What is chimeric antigen receptor T‑cell (CAR‑T) therapy, how is it performed, what are its approved indications, and how are its toxicities such as cytokine release syndrome and immune effector cell‑associated neurotoxicity managed?

CAR T-Cell Therapy Overview

CAR T-cell therapy is a revolutionary immunotherapy that genetically engineers a patient's own T-cells to recognize and destroy cancer cells, primarily approved for relapsed/refractory B-cell malignancies including B-cell acute lymphoblastic leukemia, large B-cell lymphoma, and mantle cell lymphoma 1.

What is CAR T-Cell Therapy?

CAR T-cell therapy involves extracting T-cells from a patient, genetically modifying them to express chimeric antigen receptors (CARs) that target specific cancer antigens (most commonly CD19 on B-cells), expanding these cells in a laboratory, and then infusing them back into the patient where they actively seek and destroy malignant cells 1.

How the Process Works

1. Patient Selection and Workup

• No strict age limit—decisions based on physical condition rather than chronological age 1
• Requires FACT-JACIE accreditation for delivery sites 1
• Pre-leukapheresis evaluation includes viral serology and compliance with tissue/cell directives 1

2. Leukapheresis (Cell Collection)

• Non-mobilized leukapheresis performed to collect patient's T-cells
• Minimum absolute lymphocyte count threshold of 0.2 × 10⁹/L generally recommended, though emerging evidence supports collection even with lower counts 1
• Infectious disease markers tested within 30 days of collection
• Fresh leukapheresis stored at 2-8°C before shipping to manufacturing facility 1

3. Manufacturing

• Patient's T-cells shipped to specialized manufacturing facility
• Cells genetically engineered to express CAR targeting specific tumor antigens
• Manufacturing typically takes 2-4 weeks
• Cells expanded to therapeutic doses

4. Bridging Therapy

• Patients may receive chemotherapy during manufacturing period to control disease progression
• Appropriate washout periods required before CAR T-cell infusion 1

5. Lymphodepleting Chemotherapy

• Administered 2-7 days before CAR T-cell infusion
• Creates favorable environment for CAR T-cell expansion

6. CAR T-Cell Infusion

• Modified cells infused back into patient
• Cells expand in vivo and begin targeting cancer cells

Approved Indications

Current FDA-approved indications include 1:

• Relapsed/refractory B-cell acute lymphoblastic leukemia (B-ALL)
• Relapsed/refractory large B-cell lymphoma (LBCL)
• Relapsed/refractory mantle cell lymphoma (MCL)
• Multiple myeloma and follicular lymphoma products under evaluation/approval

Major Toxicities and Management

Cytokine Release Syndrome (CRS)

CRS is a supraphysiologic inflammatory response with fever as the defining feature, occurring at median 2-7 days post-infusion (can occur up to 3 weeks), managed primarily with tocilizumab for lower grades and corticosteroids for refractory or higher-grade disease 2.

Clinical Presentation:

• Always includes fever ≥38°C as the defining symptom
• Tachycardia, hypotension (potentially requiring vasopressors)
• Hypoxia, respiratory failure
• Nausea, headache, rash
• Coagulopathy, multiorgan failure in severe cases 2

Grading and Management (ASTCT Consensus):

Grade 1 (Fever only):

• Supportive care: antipyretics, IV hydration, symptomatic management
• Consider empiric antibiotics if neutropenic
• If fever persists >3 days, escalate to Grade 2 management 2

Grade 2 (Fever + hypotension not requiring vasopressors OR hypoxia requiring ≤6 L/min oxygen):

• Continue supportive care
• Tocilizumab 8 mg/kg IV over 1 hour (max 800 mg/dose)
• Repeat every 8 hours if no improvement; maximum 3 doses per 24 hours, 4 doses total
• Continuous cardiac telemetry and pulse oximetry required 2

Grade 3-4 (Severe hypotension requiring vasopressors OR high-flow oxygen/mechanical ventilation):

• Tocilizumab as above
• Add corticosteroids (typically methylprednisolone 1-2 mg/kg/day)
• Intensive care monitoring
• Consider echocardiogram to assess cardiac function 2

Monitoring Requirements:

• CBC, CMP, magnesium, phosphorus, CRP, LDH, uric acid, fibrinogen, PT/PTT, ferritin
• Blood and urine cultures if fever present
• Chest radiograph if indicated
• Screen for CMV and EBV
• Consider chest/abdominal CT, brain MRI, lumbar puncture as clinically indicated 2

Critical Pitfall: GM-CSF is NOT recommended as it may worsen CRS 2.

Immune Effector Cell-Associated Neurotoxicity Syndrome (ICANS)

ICANS is a CNS disorder with median onset 4 days post-infusion, characterized by encephalopathy ranging from aphasia and confusion to seizures and cerebral edema, managed primarily with corticosteroids 2.

Clinical Presentation:

• Aphasia, altered level of consciousness
• Impairment of cognitive skills
• Motor weakness
• Seizures
• Cerebral edema (severe cases) 2

Management Approach:

Grade 2 or higher ICANS:

• Corticosteroids are first-line therapy (typically dexamethasone 10 mg IV every 6 hours or methylprednisolone 1-2 mg/kg/day)
• Anti-epileptic prophylaxis commonly used (93.3% of patients in real-world data received preventive anti-epileptics) 3
• Neurologic assessments using standardized tools
• Consider brain MRI and lumbar puncture to rule out other causes 2

Prevention Strategy:

• Nearly 50% of patients receive ICANS prophylaxis, primarily with anti-epileptic medications 3

Additional Toxicities

Cytopenias and infections are common complications requiring:

• Neutropenic fever protocols when indicated
• Antimicrobial prophylaxis
• Growth factor support (G-CSF acceptable; GM-CSF contraindicated) 2

Real-World Incidence Data

Recent CIBMTR data from 927 patients treated with axi-cel or brexu-cel showed 3:

• CRS occurred in 82.6% of patients (Grade ≥2 in 47.0%)
• ICANS occurred in 48.4% of patients (Grade ≥2 in 71.5%)
• 76.6% of CRS patients received treatment (primarily tocilizumab)
• 85.6% of ICANS patients received treatment (primarily corticosteroids)

Critical Care Considerations

Multidisciplinary team involvement is essential, including:

• Hematology/oncology
• Intensive care
• Neurology
• Cardiology (for cardiovascular complications including hypotension, arrhythmias, myocardial dysfunction) 4
• Pharmacy
• Specialized nursing trained in CAR T-cell toxicity recognition 5

Key nursing responsibilities include 5:

• Continuous vital sign monitoring
• Frequent neurologic assessments using standardized tools
• Early recognition of CRS and ICANS
• Patient and caregiver education about warning signs

Emerging Strategies

Preventive approaches under investigation 6:

• IL-1 receptor antagonism (anakinra) for high-grade CRS
• IFNγ and IL-6 neutralizing antibodies
• JAK inhibitors
• Prophylactic tocilizumab (12.4% of patients received CRS prevention in real-world data) 3

Common Pitfall: The treatment landscape is evolving toward more aggressive early management of CRS rather than waiting for progression, with growing interest in preventive strategies for both CRS and ICANS 3.

Long-Term Considerations

• Post-authorization safety surveillance required 1
• Long-term follow-up for B-cell aplasia and hypogammaglobulinemia
• Monitoring for secondary malignancies
• Immunoglobulin replacement as needed for recurrent infections