CAR T cell therapy involves reprogramming a patient's own T cells to recognize and kill cancer cells. The T cells are grown in laboratories and then infused back into patients. Some patients with lymphoma or leukemia have been cured or achieved remission after one treatment with CAR T cells when chemotherapy stopped working. While side effects can include sleepiness and confusion, CAR T cell therapy offers patients a healthier option to fight disease and extend their lives when other treatments have failed.