Acute Lymphoblastic Leukaemia (ALL) also known as Acute Lymphocytic Leukaemia is a type of cancer of the blood and bone marrow – the spongy tissue inside bones where blood cells are made. Also referred to as Acute Lymphoid Leukaemia and/or Acute Lymphoblastic Leukaemia, it is characterised by an overproduction of immature white blood cells, called lymphoblast or leukemic blasts. Because the bone marrow is unable to make adequate numbers of red cells, normal white cells and platelets, people with ALL become more susceptible to anaemia, recurrent infections, and to bruising and bleeding easily. The blast cells can then spill out of the bone marrow into the bloodstream and accumulate in various organs including the lymph nodes, spleen, liver and central nervous system (brain and spinal cord). While ALL is the least common kind of cancer affecting adults, among children it is the most prevalent.
The symptoms of Acute Lymphoblastic Leukaemia are caused by a lack of normal circulating blood cells. ALL advances quickly, so people are usually only unwell for only a short period of time (days, or weeks) before they are diagnosed.
Common symptoms of ALL can include:
- Anaemia due to a lack of red blood cells (RBCs). Anaemia could result in persistent tiredness, dizziness, paleness or shortness of breath when physically active.
- Frequent and/or recurring infections and slow healing, due to a lack of normal white cells, especially neutrophils
- Due to a low platelet count, there is increased or unexplained bleeding or bruising
- Bone and/or joint pain due to the marrow being overcrowded with leukemic cells.
- Other symptoms could include swollen lymph nodes, chest pain and abdominal discomfort due to a swollen spleen or liver.
Some of these symptoms mentioned above may also be seen in other illnesses, including viral infections, therefore it is important to see the doctor so that proper examination and treatment can happen. In some cases, there may be symptoms and ALL is diagnosed during a routine blood test.
While the exact causes of ALL still remain largely unknown, it is believed to result from mutations in one or more of genes that are responsible for blood cell development resulting in abnormal growth.
Ongoing research to find possible causes of this damage have identified certain factors that could put some people at an increased risk. These include:
- Very high doses of radiation either accidentally (nuclear accident) or therapeutically (to treat other cancers)
- Industrial chemicals such as benzene, pesticides, as well as certain types of chemotherapy used to treat other forms of cancers
- Certain types of viral infections and the way in which the immune system reacts to the infection could play a role in the development of some types of ALL
- Certain genetic disorders like Down’s syndrome and Fanconi’s anaemia may have a higher than average risk of developing ALL.
The World Health Organisation has classified ALL into the following types:
It accounts for approximately 75-80% of adult cases, ALL arising in the B-lymphocytes which is in the early stages of development in the bone marrow is referred to as precursor B-Cell-ALL or Pre-B-Cell-ALL.
B-cell ALL arises in more mature developing lymphocytes. This form of ALL is rarer and accounts for 3-5% of all adult cases. B-cell ALL is also referred to as Burkitt-like or Burkitt type ALL. Patients diagnosed with B-cell ALL may be treated with similar drugs to those used to treat Burkitt lymphoma.
Approximately 1/4th of ALL cases arise in developing T-cells. This can be further classified as early, mid or late, depending on the maturity of the affected cell. T-cell ALL commonly presents with a high white blood cell count and involvement of the central nervous system at diagnosis.
ALL is diagnosed by examining blood and bone marrow samples in a variety of tests.
Full blood count:
Full Blood Test (FBC) or complete blood count (CBC)is the first step in the diagnosis of ALL. Blood sample will be collected from a vein in the arm and will be investigated in the laboratory. White blood cells may be abnormal leukemic blast cells and the presence of these blast cells in the test suggests ALL. The ALL diagnosis needs to be confirmed by examining the cells in the bone marrow.
Bone marrow examination:
This is performed is the results of the blood tests suggests ALL. A bone marrow biopsy is done to help confirm the diagnosis. A bone marrow biopsy involves taking a sample of bone marrow, usually from the back of the hip bone and examined in the laboratory under the microscope. The sample is examined to determine the number and type of cells present and the amount of haemopoiesis (blood forming) activity taking place there. The diagnosis of ALL is confirmed by the presence of an excessive number of blast cells in the bone marrow.
Once ALL is confirmed, blood and bone marrow cells are examined further using special laboratory tests. These include immunophenotyping, cytogenetic and molecular tests. These tests provide more information about the exact type of disease, the likely course of the disease and the best way to treat it. A small sample of the cerebrospinal fluid (CSF) that surrounds your brain and spinal cord is also collected, during a procedure called a lumbar puncture. This fluid is tested in the laboratory to check for the presence of leukemic cells within the central nervous system.
Chest x-rays and baseline blood tests may also be required, to look at kidney and liver functions.
Since ALL progresses quickly, treatment needs to begin soon after ALL is diagnosed. The treatment plan will depend on a number of factors including the sub-type of ALL, the genetic make-up of the leukemic cells, the patient’s age and general health.
Chemotherapy is the primary form of treatment for ALL. A combination of drugs, including steroids, is usually given in several cycles with a rest period of a few weeks in between. The first priority of the treatment is to destroy leukemic cells and induce a remission. This implies that there is no evidence of leukemic cells in the blood and bone marrow and that normal blood cell production and blood counts are restored. In cases, where the risk of relapse is high, patients may be offered even more intensive therapy followed by a stem cell transplant.
Chemotherapy is administered in many different ways to treat ALL and includes intravenously (into a vein), intramuscularly (into a muscle) and in tablet form. To prevent and treat disease in the brain and spinal cord (CNS) chemotherapy is injected intrathecally, directly into the fluid that surrounds these structures. Sometimes, this area is also treated using radiotherapy. In males, radiotherapy may be given to the testes to treat relapsed disease in this area.
Treatment for ALL can be divided into three phases:
- Induction therapy
- Post-remission (consolidation) therapy
- Maintenance therapy.
Induction therapy: Soon after diagnosis an intensive course of treatment begins to bring about, or induce, a remission. If it is resistant or refractory disease, a more intensive form of therapy to treat the disease more effectively may be recommended.
Post-remission (consolidation) therapy: After induction therapy finishes and remission is achieved, more treatment is required to help destroy any leftover disease in your body. This helps prevent a relapse and/or a spread to the central nervous system. consolidation therapy chosen will depend on the estimated risk of relapse.
Maintenance therapy: Maintenance therapy is designed to help keep your disease in remission and prevent it from reappearing (relapsing) in the future. Common maintenance protocols involve chemotherapy tablets — some taken daily and others weekly — and possibly blocks of injections of chemotherapy with courses of corticosteroids. This phase of treatment usually lasts for several months.