Therapy-Related Myeloid Neoplasms After CAR-T Therapy: A Case Series with Distinct Cytogenetic Features and Comparison with Autologous Stem Cell Transplantation

Background: The emergence of therapy-related myelodysplastic syndrome (t-MN) after autologous stem cell transplantation (ASCT) is well documented. However, with the growing use of chimeric antigen receptor (CAR) T-cell therapy for relapsed/refractory B-cell malignancies, concerns about secondary myeloid neoplasms, particularly MN, have arisen. The mechanisms and cytogenetic features associated with post-CAR-T MN, especially chromosome 7 abnormalities, remain underexplored. Objectives: To compare the incidence, timing, and cytogenetic characteristics of MN developing after CAR-T-cell therapy versus ASCT, and to evaluate the potential association between CAR-T therapy, persistent cytopenias, and these specific alterations. Study Design: This was a retrospective, single-center study of 275 patients with B-cell malignancies treated between 2015 and 2024 at Hospital Universitario Central de Asturias (Spain). Of these, 259 patients underwent ASCT and 16 received CAR-T-cell therapy (axicabtageneciloleucel n = 13, tisagenlecleucel n = 2, brexucabtageneautoleucel n = 1). Clinical, cytogenetic, and laboratory data were collected and analyzed. Incidence rates were compared using Fisher’s exact test, and time-to-event outcomes was evaluated using the Mann–Whitney U test (given the small number of events). Statistical significance was set at p < 0.05. Results: Myeloid neoplasms were diagnosed in 3 of 259 ASCT patients (1.15%) and in 2 of 16 CAR-T-cell patients (12.5%) (p = 0.03). The median time to myeloid neoplasm diagnosis was numerically shorter in the CAR-T group (15.5 vs. 69 months, p = 0.096). All post-CAR-T cases presented persistent cytopenias and cytokine release syndrome (CRS). Cytogenetic analyses revealed de novo monosomy 7 and 7q deletion in both CAR-T-related cases, whereas no chromosome 7 abnormalities were detected in ASCT-related cases. Pre-treatment samples did not show these abnormalities, although limitations in the sensitivity of the assays preclude the definitive exclusion of minor pre-existing clones. Both affected CAR-T patients had prolonged CAR-T cell persistence and required transfusional support due to hematologic toxicity. One patient was diagnosed with high-risk MN with 5q and 7q deletion and the other with Clonal Cytopenia of Uncertain Significance (CCUS) with monosomy 7. Conclusions: CAR-T-cell therapy was associated with a significantly higher and earlier incidence of myeloid neoplasms compared to ASCT in this cohort. The development of post-CAR-T myeloid neoplasm was characterized by persistent cytopenias, prolonged CAR-T cell persistence, and de novo chromosome 7 alterations. While the small sample size necessitates cautious interpretation, these findings may suggest a distinct pathogenesis potentially linked to inflammation, immune toxicity, or the expansion of pre-existing clones. This highlights the need for long-term hematologic monitoring and evaluation for clonal hematopoiesis prior to CAR-T-cell therapy, especially in heavily pretreated patients.