This week in Hematology

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Welcome to This Week in Hematology. This week we're covering 10 notable papers spanning FLT3 biology and biomarkers in acute myeloid leukemia, transplantation and complement-driven disease, and treatment selection in lymphoma. Let's dive in.

We start with acute myeloid leukemia, where three papers ask how much we can learn from a mutation or a simple blood test. In Haematologica, Montesinos and colleagues report post hoc analyses of patients aged 60 and older from QuANTUM-First, the trial that established quizartinib added to intensive chemotherapy and as maintenance for newly diagnosed FLT3-ITD positive disease [1]. Among roughly two hundred older patients, median survival was about 17 and a half months with quizartinib versus about 14 with placebo, but that difference was not statistically convincing. Remission rates were essentially identical, near 55 percent, while relapse at two years was somewhat lower and remission duration numerically longer with quizartinib. The signal looked strongest in patients carrying both NPM1 and DNMT3A mutations, with median survival around 22 months versus about 10. Gastrointestinal side effects and slower count recovery were more common. Because these are unplanned subgroup analyses, they generate hypotheses rather than confirm benefit in older adults. A companion question comes from the American Journal of Hematology, where Gurnari and colleagues, on behalf of an EHA working group, studied FLT3-ITD microclones, meaning an allelic ratio below 0.05 [2]. Capillary electrophoresis and next-generation sequencing largely agreed, missing only three tiny clones. Among 658 patients, about a third of the cohort carried microclones, and these patients were older, more often had secondary-type disease and myelodysplasia-related mutations, and reached remission less often with intensive chemotherapy, about 74 percent versus 88. Yet allelic ratio itself did not independently predict disease-free survival once age, NPM1 status and transplant were accounted for. Notably, just under half of evaluable patients remained FLT3-ITD positive at relapse, many with an expanded microclone, which the authors see as a rationale for randomized testing of FLT3 inhibitors in this group. Rounding out the theme, the British Journal of Haematology carries a biomarker analysis led by Stomper from the EORTC AML21 phase 3 trial [3]. In fit older patients given 10-day decitabine, a rise in fetal hemoglobin between baseline and day 10 was associated with roughly two and a half times the odds of complete remission, although it did not translate into a significant survival difference, and baseline fetal hemoglobin predicted nothing. It is an inexpensive early marker, but one that so far tracks response rather than survival.

Our second theme is allogeneic transplantation, extending curative intent to patients without ideal donors or regimens. In Blood Advances, Walters and colleagues report BMT CTN 1507, a multicenter single-arm phase 2 trial of reduced-intensity haploidentical marrow transplant for children with severe sickle cell disease [4]. Of 41 children enrolled across 18 sites, 39 proceeded to transplant, most with donors mismatched at four HLA loci, and about seven in ten were transplanted for a neurological event, including 15 with overt stroke. The regimen used hydroxyurea pre-conditioning, low-dose total body irradiation, and post-transplant cyclophosphamide. Two-year event-free survival was about 79 percent and overall survival about 95 percent. Lung function improved, renal hyperfiltration resolved, and no new or progressive cerebral infarcts appeared among the 22 children with serial imaging. Graft failure and graft-versus-host disease were the main drags on event-free survival. This is single-arm evidence, but it strengthens the case for haploidentical transplant in children lacking a matched sibling. Also in Blood Advances, Avenoso and colleagues compared fludarabine-treosulfan with fludarabine-melphalan conditioning in 967 adults with acute lymphoblastic leukemia in a registry analysis [5]. After adjustment, treosulfan was associated with roughly 40 percent lower relapse risk and identical non-relapse mortality, but no significant difference in overall or leukemia-free survival, and the relapse benefit appeared confined to B-cell disease. The groups differed in era, donor type and remission status, so the authors frame treosulfan as a reasonable alternative pending prospective validation.

Our third theme links marrow failure and complement, from diagnosis to resistance. In Blood, de Jong and colleagues addressed a familiar dilemma in pediatric severe aplastic anemia: whether to wait for germline genetic results before treating [6]. In 149 children with full clinical data, about three quarters of patients had no clinical or laboratory hint of an inherited marrow failure syndrome, and none of those children carried a diagnostic variant on enhanced exome sequencing. Among the remaining children with suggestive features, only one had a confirmed diagnosis, a SAMD9L variant, and one more had possible ERCC6L2 disease. This retrospective work suggests the yield of genetic testing after a negative comprehensive workup is low, which the authors weigh against the hazards of treatment delay. In the American Journal of Hematology, Zhang and colleagues report a randomized open-label phase 2 study of NTQ5082, an oral once-daily factor B inhibitor, in 25 complement inhibitor-naive adults with paroxysmal nocturnal hemoglobinuria [7]. Lactate dehydrogenase fell and hemoglobin rose within a week at both 100 and 200 milligrams, every patient gained at least 20 grams per liter of hemoglobin, no transfusions were needed, and no grade 3 or higher adverse events occurred. It is small and short at 12 weeks, so durability and breakthrough hemolysis remain open questions. Complement also features in Blood Advances, where Jodele and colleagues examined why about a third of patients with high-risk transplant-associated thrombotic microangiopathy fail eculizumab [8]. Among 85 children and young adults, non-responders had more severe organ injury, needed intensified dosing, and showed persistent proteinuria with elevated markers of endothelial stress and interferon signaling, including ST2 and CXCL9, even when terminal complement was suppressed. Durable complement control took a median of about five weeks. A small subset given the interferon-gamma blocker emapalumab showed better complement pharmacodynamics, an intriguing but early observation pointing toward interferon as a driver of resistance.

Our final theme is treatment selection in lymphoma, where two retrospective studies quantify trade-offs. In Blood Advances, Dave and colleagues analyzed 810 adults with stage one or two classical Hodgkin lymphoma across eight academic centers [9]. In a propensity-matched cohort of 480 patients, overall survival was excellent either way, and the overall progression-free difference favoring combined modality therapy fell just short of significance. But in bulky disease, progression-free survival was about 92 percent with radiation versus 73 percent without, and in interim PET-positive disease about 75 versus 52 percent. Interim PET was the strongest predictor of both progression and death, and among PET-positive patients, unplanned consolidative radiation was associated with less salvage therapy than chemotherapy escalation alone. Late toxicities were more frequent with radiation, though most second cancers arose outside the field. Also in Blood Advances, Major and colleagues compared standard-of-care CAR-T with CD20 by CD3 bispecific antibodies in 228 patients with relapsed or refractory follicular lymphoma in the third line or later [10]. CAR-T was associated with longer progression-free survival, median not reached versus roughly 580 days with bispecifics, independent of age and fitness differences, yet overall survival did not differ. CAR-T also cost patients more time, about 14 to 20 additional health care contact days in the first year. These benchmarks inform sequencing conversations but are not randomized comparisons.

If you only have time for one paper this week, make it the Hodgkin lymphoma analysis from Dave and colleagues in Blood Advances [9]. It reopens the question of whether radiation can be safely omitted in early-stage disease, identifying bulky and interim PET-positive patients as a group where omission appears to carry a real cost in disease control.

Here is what this week's evidence adds up to in Hematology. First, in early-stage Hodgkin lymphoma, multicenter observational data suggest radiation omission is associated with worse disease control in bulky and interim PET-positive disease, though without a survival difference and pending prospective confirmation. Second, the FLT3-ITD story in older and microclonal AML remains unsettled: post hoc quizartinib data in older adults show no clear survival benefit, and microclones carry poorer features but not independent prognostic weight, arguing for randomized trials rather than settled practice. Third, reduced-intensity haploidentical transplant for children with severe sickle cell disease now has multicenter phase 2 support, with graft failure and graft-versus-host disease still the main limitations. Fourth, in pediatric aplastic anemia with a negative comprehensive workup, retrospective data put the risk of hidden inherited disease low, informing the trade-off against treatment delay. Finally, complement remains a growing therapeutic frontier, with an oral factor B inhibitor showing early phase 2 activity in PNH and interferon signaling emerging as a candidate explanation for eculizumab resistance in transplant-associated microangiopathy.

That's your roundup for This Week in Hematology. The full transcript and references are available on the episode page. This is an AI-curated summary — for clinical decisions, always consult primary sources and current guidelines. See you next week.

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