Small lymphocytic lymphoma (SLL) is the lymphoma (lymph nodes) form of chronic lymphocytic leukemia (CLL). Both CLL and SLL are indolent (slow-growing) blood cancers. CLL primarily affects the blood and bone marrow. SLL is a subtype of non-Hodgkin lymphoma (NHL) that primarily affects lymph nodes (part of the immune system). The two conditions are considered the same disease — typically referred to as CLL/SLL — and for the most part, they are both staged and treated the same way.
Identifying the clinical stage of your cancer after a diagnosis of CLL/SLL helps doctors determine the best treatment options as well as your prognosis, or outlook. Typically, non-Hodgkin lymphomas are staged like most other types of cancer based on the size, location, and spread of tumors. However, because small lymphocytic lymphoma is closely related to chronic lymphocytic leukemia, it is staged with the same systems used for CLL. Using CLL staging for SLL provides a more accurate prognosis than standard lymphoma staging, especially when SLL is found in the blood and bone marrow.
There are two staging systems used for CLL/SLL: the Rai system, used in the United States, and the Binet system, used in Europe. Both of these systems use a combination of physical findings and complete blood count (CBC) results (especially used for a type of white blood cell called lymphocytes).
A person with stage 0 CLL/SLL has lymphocytosis, but no enlargement of the liver, spleen, or lymph nodes. RBC and platelet counts are near normal.
In stage 1, there is lymphocytosis and lymph node enlargement. There is no enlargement of the liver or spleen. RBC and platelet counts are near normal.
In stage 2, a person shows lymphocytosis and an enlarged spleen. The liver and lymph nodes may or may not be enlarged. RBC and platelet counts are near normal.
There is lymphocytosis and RBC counts are low in stage 3. The liver, spleen, and lymph nodes may or may not be enlarged and platelet counts are near normal.
Stage 4 involves lymphocytosis and low platelet counts. The liver, spleen, and lymph nodes may be enlarged. RBC counts may be low or near normal.
The Binet staging system has three stages (A, B, and C) based on the following factors:
Binet stage A corresponds to Rai stages 0, 1, and 2. In this stage, fewer than three areas of lymphoid tissue are enlarged, and RBC and platelet counts are normal.
Binet stage B corresponds to Rai stages 1 and 2. In stage B, three or more areas of lymphoid tissue are enlarged, and RBC and platelet counts are normal.
Binet stage C corresponds to Rai stages 3 and 4. RBC and platelet counts are low in stage C, and any number of lymphoid tissue areas are enlarged.
In addition to the Rai or Binet staging systems, SLL can also be staged like other types of lymphoma by using the Lugano system. The Lugano system, based on the older Ann Arbor system, has four stages (1 through 4, often noted with Roman numerals) based on the number and location of tumors in the lymph nodes and whether or not tissue outside the lymphatic system is involved. Extranodal involvement (involvement of organs other than the lymph nodes, spleen, or tonsils and adenoids) is denoted with an “E” for Lugano stages 1 and 2 (1E and 2E).
The Lugano system is used more often in people with SLL when the bone marrow is not involved. Bone marrow involvement (seen in most cases of SLL) would make it a stage 4 lymphoma, but in the case of CLL/SLL, bone marrow involvement does not necessarily predict a worse outcome.
In stage 1 (stage I), only one group of lymph nodes is involved or one organ outside the lymphatic system is involved (stage 1E).
In stage 2 (stage II), two or more groups of lymph nodes on the same side of the diaphragm are involved or one group of lymph nodes and one nearby organ are involved (stage 2E).
In stage 3 (stage III), lymph nodes on both sides of the diaphragm are involved or lymph nodes above the diaphragm and the spleen are involved.
Stage 4 (stage IV) uses the same criteria as stage 3, plus it requires involvement of one organ outside the lymphatic system (including bone marrow).
Staging alone is not enough to predict the outcome for people with CLL/SLL. The combination of staging and the assessment of certain prognostic factors can help determine the best treatment and expected outcome for those living with CLL/SLL.
The CLL International Prognostic Index (CLL-IPI) uses a combination of factors to produce a risk score (of 1 to 10 points) to categorize people as low, intermediate, high, or very high risk. These factors are:
CLL-IPI risk categories are:
The CLL-IPI recommendations are to not treat low-risk people, to treat people in the intermediate- and high-risk categories only if they have symptoms, and to treat very high-risk individuals with new, experimental treatments or clinical trials instead of chemotherapy. Those who do not require treatment still require close follow-up, called active surveillance.
There are several risk factors, including both adverse prognostic factors (which predict shorter survival) and favorable prognostic factors (which predict longer survival) that can affect the expected outcome of CLL/SLL. Some factors also help doctors identify slow-growing versus fast-growing cancer cells (CLL cells).
Adverse prognostic factors include:
Favorable prognostic factors include:
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