Health Concerns

Leukemia

Types of Leukemia

Leukemia is categorized on the basis of how long the disease takes to progress and the kinds of blood cells affected.

Acute leukemia usually presents suddenly, and patients often develop symptoms right away. Chronic leukemia progresses slowly and may not cause symptoms for years (Siegel 2013; LLS 2012b).

Lymphocytic leukemia affects “T” and “B” white blood cells known as lymphocytes. Myeloid leukemia affects myeloid cells, which go on to form white blood cells other than lymphocytes (granulocytes and monocytes), red blood cells, and platelets.

Leukemia is classified into four main types: acute lymphocytic leukemia (ALL), chronic lymphocytic leukemia (CLL), acute myeloid leukemia (AML), and chronic myeloid leukemia (CML) (Siegel 2013; LLS 2012b).

There are several other types of leukemia as well, such as hairy cell leukemia, chronic neutrophilic leukemia, and acute megakaryocytic leukemia, but these are relatively rare (Pawarode 2006).

The Four Most Common Types of Leukemia (LLS 2012b; Siegel 2014; Garcia-Manero 2014; Cyopick 1993; LLS 2014b)

Leukemia Type

Cells Undergoing Uncontrolled Division

Age Group Affected

Estimated New Cases (2014)*

Acute lymphocytic leukemia (ALL)

Immature lymphocytes or “blasts”

Children (peak incidence in children ages 3-7), but can also affect adults

6020      

Acute myeloid leukemia (AML)

Primitive myeloid cells or blasts

Adults, typically over age 40

18 860

Chronic lymphocytic leukemia (CLL)

Mature-appearing lymphocytes

Older adults, especially over age 60

15 720

Chronic myeloid leukemia (CML)

Immature granulocytes

Middle-aged adults, rarely children

5980

*Rounded to the nearest 10; the numbers depict estimated new cases of leukemia in the United States in 2014.

Leukemias are further classified into subtypes depending on the molecular and genetic characteristics of leukemia cells. Correctly identifying the properties of each patient’s cancer is critical for prognosis and treatment (LLS 2012b; Wetzler 2012; Den Boer 2009; Vallespi 1991; Cripe 1997).

Myelodysplastic Syndrome

Myelodysplastic syndrome (MDS) is a group of leukemia-like disorders characterized by overproduction of dysfunctional blood cells in the bone marrow (Sekeres 2011), and the disease can arise without a clear cause or develop secondary to chemotherapy or radiation received as treatment for previous cancers, including leukemia (Saba 2007; Panizo 2003; Garcia-Manero 2014). MDS may be indolent, causing no or minimal symptoms, or aggressive (Cleveland Clinic 2014).

Signs and symptoms of MDS generally arise as a result of a reduction in the number of blood cells. For example, insufficient red blood cells (anemia) may cause fatigue or shortness of breath; too few white blood cells (leukopenia), which may increase susceptibility to infection; or too few platelets (thrombocytopenia), which can increase bleeding risk and cause spontaneous bruising (Cleveland Clinic 2014).

Current estimates suggest that approximately 13 000 new cases of MDS are diagnosed each year in the United States. The number of new cases appears to be increasing as the population ages (ACS 2014g). MDS is more common in older men and people who have had previous chemotherapy (Garcia-Manero 2014). MDS progresses into overt AML in about one-third of patients (Cleveland Clinic 2014).

Bone marrow transplantation offers curative potential for patients with MDS. Unfortunately, since bone marrow transplantation is complicated and has many adverse effects, especially in older individuals, and since most MDS patients are over age 60, only about 5–10% of patients are eligible for this procedure. Therefore, treatment strategies typically aim to reduce symptoms to a manageable level and improve quality of life. Blood transfusions can help overcome symptoms caused by low blood cell levels, and several drugs can help improve disordered blood parameters or, possibly, induce complete or partial remission (regression). These include thalidomide (Thalomid), lenalidomide (Revlimid), arsenic trioxide (Trisenox), amifostine (Ethyol), and immunosuppressive therapy. 5-azacytidine (Vidaza) may also be used and is the only FDA-approved drug to treat MDS. For those with less aggressive cases of MDS, treatment with growth factors such as granulocyte-colony stimulating factor (G-CSF) (Neupogen) or granulocyte macrophage colony-stimulating factor (GM-CSF) (Leukine) and erythropoietin (Procrit) may be useful (Cleveland Clinic 2014; Sekeres 2011).