Cytokine release syndrome (CRS) is a possible side effect of CAR T-cell therapy. CAR-T works by enhancing your immune system to better target myeloma cells. Because it activates the immune system, there is a chance it can cause an overreaction. 

When this happens, the immune system releases chemicals called cytokines. If too many cytokines are released, it can cause symptoms that affect your body in different ways.

CRS symptoms can range from mild to serious. They may include a fever or, in severe cases, very low blood pressure that requires care in the intensive care unit (ICU). For people with myeloma receiving ide-cel (Abecma) or cilta-cel (Carvykti), the majority of CRS cases are mild to moderate, not severe. 

Below, learn how CRS is managed based on its severity level. 

How do doctors measure how serious CRS is?

Grade 1

This is a mild reaction. Symptoms can include fever, nausea, tiredness, headache, muscle aches, or just feeling unwell. Treatment often includes fluids, medicines to reduce fever (like ibuprofen or aspirin), and medicines for nausea or vomiting.

Grade 2

This is a moderate reaction. It may include early signs of organ problems, like the kidneys or liver not working well, or low white blood cell counts that cause fevers. Your care team may give you steroids, oxygen, or fluids through an IV. A medicine called tocilizumab is often used at this stage to control CRS and prevent it from becoming more severe.

Grade 3

This is a severe reaction. Symptoms can include serious organ problems, very low blood pressure that does not improve with fluids, or low oxygen levels. At this point, you will likely be moved to the ICU for close monitoring and treatment, including oxygen support.

Grade 4

This is the most serious reaction. It involves dangerously low oxygen or blood pressure. Life-support measures, such as a breathing machine (ventilator), may be needed.