People sometimes confuse leukemia and lymphoma. Leukemia is a cancer of the blood; lymphoma is cancer of the lymphatic system (lymph glands). The word Leukemia comes from the Greek leukos, which means "white", and aima, which means "blood".
The DNA of immature blood cells, mainly white cells, becomes damaged in some way. This abnormality causes the blood cells to grow and divide continuously. Healthy blood cells die after a while and are replaced by new cells, which are produced in the bone marrow.
The abnormal blood cells do not die when they should, and accumulate, occupying more space. As more cancer cells are produced, they impede the function and growth of healthy white blood cells by crowding out space in the blood. Essentially, the bad cells crowd out the good cells in the blood.
Fast facts on leukemia
Here are some key points about leukemia. More detail and supporting information is in the main article.
- According to the Leukemia and Lymphoma Society, 60,140 people were expected to be diagnosed with leukemia in 2016.
- There are about 54,270 new cases of leukemia in the United States each year.
- Although leukemia is among the most common childhood cancers, it most often occurs in older adults.
- Leukemia is slightly more common in men than women.
- People with leukemia have many treatment options, and treatment for leukemia can often control the disease and its symptoms.
Blood clotting is poor - As immature white blood cells crowd out blood platelets, which are crucial for blood clotting, the patient may bruise or bleed easily and heal slowly - he may also develop petechiae (a small red to purple spot on the body, caused by a minor hemorrhage).
Affected immune system - The patient's white blood cells, which are crucial for fighting off infection, may be suppressed or not working properly. The patient may experience frequent infections, or his immune system may attack other good body cells.
Anemia - As the shortage of good red blood cells grows the patient may suffer from anemia - this may lead to difficult or labored respiration (dyspnea) and pallor (skin has a pale color caused by illness).
Other symptoms - Patients may also experience nausea, fever, chills, night sweats, flu-like symptoms, weight loss, bone pain, and tiredness. If the liver or spleen becomes enlarged the patient may feel full and will eat less, resulting in weight loss.
Weight loss can also occur independent of hepatomegaly (enlarged liver) or splenomegaly (enlarged spleen). Headache is more common among patients whose cancerous cells have invaded the CNS (central nervous system).
As all these symptoms could be due to other illnesses, a diagnosis of leukemia can only be confirmed after medical tests are carried out.
Leukemia risk factors
Some factors put certain people at higher risk of developing leukemia. The following are either known or suspected factors:
- artificial ionizing radiation
- viruses - HTLV-1 (human T-lymphotropic virus) and HIV (human immunodeficiency virus)
- benzene and some petrochemicals
- alkylating chemotherapy agents used in previous cancers
- maternal fetal transmission (rare)
- hair dyes
Genetic predisposition - some studies researching family history and looking at twins have indicated that some people have a higher risk of developing leukemia because of a single gene or multiple genes.
Down syndrome - people with Down syndrome have a significantly higher risk of developing leukemia, compared with people who do not have Down syndrome. Experts say that because of this, people with certain chromosomal abnormalities may have a higher risk.
Electromagnetic energy - studies indicate there is not enough evidence to show that ELF magnetic (not electric) fields that exist currently might cause leukemia. The IARC (International Agency for Research on Cancer) says that studies which indicate there is a risk tend to be biased and unreliable.
Leukemia and bone marrow function
The bone marrow is found inside of bones. The marrow in the large bones of adults produces blood cells. Approximately 4 percent of our total bodyweight consists of bone marrow.
There are two types of bone marrow:
- Red marrow, made up mainly of myeloid tissue.
- Yellow marrow, made up mostly of fat cells.
Red marrow can be found in the flat bones, such as the breast bone, skull, vertebrae, shoulder blades, hip bone, and ribs. Red marrow can also be found at the ends of long bones, such as the humerus and femur.
White blood cells (lymphocytes), red blood cells, and platelets are produced in the red marrow. Red blood cells carry oxygen, white blood cells fight diseases. Platelets are essential for blood clotting. Yellow marrow can be found in the inside of the middle section of long bones.
If a person loses a lot of blood the body can convert yellow marrow to red marrow in order to raise blood cell production.
White blood cells, red blood cells and platelets exist in plasma - blood plasma is the liquid component of blood, in which the blood cells are suspended.
Experts divide leukemia into four large groups. These groups are classified as acute vs. chronic and lymphocytic vs. myelogenous
Chronic and acute leukemia
There are several stages of maturation in a white blood cell's lifespan. Acute leukemia is a rapidly progressing disease that results in the accumulation of immature, useless cells in the marrow and blood. They are squeezed out of the bone marrow too early and are not functional. Chronic progresses more slowly and allows more mature, useful cells to be made. In other words, acute leukemia crowds out the good cells more quickly than chronic leukemia.
Lymphocytic and myelogenous leukemia
Leukemias are also subdivided into the type of affected blood cell. If the cancerous transformation occurs in the type of marrow that makes lymphocytes, the disease is called lymphocytic leukemia. A lymphocyte is a kind of white blood cell inside the vertebrae immune system. If the cancerous change occurs in the type of marrow cells that go on to produce red blood cells, other types of white cells, and platelets, the disease is called myelogenous leukemia.
To recap, there are two groups of two groups - four main types of leukemia, as you can see in the illustration below:
Acute lymphocytic leukemia (ALL)
Also known as acute lymphoblastic leukemia - this is the most common type of leukemia among young children, although adults can get it as well, especially those over the age of 65. The 5-year survival rate is greater than 85 percent among children.
The following are subtypes of ALL: precursor B acute lymphoblastic leukemia, precursor T acute lymphoblastic leukemia, Burkitt's leukemia, and acute biphenotypic leukemia.
Chronic lymphocytic leukemia (CLL)
This is most common among adults over 55, although younger adults can get it as well. It is the most common type of leukemia in adulthood. CLL hardly ever affects children. The majority of patients with CLL are men, over 60 percent. The 5 year survival rate of treated CLL patients is 82 percent. Experts say CLL is incurable. A more aggressive form of CLL is B-cell prolymphocytic leukemia.
Acute myelogenous leukemia (AML)
AML is more common among adults than children, and affects males significantly more often than females. Patients are treated with chemotherapy. In children diagnosed with AML, the 5-year survival rate is 60-70 percent, though the overall survival rate is 26.6 percent.
Under the WHO classification system, there are six main groups of AML: AML with recurrent genetic abnormalities, AML with myelodysplasia-related features, therapy-related AML and MDS, AML not otherwise specified, myeloid sarcoma, and myeloid proliferations related to Down Sydrome.
Chronic Myelogenous Leukemia (CML)
The vast majority of patients are adults. According to the National Cancer Institute, the 5-year survival rate is 65.1 percent. However, many people with CML have a gene mutation that responds to targeted cancer therapy, called Gleevec. Gleevec (imatinib) is commonly used to treat CML, as well as some other drugs. For those people whose cancer is susceptible to Gleevec, their survival rate can be as high as 90 percent. Chronic monocytic leukemia is a subtype of CML.
As the various types of leukemias affect patients differently, their treatments depend on what type of leukemia they have. The type of treatment will also depend on the patient's age and his state of health.
In order to get the most effective treatment the patient should get treatment at a center where doctors have experience and are well trained in treating leukemia patients. As treatment has improved, the aim is complete remission - that the cancer goes away completely for a minimum of five years after treatment.
Acute leukemia treatments
Treatment for patients with acute leukemias should start as soon as possible. The mainstay of treatment is still chemotherapy, which will be tailored to the type of cancer a patient has. Sometimes, chemotherapy may be given in three phases: induction, consolidation and maintenance. In some cases, a bone marow transplant may be warranted (allogeneic stem cell transplantation).
Chronic leukemia treatments
Chronic leukemia treatment is tailored to the type of cancer a person has and what phase it is in. Types of treatment include targeted therapy, interferons, chemotherapy, radiation therapy, surgery and stem cell transplant. Targeted therapy is different than chemotherapy, because it attacks a specific part of the cancer cell. Examples of this include Gleevec (imatinib mesylate) for CML, Sprycel (dasatinib), and Tarigna (nilotinib).
In some cases of CLL, treatment isn't necessary in the early stages. Instead, an oncologist may opt for watchful waiting with frequent doctor's visits.
A bone marrow transplant is the only current way of curing a patient with CML. The younger the patient is the more likely the transplant will be successful.
Leukemia prognosis and life expectancy
All leukemia patients, regardless of what type they have or had, will need to be checked regularly by their doctors after the cancer has gone (in remission). They will undergo exams and blood tests. The doctors will occasionally test their bone marrow. As time passes and the patient continues to remain free of leukemia the doctor may decide to lengthen the intervals between tests.