[Image: Leukemia cells.jpg|250px|right]
Leukemia is a kind of [cancer] that involves the blood-forming [stem cells] of the [bone marrow]. It is primarily characterized by abnormally high levels of [white blood cells].
Normal blood formation
Blood cell formation, or [hematopoiesis], begins with stem cells in the bone marrow. Stem cells are undifferentiated cells that give rise to specialized cells. Bone marrow stems cells first mature into either of two lines:
- Myeloid stem cells which form the [red blood cells], [platelets] and the granulocyte or monocyte types of white blood cells; or
- Lymphoid stem cells, which become lymphocytes, another type of white blood cells.
In leukemia, abnormalities occur during the development of these stem cells.
Mortality and incidence in the Philippines
According to the 2005 Philippine Health Advisories Report of the Department of Health (DOH), leukemia ranks fifth in over-all mortality. It is the fourth leading cause of death among Filipino males, and sixth among Filipino females. According to data from the DOH, leukemia is among the top three cancer killers of Filipino males from 1991 to 1995, along with lung and liver cancers.
From 1993 to 1995, the incidence of leukemia was at 6.6 per 100,000 Filipinos. Leukemia is also the leading cancer among children ages 0-14, comprising 47.8% of all cases among boys and 48% among girls.
Types of leukemia
Depending on the line of stem cells affected, leukemia can be divided into two major types - myelocytic (or myelogenous) and lymphocytic (or lymphogenous).
Leukemia may also be acute or chronic. Acute forms of leukemia progress rapidly, as immature or undifferentiated cells accumulate. When left untreated, acute leukemia may cause death in a few weeks or months. Chronic forms, on the other hand, progress more slowly over the course of several months or even years. Cells are unable to do their normal function as they mature, and often accumulate in different organs.
Based on the two groupings above, leukemia has four main types:
- Acute Lymphocytic Leukemia (ALL). Also called acute lymphoblastic leukemia and acute childhood leukemia, this is the most common type of cancer in children. In the Philippines, it is the most common type of leukemia. With treatment, prognosis for children with ALL is good.
- Chronic Lymphocytic Leukemia (CLL). This type of leukemia is more common in adults aged 60 and above, although adults in their 30s and 40s may also get CLL. On the other hand, children do not get CLL.
- Acute Myeloid Leukemia (AML). Also called acute myelogenous leukemia and acute nonlymphocytic leukemia (ANLL), this type of leukemia can develop in both adults and children. Risk factors associated with AML include [Down syndrome|Down Syndrome] and rare genetic disorders such as [Fanconi anemia].
- Chronic Myeloid Leukemia (CML). Also called chronic granulocytic leukemia, CML usually occurs in middle-age or older. CML patients have the “Philadelphia chromosome” (Ph [chromosome]), which is formed when a part of chromosome 22 attaches to the end of chromosome 9, and a part of chromosome 9 also attaches to the end of chromosome 22. These chromosomal changes result to the formation of the CML-causing gene called the Bcr-Abl cancer gene.
Causes and risk factors
The causes for most types of leukemia are unknown. There are risk factors which are often associated with leukemia:
- Age. About 70% of patients diagnosed with leukemia are over 50 years old.
- Radiation. Exposure to high levels of radiation makes a person more prone to developing leukemia. This has been observed in survivors of atomic bomb explosions in Hiroshima and Nagasaki during World War 2. Radiation therapy and diagnostic radiation such as x-rays are other sources of radiation exposure.
- [Benzene]. Benzene, a sweet-smelling toxic solvent, is common in chemical industries. It is also found in cigarette smoke, gasoline, and crude oil. Prolonged exposure to benzene has been linked to AML and CLL.
- Chemotherapy. Chemotherapy for cancer has been linked with the development of ALL and AML several years later.
- [Smoking]. Cigarette smoking increases the risk for AML.
- Down Syndrome and other hereditary disorders. These increase the risk of developing acute leukemias.
- Familial history of leukemia. This risk factor, though uncommon, has been seen in CLL cases.
Symptoms of acute and chronic leukemia are similar to symptoms of other less serious illnesses.
- Painless swelling of cervical and axillary [lymph nodes]
- Tiredness or weakness (fatigue)
- Shortness of breath ([dyspnea])
- Night sweats or unexplained fever
- Frequent infections
- Easy bruising of skin with no apparent reason
- [Petechiae] which are pinpoint-sized haemorrhages
- Paleness of skin, nail beds, and conjunctiva (pallor)
- Slow-healing wounds or excessive bleeding
- Pain in bones or joints
- Abdominal pain or swelling (from enlarged spleen)
- Unexplained weight loss
Leukemia is usually diagnosed and managed by a team of specialists, which includes an [oncologist] (cancer specialist) and a [haematologist] (specialist on blood diseases). The doctors will order several tests and procedures to be done.
- A [complete blood count] (CBC) will show very high levels of white blood cells ([leukocytosis]). Platelet and red blood cell counts are sometimes low.
- A [differential blood count] (DBC) will determine the proportion of leukemic cells in the blood, aiding in further identifying specific types of leukemia.
- [Blood morphology and staining] will demonstrate any abnormalities in cell shape, structures and in the nucleus.
- Specific blood chemistry tests are done to determine the type of leukemia. Increased leukocyte enzyme alkaline phosphatase and serum vitamin B12 levels are indicative of CML. Hyperuricemia (elevated blood uric acid levels) has been observed in lymphocytic leukemias.
- Bone marrow aspiration or [biopsy] is done to confirm the presence of cancer cells in the bone marrow. This is done by inserting a needle into the breast or hip bone to take bone marrow tissue. Similarly, lymph node biopsy can also be done to determine the spread of the disease.
- A spinal tap may also be performed to take samples of the [cerebrospinal fluid] (CSF) to check for presence of leukemia cells.
- Cytogenetics involves the study of chromosomes of cells from the bone marrow, blood or lymph nodes to identify the specific type of leukemia.
Other diagnostic procedures such as ultrasound and MRI may be done to determine the presence of abnormal growth in other organs in case of [metastasis].
- [Chemotherapy] uses drugs to either kill cancer cells or prevent them from proliferating. Drugs are introduced into the body through the mouth as oral medication, or intravenously. A better alternative is through a catheter, which is a tube inserted into a main vein where drugs are injected. The catheter remains inserted in the vein, preventing repeated direct injections. Intrathecal chemotherapy involves direct injection of drugs into the CSF.
Chemotherapy is often used in the induction stage (initial phase) of treatment and subsequently done in a series of cycles over a period of several months. Chemotherapy kills not just cancer cells, but also normal cells. Adverse effects include hair loss, bruising, fatigue, weakness, frequent infections, nausea, vomitting, diarrhea, poor appetite, mouth sores, and sterility or infertility. In children, chemotherapy may lead to stunted growth.
- [Radiation therapy] (or radiotherapy) involves the use of powerful rays such as protons, electrons, gamma rays and x-rays to eradicate cancer cells. This may either be targeted at specific organs that have a high concentration of leukemic cells or at the whole body. Side effects depend on the body parts being irradiated. Abdominal irradiation may result to gastrointestinal side effects. The skin on the area exposed to radiation may also become red, dry and tender.
- Interferon therapy uses interferons, which are proteins that are released by virus-infected cells. [Interferons] help the body reduce production of leukemia cells and strengthen the immune system. Interferon-alpha (INFa) [Fondue Forks is commonly used to treat leukemia, and may be injected subcutaneously, intravenously, or intramuscularly. Patients may experience headaches, nausea, vomitting, and flu-like symptoms after interferon therapy.
- Stem cell transplant replaces unhealthy blood cells, and is often done after high-dose chemotherapy or radiotherapy. Stem cells may be harvested from the bone marrow (bone marrow transplant), the blood (peripheral stem cell transplant), or umbilical cord blood which has been frozen right after birth ([umbilical cord blood] transplant). Stem cells are delivered intravenously into the body where they develop into new blood cells.
Stem cells from the patient himself/herself (autologous stem cell transplant) are harvested right before treatment and transfused back afterwards. An allogeneic stem cell transplant involves a donor, usually a family member, whose cells closely match those of the patient's. If the patient has a twin, a syngeneic stem cell transplant can be an option.
A primary concern after an allogeneic stem cell transplant is [graft-versus-host disease] (GVHD), where the donated stem cells attack healthy tissues of the transplant patient.
Follow-up and support
After a cycle of therapies, a person with leukemia may go on remission for several months or years. During this symptom-free period, it is important for the patient to consult the oncologist for follow-up and monitoring.
Leukemia is a challenging illness and requires a strong support system to ensure successful management. In the Philippines, there are several support groups. [Project Brave Kids], Cancer Warriors Foundation and [Kythe Foundation] are some groups that support childhood cancer sufferers. These groups have projects with other private organizations and companies such as provision of free cancer medication.
The Philippine Cancer Society has an extensive list of cancer support groups in its website.
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- Image source: http://commons.wikimedia.org/wiki/File:Leukemia_cells.png
DEFAULTSORT: Leukemia [Category: Diseases and illnesses] [Category: Cancers]