Cervical cancer is the name for cancers that form in the cervix, the lower part of the uterus where it meets the vagina. Most cases arise from human papillomavirus infection. Abnormal cells can form a tumour and spread to other parts of the body.…
- Leukemia is the general name for a group of cancers that affect a type of blood cells known as white blood cells.
- Most of the time, leukemia is discovered during a routine blood test ordered for other reasons.
- Leukemia is a serious disease; however, large advances in diagnosis and treatment in the last decade has dramatically improved survival rates.
What is leukemia?
Leukemia is a type of cancer of the white blood cells (also called leukocytes).
The cause of leukemia, as with other cancers, is damage to the DNA of white blood cells. The exact cause of this damage is unknown in most cases, but can sometimes be due to irradiation or exposure to a toxic chemical. Certain chemotherapy drugs and benzene are known to cause leukemia.
White blood cells circulate throughout your body and have roles in fighting infection and disease. Damage to a white blood cell's DNA can cause the cell to multiply quickly and without control.
There are many types of white blood cells, broadly divided into two categories: myeloid cells and lymphoid cells. That is why some types of leukemia are referred to as myeloid or lymphoid, depending on their cell of origin.
Leukemia is one type of cancer that can occur in blood cells. Other types of blood cancers include lymphomas (cancers affecting the lymphatic system) and myelomas (cancers of plasma cells - the cells in our body that produce antibodies).
Risk factors for leukemia include:
- Exposure to high levels of ionizing radiation;
- Exposure to benzene, a chemical compound found in crude oil, petroleum and cigarette smoke, and used in industries such as plastic manufacturing;
- Cigarette smoke: smoking has been shown to increase the risk of developing some types of leukemia;
- Leukemia can develop as a side effect of chemotherapy that was used to treat a previous cancer;
- Obesity: it is not fully clear how obesity increases the risk of leukemia, but it is thought that it may weaken the immune system, which can allow cancers to develop without resistance;
- Male gender: leukemia is more common in men;
- Increasing age, and;
- Genetics and family history: the role of genetics in leukemia is an area of ongoing research. Currently, only a few genetic links are known. One type of leukemia, in which a clear genetic link is known, is chronic myeloid leukemia (see 'Types', below).
There are several types of leukemia. Some types of leukemia spread quickly and aggressively (acute leukemia), while others can take a long time before they start causing symptoms (chronic leukemia). Leukemia is classified further by the type and maturity of the blood cells that are affected.
Acute myeloid leukemia
Acute myeloid leukemia (AML) occurs when the bone marrow produces large numbers of immature blood cells, called blasts. These blasts flood the bone marrow and the blood, displace mature blood cells, and can cause symptoms such as anemia, easy bruising, and fatigue.
AML is the most common form of acute leukemia in adults. Men are more affected than women. The risk of AML increases with age.
Acute lymphoblastic leukemia
Acute lymphoblastic leukemia affects lymphoid cells. This type of leukemia is more common in children, often diagnosed between 3-5 years of age. Boys are more commonly affected than girls.
Chronic myeloid leukemia
In chronic myeloid leukemia (CML), a fusion of two chromosomes in a cell creates a new gene, called BCR-ABL. This gene produces a protein that drives the development of the leukemia. CML is treated by medications that target the BCR-ABL protein.
Chronic lymphocytic leukemia
Chronic lymphocytic leukemia (CLL) is the most common type of leukemia in the developed world. It is a diverse group of leukemias that are more common in older people and affect slightly more men than women.
Signs and symptoms
Signs and symptoms of leukemia vary slightly according to type, but in general they may include:
Methods for diagnosis
Most of the time, leukemia, particularly the chronic type, is discovered during a routine blood test ordered for other reasons. In general, the presence of leukemia is suspected from the examination of the blood and confirmed by performing a bone marrow biopsy.
In patients with leukemia there is usually a higher-than-normal number of white blood cells and a lower-than-normal number of red blood cells or platelets.
Bone marrow biopsy
This involves taking a small sample of bone marrow from the center of a bone, usually the hipbone. The biopsy can be performed under local or general anesthesia.
The bone marrow sample is then examined to help determine the type and stage of leukemia. The sample is also subjected to genetic testing (see below).
The blood or bone marrow are analyzed for specific genetic mutations that cause certain types of leukemia. This is known as cytogenetic testing, If certain mutations are found, targeted therapies can be offered.
In addition to the above tests, which are essential for the diagnosis of leukemia, a patient diagnosed with leukemia may undergo additional tests. These can include:
- Computerized tomography (CT) scan;
- Magnetic resonance imaging (MRI) scan;
- Positron emission tomography (PET) scan;
- Echocardiography, an ultrasound scan of the heart that is used to determine if your heart function is normal and will be able to withstand chemotherapy, and;
- Lumbar puncture, also known as a spinal tap. This procedure is performed to check if the cancer has spread to the spine and brain. It can also be used to administer chemotherapy to this area.
The outcome of treatment for leukemia can vary greatly depending on the stage at which the cancer was detected and treated.
The stages of chronic leukemia are:
One or two enlarged lymph nodes; normal red blood cell and platelet counts.
More than three enlarged lymph nodes; normal red blood cell and platelet counts, but high white blood cell counts.
Enlarged lymph nodes and enlarged spleen; high white blood cell counts, and low red blood cell and/or platelet counts.
Acute leukemia progresses too quickly to have distinct stages.
Types of treatment
The treatment for leukemia depends largely on the type of leukemia you have been diagnosed with. Chemotherapy, stem cell transplant, leukapheresis and targeted therapies are common treatments for all leukemia types.
Chemotherapy works by attacking cancer cells, either destroying them or stopping them from multiplying.
Acute leukemia is treated in three phases: induction, consolidation and maintenance:
The aim of induction therapy is to get rid of the cancer and induce a remission. This involves using chemotherapy to clear as many leukemia cells from the bone marrow as possible. However, some leukemia cells are bound to escape treatment.
Consolidation therapy is used once the cancer is in remission - i.e., that cancer cells are gone from the blood and the bone marrow. In this phase of treatment, drugs or radiotherapy are used to remove any lingering cancer cells.
The aim of maintenance therapy is to prevent the return of leukemia. It usually involves the use of chemotherapy.
Side effects of therapy occur because chemotherapy can also affect healthy cells. Your doctor will monitor your dosage carefully to ensure that your dosage is optimal.
Stem cell transplant
A side effect of chemotherapy treatment is that it destroys healthy blood cells. In order to replace and replenish the lost cells, stem cell transplant can be used.
Stem cells are cells that have the potential to mature into various types of blood cells in the bone marrow. A stem cell transplant is often used in acute leukemias, where remission has occurred, particularly in cases where the leukemia is likely to recur. The procedure is less commonly used for treating chronic leukemias, but still has a role if other treatments have failed.
Before chemotherapy starts, a supply of stem cells (taken from your body or from a donor) will be prepared and stored. After the chemotherapy regimen is completed, the stem cells are then given through an intravenous drip. Once in the bloodstream, they settle in the bone marrow and begin multiplying to produce new, healthy blood cells.
Stem cell transplants can only be performed if you are fit enough to undergo the procedure and if you have an aggressive form of leukemia that is not responding to other treatments.
Leukapheresis involves your blood being cycled through a machine that removes abnormal white blood cells before returning the blood to your body, much like a dialysis machine removes waste products from your blood when your kidneys are not functioning properly. This is sometimes performed if the number of abnormal white cells in your blood is sufficiently high to endanger your wellbeing.
Targeted therapies are new therapies that specifically target the cancerous cells and spare all other cells.
This type of treatment is used in the treatment of patients with chronic myeloid leukemia who are prescribed medications (such as imatinib and nilotinib) that target BCR-ABL (see above). The treatment stops the cells dividing, halting the progression of the leukemia. Another example of targeted therapy is the use of antibodies that are created in the laboratory to specifically target the cancer cells. Patients diagnosed with pro-myelocytic leukemia are also treated with targeted therapy, which includes the use of a vitamin A analogue and arsenic. These treatments prevent cancer cells from multiplying.
Treatment side effects
Chemotherapy side effects
Chemotherapy often results in nausea, vomiting, fatigue, constipation, hair loss and joint and muscle pain. Some chemotherapeutic agents can affect nerve function. It is important to tell your doctor if you develop these symptoms.
While undergoing chemotherapy, you will be prone to contracting infections, may bleed and bruise easily, experience weakness and fatigue, nausea, vomiting and diarrhea. It is generally necessary to be in a single room during your hospital admission to minimize these complications.
In some cases, chemotherapy can result in development of another type of leukemia, but the overall benefits of this treatment outweigh this risk.
In some cases, when you receive bone marrow from a donor, you can develop graft versus host disease (GVHD). This occurs when the donor cells attack your tissues and organs, commonly the skin, gut and liver. There are several strategies to control GVHD, and your doctor will discuss them with you if needed.
Complications of leukemia
It is common for the cancer to return after remission.
In leukemia, the body produces many white blood cells, but they are immature and do not do a good job of protecting the body from infections, so people with leukemia are more at risk of infection.
Bruising and anemia
Because the bone marrow is producing too many white blood cells, the number of platelets or red blood cells is drastically reduced. This results in easy bruising as well as the development of anemia.
The prognosis of leukemia varies greatly according to many factors, including:
- The type of leukemia;
- The stage at which it was first diagnosed;
- Age - younger people usually have a better prognosis, and;
- How well the cancer responds to treatment.
Leukemia, and particularly acute leukemia, is a serious disease that can often be fatal, but the last decade has seen large advances in diagnosis and treatment of the disease, and the survival rates have improved dramatically.
If you have leukemia, your doctor will discuss with you the likely outcomes of your treatment based on the specifics of your case.