Bone Marrow Suppression

Also called myelosuppression

Blood cells produced in the bone marrow are rapidly dividing cells. The bone marrow makes:

• red blood cells
• white blood cells
• platelets

Each blood cell lives for a certain amount of time. When they die, they are normally replaced by new ones made within the bone marrow.

Lifespan of blood cells

Bone marrow suppression is a common problem for people with cancer. It describes a condition where one or more of the main types of blood cells are decreased. A decrease in:

• red blood cells can lead to anemia
• white blood cells can increase the risk for infection (leukopenia or neutropenia)
• platelets can cause easy or excessive bleeding (thrombocytopenia)

Pancytopenia refers to low levels of all 3 types of blood cells in the blood.

Causes

The risk for bone marrow suppression is increased:

• When cancer cells are present in the bone marrow, because of blood-related cancers like leukemia or multiple myeloma, or when lymphoma or solid tumours spread to the bone marrow and affect blood cell production.
• In elderly people or people with a poor nutritional status, because their ability to produce new cells is decreased.
• With major cancer surgery. The reason for this is not completely clear but may be related to a decrease in immune function following surgery or anesthesia.
• When chemotherapy drugs are given, such as alkylating drugs and the nitrosureas; high doses of chemotherapy; combinations of chemotherapy drugs; and when chemotherapy is given along with radiation therapy. Chemotherapy and radiation therapy can damage the blood cell producing tissue of the bone marrow.
• With some biological therapies, such as monoclonal antibodies, because some monoclonal antibodies can also affect the bone marrow in a way similar to what chemotherapy drugs can do.
• In people with kidney or liver problems receiving chemotherapy, because they are not able to break down (metabolize) the drugs.
• When radiation therapy is given, especially to areas that contain a large amount of bone marrow, such as the pelvic bones, or if a large part of the skeleton is radiated.

Effect of cancer treatments on blood counts

Chemotherapy and radiation therapy given to kill cancer cells can also damage rapidly dividing normal cells. After chemotherapy or radiation therapy, blood cells are not replaced as they normally would be. The bone marrow may not be able to make enough of the blood cells fast enough to replace the healthy cells lost during treatment, so blood cell counts begin to drop.

The nadir is the lowest level that blood cell counts reach after cancer therapy. It is different for each blood cell and occurs at different times. Since red blood cells live the longest, it takes them longer to reach their nadir. White blood cells and platelets reach their lowest levels sooner, about 7–14 days after treatment. Side effects caused by low blood cell counts are often worse when blood cells are at their nadir.

Blood counts often begin to recover and rise on their own, usually within 2–4 weeks after treatment, but sometimes medications or blood transfusions are needed to treat severe problems caused by low blood counts. Drops in blood cell counts may require cancer treatment to be postponed until blood counts recover.

Diagnosis

A complete blood count (CBC) is done to measure the levels of blood cells and platelets before treatment is started and provides a baseline to compare blood test results done during and after treatment. CBCs are routinely done throughout treatment to check for bone marrow suppression.

Sometimes a bone marrow aspiration and biopsy will be done to find out the cause of low blood counts, if they stay low for a long period of time.

Management

Bone marrow suppression is grouped according to which type of blood cell is affected. Management of these decreases will depend on the particular blood cell affected.