Leukemia is a term used to describe cancer of blood. Leukemia begins in the bone marrow, the spongy part in the center of the bone where blood cells are produced.
The bone marrow contains stem cells. These are unspecialized blood cells that first develop into immature cells known as blast cells. Normally, the blast cells become mature red or white blood cells or platelets and carry out their set functions but if the blasts fail to mature properly or if there are too many in the blood, it can cause leukemia. There are two types of stem cells;
• Myeloid stem cells. This develop into myeloblast cells that further develop into red blood cells, most types of white blood cells and platelets.
• Lymphoid stem cells. This develop into lymphoblast cells which then becomes lymphocytes which are type of white blood cells.
Following failure to mature properly into normal blood cells, myeloblast cells will result into development of type of leukemia known as myeloid leukemia while lymphoblast cells will result into lymphoblastic leukemia. In leukemia, abnormal white blood cells grow out of control and multiply in such a way that they crowd the bone marrow. This affects bone marrow’s ability to produce normal levels of other blood cells, hence affecting the way the rest of the body work.
As leukemia progresses, more abnormal blood cells and fewer normal blood cells are produced in the marrow. Those abnormal cells in the marrow will spill out into the blood stream and build up in the blood, which may result into spread to other parts of the body such as lymph nodes, lungs, liver, spleen and kidneys
Types of leukemia
There are mainly four types of leukemia.
• Acute lymphocytic leukemia (ALL)
• Acute myeloid leukemia (AML)
• Chronic lymphocytic leukemia (CLL)
• Chronic myeloid leukemia (CML)
Lymphocytic leukemia is a type of leukemia which begin when immature white blood cells called lymphocytes start to grow out of control. Lymphocytic leukemia is also known as lymphoblastic leukemia or lymphoid leukemia. Myeloid leukemia is a type of blood cancer that start from cells that would normally develop to form white blood cells other than lymphocytes. Myeloid leukemia is also known as myelogenous leukemia, non-lymphocytic leukemia or granulocytic leukemia
Blood is a fluid flowing in our bodies and it is the one that usually conveys nutrients and oxygen. In the body blood is carried in specified tubes known as vessels (veins and arteries). Blood is pumped around the body by a muscular organ called heart. Blood is made up of blood cells carried in a clear fluid called plasma. Blood cells are mainly of three types, red blood cells, white blood cells and platelets.
• Red blood cells. These carry oxygen around the body
• White blood cells. These are responsible for fighting infections
• Platelets. These help the blood to clot.
All these blood cell types have a limited life span, hence they are continually replaced. Most are made in the bone marrow, which is the spongy part in the center of the bones such as the skull, ribs, hip bones, shoulder blades and backbones (vertebrae). Since leukemia is a blood cancer that mainly involves white blood cells, it is important to have a bit more knowledge on white blood cells.
Types of white blood cells
• Lymphocytes. These are the cells responsible for fighting infections and they develop from stem cells known as lymphoblast. Lymphocytes are the cells that mainly make up lymphoid tissue, which are major part of the immune system. The two main types of lymphocytes are;
• B- Cell lymphocytes. These cells make antibodies that fight germs and other infections. These are also called B-Cells.
• T-Cell lymphocytes. These are responsible for destroying germs and they also trigger B-cell lymphocytes to produce antibodies
• Granulocytes. These are mature cells that are responsible for fighting infections. These cells develop from myeloblasts. They are known as granulocytes because they have granules that show up as spots under the microscope. Types of white blood cells known as granulocytes include; neutrophils, eosinophils and basophils. These three are differ on color and size of granule.
• Monocytes. These develop from blood-forming monoblasts in the bone marrow. After sometime in the blood stream, monocytes will enter body tissues to become macrophages. Macrophages destroy germs as well as help lymphocytes recognize germs.
Types of Childhood leukemia
Childhood leukemia simply means types of leukemia that are common to children (between infancy and puberty). People at this age, normally develop acute leukemia. By the term “Acute’’ simply means leukemia can progress quickly and without treatment it is likely to be fatal within a few months although if treated in time, most cases of ALL respond to treatment very well. Acute leukemia include acute myeloid leukemia (AML) and acute lymphocytic leukemia (ALL). Between the two acute leukemia, ALL is the most common one among children.
Sometimes children develop a type of cancer called mixed type leukemia which has properties of both ALL and AML. However this type is normally managed in the same way as ALL.
Chronic leukemia are normally very rare among children. In addition to above types, there is another type of leukemia called Juvenile myelomonocytic leukemia (JMML) which is common among children. This kind of leukemia (JMML) doesn`t grow as fast as AML or as slow as CML.
Risk factors of childhood leukemia
For other cancers that affect adults, cancers are most of the time linked with their environmental factors and life style such as exposure to harmful chemicals and being obese. Developing cancer due to such factors, it takes a lot of time (years), But this is not the case for childhood cancers including leukemia, because a child has not been exposed to such environment for long period and some are not even exposed to such environment but they develop leukemia. Risk factors for childhood leukemia include the following;
• Family history of the disease. Having a sister or brother with leukemia increases a chance for a child to develop leukemia however having a parent who developed leukemia at older age doesn`t seem to increase chance for a child to develop leukemia too.
• Radiation exposure. Exposing a pregnant woman to radiations especially during the first trimester, is said to increase chances for a child to develop cancers including leukemia. In addition to that, children whose parents had radiation accidents such as nuclear reactors accidents and atomic bombs are at increased risk of developing leukemia at some point in their life. For instance, children of Japanese atomic bomb survivors had increased chance of developing leukemia for several generations. The risk of developing leukemia due to radiation exposure is also slightly increased to those children who had radiation therapy for other cancers at some point in their life.
• Genetic factors. Children with some inherited genetic factors are at an increased risk of developing leukemia than those who don`t have such genetic factors. These factors include;
• Ataxia telangiectasia
• Bloom syndrome
• Schwachman-Diamond syndrome
Prevention of childhood leukemia
To prevent something you need to know the specific cause of it. For childhood leukemia, there is no known specific cause of the disease so completely prevention of the disease is not possible. If the risk factors of this type of cancer could be environmental related or lifestyle related, it could have been possible to reduce the risk of developing the disease, but since even risk factors cannot be avoided (controlled), then even reducing the risk of developing the disease is not possible.
Although there is no possible way of completely preventing development of childhood leukemia, pregnant women are advised to avoid radiation exposure so as to reduce risk of affecting the baby.
Screening and early detection
When it comes to cancer, early detection normally provide better treatment outcome. If childhood leukemia is found early, chances for better treatment outcome are very high. For most cancers, early detection has been greatly contributed by the presence of screening process.
Screening is the process of running some tests to someone with no symptoms of the disease with the intention of determining presence or absence of the disease. Unfortunately, currently there are no widely recommended screening tests for children leukemia. The best way for early detection of this leukemia is early reporting to the hospital upon experiencing any possible signs or symptoms of this disease.
For those known to have higher risk of developing leukemia such as those with inherited genetic disorder like Downs syndrome, li-fraumeni syndrome and those who have been exposed to radiations, it is recommended that they have regular medical checkups.
Signs and symptoms of leukemia in children
Children with leukemia may experience the following signs and symptoms. Sometimes those children may not have any of these changes, or the cause of those symptom may be another medical condition that is not cancer, hence looking for medical help when your child start experiencing any of those symptoms is strongly advised. Signs and symptoms of childhood include the following;
• Feeling tired
• Feeling weak
• Easily bruising and bleeding
• Blurred vision
• Persistent infections
• Shortness of breath
• Frequent or severe nosebleed
• Swollen stomach (abdomen)
• Unexpected weight loss
• Enlarged lymph nodes
• Nausea and vomiting
Diagnosis of childhood leukemia
Following suspicion of leukemia, various tests are used to verify the suspicion and learn if the disease has spread to other organs of the body. some tests will help to determine prognosis of the disease. When running those diagnostic tests, your doctor will consider some of the factors including;
• Results of previous tests
• General health condition of the child
• Type of leukemia suspected
The following are some of the diagnostic tests for childhood leukemia (CML) although not everyone will need to go through all those tests during diagnosis.
• Medical history and physical examination. The doctor will review child`s history for risk factors but also do some physical examinations to check if there is any enlarged lymph nodes (lymphadenopathy) and abdominal swelling which can be a result of enlarged liver (hepatomegaly) and spleen (spleenomegaly).
• Blood tests. Blood samples will be taken and checked in the laboratory for full blood count (FBC). The results will reveal whether the levels of blood cells are normal or not. Blood sample may also be used to find if the blood cells are normal or abnormal (leukemia cells).
• Bone marrow tests. If the blood test shows abnormalities in the number or appearance of the white blood cells, the doctor may take some bone marrow sample to check for signs of leukemia. There are two main procedures used in taking bone marrow samples for testing;
• Bone marrow aspiration. This involves the removal of a fluid sample by using a needle (fluid part of bone marrow).
• Bone marrow biopsy. This involves the removal of a small amount of solid tissue using a needle.
If the results from blood tests suggest presence of leukemia, bone marrow tests are advised to be done at the hospital where treatment will be given so as not to do these tests twice.
• Cytochemistry. This diagnostic test is used to find out the specific subtype of leukemia. During the test, cells are exposed to chemical stains (dyes) that react with only some types of leukemia cells and become colored. After the reaction, cells are viewed under microscope and the doctor will be able to know the exact type of cells that are present.
• Immunophenotyping. This test is also known as flow cytometry. It involves using a machine called flow cytometer to look for certain markers (antigens) on the surface of the cell. This test can indicate the subtype of leukemia your child has.
• Genetic tests. These include cytogenetics and molecular tests. The tests are specific for studying genetic makeup of cancer cells which is different to that of normal cells as cancer cells have some faults to their genetic makeup.
• Lumbar puncture. Lumber puncture is a procedure in which a needle is used to take a sample of cerebral spinal fluid (CSF) for examination of fluid makeup and check if it contains cancer cells or blood. AML tends to spread to the CSF, which is the fluid that flows around the brain and spinal cord, so by taking the CSF sample for tests will help reveal if the disease has spreads to the fluid or no.
• Imaging tests. Imaging tests like CT scan, MRI scan, chest X-ray and PET scan are used to determine if the disease has spread to other structures of the body such as lymph nodes, liver and spleen.
Treatment of childhood leukemia
Children cancers are not common, so even their management is normally slightly different from the way adult cancers are managed. This is why children cancers are treated in a specialized centers that deals with management of children cancers.
Children with cancers and their families have special needs different to those of adults. To meet those needs they are treated in specialized centers (children cancer centers). The centers have teams of specialists for children cancers who understand the differences between cancers in adults and children.
Making treatment decision.
Since a person with cancer is a child then treatment decision has to be made by parents. With the help of a child`s doctor, parents have to take time to understand about the condition their child, treatment options and possible outcome of treatment. Parents are free to ask if there is anything they do not understand clearly for example any possible side effects of treatments.
Normally when making treatment plan, doctors normally provide treatment options basing on the following;
• Stage of the disease
• General health condition of a child
• Possible side effects
• Parent`s preference
Taking part in clinical trial
Clinical trials are new drugs or modified mode of treatment or new treatment combination for cases like yours that are to be tested if they are effective to be used as standard care treatment options or not. Your child`s doctor or nurse will discuss with you if you want your child to take part in clinical trial.
Over the years, trials have improved treatments and led to better outcomes to children cancers. It may be helpful to talk with another specialist to get second opinion before letting your child take part in clinical trials. And if your child decides to take part, he/she can also withdraw at any time.
Treatment of childhood leukemia requires a team of doctors and other health care professionals. This team work together and it is called multidisciplinary team. Team may vary depending on the treatment option for a particular case. But generally multidisciplinary team for treatment of childhood leukemia includes hematologist, pediatric oncologist and other health care professionals like oncology nurses and palliative care team.
Also pediatric cancer centers normally have additional support services for children and their families, such as child life specialists, dietitians, physical and occupational therapists, social workers, and counselors. Treatment options include the following
Chemotherapy is a treatment option that involves using drugs to destroy cancer cells or slow its growth. It is given by a specialized doctor known as pediatric oncologist or hematologist. Chemotherapy is normally the main treatment option given to children with leukemia. It is normally given through injection into veins (intravenously) and rarely swallowed as pill or capsule.
A chemotherapy schedule normally consists of a specific number of cycles that are given over a set period of time. Patients with leukemia normally tend to receive several different drugs throughout their treatment.
Side effects of chemotherapy
Side effects of chemotherapy depend on type of drug used, dose given and periodic time by which the drug has been used. Some of the possible side effects of chemotherapy include the following;
• Loss of hair
• Mouth sores
• Nausea and/or vomiting
• Risk of infections
• Easily bruised and bleeding
Targeted therapy is an option that involves targeting specific molecules in the cancer cells using drugs. The drug will stop the growth and spread of cancer cells and at the same time limit harm to normal cells. Drugs for this kind of treatment work differently to that of normal chemotherapy drugs. The drugs for this option can sometimes help even when chemo isn’t, but they can also be used along with normal chemotherapy to help it work better.
Side effects of targeted therapy
Some of the possible side effects of targeted therapy include the following;
• Nausea and/or vomiting
• Mouth sores
• Muscle or bone pain
• Increased risk of infection
• Upper respiratory infection
• High blood sugar level
• Increased level of bilirubin
• Loss of appetite
Stem cell transplantation
Stem cell transplantation is a treatment option that involve replacing a patient`s bone marrow by highly specialized cells called hematopoietic stem cells. Bone marrow that contain cancer cells is destroyed first by using high dose of chemotherapy or radiation therapy, then replaced by healthy stem cells.
This treatment option is sometimes known as bone marrow transplantation. These cells will mature into heathy bone marrow. Hematopoietic stem cells are blood forming cells found in the bone marrow.
A transplant is normally done in several stages and the entire procedure, including recovery, can take months. There are two types of stem cell transplantation;
• Autologous stem cell transplantation. This type uses stem cells that were previously removed from your blood stream and later are transplanted (reinfused) back into your body.
• Allogeneic transplantation. This involve the use of stem cells taken from another person (donor). The donor may be a family member or from a donor registry.
When dealing with childhood leukemia, allogeneic stem cell transplantation is normally used.
Side effects of stem cell transplantation
Most of the side effects of this treatment option resemble to those of chemotherapy but with this treatment options the side effects may be a little bit severe. Some of the possible side effects of include the following;
• Nausea and vomiting
• Hair loss
• Risk of infection
• Easily bruising and bleeding
Radiation therapy involve using high energy x-rays or other radiation particles to destroy cancer cells. It is a treatment option given by a specialized doctor known as radiation oncologist. When dealing with childhood leukemia, radiation therapy is used to destroy cancer cells around the brain or spinal column.
Radiotherapy is also sometimes given to the whole body (total body irradiation) before a stem cell transplant.
Side effects of radiation therapy
Side effects of radiation therapy normally vary depending on the site of treatment and dose of radiations given. Some of the possible side effects of include the following;
• Mild skin reactions
• Loss of hair
• Feeling tired
• Upset stomach
• Loose bowel movement