Cytopenias After CAR T-cell Therapy: Varying Predictive Markers, Duration

Mr. X is a 63-year-old male with a history of relapsed/refractory diffuse large B-cell lymphoma who initially received R-CHOP (rituximab, cyclophosphamide, doxorubicin HCl, vincristine [Oncovin], and prednisone) with interim restaging, demonstrating partial response and complete metabolic response at the end of treatment. After a year he relapsed and received RICE (rituximab, ifosfamide, carboplatin, and etoposide) with interim restaging demonstrating stable disease and partial response at the end of treatment. In preparation for CAR T-cell therapy, Mr. X did not require bridging therapy, and he ultimately received lymphodepleting chemotherapy with fludarabine and cyclophosphamide followed by axicabtagene ciloleucel (axi-cel).

Throughout his treatment history Mr. X experienced chemotherapy-induced cytopenias, which recovered without requirement of transfusion and minimal growth factor replacement. On day 3 post-product infusion, he experienced grade 2 cytokine release syndrome (CRS) and cytopenias (absolute neutrophil count [ANC]: 300/µL ; hemoglobin [Hgb]: 7.5 g/dL; platelets: 110,000/µL). He was treated with tocilizumab, one unit of packed red blood cells, antibiotic prophylaxis, and 2 days of granulocyte colony-stimulating factor (G-CSF), resulting in improvement. Mr. X was discharged and followed up in the outpatient setting.

At day 30 Mr. X’s PET/CT demonstrated very good partial response, and he was clinically well without requirement of transfusions and only intermittent G-SCF administration. At day 60 it was noted that he was still experiencing significant cytopenias. 

Workup, Diagnosis, and Treatment

At day 60, the following noteworthy labs demonstrated:

• Hgb: 7.9 g/dL; platelets: 60/µL; white blood cell [WBC] count: 1.0/µL; ANC: 0.1/µL; absolute lymphocyte count [ALC]: 0.9)
• Lymphocyte subset: CD4+, 170/µL
• Immunoglobin G (IgG): 800 g/L (normal)
• Ferritin: 500 µg/L (normal)
• Lactic acid dehydrogenase (LDH): 100 units/L (low tumor burden)

A bone marrow biopsy showed normocellular bone marrow (no lymphoma, myelodysplastic syndrome, or leukemia), with trilineage hematopoiesis. Any active infections were ruled out and Mr. X was not receiving any myelosuppressive or immunosuppressive medications. Along with assessment of other risk factors (prior R-CHOP administered more than 1 year ago and RICE administered less than 6 months ago, without history of severe CRS or immune effector cell-associated neurotoxicity syndrome [ICANS], baseline anemia, or clonal hematopoiesis of indeterminate potential [CHIP]), treatment included the following:  

• Transfusion of 1 unit of packed red blood cells
• Double-strength pneumocystis pneumonia prophylaxis 3 times a week (start)
• Levofloxacin (500 mg) once daily for neutropenic precaution
• Neupogen (480 µg) once daily every 3 days

Mr. X was evaluated 3 days later, and his CBC demonstrated improvement: Hgb: 9.0 g/dL, platelets: 75/µL, WBC: 5.6/µL, and ANC: 2.4/µL.

Discussion

The definition of prolonged/recurrent cytopenia is heterogeneous and arbitrary, occurring between 14 and 90 days after CAR T-cell therapy being used as a framework for examination of the incidence of cytopenia.

Although increasingly studied, the incidence of prolonged cytopenia after CAR T-cell therapy remains both underrecognized and underreported despite predisposing patients to infection and nonrelapse mortality.¹ Mechanisms for the various depressed counts are not well understood, and predictors of risk for prolonged cytopenia vary in the literature.^2-6 Reported rates of prolonged or recurrent cytopenias, as defined as grade 3 or higher and lasting for more than 30 days, occur in 20% to 40% of patients who receive CAR T-cell therapy.² Late cytopenias, occurring 90 days after therapy, are also relatively common—occurring in approximately one-third of patients.² 

Although the cause(s) of cytopenias are poorly understood, the number of previous lines of therapy was statistically significant as a contributing variable, and one study noted an association between baseline thrombocytopenia/hyperferritinemia and prolonged cytopenia occurring at day 60 or later after treatment.² Bacterial, fungal, and viral infections can occur because of the immunosuppression necessary for CAR T-cell therapy, and these can play a role in the development of cytopenias.⁷ In addition, the CAR T-cell constructs themselves are associated with a class effect of hematologic toxicity, so there is speculation as to whether the cytopenias are due to the expansion and persistence of CAR T cells⁸ or could be associated with the different costimulatory domains for the differing constructs.⁹

Management is typically limited to symptomatic treatments such as transfusions and supportive care with colony stimulating factors, although the use of G-CSF is a point of contention among sources due to concerns about CRS.²

Because cytopenias after CAR T-cell therapy can be self-limited and early or intermittent, continuous, or even late appearing, it is difficult to establish an understanding of the effects of these on CAR T-cell therapy effectiveness or of appropriate interventions and their timing, although a suggested need for antimicrobial prophylaxis against opportunistic infections has been suggested.³

In an effort to identify predictive biomarkers of and to develop a severity score for hematotoxicities, Rejaski and colleagues developed the CAR-HEMATOTOX model in 2021.⁶ The model includes hematopoietic reserve counts and levels to be used as suggested markers, as well as information about baseline inflammatory markers. The researchers found that a higher CAR-HEMATOTOX score resulted in a higher incidence of severe thrombocytopenia and anemia and in longer duration of neutropenia. They also defined neutrophil recovery using three clinical phenotypes. Although the model was developed using retrospective data that included heterogenous cohorts and was limited due to a small sample size, the model was externally validated in both the United States and Europe. These independent cohorts showed a sensitivity of 89% and a specificity of 69% for prediction of severe neutropenia more than or less than 14 days post CAR T-cell therapy.

Future research is needed to elaborate on the role of the host in the development of hematotoxicities. Standardized management strategies for antimicrobial and fungal prophylaxis, as well as for use of granulocyte colony-stimulating growth factor and TPO, are also needed.

References

1. Faramand RG and Davila ML. CAR T-cell hematotoxicity: Is inflammation the key? Blood. 2021;138(24):2447-2448.
2. Sharma N, Reagan PM, Liesveld JL. Cytopenia after CAR-T cell therapy—A brief review of a complex problem. Cancers (Basel). 2022;14(6):1501. doi: 10.3390/cancers14061501.
3. Strati P, Varma A, Adkins S, et al. Hematopoietic recovery and immune reconstitution after axicabtagene ciloleucel in patients with large B-cell lymphoma. Haematologica. 2021;106(10):2667-2672.
4. Locke FL, Ghobadi A, Jacobson CA, et al. Long-term safety and activity of axicabtagene ciloleucel in refractory large B-cell lymphoma (ZUMA-1): A single-arm, multicentre, phase 1-2 trial. Lancet Oncol. 2019;20(1):31-42. doi: 10.1016/S1470-2045(18)30864-7. Epub 2018 Dec 2.
5. Xing L, Wang Y, Liu H, et al. Case report: Sirolimus alleviates persistent cytopenia after CD19 CAR-T-cell therapy. Front Oncol. December 23, 2021. https://doi.org/10.3389/fonc.2021.798352.
6. Rejeski K, Perez A, Sesques P, et al. CARHEMATOTOX: A model for CAR T-cell–related hematological toxicity in relapsed/refractory large B-cell lymphoma. Blood. 2021;138(24): 2499-2513.
7. Wudhikarn K, Palomba ML, Pennisi M, et al. Infection during the first year in patients treated with CD19 CAR T cells for diffuse large B cell lymphoma. Blood Cancer J. 2020;10(8):79.
8. Hockings C, Kuhnl A, Wong S, et al. Characterisation of early and late cytopenias in lymphoma patients following treatment with antiCD19 CAR-T therapy. In: Bone Marrow Transplant. Springer, Nature: London, 2020; Volume 55, pp. 238-239.
9.  Savoldo B, Ramos CA, Liu E, et al. CD28 costimulation improves expansion and persistence of chimeric antigen receptor–modified T cells in lymphoma patients. J Clin Investig. 2011;21:1822-1826.