Acute lymphoblastic leukemia: Causes and treatments
It is also known as ALL, acute lymphocytic leukemia, or B-Cell Acute lymphoblastic leukemia.
ALL accounts for 80 percent of childhood leukemias. It is the only leukemia more common in children under 5 years than in adults. It often affects children aged 2 to 3 years.
In the United States (U.S.) there are about 6,500 new cases of ALL annually, or 1.7 in every 100,000 people.
The American Cancer Society estimate that 2017 will see 5,970 new ALL diagnoses and 1,440 deaths from ALL.
ALL occurs when there are too many immature blast cells in the blood.
Symptoms of ALL usually start slowly and then escalate in severity as the number of blast cells in the blood rises.
In people with ALL, the blood and bone marrow have large numbers of early white blood cells, or lymphocytes, which become leukemia cells.
Signs and symptoms may include:
- excessive sweating
- frequent unexplained bleeding, such as nosebleeds or bleeding gums
- high fever
- painful joints and/or bones
- several infections over a short period
- swollen glands (lymph nodes)
- swollen liver
- swollen spleen
- skin bruises easily
- skin is paler than it should be
- unexplained weight loss
The affected cells can spread into the central nervous system (CNS), affecting the brain and spinal cord. If this happens, the patient may have neurological symptoms, such as dizziness, vomiting, blurred vision, fits (seizures), and headaches.
Causes and risk factors
The causes of ALL are mostly not yet known, but there are some common risk factors.
Experts say the main causes of ALL are exposure to high levels of radiation or benzene. It has also been linked to some medical conditions.
Radiation can come from air travel. Individuals who have spent over 5,000 hours in airplanes have a higher risk of developing ALL, because flying increases exposure to the sun's radiation.
Benzene is a chemical found in crude oil, petroleum and many solvents and plastics. It can also be found in cigarette smoke, which is one of the factors linking ALL and smoking.
About 1 in every 20 cases are thought to be caused by genetic disorders, such as Down's syndrome.
How does leukemia progress?
Leukemia can be acute or chronic.
Chronic leukemia develops slowly, and it allows more mature, useful cells to be made, but acute leukemia progresses rapidly.
Acute leukemia crowds out the good cells more rapidly than chronic leukemia. There is a speedy accumulation of immature, useless cells in the marrow and blood.
These are called B-lymphocytes and T-lymphocytes, or B-Cells and T-Cells.
A 1999 study looked at whether early exposure to germs might protect children from developing ALL.
A significantly lower percentage of children who went to playgroups at an early age develop ALL compared to those who did not, suggesting that early exposure to a variety of microbes may offer some protection.
Chemotherapy is the main course of treatment for ALL.
Treatment options will depend on the type of ALL as well as the age and general health levels of the patient
Treatment involves two stages:
- The first phase aims to destroy leukemia cells in the blood or bone marrow. This is called remission induction.
- The second phase takes place after remission is confirmed. Treatment continues to work against the recurrence, or reappearance, of ALL.
Remission is the name for the absence of leukemia cells in the blood or bone marrow.
At each stage, chemotherapy is used. Chemotherapy is given intravenously through a central line, or a central venous catheter.
Chemotherapy is used to kill cancer cells. It is often given intravenously or by mouth.
However, the chemicals may not reach the brain or a man's testes. Since leukemia can affect both of these areas, so, to reach them, an injection may be made directly into the spinal column. This is known as an intrathecal injection.
Radiotherapy is used for cases in which ALL has spread to either the brain or the CNS. In this case, more targeted treatment is needed.
A bone marrow or stem cell transplant may be used as part of intensive chemotherapy or radiotherapy. The high-dosage chemotherapy and radiotherapy treatment kills the bone marrow cells, and new cells need to be generated.
A transplant normally comes from a donor, but sometimes a patient's own cells may be used. It depends on the type of leukemia.
There is a strong risk of bleeding throughout any of the treatment options. This is due to the reduced number of platelets in patients with leukemia.
Outcomes and prevention
Leukemia is curable, especially in younger patients, and a full life can be lived after treatment.
However, there are long-term considerations for patients of ALL who are in remission.
The immune systems of those who are not fully cured are very low in white blood cells. The patient becomes vulnerable to infections, some of them life-threatening.
The patient will need to continue undergoing regular diagnostic tests for some years following active treatment to rule out the recurrence of the cancer.
Diagnostics will decrease in regularity and then stop once there has been sufficient progress.
The medical requirement to continue with testing depends on the type of ALL and the condition of the recovered patient.
Forty percent of adults aged 25 to 64 years will survive ALL for at least 5 years following diagnosis.
The 5-year survival rate for children under 19 years is 85 percent when given the right treatment.
New methods of diagnosis and treatment mean that there is an optimistic outlook for an increase in adult survival rates for ALL.