By Drs. David Niesel and Norbert Herzog
Every now and then things go right, really, really right. In an immunotherapy clinical trial, 27 of the 29 leukemia patients went into sustained remissions, which is a whopping 93 percent success rate!
Acute lymphocytic leukemia, or ALL, is a cancer that arises in the bone marrow, the soft center of flat bones. In the bone marrow, blood stem cells give rise to all blood cells. ALL arises from the cells that become lymphocytes, a type of white blood cell. Acute in the name means that it can progress quickly and if not treated can be fatal within a few months. If the ALL cancer cells occupy more than 25% of the bone marrow, the disease is called leukemia.
Lymphocytes are a major part of the immune system found in lymphoid tissues as well as circulating in the blood. Lymphocytes come from immature cells called lymphoblasts and mature into 2 main types of cells, B cells and T cells. T cells serve a variety of functions, from orchestrating the immune response to an invader, to killing infected cells or killing microbes directly.
ALL does not form masses, but rather takes over the bone marrow and spreads to the lymph nodes, spleen and liver. The prognosis for ALL depends on age - the younger you are, the better. Prognosis also depends on the numbers of cancer cells, abnormalities the tumor DNA, and how quickly the leukemia responds to treatment. Treatment usually involves chemotherapy, targeted therapy or stem cell transplants and can last about 2 years. About 80-90 percent of adult patients have complete remissions, but about half relapse giving an overall cure rate of about 40 percent.
The study with the 93 percent response rate involved patients whose other treatments had failed and they had only a few months to live. Scientists isolated what are called killer T-cells from the patients. These cells can attack and kill cancers cells. The researchers engineered these T cells to target the patients ALL cells. They genetically engineered the T cells with synthetic molecules called chimeric antigen receptors, or CARs, that enable them to target and destroy tumor cells. Cells were expanded and then infused into the patients. More than ninety percent of the patients achieved remission of their cancers within 30-60 days however, 7 developed a severe immune response that required time in intensive care and an additional 2 patients died. Adjusting T cell dosages infused eliminated these unwanted effects. Unlike other treatments, the T cells will continue to grow and provide ongoing protection. These results from patients with such advanced stages of ALL is impressive.
This is a relatively new type of approach called immunotherapy by which our body's own immune system is programmed to attack a cancer. An advantage of this type of therapy is that it is likely to have fewer side effects and would have long lasting cancer-killing abilities should cancer cells arise later. For those patients that relapse or for whom conventional treatments fail, this approach provides new hope. So stay tuned, we will undoubtedly be hearing much more about immunotherapy in the future and the future looks pretty good already.
Medical Discovery News is a weekly radio and print broadcast highlighting medical and scientific breakthroughs hosted by professor emeritus, Norbert Herzog, and professor, David Niesel, biomedical scientists at the University of Texas Medical Branch at Galveston. Learn more at www.medicaldiscoverynews.com