Leukemia is an umbrella term for cancers of the blood and the blood-forming tissues of the body. Chronic myeloid leukemia (CML) is a slow-growing form of the disease that primarily impacts people over age 55.
Like all types of leukemia, CML starts with problems in the creation of blood cells.
Blood cell creation
The body produces millions of blood cells each day. Most develop in the bone marrow, the spongy interior of bones that contains immature stem cells.
In a healthy person, these immature stem cells first become either lymphoid stem cells or myeloid stem cells.
Lymphoid stem cells develop into white blood cells, which are immune system cells. They start by becoming immature white blood cells known as lymphoblasts, then mature into lymphocytes. The two types of lymphocytes that are usually involved in leukemia are B cells and T cells. B cells produce the antibodies responsible for attacking bacteria and viruses that invade the body. T cells help alert other immune cells to the presence of infection or fight infection directly.
Myeloid stem cells also develop into white blood cells. The myeloid stem cells first become immature white blood cells known as myeloblasts. They then mature into monocytes and granulocytes, including neutrophils, all of which fight disease. Other myeloid stem cells develop into red blood cells, which carry oxygen throughout the body; and platelets, which help the blood clot.
Leukemia occurs when the DNA (the genetic instructions that control cell activity) of a bone marrow stem cell mutates at some point in its development. The cell becomes cancerous, begins multiplying rapidly and crowds out healthy cells in the blood and bone marrow. These diseased cells can also gather in specific parts of the body, including the liver, lymph nodes, spleen and skin.
How is leukemia classified?
While there are many types of leukemia, they are typically classified by the type of stem cell that has turned cancerous, either lymphoid or myeloid.
Many types are also classified as either chronic or acute. Acute leukemia impacts immature cells, preventing them from developing and carrying out their function. These cells tend to multiply rapidly, making acute leukemia more aggressive.
Chronic leukemia involves mature or partially mature cells. These cells multiply more slowly and are less aggressive, making chronic leukemia less aggressive than acute leukemia.
About CML
CML develops from myeloid stem cells, which produce red blood cells, platelets and several white blood cell types that are together called granulocytes.
In patients with CML, too many myeloid cells become granulocytes. These cancerous cells are poor at fighting disease. They also crowd out healthy blood cells, which can make CML patients weak and prone to infection.
CML primarily impacts older patients, with about half of all cases occurring in people age 65 and older. It is very rare in pediatric patients.
Nearly all CML patients have a particular chromosome abnormality known as the Philadelphia chromosome.
Chromosomes are sections of DNA found in every cell; each person’s DNA contains his or her unique genetic instructions. The Philadelphia chromosome forms when pieces of chromosomes 9 and 22 swap places in a blood cell.
As a result, the now-cancerous cell produces a protein (in the tyrosine kinase family of proteins) that encourages it to multiple rapidly. Leukemias with the Philadelphia chromosome can be treated with targeted therapies called tyrosine kinase inhibitors. These drugs interfere with the tyrosine kinase protein and therefore the multiplication of cancerous white blood cells.
Over the past few decades, targeted therapy drugs that stop tyrosine kinase from working have been introduced. These drugs, known as tyrosine kinase inhibitors, result in a much better outlook and longer survival times for CML patients. The disease’s five-year survival rate is now more than 70%.
CML risk factors
A risk factor is anything that increases the chance of developing a disease. Knowing a disease’s risk factors can be an important step towards catching it early. It's important to note that not everyone with risk factors will develop the disease.
Risk factors for CML include:
- Age: A majority of CML cases are in people age 65 or older.
- Sex: Men are more likely to get CML than women.
- Radiation exposure: After World War II, people in Japan who were exposed to radiation from nuclear bombs were more likely to develop CML. Radiation therapy from cancer treatment is not a risk factor for CML.
Blood cell creation (click to enlarge).
Why choose MD Anderson for your leukemia treatment?
Choosing the right cancer center may be the most important decision you can make as a leukemia patient. At MD Anderson’s Leukemia Center and Stem Cell Transplantation and Cellular Therapy Center, you’ll get treatment from one of nation’s the largest, most experienced leukemia teams at a top-ranked cancer center.
Using a comprehensive team approach, we work together to give you customized care that includes the most advanced diagnostic methods and treatments. These include clinical trials of new drugs and drug combinations. We offer clinical trials for all situations – from patients receiving their first treatment, to patients who have exhausted all standard treatment options.
As a leading center for leukemia care, we offer access to innovative new therapies and clinical trials that may help increase your chances for successful treatment. Many of these were developed by our own researchers.
We are constantly striving to find new and better ways to fight leukemia. We are one of the few cancer centers in the nation to house a prestigious federally-funded SPORE (Specialized Program of Research Excellence) focused on leukemia. We offer a wide range of clinical trials and innovative, advanced leukemia treatment for all patients who seek care at MD Anderson.
Treatment designed specifically for you
Successful leukemia treatment begins with accurate and precise diagnosis. Many of our leukemia patients have been misdiagnosed before they come to MD Anderson. We have the expertise and experience gained from being one of the most active programs in the world, and our specialized pathologists are highly skilled in diagnosing leukemia.
Our approach to leukemia is customized especially for you. We carefully evaluate your risk factors and the specific characteristics of your leukemia to determine if immediate treatment is necessary. If it is, we recommend the most effective therapies while aiming to limit treatment side effects.
Whether you are treated as an inpatient or outpatient, our comprehensive program offers all the services needed to care for leukemia and respond to its impact on your body. We aim to accomplish as much care as possible on an outpatient basis. If hospitalization is needed, our expert staff is specially trained to care for patients at every phase of the treatment journey.
MD Anderson is my hope. I know that without it, I wouldn’t be alive today.
