Chronic myeloid leukemia (CML) is a type of cancer that affects the bone marrow. It starts in the cells that form blood, with cancer cells building up slowly over time. The diseased cells don’t die when they should and gradually crowd out healthy cells. People often don’t realize that they have CML for several years. But if left untreated, the cancer can eventually invade the blood and spread to other organs.
CML is likely caused by a genetic mutation that causes a blood cell to produce too much of the tyrosine kinase protein. This protein is what allows the cancer cells to grow and multiply.
In some cases, CML can be treated and cured with a stem cell or bone marrow transplant.
The first step in treatment, however, is often a class of medications called tyrosine kinase inhibitors (TKIs). They can be very effective in managing the disease. TKIs work by blocking the action of tyrosine kinase and stopping the growth of new cancer cells. These drugs can be taken orally at home. The first TKI, which was approved by the FDA in 2001, quickly became the standard treatment for CML. Several more TKIs have since been introduced.
Gleevec was the first TKI to hit the market in 2001. Blood tests show that CML responds quickly to Gleevec, generally within one to three months. Side effects are usually mild and may include:
- nausea and vomiting
- fluid buildup
- weight gain
- joint and muscle pain
- low blood count
- skin rash
- feeling tired
Dasatinib can be used as a first-line treatment, or when Gleevec doesn’t work or can’t be tolerated. Along with the same side effects as Gleevec, Sprycel appears to increase the risk of pulmonary arterial hypertension (PAH). PAH is a dangerous condition that occurs when blood pressure is too high in the arteries of the lungs. Sprycel isn’t recommended for those who have heart or lung problems.
Nilotinib (Tasigna) can also be a first-line treatment, or it can be used if other drugs aren’t effective or side effects are too great. It has the same side effects as other TKIs, along with some potentially more serious side effects that doctors should monitor. These may include:
- bleeding in the brain
- inflamed pancreas
- liver problems
- a heart condition called QTc prolongation
Bosutinib (Bosulif) is only approved for those who have already tried another TKI. Besides the side effects that are common to other TKIs, Bosulif may also cause liver or kidney damage. However, this type of damage is rare.
Ponatinib (Iclusig) is the only drug that targets a specific gene mutation that can be caused by other TKIs. Because of the potential for severe side effects, it’s only appropriate for those who have this gene mutation or who have tried all other TKIs without success. Iclusig increases the risk of blood clots that can cause heart attack or stroke. It may also cause congestive heart failure.
Chemotherapy was the standard treatment for CML before TKIs. It’s still helpful for some patients who haven’t had good results with TKIs. Sometimes chemotherapy will be prescribed along with a TKI. Because chemotherapy lowers white blood cell count, it can be used to kill existing cancerous cells. TKIs keep new cancer cells from forming.
Although some TKIs have a long list of possible side effects, they can be very effective. The majority of people go into remission for several years on TKIs, though they may need to continue taking the drug for the rest of their lives.