Leukemia, or commonly known as blood cancer is a common disease amongst many. However, the development in the medical field has brought various treatment procedures into light that has been instrumental in treating it. One of the most common types of leukemia in the adults, the myeloid leukemia can spread fast if it is in the acute stage of the disease. It occurs mostly in adults and is very rare in people, who are below 20 years of age. In fact, men seem to suffer from this disease more than women.
What is Myeloid Leukemia?
Occurring from the bone marrow, the myeloid leukemia is the type of blood cancer, in which abnormal and immature blood cells are produced. These cells are produced from the spongy, inner most part of the bone known as the marrow of the bone and whereas, the cells are normally meant to be transformed into neutrophils, basophils, eosinophils as well as monocytes, they become cancerous and start to replace the normal bone marrow cells, extremely rapidly.
The fact is that, blood stem cells are formed from the bone marrow. They are responsible for building up new blood cells, including white blood cells such as lymphocytes, a kind of white blood cell that is the main component for lymph tissue. But instead of being transformed into lymphocytes, they start forming abnormal and immature blood cells.
Types of Myeloid Leukemia: Acute and Chronic
Myeloid leukemia can be of two types – acute and chronic. When, it is found to be rapidly spreading to the lymph nodes, spleen, liver, brain, spinal cord as well as the testicles, it is known as the acute myeloid leukemia or AML. Unlike the chronic myeloid leukemia, this spread fast and can be fatal, making the patient succumb within a few weeks.
On the other hand, when it slowly progresses from the bone marrow and blood, it is known as the chronic myeloid leukemia. This also occurs after middle age, just like the acute version and is rarely seen in children.
In case of the chronic myeloid leukemia there is a genetic change that takes place in the immature or early versions of the myeloid cells. This change of the genes is known as the BCR-ABL, which causes the cancerous chronic myeloid leukemia cells. These chronic myeloid leukemia cells are very likely to build up the bone marrow and gradually spill over into the blood. This type of myeloid leukemia will grow slowly, but it can turn into the acute version without any prior notice and the acute myeloid leukemia is very hard to treat.
Signs and symptoms of Myeloid Leukemia:
As acute myeloid leukemia or AML is a fast and rapidly spreading disease, timely diagnosis and treatment is a must. However, in the initial stage, the signs and symptoms of acute myeloid leukemia may confuse the symptoms with that of flu or any other common disease. Not only these, but the symptoms of chronic myeloid leukemia are also similar to those of the acute version of the disease. These general symptoms are:
- Bone pain
- Pale skin and anaemia
- Shortness of breath
- Easy bruising
- Lethargy and fatigue
- Unusual bleeding from nose or gums or other types of bleeding
- Frequent infections
- Loss of appetite
- Minor trauma
- Enlargement of spleen
- Weight loss
- Night sweats
Most of these symptoms are caused by the absence of proper, normal and mature blood cells that include the red blood cells, white blood cells and platelets. The blood making cells released from the bone marrow are supposed to make these new blood cells or get transformed into these mature blood cells, but in the absence of proper functioning and lack of normal blood cells, these symptoms occur.
How Common is Myeloid Leukemia?
If overall occurrence of different kinds of cancer in people is taken into consideration, the acute myeloid leukemia would seem rather uncommon but it is the most common type of leukemia in adults that affects about 2,000 adults in the United Kingdom each year along with 50 children as well. Around 900 people are diagnosed with acute myeloid leukemia in Australia each year, making the occurrence rate 3.7 per 100,000 of the population and 0.8% of all cancers that are diagnosed. According to the estimates of The American Cancer Society, in the year 2014, almost 18,860 new cases of acute myeloid leukemia were found mostly in adults and of whom, 10,460 deaths were reported.
The chronic myeloid leukemia on the other hand is an even rarer type, when compared to the acute myeloid leukemia. Among the 8,600 adults in the United Kingdom, who are diagnosed with leukemia each year, CML or chronic myeloid leukemia affects only 700 people.
Causes of Myeloid Leukemia:
The causes of occurrence of the myeloid leukemia are the same with risk factors. The following are the causes of this disease and those, who are exposed to these causes, are at risk.
The only lifestyle related risk factor that has been proved is smoking
- Exposure to benzene and certain other chemicals in factories like oil refineries and rubber industry, chemical plants, gasoline-related industries
- Exposure to certain drugs such as mechlorethamine, procarbazine and chlorambucil etc.
- Previous radiation treatment and chemotherapies
- Certain blood disorders and congenital syndromes like myeloproliferative disorders or Down Syndrome
Diagnosis of Myeloid Leukemia:
Depending upon the signs and symptoms, the doctor makes the general physical diagnosis and then recommends for further tests and they are:
- Blood Test: The acute myeloid leukemia can be roughly diagnosed through blood tests in which the number of red blood cells, platelets would be too less and white blood cells would be too high. However, further testing of the immature white blood cells can be done to find whether they are present only in the bone marrow and not in the blood of the rest of the body. This is a clear indication of myeloid leukemia.
- Bone Marrow Test: In this test, the doctor inserts a small needle right inside the bone marrow to take a little sample of the marrow and test the presence of the blast cells or the immature white blood cells. Normal blood test does not assure of the diagnosis and therefore, the bone marrow test is done.
- Lumbar Puncture: This is yet another test in which the fluid from the spinal cord is collected and tested for the presence of the leukemia or cancer cells. It is done by professional doctors and oncologists and done under special supervision.
Treatments for Myeloid Leukemia:
For both the acute and chronic types of myeloid leukemia, the treatment procedures are almost same. However, whereas the acute myeloid leukemia is a rapid growing disease and does not give much time, the chronic myeloid leukemia is a slow growing process that gives time to cure the disease. The basic goal of treatment for acute myeloid leukemia is to eliminate those blood cells, which contain abnormal BCR-ABL. Although the treatment for acute myeloid leukemia will need to damage all the diseased cells, in case of chronic myeloid leukemia, even if there is not a complete removal of the chronic myeloid leukemia cells, the patient can still achieve a longer remission period.
Chemotherapy and Targeted Drugs For Treating Myeloid Leukemia:
To fight the presence of the cancerous cells, special drugs are given to the patient and they are anthracycline drugs, cytarabine, hydroxyurea, 6-thioguanine or prednisone. Sometimes, two or three of these anticancer drugs are punched together to increase the intensity. The medicines that are specifically given for chronic myeloid leukemia treatment are Imatinib (Gleevec), Nilotinib (Tasigna), Dasatinib (Sprycel), Omacetaxine (Synribo) and Bosutinib (Bosulif).
Radiation Therapy For Treating Myeloid Leukemia:
Like most other types of cancer, in case of acute myeloid leukemia also, a high-energy radiation is used to kill the cancer cells. But this is not the common type of treatment. Although it is not very useful in killing the cancer cells in the bone marrow, yet it is given in case the disease and the blast cells have spread to the testicles or brain.
Bone Marrow Transplant For Treating Myeloid Leukemia:
This is probably the most useful treatment process for acute myeloid leukemia. In case of this treatment, the patient will previously have to undergo chemotherapy and radiation therapy in order to completely destroy the cancer cells in the bone marrow and destroy every possibility for the bone marrow to survive and reproduce the blast cells. Once it is done, healthy bone marrow from a suitable donor is replaced in that place, so that healthy blood cells can be produced.
Biological Therapy For Treating Myeloid Leukemia:
When other drugs do not work, or when the patients cannot take other drugs, a biological drug interferon, which is a synthetic version of an immune system cell is given. This helps to reduce the growth of the leukemia cells in case of chronic myeloid leukemia. As chronic myeloid leukemia does not grow rapidly, the doctors take this chance and time to reduce the growth of the cells through this therapy.
When the acute myeloid leukemia is diagnosed at an early stage and all these treatment procedures are done; then there is high chance of complete cure. Otherwise, it is a highly fatal disease that can cause death in a few weeks. But, chronic myeloid leukemia can be resisted from growing further and treated well in many cases.
Life Expectancy or Survival Rate in Myeloid Leukemia:
The rate of longest term of survival for the acute myeloid leukemia is approximately 65%. It has been found from the cytogenetic analysis of the bone marrow constitute that those, who have t(8;21), t(15;17), or inversion 16, are at best prognosis. Patients with normal cytogenetic findings can be categorised into intermediate prognosis, with a rate of long term survival of 25% and those with -7, -5 cytogenetic findings can be categorised into poor prognosis with a rate of long term survival of only 10% or less than that. With the current chemotherapy regimen standards, among the patients below the age of 60 years, 30-35% of those adults survive for more than 5 years and are considered cured. However, patient above the age of 60 years are considered to be surviving only 10% of the term or lesser.
Using imatinib, 832 patients achieved a stable cytogenetic response in the year 2011. Hence, tyrosine kinase inhibitors are widely used in improving the survival rate for CML over the past few years. Whereas, in 2006, 553 patients, who were using imatinib (Gleevic) for 5 years, found a survival rate of 89%, the rate has now increased up to 95.2%.
The average of treatment and its success rate is between 20% and 40%. As there are high chances of relapse of the acute myeloid leukemia, many people fail to make it till the end. However, as the relapse can take place only within the 5 years of the treatment, for whom the relapse does not occur, they are considered to be completely cured.