Leukemia

Description

Leukemia is a group of cancerous diseases affecting the blood and lymph tissues. There are four main types of leukemia:

- Acute lymphocytic leukemia (ALL)
- Acute myelocytic leukemia (AML)
- Chronic lymphocytic leukemia (CLL)
- Chronic myelocytic leukemia (CML)

In all four types, white blood cells developing in the bone marrow do not mature correctly making them leukemic cells. Two groups of cells produced by the bone marrow are affected; myeloid cells and lymphocyte cells. Myeloid cells are responsible for forming red blood cells, some types of white blood cells, and platelets. Lymphocyte cells form an important part of the immune system. The leukemic cells replace or suppress the development of normal cells.

Acute leukemia affects young cells. Chronic leukemia affects mature cells. Acute lymphocytic leukemia is most common in children with prevalence in the 2-5 year age group. The other groups of leukemia tend to develop in an older population between the ages of 50-75. Only 2% of chronic leukemia victims are children.

Causes

The cause of leukemia is still unknown. For some types of leukemia, risk factors have been identified; for others, more research is needed.

Acute Lymphocytic Leukemia

This type of leukemia is most common in children. Risk factors are thought to be a mix of environmental factors mixed with a family history of the disease. One theory suggests that excess hygiene causes children to be protected from normal childhood infections, which could give them a predisposition to the disease. Only 5% of cases are linked to an inherited genetic syndrome. Often, previously healthy children with none of these risk factors will present with the disease.

Acute Myelocytic Leukemia

Although common in all ages, this disease is more prevalent in people over 65 years old. Myelocyctic leukemia has a group of identified specific risk factors. Exposure to ionizing radiation, drugs that damage DNA makeup, and two types of chemotherapy have been linked to disease development.

Chronic Lymphocytic Leukemia

Disease incidence is rare in people under 50 years old. Speculated risk factors are family history and exposure to radiation/chemicals, although no concrete evidence yet exists proving these links.

Chronic Myelocytic Leukemia

Affecting only 1-2 persons per 100,000, this type of leukemia is rare. Incidence is higher in men, with women having a better survival rate. Although research has identified that a gene translation causes the leukemia, what exactly spurs this change is still unknown. As with other leukemia, a genetic and radiation factor is thought to exist.

Treatment

Acute Lymphocytic Leukemia

As the disease is acute, treatment is started promptly after diagnosis. Initial treatment, called induction therapy, usually consists of combination chemotherapy delivered intravenously along with steroids. Common chemotherapies used are vincristine (Oncovin*) and asparaginase (Elspar*), with the steroid dexamethasone (Tobradex*). After the initial phase of treatment, therapy is continued in the consolidation and maintenance stages to prevent relapse. Methotrexate (Rheumatrex*) is another chemotherapy drug often used for these stages. Treatment can continue up to 2-3 years after diagnosis, depending on whether the person is male or female. Bone marrow transplant is considered if chemotherapy is unsuccessful.

Acute Myelocytic Leukemia

Treatment is carried out in two phases. The induction phase aims to achieve complete remission. This is completed through using a combination of chemotherapy drugs such as daunorubicin (Cerubidine*) and cytarabine liposome (DepoCyt*). In the consolidation phase, often cytarabine is used. Stem cell transplantation is also considered, depending on what type of gene mutation caused the leukemia.

Chronic Lymphocytic Leukemia

Due to new drug developments, the treatment of this chronic leukemia now mimics that of the acute leukemia. Induction and consolidation phases can be effective. Purine analogues, such as fludarabine, is often combined with rituximab (Rituxan*) in the induction phase. Response and complete remission rates are high.

Chronic Myelocytic Leukemia

This chronic cancer is often first treated with a drug called imatinib (Gleevec*). The drug works by turning off the enzyme that causes the cells to become cancerous. If unsuccessful, stem cell transplantation is considered.