What Are Bone Marrow Stimulators Used For?

A blood test known as a complete blood count, or CBC, counts your levels of red blood cells, white blood cells, and the platelets that help your blood to clot. When cell counts are low or expected to become low, bone marrow stimulating drugs can be given to boost your body’s production of these blood cells.

These agents have potentially serious risks and side effects, in addition to their blood-boosting benefits, and so not all cases of "low counts" are treated with these drugs. In the treatment of cancer, the use of bone marrow boosting drugs is considered supportive care, meaning that the drug does not directly fight cancer, but helps in other ways.

Compact & spongy (cancellous) bone. Cross section of a long bone. Shows: compact bone, spongy (cancellous) bone, and marrow cavity.
Ed Reschke / Getty Images

Your Bone Marrow, Up Close

Bone marrow is the living tissue that is packed inside the hollows of certain bones, especially the hipbones and the vertebrae, or the bones of the spinal column. The bone marrow is where most of your hematopoietic stem cells live and work. Hematopoietic stem cells divide and give rise to all of the different kinds of blood cells, including red cells, white cells, and platelets.

Without healthy bone marrow, production suffers—new blood cells can’t be made to keep pace with the loss of old or worn out cells, or cells that die as a side effect of cancer treatment. Bone marrow may be unhealthy for a variety of reasons. In the case of certain blood cancers or hematologic malignancies, bone marrow is the site of the cancer, in addition to the site of potential toxicity from treatment.

What Is Bone Marrow Stimulation?

Healthy bone marrow responds to the body’s chemical signals that essentially communicate the need to boost blood cell production. Scientists have learned to make some of these chemical signals outside the body, and in large amounts, so that they can be used medically to boost production. They are often given in larger doses than would normally be produced within the body.

Different “families” or progenitors of blood cell types in the marrow may respond to different chemical signals. One general term for a chemical signal that boosts production is hematopoietic growth factor. Not all drugs that boost the bone marrow are growth factors, however.

Why Is Bone Marrow Stimulation Done?

To Fight Low Counts: Stimulating the body to produce more new blood cells can be helpful when one or more of your blood cell counts are low or your counts are expected to become very low. For instance, sometimes the bone marrow is stimulated in advance, as a preventive measure, when counts are expected to fall due to planned cancer therapy.

Certain patients who receive cytotoxic chemotherapy may have periods of extremely low counts for long periods of time. Levels of the white blood cells known as neutrophils are carefully tracked. Low levels of these neutrophils, in particular, correlate well with the risk of infection. Low neutrophil counts below a certain threshold is generally termed neutropenia, and when levels of neutrophils go very low, it is known as profound neutropenia.

Experts have written volumes, drafting multiple sets of guidelines, about when bone marrow stimulating agents should and should not be used. Much of the discussion comes down to making sure the risks and benefits are balanced in a patient’s favor. There is a multitude of different clinical factors to consider.

To Help Someone Else: Bone marrow stimulation is also used sometimes in healthy people, when they are going to donate stem cells to another person, in something called a peripheral blood stem cell transplant. It turns out that a very small number of blood-forming hematopoietic stem cells can be found out in the bloodstream, and healthcare providers have learned to collect them from healthy people; volunteers can donate their stem cells for a marrow/stem cell transplant simply by giving blood, in some instances. Part of this process involves boosting the bone marrow so that more stem cells can more easily be collected from the circulating blood.

According to the National Marrow Donor Program, or “Be The Match,” a person donating stem cells receives injections of filgrastim, a growth factor, over a period of 5 days prior to donation. Filgrastim is used to increase the number of blood-forming cells in the bloodstream. Then, on the day of donation, the volunteer’s blood is drawn through a needle on one arm and passed through a machine that collects the needed blood-forming cells. The remaining blood is returned to the volunteer through the other arm.

Types of Bone Marrow Stimulating Medications

Growth factors are medications that are usually given through injections beneath the skin. Some may also be given intravenously, into a vein. Your healthcare team can administer the medication by injection, and sometimes individuals and family members learn to administer them, too.

Growth Factors to Boost White Blood Cells

Growth factors or “colony-stimulating factors” that help boost white blood cells include the following:

  • Filgrastim and lenograstim are granulocyte colony-stimulating factors (G-CSFs)
  • Pegfilgrastim is a long-acting form of G-CSF. It works in the same way as filgrastim but can be given less often.
  • Sargramostim is a granulocyte macrophage-colony stimulating factor (GM-CSF).

Both types of growth factors—G-CSFs and GM-CSFs—can improve white blood cell production. Data from randomized controlled trials comparing the two types of blood boosters are currently lacking. Most medical institutions use G-CSF, and this is the most established type and one that has been studied the most.

G-CSFs may be given during the first cycle of chemotherapy to help prevent problems due to neutropenia throughout all of the chemotherapy cycles. G-CSFs also help limit the incidence of fever in patients with neutropenia, and they may reduce the need for hospitalization. They can also be used with chemotherapy in order to give higher doses of chemotherapy, in scenarios where lowering the chemotherapy dose might lead to a worse prognosis.

G-CSFs are sometimes given during chemo re-treatment when a previous cycle of chemotherapy caused a neutropenic fever, and also to shorten the length of time a person has severe neutropenia from chemo when there is no fever. G-CSFs are generally not recommended for routine when a patient already has a fever and neutropenia.

Growth Factors to Boost Red Blood Cells

Growth factors that help boost red blood cells, or erythrocytes, include the following:

  • Erythropoietin is a growth factor that boosts red blood cell production.
  • Darbepoetin is a long-acting form of erythropoietin that works in the same way but can be given less often.

Giving erythropoietin can help avoid transfusions of red blood cells in some patients. Giving some patients both erythropoietin and G-CSF improves their response to the erythropoietin.

As with the growth factors that boost white blood cells, there have been many efforts to draft guidelines and recommendations about when erythropoietin and darbepoetin should be used. A balancing act between risks and benefits is involved.

Boosting Platelets

Rarely used, a drug called oprelvekin is an engineered form of a chemical signal called interleukin-11, or IL-11. Oprelvekin can be used to stimulate platelet production after cancer chemotherapy or in other medical scenarios involving low platelets (thrombocytopenia). This drug can help increase the platelet counts of some patients for a time, however, it is not helpful in all patient types, nor for all cases of low platelets.

Another medication called romiplostim also helps boost platelets, but it is only indicated when a person has low platelets that are caused specifically by something called chronic immune thrombocytopenia, or chronic ITP. Romiplostim is not a naturally occurring growth factor, but it works by mimicking thrombopoietin, a growth, and development factor that boosts platelets.

Future Studies

More studies have been initiated to try to find out the best way to tell which patients might benefit from growth factors that boost blood cell and platelet production.

There is also a lot of interest in determining the best way to combine growth factors with each other—and with other agents—including chemotherapy and hormone therapy.

When to See Your Healthcare Provider

If you are taking a bone marrow stimulating medication, notify your healthcare provider if you are experiencing any untoward effects. Contact your healthcare provider immediately if you experience any of the following symptoms:

  • Fever of 100.4° F (38° C) or higher, chills—possible signs of infection
  • Shortness of breath
  • Rapid heartbeat
  • Bleeding that does not stop after a few minutes
  • Any new rashes on your skin

If you have been told you have low counts and find yourself wondering why you are not receiving blood-boosting medication, bring these questions up with your healthcare team. Often, there are very specific criteria for such therapy, and decisions are made in view of your particular illness, medical history, and treatment plans.

A Word From Verywell

Because of the expense and potential for serious side effects, expert committees have been issuing and updating guidelines for years, to help guide healthcare providers on the use of colony-stimulating factors. The use of these medications can depend on things like the specific type of malignancy, your age, and which other treatments are planned.

Not everybody is a good candidate, but in the right scenario, these medications can help prevent serious neutropenia, fevers, and infections that are associated with worse outcomes.

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7 Sources
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