leukapheresis

leukapheresis, the separation and collection of white blood cells (leukocytes) from other blood components, including red blood cells, plasma, and platelets. Leukapheresis is a type of therapeutic apheresis, in which excess, often abnormal blood cells are removed from the body; it is used specifically in the treatment of diseases in which white blood cells multiply uncontrollably. Examples of such diseases include cancers of the blood and bone marrow, such as chronic lymphocytic leukemia (CLL), acute myeloid leukemia (AML), and acute lymphocytic leukemia (ALL).

Procedure

Leukapheresis begins with the placement of an intravenous (IV) line in each of the patient’s arms. Blood is collected through one line and passed through an apheresis machine, which uses a centrifuge or a rotating belt to separate out white blood cells. Through the other IV line, red blood cells, platelets, and plasma are returned to the patient’s bloodstream. In some patients central line placement is necessary, with a single catheter used instead of two IV lines. In such cases a small incision is made beneath the clavicle or near the neck, providing access to the main blood vessel leading to the heart; two long, thin tubes are then inserted into the blood vessel. The entire process of leukapheresis lasts at least two to three hours.

Side effects

During leukapheresis a condition known as hypocalcemia, in which a patient’s calcium levels decrease, causing numbness, tingling sensations, or muscle spasms, may occur. Calcium can be replaced orally or intravenously through the line returning blood to the patient’s body. Other possible side effects of the procedure include anemia and thrombocytopenia, which can be treated with blood transfusions. After the procedure patients may experience dizziness, fainting, nausea, and pain or bruising at the site of IV insertion.

Therapeutic applications

Leukapheresis may temporarily relieve leukostasis (or symptomatic hyperleukocytosis), a potentially fatal medical emergency in which abnormal white blood cells multiply in excess and clog smaller blood vessels. Leukapheresis is only a temporary measure for leukostasis, and although it may help stabilize patients until chemotherapy or other treatments can be initiated, its effectiveness is unclear. The procedure may need to be performed more than once if white blood cell levels again become too high.

Leukapheresis serves an important role in chimeric antigen receptor T-cell therapy (CAR T-cell therapy), which is used to treat such cancers as B-cell acute lymphoblastic leukemia and B-cell non-Hodgkin lymphoma. White blood cells, specifically T cells, that have been collected via leukapheresis for CAR T-cell therapy are genetically altered to enhance their ability to kill cancer cells. Genetic modification can take several weeks, and in the meantime, patients undergo chemotherapy for several days to increase the chances that white blood cells will destroy the cancer cells. The patient then receives an infusion containing millions of the altered white blood cells, referred to as CAR T cells, which become activated once inside the patient’s body. A patient who receives CAR T-cell therapy may remain in the hospital, sometimes in the intensive care unit, for several days to recover from side effects that can cause cytokine release syndrome, a systemic inflammatory reaction.