What are colony-stimulating factors?
Colony-stimulating factors (CSFs) are medications used to stimulate production of infection-fighting white blood cells. Myeloma patients may have low numbers of white blood cells as a result of their cancer treatment or as a result of myeloma cells crowding out the normal blood-producing cells in the bone marrow. In either case, a reduced white blood cell count can lead to an increased risk of infection.
One type of white blood cell that is particularly important in fighting off infection is called a neutrophil. When neutrophil levels drop below normal (a condition known as neutropenia), the body is less able to fight off infection. Low levels of neutropenia sometimes result in fever, a condition call febrile neutropenia. Febrile neutropenia is a sign of a very serious and sometimes life-threatening infection.
There are two main types of colony-stimulating factors:
Granulocyte colony-stimulating factor (G-CSF) stimulates the production of neutrophils. There are two brands of G-CSFs available ─ Neupogen® (filgrastim) and Neulasta® (pegfilgrastim). The only difference between these drugs is that Neulasta is given less often.
Granulocyte-macrophage colony-stimulating factor (GM-CSF) stimulates the production of both neutrophils and macrophages (another type of white blood cell that helps fight infection). The brand name for GM-CSF is Leukine® (sargramostim).
All three of these medications appear to work equally well.
How are colony-stimulating factors used in multiple myeloma?
Colony-stimulating factors are used in several different ways in multiple myeloma.
- To prevent fever and serious infections in patients who are receiving anti-myeloma drugs that tend to cause low blood counts. Keeping white blood cell counts up and preventing infection can help keep patients on track with their cancer treatment dose and schedule, which helps ensure that they receive the maximum benefit from their therapy.
- Typically, only patients who are at “higher risk” for fever and serious infections are given colony-stimulating factors preventatively.
- Treatment of fever due to low white blood cell counts (febrile neutropenia)
- After high-dose chemotherapy and stem cell transplantation to help speed up the production of white blood cells and allow for a faster recovery.
In addition, colony-stimulating factors are used as part of the preparation for high-dose chemotherapy and stem cell transplantation.
Who is a candidate for preventative therapy with colony-stimulating factors?
Generally, preventative therapy with colony-stimulating factors is only given to patients considered at “higher risk” for fever and serious infections.
Patients who are at higher risk include:
- Patients over the age of 65
- Patients who already have very low white blood cell counts (prior to anti-myeloma treatment)
- Patients who already have infections
How are colony-stimulating factors given?
Colony-stimulating factors are administered as an injection under the skin or into a vein.
Typical doses are as follows:
- Neupogen: 5 mcg/kg daily
- Leukine: 250 mcg/m2 daily
- Neulasta: 6 mg once per treatment cycle (eg, once every 3 weeks).
What are the possible side effects and how are they managed?
Colony-stimulating factors are generally well tolerated. The most common problem is mild to moderate bone pain, which is usually controlled by pain killers
There have been rare reports of more serious side effects, particularly a severe type of allergic reaction, lung and heart problems.
Remember to talk to your doctor about any side effects you experience.