What Are Bone Marrow Stimulators Used For?

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

When you have a common blood test known as a complete blood count, your counts or levels are reported for things like red blood cells, white blood cells, and the platelets that help your blood to clot. Each of these cell types or blood components normally occurs in a range of levels that are considered normal. In certain circumstances, 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 can have potentially serious risks and side effects, in addition to their blood-boosting benefits, and not all cases of low cell counts are treated with these drugs. Typically, you and your healthcare team will discuss when bone marrow stimulating drugs might be best used and when they are less likely to be necessary or helpful. The use of bone marrow stimulating drugs in cancer patients is considered supportive care, meaning that the drug does not directly fight the cancer, but supports the patient in other ways.

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.

So, without healthy bone marrow, the production line suffers—new blood cells can’t be made to keep pace with loss of cells that are old or warn out, or that die as a side effect of certain cancer treatments. Bone marrow may be unhealthy for a variety of reasons, including certain blood cancers, or hematologic malignancies.

What Is Bone Marrow Stimulation?

Healthy bone marrow responds to the body’s chemical signals that essentially communicate the need to boost 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 is 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 a 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 are 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, and there are many, many 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 those blood-forming hematopoietic stem cells can be found out in the blood stream, and doctors have learned to collect them from healthy people who are donating their stem cells for a marrow/stem cell transplant. Part of that process involved boosting the bone marrow so that more stem cells can be more easily 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 health care 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

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 chemotherapy and in some other diseases. This drug can help increase the platelet counts of some patients for a time, however it is not helpful in all patient types or for all cases of low platelets, or thrombocytopenia.

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 ocuring 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 Doctor

If you are taking a bone marrow stimulating medication, notify your doctor if you are experiencing any untoward effects. Contact your health care 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 heart beat
  • 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 health care 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 health care 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 the serious neutropenia, fevers and infections that are associated with worse outcomes.

Sources:

Be The Match National Marrow Donor Program. Steps of PBSC or bone marrow donation.

Smith TJ, Bohlke K, Lyman GH, et al. Recommendations for the use of WBC growth factors: American Society of Clinical Oncology clinical practice guideline update. J Clin Oncol. 2015;33:3199–3212.

Kuter DJ, Rummel M, Boccia R, et al. Romiplostim or standard of care in patients with immune thrombocytopenia. N Engl J Med. 2010;363:1889-1899.

Continue Reading