Chronic Lymphocytic Leukemia
Chronic lymphocytic leukemia (CLL), also known as B-cell chronic lymphocytic leukemia (B-CLL), is a disorder associated with morphologically mature but immunologically less mature lymphocytes, which accumulate in the bone marrow, lymphatic tissue and blood. CLL is often characterized by the expression of B-cell antigens CD19, CD20, CD23 and CD5, as well as relatively low surface membrane immunoglobulin. This immunophenotype as well as an absolute increase in bone marrow infiltration and/or lymphocytosis can be used to diagnose CLL.
The most common leukemia in Europe and North America, CLL typically affects an elderly population, progresses slowly, and is generally incurable. CLL is often identified in a blood test requested for an unrelated reason, but is usually not treated until a patient becomes symptomatic, as the disease progression rate can vary greatly between patients, and B-cell lymphocytosis is detected in 3% of the population over 40 and 6% of the population over 60, with many of these not progressing to the symptomatic stage. Additionally, there is no survival benefit of immediate compared to delayed treatment in patients with early-stage CLL.
Once progression is detected, treatment is initiated to induce remission. The majority of patients will show relapse, with short remission durations of less than 3 years indicative of a poor prognosis, particularly as the patient may not respond to the same treatment regimen again. Several prognostic factors are under investigation, which may help to assess the need for therapy and assist in the selection of therapy type.