DUSP22-R ALCL. Here, we sought to validate this finding and examine models for predicting DUSP22-R using immunohistochemistry for LEF1 and TIA1 or phospho-STAT3Y705. We evaluated these 3 markers in our original discovery cohort (n=45) and in an independent validation cohort (n=46) of ALCLs. The correlation between DUSP22-R and LEF1 expression replicated strongly in the validation cohort (P<0.0001). In addition, we identified and validated a strategy using LEF1 and TIA1 immunohistochemistry that predicted DUSP22-R with positive and negative predictive values of 100% after exclusion of indeterminate cases and would eliminate the need for fluorescence in situ hybridization in 65% of ALK-negative ALCLs. This approach had similar results in identifying DUSP22-R in the related condition, lymphomatoid papulosis. Together with previous data, these findings support a 4-marker immunohistochemistry algorithm using ALK, LEF1, TIA1, and p63 for genetic subtyping of ALCL.

Abstract Objectives Patients with clonal cytopenia of undetermined significance (CCUS) are at increased risk of developing myeloid neoplasia (MN). We evaluated whether a simple flow cytometry immunophenotyping (FCIP) assay could differentiate the risk of development of MN in patients with CCUS. Methods Bone marrow aspirates were assessed by FCIP panel in a cohort of 80 patients identified as having CCUS based on next-generation sequencing or cytogenetics from March 2015 to May 2020, with available samples. Flow cytometric assay included CD13/HLA-DR expression pattern on CD34-positive myeloblasts; CD13/CD16 pattern on maturing granulocytic precursors; and aberrant expression of CD2, CD7, or CD56 on CD34-positive myeloblasts. Relevant demographic, comorbidity, and clinical and laboratory data, including the type and extent of genetic abnormalities, were extracted from the electronic health record. Results In total, 17 (21%) patients with CCUS developed MN over the follow-up period (median survival follow-up, 28 months [95% confidence interval, 19-31]). Flow cytometry immunophenotyping abnormalities, including the aberrant pattern of CD13/HLA-DR expression, as detected at the time of the diagnosis of CCUS, were significantly associated with risk of developing MN (hazard ratio, 2.97; P = .006). Additional FCIP parameters associated with the development of MN included abnormal expression of CD7 on myeloblasts and the presence vs absence of any FCIP abnormality. Conclusions A simple FCIP approach that includes assessment of CD13/HLA-DR pattern on CD34-positive myeloblasts can be useful in identifying patients with CCUS at higher risk of developing MN.