White blood cells (courtesy CDC
Small lymphocytic lymphoma (SLL), is a type of non-Hodgkin lymphoma characterized by an excess of white blood cells in the lymph nodes. When cancer cells are found in the blood and bone marrow the disease is called chronic lymphocytic leukemia (CLL).
As a lymphoma, SLL accounts for about 4-5% of non-Hodgkin's lymphoma. As a leukemia, CLL accounts for about 30% of adult leukemias in Western countries. In SLL the patients are elderly (median age 60 years) and usually present with diffuse lymphadenopathy and some degree of marrow and peripheral blood involvement (Stage IV disease). Men appear to get the disease as equally as women.
Small lymphocytic lymphoma is very indolent but relentless, with median survivals of almost a decade. Although the slowly proliferating cells are sensitive to chemotherapeutic agents, chemotherapy is almost never curative and relapse inevitably follows.
Most studies find no benefit in treating patients until they develop symptoms. Therapy tends to be low-intensity: single alkylator therapy such as chlorambucil or combination therapy with cyclophosphamide/vincristine/prednisone. A new and promising drug is fludarabine, but it has not been shown to prolong survival so far.
High dose chemotherapy with bone marrow or stem cell transplant has been used to treat a small number of people with SLL / CLL. As side effects can be severe, some type of transplant are not given to people over the age of 45-50 and others can be given to people up to 65 years old who are in otherwise good health. The intensity of the treatment increases the risks of serious side effects for people over this age.
About 30% of cases of SLL progress to a higher grade process such as prolymphocytic lymphoma or diffuse large cell lymphoma (Richter's syndrome). Over time, 10% to 20% of cases of small lymphocytic lymphoma progress to chronic lymphocytic leukemia.
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