Blood contains different types of cells that each have different functions. Red blood cells (erythrocytes) transport oxygen to the different body parts and organs; platelets (thrombocytes) are important for blood clotting. The white blood cells (granulocytes and lymphocytes) are responsible for the body’s defences.
All blood cells, white and red blood cells and platelets, originate from a common “mother cell” in the bone-marrow, the haematopoietic stem cell. The process of blood building is called haematopoiesis (see illustration). From stem cells, the so-called myeloid and lymphatic stem cells are formed initially. These then develop into the different types of blood cells and are later released into the blood stream.
Just like other cells in the body, blood cells, too can be subject to degenerative changes at any point in their development and thus result in cancer. Rudolf Virchow first named cancer of the blood leukaemia. The term comes from the Greek and means “white blood”, as in a certain type of leukaemia a significantly increased number of white blood cells can often be found in the patient’s blood.
Approximately 10,000 people a year develop leukaemia in Germany. This accounts for around 2.1 per cent of all new cancers. More than 600 of these patients are children below the age of 15. In this age group, the rate of leukaemia compared to other cancers is over a third.
Depending on which blood cells underwent degenerative changes leukaemia is divided into myeloid or lymphatic leukaemia. A further subdivision into “acute” and “chronic” is made depending on the development level of the malignant cells.
Acute leukaemia usually comes on suddenly and can occur at any age. Immature, malignant cells accumulate in the bone marrow and inhibit the normal blood cell formation.
Chronic leukaemia proceeds at a slower rate. This type is found in particular in older people. Chronic leukaemia is often detected by chance, e.g. during routine blood tests.
Consequently, there are four types of leukaemia:
- acute lymphatic leukaemia (ALL)
- acute myeloid leukaemia (AML)
- chronic lymphatic leukaemia (CLL)
- chronic myeloid leukaemia (CML))
Leukaemia can develop if the normal maturing process of the white blood cells (lymphocytes) in the bone marrow or the lymphatic system is interrupted through the malfunctioning of certain genes.
White blood cells that are more or less immature are produced instead of mature, i.e. fully developed and functioning white blood cells.
These cells are usually not functional and are additionally characterised by the ability to reproduce quickly and unchecked.
Increasingly, they suppress the normal blood forming process in the bone marrow, preventing the necessary number of healthy white and red blood cells and platelets from being formed.
This can result in the following:
- Anaemia caused by a lack of functional red blood cells
- Increased susceptibility to infections caused by a lack of functional white blood cells
- Increased bleeding tendency caused by a lack of platelets
As these symptoms can also occur because of other diseases a firm diagnosis can only be made by a physician following further examinations.
What role does lifestyle play in leukaemia?
The causes of leukaemia are only partially known. Suspected causes are radiation, chemical substances (such as the previous treatment of a different cancer), chemicals or smoking. Experts estimate that around 10 per cent of leukaemia cases are caused by smoking.
An increased risk of acute leukaemia was shown for e.g. children with certain hereditary conditions, in particular trisomy 21 (Down syndrome).
Several different examinations are carried out to arrive at a precise diagnosis:
- Physical examination; including the liver and spleen (may be enlarged in case of leukaemia) and lymph nodes
- Blood test
- Bone marrow biopsy; a bone marrow sample is obtained under local anaesthesia. As blood is formed in the bone marrow, changes can be detected here. Along with the bone marrow cells, the cell’s chromosomes (cytogenetics) are also examined. The result of these tests can be of vital importance for both the diagnosis and treatment, and for prognosis.
- Puncture of the spinal fluid (lumbar puncture); in certain types of leukaemia the nervous system may be affected which might make this test necessary. Here, a syringe is used to extract a small amount of cerebrospinal fluid for testing from the lumbar region.
The goal of every leukaemia therapy is to destroy the leukaemic cells and restore normal blood-forming function. Depending on the course of the disease, the type of leukaemia treatment may differ and will always be performed by specialised physicians.
In acute leukaemia patients it is important to start immediate and very intensive treatment. The therapy will be adapted to the type of leukaemia and the patient’s individual situation and will either be intensive or a little less intensive in order to achieve the best effect with the fewest side effects possible.
In acute leukaemia, chemotherapy results in a permanent cure in only a part of the patients, and never in chronic leukaemia. Therefore, for many leukaemia patients a stem-cell transplant, derived from e.g. the bone marrow, is the only chance of a cure. In a so-called allogeneic stem cell transplant the patient’s diseased bone marrow is replaced with the healthy bone marrow of a donor. Other possibilities for deriving stem cells are to extract them from the donor’s blood, or from umbilical cord blood.
Chronic leukaemia usually progresses at a slower rate and is often detected during routine examinations. As in acute leukaemia, medicinal products that inhibit the growth of malignant cells are used to treat chronic leukaemia.
Chemotherapy is aimed at destroying cancer cells in the whole body with medicinal products that inhibit cell growth (cytostatics). Cytostatics are very effective against rapidly growing cells. Cancer cells are particularly fast-growing. The type and scope of chemotherapy is decided on an individual basis and depends on the type of leukaemia, and on how far advanced the cancer is.
Classification of leukaemia is based on the morphological and immunological properties of the leukaemia cells.
Increasingly, cytogenetic and molecular biological characteristics have become significant in recent years.
A preliminary diagnosis is often made from blood counts and differential blood counts alone, for the precise classification a bone-marrow puncture is usually necessary.
Treatment of acute myeloid leukaemia (AML) consists of different phases:
- Induction treatment: Two to three medicinal products are administered in blocks over a period of several days. These blocks are repeated depending on the treatment regimen used. Induction treatment is aimed at destroying the leukaemia cells and to restore normal blood formation. If it is successful, the treatment has achieved remission.
- Consolidation treatment: To prevent the leukaemia from coming back (recurrence). The number of leukaemia cells is reduced even further.
- In certain cases, maintenance therapy follows which is also aimed at minimising the risk of recurrence.
Clinical studies are conducted by different AML study groups (see internet links).
Treatment of acute lymphatic leukaemia (ALL) consists of several phases, too and takes about two to three years in total:
- Induction treatment with several different medicinal products for achieving remission (see AML)
- Consolidation treatment to stabilise remission
- Re-induction treatment with similar medicinal products as during induction treatment. This block is needed to minimise the risk of recurrence
- Maintenance treatment to reduce the risk of recurrence even further
Clinical studies in adults are conducted in Germany by the German Multicenter ALL (GMALL) study group; children are generally treated in studies of the Berlin-Frankfurt-Münster (BFM) group or the cooperative ALL study group (COALL) (see internet links).
Chronic myeloid leukaemia (CML) usually progresses in three phases:
- The first phase is the chronic phase, characterised by slow cell division. Most cases are diagnosed in this phase, which is well treatable.
- During the second, the accelerated phase, cell division is sped up and blood counts decline.
- The third phase is the so-called blast crisis which resembles acute leukaemia.
The presence of a certain type of genetic mutation, the so-called Philadelphia chromosome, in the leukaemia cells is typical for CML (in all phases of the disease). This causes the cells to make a new enzyme (“tyrosine kinase”) which is constantly active and allows leukaemia cells to grow out of control. This enzyme then is the starting point for treating CML. New medicinal products inhibit the tyrosine kinase and thus the proliferation of the leukaemia cells. They need to be taken daily and permanently as this is the only way to check the course of the disease.
Studies are conducted by the German CML study group, for example (see internet links).
Treatment of chronic lymphatic leukaemia (CLL) depends on the clinical picture. In some cases, no chemotherapy but only close monitoring of the progress (“watch and wait”) is needed. In more aggressively progressing cases, treatment with medicinal products is necessary. Studies on optimising the treatment are conducted by the German CLL study group (DCLLSG), for example (see internet links).