Leukemia

Leukemia is a cancer that begins in abnormal blood cells within the bone marrow of both children and adults. Normal white blood cells help fight infection as part of the body’s immune system. When these cells become old or damaged, they die and are replaced with healthy new cells. But in leukemia, some of the white blood cells behave abnormally. They cannot fight infection properly, they grow uncontrollably and they don’t die when they should.

As a result, large numbers of the abnormal cells accumulate in the bone marrow, crowding out healthy blood cells and slowing or preventing new healthy cells from being produced. Unlike many other types of cancer, leukemia does not form solid tumors. Instead, when these abnormal cells continue to grow unchecked, the number of healthy white blood cells, red blood cells and platelets is reduced, putting the individual at increased risk of infection. As leukemia cells spill into the bloodstream, they travel to the lymph nodes, spleen, liver and elsewhere in the body, affecting normal body functions.

Leukemia is most often diagnosed in people older than 55, but it’s also the most common cancer diagnosed in children younger than 15 (see Pediatric Cancer, page 12).

BONE MARROW AND TYPES OF BLOOD CELLS

Leukemia begins in the bone marrow, where blood is created, so knowing more about these important structures may help you better understand the disease (see Figure 1).

Bone marrow is the soft, spongy center of some bones. It contains immature blood stem cells, more developed blood-forming cells, fat cells and tissues that support cell growth.

Platelets are blood cells that gather around wounds, forming clots to stop the bleeding. They also help repair wounds and create blood vessels.

Red blood cells (erythrocytes) carry oxygen from the lungs to other parts of the body.

Index


White blood cells (leukocytes) are essential to the immune system as the infection fighters of the body. There are several types of white blood cells. These two types are
involved in leukemia:

  1. Lymphocytic cells (lymphocytes) make up lymphoid tissue found in the lymph nodes, thymus, spleen, tonsils and elsewhere in the body. Lymphocytes can be B-lymphocytes (B-cells), T-lymphocytes (T-cells) or natural killer (NK) cells.
  2. Myeloid (myelogenous) cells begin as immature blood stem cells that develop into red blood cells, white blood cells (excluding lymphocytes) and platelets.

MORE ABOUT LEUKEMIA

Leukemia is classified by how rapidly the abnormal cells grow, the kind of blood cell in which the disease starts and its response to treatment.

Acute leukemia cells grow rapidly. They look similar to immature white blood cells, and as their numbers increase, the bone marrow is prevented from making normal, healthy blood cells.

Chronic leukemia cells look similar to healthy, mature white blood cells, but the cells are unable to mature fully. These leukemia cells grow slowly, and the progression of chronic leukemia varies from person to person.

Lymphocytic leukemia begins in bone marrow in cells that develop into white blood cells called lymphocytes. Lymphocytic leukemia is also sometimes called lymphoid or lymphoblastic leukemia.

Myeloid leukemia begins in early myeloid blood cells in the bone marrow. Myeloid leukemia is sometimes called myelogenous, myelocytic or myeloblastic leukemia.

Refractory leukemia is when leukemia cells are still present after some other treatment has been tried. Immunotherapy is available to treat some types of refractory leukemia. Your doctor will take into account the therapies you have already tried and your overall health before recommending another treatment plan.

Relapsed leukemia is the name given to leukemia that initially responds to treatment but stops responding after six months or more. Some types of leukemia have multiple relapses, which are also referred to as recurrences. If your cancer relapses, your doctor will begin a new cycle of diagnostic tests. These tests may include another tissue biopsy and laboratory tests. The doctor will confirm if the cancer is recurrent and determine if it has transformed into a more aggressive subtype, which will affect your new treatment plan.

IMMUNOTHERAPY FOR LEUKEMIA

Immunotherapy and other research advances are enabling more people with leukemia to live longer after treatment. Some types of leukemia are treated with approved immunotherapies, and some are treated in clinical trials. Each type of leukemia responds differently to various therapies, so your medical team will recommend treatment options based on your type of blood cancer and other factors, including your age, overall health and prognosis (predicted outcome from treatment). One or a combination of treatments may be used with immunotherapy, including chemotherapy, targeted therapy and stem cell transplantation.

It’s important to find a doctor experienced in treating the type of leukemia you have. A hematologist who specializes in your type of leukemia will be familiar with the most suitable options, including immunotherapy treatments that are being evaluated in clinical trials. If receiving treatment from an expert in the field will involve traveling and that isn’t an option, you may find a specialist willing to consult with your local doctor.

Following are some types of leukemia and the immunotherapies available to treat them.

Acute lymphocytic leukemia (ALL) progresses rapidly and, if untreated, can spread from the blood and bone to other parts of the body. Treatment is recommended soon after diagnosis because these fast-growing cells can quickly become life-threatening. ALL is the most common type of leukemia diagnosed in children and adolescents. 

Biomarker testing can now identify molecular abnormalities associated with ALL. Testing for these abnormalities allows your doctor to choose treatments that target specific biological features. Chromosomal abnormalities have been found with ALL, specifically the Philadelphia chromosome. Genes that may be tested include BCR-ABL, TEL and AML1.

The first immunotherapy approved to treat a form of ALL was a monoclonal antibody in 2014. In 2017, the first gene therapy was approved in the United States to treat children and young adults with B-cell ALL. This breakthrough treatment is called chimeric antigen receptor (CAR) T-cell therapy (see Figure 2, page 2).

Chronic lymphocytic leukemia (CLL) is a slow-growing blood cancer of the lymphatic system and the most common type of leukemia diagnosed in adults. Abnormal white blood cells (lymphocytes) multiply, accumulating over time in the blood, bone marrow, lymph nodes and spleen. This interferes with the production of red blood cells, which carry oxygen; white blood cells, which fight infection; and platelets, which are needed for blood to clot. 

Genetic testing, also referred to as molecular profiling, may be done to look for certain gene abnormalities or mutations, proteins and changes in chromosomes that may indicate how the disease may progress. Doctors use these tests to determine whether there are chromosomal or other genetic changes in lymphocytes. Healthy cells in the body contain 23 pairs of chromosomes, but CLL cells often have abnormal chromosome changes, such as deletions or missing parts. In CLL, it is common for parts of chromosomes 11, 13 or 17 to be missing. This is known as a deletion and is often an indication of how slowly or quickly the disease will progress. For example, a deletion in chromosome 13 means that the CLL cells grow slowly, and a deletion in chromosome 17 means the disease will progress quickly and be difficult to treat.

Some monoclonal antibodies, used alone and in combination with other therapies, are approved to treat CLL.

Chronic myeloid leukemia (CML) is a slow-growing cancer that develops in abnormal immature myeloid cells, which become white blood cells (other than lymphocytes), red blood cells or cells that make platelets. Biomarkers used to confirm a diagnosis of CML include tests for the BCR-ABL1 fusion gene and Philadelphia chromosome.

CML may be treated with an interferon, a type of immunotherapy called a cytokine. It is typically not used as a first-line treatment. Ask your doctor if it is appropriate for you.

Hairy cell leukemia is rare. The unique name comes from the appearance of its cells under a microscope. Hairy cell leukemia begins when certain blood stem cells become abnormal, accumulating in the blood and bone marrow to leave less room for healthy cells and platelets.

One type of immunotherapy approved for this type of leukemia is a cytokine. The approval of alpha interferon in 1986 represented a new advance for treating hairy cell leukemia. Before then, splenectomy (spleen removal) was the only known effective therapy for this disease. Interferon benefited people with active hairy cell leukemia, with or without having a splenectomy. Today, interferon has a relatively limited role in treating this type of leukemia. Ask your doctor if it may be beneficial for you.

It is important to learn as much as possible about your type of leukemia and the available options so you can confidently partner with your medical team to make treatment decisions and manage your disease.

 

Illustration: Figure 1 Leukemia Blood Cells (filename: Leukemia Fig 1)

FDA-APPROVED CANCER IMMUNOTHERAPIES FOR SOME TYPES OF LEUKEMIA*

  • alemtuzumab (Campath)
  • blinatumomab (Blincyto)
  • interferon alfa
  • interferon alfa-2a (Roferon-A)
  • interferon alfa-2b (Intron A)
  • moxetumomab pasudotox-tdfk (Lumoxiti)
  • obinutuzumab (Gazyva)
  • rituximab (Rituxan)
  • rituximab and hyaluronidase human (Rituxan Hycela)
  • tisagenlecleucel (Kymriah)
  • venetoclax (Venclexta)

*Each therapy is prescribed based on specific criteria. Discuss your options with your doctor.

As of 3/14/19

 

SIDEBAR: QUESTIONS TO ASK YOUR DOCTOR         

  • What type of leukemia do I have?
  • How does immunotherapy work?
  • Do you recommend it for my type of leukemia?
  • Have you had success treating leukemia with immunotherapy?
  • How and where will I receive treatments, and for how long?
  • What side effects should I expect – short term and long term – and how will we manage them?