Most types of cancer are given stages of I, II, III, or IV. These stages are based on the size of the tumor and how far from the original site in the body the cancer has spread. Because leukemia already involves all of the bone marrow in the body, and in many cases, has spread to other organs such as the liver, spleen, and lymph nodes, the staging of leukemia depends on other information that reflects the patient's outlook for survival. Different staging systems are used for different types of chronic leukemia. Some types do not have any staging system.

Staging for Chronic Myelogenous Leukemia (CML)

CML is divided into three groups. For this type of leukemia, doctors call these groups "phases" instead of "stages."

Chronic phase: Patients in this phase have fewer than 5% blasts and promyelocytes (immature cells that can reproduce) in blood and bone marrow samples. These patients usually have relatively mild symptoms, and usually respond to standard treatments.

Accelerated phase: The standard definition of this phase is that bone marrow and blood samples have more than 5% but fewer than 30% blasts. These patients often have fever, poor appetite, and weight loss. Symptoms and blood counts are not as responsive to treatments as they are during the chronic phase. The leukemic cells have new chromosome changes, in addition to the Philadelphia chromosome.

Blast phase (also called acute phase or blast crisis): Bone marrow and/or blood samples from a patient in this phase have more than 30% blasts. The blast cells often spread to tissues and organs beyond the bone marrow. At this point the chronic leukemia has transformed into a very aggressive acute leukemia.

Staging for Chronic Lymphocytic Leukemia (CLL)

There are two different systems for staging chronic lymphocytic leukemia. The Rai classification is used more often in the United States, whereas the Binet system is used more widely in Europe.

The Rai stages can be separated into low, intermediate, and high-risk categories. Stage 0 is considered low-risk, 1 and 2 are considered intermediate-risk, and 3 and 4 are considered high-risk. The Rai classification recognizes 5 stages:

• Rai Stage 0:Lymphocytosis (blood lymphocyte count is too high, defined as over 15,000 lymphocytes per cubic millimeter).
• Rai Stage I: Lymphocytosis plus lymphadenopathy (enlarged lymph nodes).
• Rai Stage II: Lymphocytosis plus hepatomegaly (enlarged liver) or splenomegaly (enlarged spleen). Lymphadenopathy may be absent or present.
• Rai Stage III: Lymphocytosis and anemia (too few red blood cells). Lymphadenopathy, hepatomegaly, or splenomegaly may be absent or present.
• Rai Stage IV: Lymphocytosis and thrombocytopenia (too few blood platelets).

In the Binet staging system, CLL is classified according to the number of affected lymphoid tissue groups (the lymphoid tissue groups are neck lymph nodes, groin lymph nodes, underarm lymph nodes, and the spleen) and the presence of anemia (too few blood cells) or thrombocytopenia (too few blood platelets).

• Binet Stage A: Fewer than three areas of lymphoid tissue enlargement.
• Binet Stage B: More than three areas of palpable lymphoid tissue enlargement.
• Binet Stage C: Anemia and thrombocytopenia .

Staging for Hairy Cell Leukemia (HCL)

Patients with hairy cell leukemia are sometimes staged based on whether they have anemia (not enough red blood cells) and whether their spleen is too large (a sign that the leukemia cells are growing in the spleen).

• Stage I: No anemia or slight anemia and moderately large spleen, or moderate anemia and normal size spleen.
• Stage II: No anemia or slight anemia and very large spleen, or moderate anemia and moderately large spleen, or severe anemia and normal size spleen.
• Stage III: Moderate anemia and very large spleen or severe anemia and moderately large or very large spleen.

Not all oncologists use this staging system.

Prognostic Factors for Chronic Leukemias

In addition to a patient's stage, there are other factors that help predict his or her outlook for survival. These factors are sometimes used in addition to staging information when deciding possible treatment options. Some of these prognostic factors apply to all types of chronic leukemia while others are specific to only one type. Factors that tend to be associated with shorter survival time are called adverse prognostic factors. Those that predict longer survival are favorable prognostic factors.

Adverse Prognostic Factors for Chronic Myelogenous Leukemia

• Accelerated phase or blast phase
• Enlarged spleen
• Areas of bone damage due to growth of leukemia
• Increased number of basophils (a type of granulocyte) in circulating blood samples
• Very high or very low platelet counts
• Age 60 years or older
• Multiple chromosome changes
• Absence of Philadelphia chromosome (translocation between chromosomes 9 and 22).

Many of these factors have been taken into account in the Sokal system which develops a score to predict prognosis. It takes into account the person's age, the percentage of blasts, the size of the spleen, eosinophils and basophils, and the number of platelets. A person with a low score will have an average survival of around 8 years while a person with a high score will average a 3 to 4 year survival.

Adverse Prognostic Factors for Chronic Lymphocytic Leukemia

• Diffuse pattern of bone marrow involvement (indicates more extensive replacement of normal marrow by leukemia)
• Abnormal chromosome changes
• High blood levels of certain substances, such as beta-2-microglobulin
• Increased proportion of large or atypical lymphocytes in blood samples