Chimeric antigen receptor (CAR) T cells therapies are generated by taking T cells from a patient's blood, engineering them in a laboratory setting to add a gene to help the immune cells attack cancer cells, and administering them back to the patient. The gene added to the patient's T cells is called a chimeric antigen receptor. CAR T cells are used in the treatment of a variety of cancers, primarily those which involve the blood and bone marrow.