# Prolonged low blood counts after CAR T-cell therapy (ICAHT): grading, work-up and treatment

Source: https://onco.cc/protocols/icaht-prolonged-cytopenia/  
OnCo record `icaht-prolonged-cytopenia` (Protocol). Data CC BY-NC 4.0, attribute "Data from OnCo (onco.cc)"; commercial use needs a licence.

## TL;DR

Low blood counts are the commonest side effect of CAR T-cell therapy. Most recover within weeks, but in some people counts stay low for months, raising infection risk. Teams check counts often, give growth factor injections, transfusions and infection-preventing tablets, and look at the bone marrow if counts stay low after about a month. Some need their own stored stem cells.

## Summary

EHA/EBMT 2023 named immune effector cell-associated haematotoxicity (ICAHT) and graded it by depth and duration of neutropenia, separately for early (day 0 to 30) and late (after day +30) cytopenia; it also set out risk factors, the pre-infusion CAR-HEMATOTOX score and recommendations on growth factors, prophylaxis, transfusion, autologous stem cell boost and allogeneic transplant. Only its abstract could be read. ASTCT's 2026 consensus grading update also addresses ICAHT (abstract only).

SITC 2020 (LE: 4 unless stated): for cytopenias in the first 28 days, follow blood counts without marrow biopsy; for cytopenias beyond 28 days, bone marrow aspirate and biopsy with viral studies; consider holding G-CSF until day 14 or CRS has resolved; consider growth factors for ANC under 500 per microlitre after day 28; no GM-CSF in the CRS window (LE: 5); antibacterial and antifungal prophylaxis for all with persistent neutropenia. The Haematologica 2025 review (Beyar-Katz, Rejeski, Shouval): watch and wait for early cytopenias; irradiated red cells and platelets because of fludarabine exposure; red cell threshold 7 to 8 g/dL; platelets at 10 or below (20 with bleeding, fever or infection); thrombopoietin receptor agonists for persistent thrombocytopenia (retrospective data only); autologous CD34+ boost for G-CSF-refractory ICAHT, with 70 to 100% neutrophil recovery in retrospective series, and allogeneic transplant as a last option. No prospective or randomised trial of any ICAHT treatment exists.

## Fields

- Kind: Protocol
- Last checked: 2026-11-11
- Also known as: ICAHT; immune effector cell-associated hematotoxicity; prolonged cytopenia after CAR T; post-CAR T neutropenia; CAR-HEMATOTOX; stem cell boost after CAR T
- Tags: protocol; cell-therapy; car-t

## Connected records

- protocols: [Cytokine release syndrome after CAR T-cell therapy: ASTCT grading, tocilizumab and steroids](https://onco.cc/protocols/crs-grading-and-management/), [IEC-HS after CAR T-cell therapy: recognition and stepwise treatment](https://onco.cc/protocols/iec-hs-management/), [Infection screening, prophylaxis and immunoglobulin replacement around CAR T-cell therapy](https://onco.cc/protocols/car-t-infection-prevention/), [Lymphodepleting chemotherapy before CAR T-cell infusion](https://onco.cc/protocols/car-t-lymphodepletion/)
- technologies: [Blood counts that do not come back after CAR-T: ICAHT](https://onco.cc/technologies/rejuv-tx-prolonged-cytopenias/), [CAR-T cell therapy](https://onco.cc/technologies/car-t/)
- drugs: [Eltrombopag](https://onco.cc/drugs/eltrombopag/), [Filgrastim (G-CSF)](https://onco.cc/drugs/filgrastim/), [Romiplostim](https://onco.cc/drugs/romiplostim/)
- institutions: [European Hematology Association](https://onco.cc/institutions/eha/), [Society for Immunotherapy of Cancer](https://onco.cc/institutions/sitc/)
- terms: [Cytopenias and myelosuppression](https://onco.cc/terms/cytopenias/), [Lymphodepletion before CAR-T](https://onco.cc/terms/lymphodepletion/)

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