What is Leukemia?

Leukemia is a cancer of the white blood cells and is characterized by an abnormal proliferation (production by multiplication) of white cells in the bone marrow. Normally the white cells reproduce in an orderly and controlled manner. In Leukemia the process is disturbed and the cells continue to divide but not mature, It is part of the broad group of diseases called hematological neoplasms.

The word Leukemia, which means ‘white blood,’ is derived from the disease’s namesake, high white blood cell counts that most Leukemia patients have before treatment. The high number of white blood cells are apparent when a blood sample is viewed under a microscope. However these cells are defective and hence cannot perform their normal role ie protecting the body from infection. As this disease progresses, it will interfere with the ability of the bone marrow to produce the other types of blood cells, namely the red cells and platelets.

What are the types of Leukemia?

Leukemia can be acute (fast growing) or chronic (slow developing). In children about 95% of Leukemias are acute.

• Acute lymphocytic Leukemia (also known as Acute Lymphoblastic Leukemia, or ALL) is the most common type of Leukemia in young children.
• Acute myelogenous Leukemia (also known as Acute Myeloid Leukemia, or AML) occurs more commonly in adults than in children.
• Chronic lymphocytic Leukemia (CLL) most often affects adults over the age of 60. It sometimes occurs in younger adults, but it almost never affects children.
• Chronic myelogenous Leukemia (CML) occurs mainly in adults. A very small number of children also develop this disease.

Acute Leukemia is the most common form of childhood cancer and is the primary cause of cancer-related mortality in children. One third of all childhood cancers are Leukemia.

What are the symptoms and signs of Leukemia?

In Leukemia, the high numbers of immature white blood cells grow rapidly and ‘cramp’ the bone marrow space. This leads to reduced production of platelets, normal white blood cells and red blood cells.

• Low platelets result in easy spontaneous bleeds such as bruises, petechiae (pinprick bleeds), and bleeding from mucosa such as nose and gum bleeds.
• The white blood cells, which are involved in fighting pathogens, may be suppressed or dysfunctional. This could result in increased episodes of fever and infections.
• Deficiency in the red blood cell leads to anemia. The child will appear pale, become abnormally tired and short of breath.

Other symptoms and signs:

• Weakness and fatigue.
• Loss of appetite and/or weight.
• Swollen or bleeding gums.
• Headache.
• Swelling of the abdomen due to enlarged liver and spleen.
• Bone Pains (can cause a limp).
• Joint Pains.
• Swelling of Lymph nodes. If the nodes in the neck and chest are involved, it could cause obstruction to the blood flow and airway, leading to swelling of the face and noisy breathing.

What are the causes and risk factors for Leukemia?

• There is no single known cause for all of the different types of Leukemia. Researches are actively going on to identify possible causes. However, there are several factors that can predispose a person to develop Leukemia.
• Environmental factors such as ionising radiation and chronic exposure to toxic chemicals such as benzene. There has been concerns about the relationship between living very close to high voltage power supplies and the development of Leukemia, but so far the evidence have not been conclusive.
• Viral infections such as by Epstein barr virus.
• Genetic predispositions. Children who have Down’s syndrome have a 15 times higher risk of developing Leukemia compared with normal children.
• Immunodeficiency. Children with congenital or acquired immunodeficiency diseases are at higher risk of developing lymphoid malignancies.

Until the cause or causes of Leukemia are found, there is no way to prevent the disease.

How is Leukemia diagnosed?

• Full history and complete physical examination. The doctor will examine the child and assess his health status and look for signs of the disease, such as pallor, bleeding tendencies, presence of enlarged liver, spleen, lymph nodes or anything else that seems unusual. A history of the patient’s health habits and past illnesses and treatments will also be taken.
• If Leukemia is suspected, the doctor will ask for a Complete Blood Count (CBC). A CBC measures the number of white blood cells, hemoglobin, hematocrit, and platelet count in a sample of blood. A blood smear will be done on the same sample to look for presence of any abnormal white cell or “blast”.
• If the blood test is suggestive or suspicious of Leukemia, a bone marrow aspiration and biopsy will have to be carried out to confirm the diagnosis and type of Leukemia. This involves the insertion of a needle into the posterior hipbone to obtain a sample of the marrow and a small piece of bone. A hematologist views the bone marrow samples under a microscope to look for presence of Leukemia cells. This test is is essential to diagnose Leukemia.
• Additional test are then carried out on this sample to determine the specific type or subtype of Leukemia. Cytogenetic analysis and molecular study are also done to look for any abnormality. These tests will help the doctor in planning treatment for the child.

How do you stage the Leukemia?

Leukemia is a systemic disease. Unlike cancers of the solid organs, there is no stage in Leukemia. However other tests will have to be done to look for the extent of the disease. This includes:-

• Lumbar puncture: A procedure used to collect cerebrospinal fluid from the spinal column for microscopic examination to look for presence of leukaemic cells. This is done by inserting a needle into the spinal column at the lower back. This procedure is also called an LP or spinal tap.
• Chest x-ray: To look for evidence of enlarged lymph nodes in the chest.
• Lymph nodes biopsy: The removal tissues from the tlymph nodes so they can be viewed under a microscope to check for signs of cancer. This procedure is done only if there seems to be anything unusual about the lymph nodes during the physical exam.

The patient is then stratified into risk groups. This is to enable the doctor to plan treatment in order to achieve the best outome but at reduced toxicity. Several parameters are used to determine risk groups. These include age of patient, total white count at presentation, and involvement of central nervous system, initial response to treatment and presence of certain chromosomes such as the Philiadelphia chromosome.

Risk groups are described as:

• Standard (low) risk.
• Intermediate or moderate risk.
• High risk.

How is Leukemia treated?

Children who have been diagnosed with cancer should be managedby a paediatric oncologist (a doctor who specializes in treating children with cancer). The paediatric oncologist will work closely with other doctors and health personnel who have the experience and expertise in treating children with cancer and who specialize in certain areas of medicine. These may include the following specialists:

• Haematologist.
• Paediatric surgeon.
• Radiation oncologist.
• Endocrinologist.
• Neurologist.
• Radiologist.
• Social worker.
• Rehabilitation specialist and psychologist.
• Dietitian.

Chemotherapy is the mainstay of treatment of childhood leukaemia.

Radiation therapy is less commonly used now. It is given prophylactically in patients with the T-cell type of leukaemia and as treatment in patients with central nervous system leukaemia.

Bone marrow/ Stem cell transplant is the most intensive treatment that can be given. It is used in patients with AML and High risk ALL or Relapsed ALL.

The treatment of childhood ALL is done in phases:

• Induction therapy: This is the first phase of treatment. Its purpose is to kill the Leukemia cells in the blood and bone marrow. This puts the Leukemia into remission.
• Consolidation/intensification therapy: This is the second phase of therapy. It begins once the Leukemia is in remission. The purpose of consolidation/intensification therapy is to kill any remaining leukemia cells and prevents the cells from becoming resistant.
• Maintenance therapy: This is the third phase of treatment and is done on an outpatient basis. The chemotherapy is given orally and in lower doses than those used for induction and consolidation/intensification therapy.

Treatment is usually given for a period of 2-3 years. Because boys generally do worse, treatment for boys is longer. Childhood ALL has a good chance of cure. Most centres are now reporting 90% cure rates for standard risk patients.

Side effects can result from treatment long after it ends. Radiation therapy to the head may affect the child’s developing brain and may cause secondary cancers. Regular follow-up examinations are very important.

Can the disease recur after it has been cured?

Recurrent childhood ALL is cancer that has recurred (come back) after it has been treated. The Leukemia may recur in the blood and bone marrow, brain, testicles, spinal cord, or in other parts of the body. The modalities of treatment are the same as above but will be more intensive.