All About Pediatric Acute Leukemia

What is leukemia?

Leukemia is a cancer of the blood or blood cells. It is helpful to understand what normal blood cells do to understand leukemia. The types of blood cells are:

• White blood cells (also called leukocytes) fight infection. There are many kinds of these cells.
• Red blood cells (also called erythrocytes) carry oxygen from the lungs to the rest of the body and return carbon dioxide to the lungs as waste.
• Platelets (also called thrombocytes) help the body form blood clots to control bleeding.

Blood cells are made in the bone marrow, a spongy area in the center of bones. Larger bones have more bone marrow and make more cells. The larger bones include:

• The femur (top part of the leg or thigh).
• The hip bones.
• Parts of the rib cage.

Some blood cells are not yet mature. These cells are called blasts. Once the cell has matured, it moves out of the bone marrow and into the blood. A healthy body has ways to know when more cells are needed and is able to make them.

In the case of leukemia, one blood cell stops working correctly (in most cases this cell is a white blood cell). The body then makes too many of this cell. These abnormally made cells look different than the healthy cells and do not work properly. The body continues to make these abnormal, non-functional cells, leaving little space for healthy cells. This imbalance of healthy and unhealthy cells is what causes the symptoms of leukemia.

There are several types of leukemia. These are classified by how quickly they progress and what cell they affect. Leukemia is either acute or chronic. This refers to how quickly the disease develops and progresses. In acute leukemia, the white blood cells multiply very quickly and are very immature. They don't work like they should (remember, immature cells are called blasts). The blood fills with blasts quickly, causing symptoms. In chronic leukemia, the blasts form more slowly, allowing the body to make some correctly working cells.

Leukemia subtypes include:

• Acute lymphocytic (lymphoblastic) leukemia (ALL). Types of ALL include B-cell ALL and T-cell ALL.
• Acute myeloid leukemia (AML).
• Chronic myeloid leukemia (CML).

This article will focus on the two most common types of childhood leukemia, acute lymphoblastic leukemia (ALL) and acute myeloid leukemia (AML). There are subtypes of ALL and AML. Chronic leukemia (CML and CLL) is very rare in children.

What causes leukemia and who is at risk?

Leukemia is the most common childhood cancer and makes up about 25.8% of cancer cases. There are about 3,715 new cases of childhood leukemia diagnosed each year. The exact cause of childhood leukemia is not known and it continues to be studied. There are a few known risk factors, such as:

• Genetic syndromes including Down syndrome, Li-Fraumeni syndrome, neurofibromatosis, and Fanconi anemia.
• Having a poorly functioning immune system, either inherited or caused by a medicine or disease. Some children are born with (inherited) immune system problems including those with Ataxia-telangiectasia, Wiskott-Aldrich syndrome, Bloom syndrome, and Shwachman-Daimond syndrome. A child's immune system may be depressed if they are taking suppressant medications after an organ transplant.
• Having a sibling with leukemia.
• Exposure to radiation, chemotherapy, and certain chemicals.

How can leukemia be prevented in a child?

Children who are diagnosed with leukemia often do not have any risk factors. Because of this, there is no way to prevent leukemia.

What screening tests are used?

There are no recommended screening tests for childhood cancer. A child won't be tested for leukemia unless they are showing signs or symptoms of the disease.

What are the signs and symptoms?

The symptoms of childhood leukemia are not specific to leukemia. This means that the symptoms seen are caused by a number of different health issues. Leukemia affects the blood so many of the symptoms are a result of abnormal numbers of the blood cells discussed above.

• Not enough red blood cells can make a person feel tired, weak, cold, dizzy, short of breath, and look pale.
• A low platelet count can cause bleeding more easily than usual and bruising.
• A low or very high white blood cell count can cause fevers and recurrent infections.

Some other symptoms are:

• Bone and joint pain. This is caused by the bone marrow being full of immature blood cells.
• Stomach pain, loss of appetite, and weight loss. Leukemia cells can build up in the organs in the belly like the kidneys, liver, and spleen. This can lead to the organs becoming bigger than normal which leads to pain. The pain can lead to loss of appetite and weight loss.
• Swollen lymph nodes. The lymph nodes work to filter and clean your blood. Leukemia cells can build up in the lymph nodes and cause them to become enlarged.

There are other symptoms of leukemia depending on how the cancer is affecting the body. The important thing is to check in with your child's provider if they are not feeling well.

How is childhood leukemia diagnosed?

If a provider thinks that a child could have leukemia, the first step is for the provider to perform a thorough physical. The provider may ask the child about how they are feeling and what symptoms they have been having. Along with a physical exam and history, the provider will order other tests which may include:

• Bone marrow biopsy: A biopsy is when a piece of tissue is removed to check for cancer cells. A small amount of fluid or tissue is taken from the bone marrow. A needle is placed into a bone, often the hip bone, to obtain this fluid or tissue. The process can be painful, but every effort will be made to keep a child comfortable for the test.
• Blood tests will be taken. A complete blood count (CBC) will be done to count and look at the different types of blood cells. Tests will check how well the kidney and liver are functioning. Blood may be drawn to do genetic studies.
• A child may also need CT, MRI, X-ray, and ultrasounds to look at certain parts of the body.
• Lymph node biopsy: In some cases, a lymph node may be removed and looked at for cancer cells.
• Lumbar Puncture: If there is concern that there are cancer cells in the cerebrospinal (CSF) fluid, then a lumbar puncture may be done. The cerebrospinal fluid is the fluid that surrounds the brain and spinal cord. A needle is placed in the lower back and into the spinal canal to remove some fluid for testing. The pressure in the brain can also be checked during this procedure. Providers will ensure that your child is comfortable for the procedure.

The results of these tests will help the care team to come up with a treatment plan.

How is childhood leukemia treated?

Treatment for childhood leukemia will depend on many factors including the age of the child, the type of leukemia being treated, the symptoms the child is having, and the goals of treatment. More than one treatment may be used. There are also different stages of treatment that can include:

• Induction. The goal of treatment during the induction period is to stop cancerous cells being made in the bone marrow. Remission is when cancerous cells are no longer being made and the cancer cannot be detected. This stage of treatment usually lasts about a month.
• Intensification. Also called consolidation, this is the continuation of treatment. Even though cancer cells in the blood may not be detected, they could still be there. Because of this, it is best to continue treatment. Some children will be given large doses of chemotherapy and a stem cell transplant during this stage of treatment.
• Maintenance. The purpose of this stage of treatment is to keep the bone marrow leukemia free. Treatment continues for months to years but not as intensely. During this stage, a child is monitored for relapse (return of cancer).

The patient, caregivers, and care team will discuss the best course of treatment. Something to consider when planning a treatment course is that there is potential for late or long-term side effects, meaning side effects that can occur after treatment has ended. The provider should speak about these possible side effects.

Chemotherapy

Often, chemotherapy is the primary treatment used for childhood leukemia. Chemotherapy is the use of medications to kill cancer cells. Chemotherapy can be given in a number of ways including into a vein, by mouth, into a muscle, or into the cerebrospinal fluid. It is most commonly given into a vein (intravenous or IV). Chemotherapy is often used because it can reach almost any cell in the body. Because of this, it is called a systemic (goes through the whole body) therapy. The type(s) of chemotherapy given and how often will be determined by your provider.

Stem Cell Transplant

A stem cell transplant, also called a bone marrow transplant, is used to treat some cases of childhood leukemia. It is done in cases where very high doses of chemotherapy are given which kills off the body’s own blood cells. Then the body is "rescued" with new stem cells which will begin to form new blood cells. The stem cells can either come from blood, bone marrow or a baby's umbilical cord blood.

There are two different types of stem cell transplants. An allogenic stem cell transplant uses cells from a donor. The donor's tissue type is tested to make sure it is a match for the patient. An autologous transplant uses the patient's own healthy stem cells.

The process starts when a child is given very high doses of chemotherapy and sometimes whole body radiation. The goal is to get rid of any cancer cells in the body but it also severely weakens the immune system. Stem cells are then infused into the child's body to help rebuild the immune system with the hopes of no cancer cells growing. There are a number of possibly severe side effects. This treatment requires a long hospital stay in a facility equipped to take care of patients who have had transplants.

Targeted Therapy

Targeted therapy is medication that targets specific parts of a cancer cell. Targeted therapy can be used on its own or with chemotherapy. Different types of leukemia are treated with different targeted therapies.

• CML and some cases of ALL have an abnormal chromosome on their leukemia cells called the Philadelphia chromosome. This gene mutation is called BCR-ABL and there are targeted therapies called tyrosine kinase inhibitors that can be used to treat these leukemias. Imatinib, dasatinib, and nilotinib are examples of these medications.
• AML is sometimes treated with a medication called gemtuzumab ozogamicin. This targeted therapy is a monoclonal antibody. It works to bring chemotherapy to leukemia cells and kill them.
• APL can be treated with targeted therapies called differentiation agents. These medications work to help blasts mature into normal white blood cells. Examples are all-trans-retinoic acid and arsenic trioxide.

Immunotherapy

Immunotherapy medications use the body's own immune system to kill cancer cells. Chimeric antigen receptor (CAR) T-cell therapy is when T cells are removed from the blood, altered in a lab, and then put back into the blood stream. In the lab, specific receptors (CARs) are placed on these cells. These receptors attach to the proteins on leukemia cells. The cells are put back into the child's blood where they find leukemia cells and kill them. Tisagenlecleucel is an example of CAR T-cell therapy. It targets the CD19 protein that is found on some leukemia cells. It is used to treat some cases of ALL.

Radiation

Radiation is the use of high energy x-rays to kill cancer cells. It can be used to prevent the spread of leukemia cells or to treat leukemia cells already in a part of the body. In some cases, it is used to treat the brain, testicles or a tumor pressing on the windpipe (trachea). In most cases, chemotherapy is the preferred treatment. If a child needs a stem cell transplant then radiation to the whole body will be done prior to the transplant.

Clinical Trials

There are clinical research trials for most types of cancer, and every stage of the disease. Clinical trials are designed to determine the value of specific treatments. Trials are often designed to treat a certain stage of cancer, either as the first form of treatment offered, or as an option for treatment after other treatments have failed to work. They can be used to evaluate medications or treatments to prevent cancer, detect it earlier, or help manage side effects. Clinical trials are extremely important in furthering our knowledge of disease. It is through clinical trials that we know what we do today, and many exciting new therapies are currently being tested. Talk to your provider about participating in clinical trials in your area. You can also explore currently open clinical trials using the OncoLink Clinical Trials Matching Service.

Follow-up Care and Survivorship

After treatment for childhood cancer, you will be followed closely to monitor for the cancer coming back, to manage ongoing side effects, and to transition to survivorship. At first you will have frequent appointments with providers and have ongoing tests to monitor your health. As time goes on, these visits and testing will become less frequent. The oncology team will discuss the plan for follow up.

What can you do to live a healthy life after treatment? There is no supplement or specific food you can eat to assure good health, but there are things you can do to live healthier, prevent other diseases, detect cancers early and work with the social and emotional issues, including insurance, employment, relationships, sexual functioning, and fertility, that a prior cancer diagnosis sometimes brings with it. Your oncology team is there to support you and can help you find support resources.

It is important to have a plan for who will provide follow up care (an oncologist, survivorship doctor or primary care doctor). Talk with the team about developing a survivorship care plan or develop one using the Smart ALACC tool. Your child may benefit from being seen in a survivorship clinic. At a survivorship clinic a provider can review your child's history and provide recommendations. You can contact cancer centers in your area to see if they have a survivor's clinic or search for a clinic on OncoLink's survivorship clinic list.

Resources for More Information

Leukemia and Lymphoma Society: A global leader in the fight against cancer. Their mission is to cure leukemia, lymphoma, Hodgkin's disease, myeloma, and improve the quality of life of patients and their families.

Childhood Leukemia Foundation: Provide patient education, advocacy, self-esteem and smiles. All programs are free of charge.

Alex's Lemonade Stand: Their mission is to change the lives of children with cancer through funding impactful research, raising awareness, supporting families, and empowering everyone to help cure childhood cancer.