Research recently published in the New England Journal of Medicine has provided new hope for a safer, more effective treatment for chronic lymphocytic leukemia, a disease that affects approximately 2,000 Canadians each year.
Leukemia is a type of cancer that affects the bone marrow and blood. When functioning properly, bone marrow stem cells produce healthy blood cells that transport oxygen, fight bacteria, and keep the organism free of infections. Leukemia occurs when bone marrow stems cells produce mutated blood cells. Over time, these mutated blood cells crowd out the healthy blood cells, resulting in the manifestation of the disease.
While treatments exist for leukemia, they have significant limitations. For instance, in chronic lymphocytic leukemia, radiation and chemotherapy treatments are effective, but cannot cure the disease and must be repeated when the cancer returns. If a suitable donor can be found, a bone marrow transplant can cure the disease 50 per cent of the time, but the procedure itself has serious side effects such as long-term pain and infection.
To address these treatment limitations, David Porter and his colleagues from the Department of Medicine at the University of Pennsylvania, found a way to genetically modify T-cells (a type of white blood cell that fights infection) so that they would significantly increase their replication rate once introduced into the bodies of cancer patients. This increased replication rate would produce T-cells in numbers sufficient enough to overwhelm and kill cancerous blood and stem cells. To ensure that the T-cells only targeted the cancerous cells, the T-cells were further infused with a modified (and harmless) version of the HIV virus.
Porters’ paper indicated that following the injection of the modified T-cells into his cancer patient, mild side-effects occurred such as fever and general malaise (similar to that of the common cold). After three weeks, medical tests indicated that there were no traces of leukemia left in the bone marrow. At an eight-month follow-up, his patient was still cancer free.
While Porter’s paper only discusses the case of a single patient who underwent the treatment (which might suggest that the observed effect was a fluke), two others patients have since been treated with remarkable success. One patient was also completely cured while another had a 70 per cent reduction in cancerous cells. While only a small number of patients have undergone this cutting-edge treatment, the results are very encouraging; both because it appears to work and because it is safer than other treatments. Further research over the coming year will determine whether this new treatment is indeed a breakthrough for leukemia patients.
