(See also Overview of Leukemia. Overview of Leukemia Leukemia is a malignant condition involving the excess production of immature or abnormal leukocytes, which eventually suppresses the production of normal blood cells and results in symptoms... read more )
Chronic lymphocytic leukemia is the most common type of leukemia in the Western world. The American Cancer Society estimates that in the United States in 2022 there will be 20,000 new cases of CLL and about 4400 deaths; most cases and almost all deaths will be in adults. The average age of a patient with CLL is 70 years; CLL is extremely rare in children. In the US, the average lifetime risk of CLL in both sexes is about 0.57% (1 in 175).
Although the cause of CLL is unknown, some cases appear to have a hereditary component. CLL is rare in Japan and China, and the incidence does not seem to be increased among Japanese expatriates in the United States, suggesting the importance of genetic factors. CLL is more common among Jews of Eastern European descent.
Pathophysiology of CLL
In chronic lymphocytic leukemia, CD5+ B cells undergo malignant transformation. The B cells become continuously activated by acquisition of mutations that lead to monoclonal B-cell lymphocytosis (MBL). Further accumulation of genetic abnormalities and subsequent oncogenic transformation of monoclonal B cells leads to CLL. Lymphocytes initially accumulate in the bone marrow and then spread to lymph nodes and other lymphoid tissues, eventually inducing splenomegaly, hepatomegaly, and systemic symptoms such as fatigue, fever, night sweats, early satiety, and unintentional weight loss.
As CLL progresses, abnormal hematopoiesis results in anemia, neutropenia, thrombocytopenia, and decreased immunoglobulin production. Hypogammaglobulinemia can develop in up to two thirds of patients, increasing risk for infectious complications. Patients have increased susceptibility to autoimmune hemolytic anemia (with a positive direct antiglobulin test) and autoimmune thrombocytopenia.
CLL can evolve into B-cell prolymphocytic leukemia and can transform to a higher grade non-Hodgkin lymphoma Non-Hodgkin Lymphomas Non-Hodgkin lymphomas are a heterogeneous group of disorders involving malignant monoclonal proliferation of lymphoid cells in lymphoreticular sites, including lymph nodes, bone marrow, the... read more 
. About 2 to 10% of CLL cases develop into diffuse large B-cell lymphoma (called Richter's transformation).
Symptoms and Signs of CLL
Patients are often asymptomatic early on, with insidious onset of nonspecific symptoms (eg, fatigue, weakness, anorexia, weight loss, fever, and/or night sweats) that may prompt evaluation. More than 50% of patients have lymphadenopathy. Lymphadenopathy can be localized (with cervical and supraclavicular nodes being the most commonly involved) or generalized. Splenomegaly and hepatomegaly are less common than lymphadenopathy. Skin involvement (see photo ) is rare.
Diagnosis of CLL
Complete blood count (CBC) and peripheral smear
Flow cytometry of peripheral blood
Immunophenotyping
The diagnosis of chronic lymphocytic leukemia is first suspected when an absolute peripheral lymphocytosis of > 5000/mcL (> 5 × 109/L)) is found. Peripheral blood flow cytometry can confirm clonality in circulating B cells. The circulating lymphocytes should express CD5, CD19, CD20, CD23, and kappa or lambda light chains. Patients with an absolute lymphocyte count < 5000/mcL (< 5 × 109/L) but evidence of clonality are diagnosed with monoclonal B cell lymphocytosis (MBL). About 1 to 2% of monoclonal B-cell lymphocytosis cases progress to CLL per year (1 Diagnosis reference Chronic lymphocytic leukemia (CLL) is characterized by progressive accumulation of phenotypically mature malignant B lymphocytes. Primary sites of disease include peripheral blood, bone marrow... read more ). Bone marrow aspirate and biopsy are not required for the diagnosis of CLL. However, if done, the marrow often demonstrates > 30% lymphocytes.
Other findings at diagnosis can include hypogammaglobulinemia (< 15% of cases), elevated lactate dehydrogenase (LDH), elevated uric acid, elevated hepatic enzymes, and rarely, hypercalcemia. Cytogenetic and molecular studies done from a peripheral blood sample at the time of diagnosis help in determining prognosis.
Classification uses the Rai or Binet staging systems. Neither system effectively predicts early disease progression. Routine imaging is not recommended for initial staging (see table Clinical Staging of CLL Clinical Staging of Chronic Lymphocytic Leukemia* 
).
Diagnosis reference
1. Rawstron AC, Bennett FL, O'Connor SL, et al: Monoclonal B-cell lymphocytosis and chronic lymphocytic leukemia. N Engl J Med 359(6):575–583, 2008.
Prognosis for CLL
The natural history of chronic lymphocytic leukemia is highly variable. Survival ranges from about 2 to > 20 years, with a median of about 10 years. Patients presenting as Rai stage 0 to II may survive for 5 to 20 years without treatment.
Other prognostic features of CLL include
Lymphocyte doubling time
Specific genetic abnormalities
Lymphocyte doubling time is the number of months it takes the absolute lymphocyte count to double. Untreated patients with a lymphocyte doubling time < 12 months have a more aggressive clinical course.
Specific high-risk cytogenetic abnormalities include del(17p) and del(11q). Other adverse prognostic features include an unmutated immunoglobulin heavy chain variable gene, presence of CD38 on flow cytometry, and expression of ZAP-70.
Treatment of CLL
Chemoimmunotherapy, targeted therapy, and sometimes radiation therapy
Supportive care
Chronic lymphocytic leukemia is considered incurable with the current standard of care; treatment is aimed at symptom amelioration. Thus, treatment is withheld until patients have one of the following:
Symptoms attributed to CLL
Progressive lymphocytosis with an increase of ≥ 50% over a 2-month period
Lymphocyte doubling time (increase of ≥ 100%) < 6 months
Symptoms that prompt treatment in patients with CLL include
Constitutional symptoms (fever, night sweats, extreme fatigue, weight loss)
Significant hepatomegaly, splenomegaly, or lymphadenopathy
Recurrent infections
Symptomatic anemia and/or thrombocytopenia
Disease-directed treatment options include
Chemoimmunotherapy
Targeted therapy
Radiation therapy
Supportive care includes
Transfusion of packed red blood cells for anemia
Platelet transfusions for bleeding associated with thrombocytopenia
Antimicrobials for bacterial, fungal, or viral infections
Because neutropenia and hypogammaglobulinemia limit bacterial killing, antibiotic therapy should be bactericidal. Gamma-globulin infusions should be considered for treatment in patients with hypogammaglobulinemia and refractory infections or for prophylaxis when ≥ 2 severe infections occur within 6 months.
Initial therapy
The intent of initial therapy is to
Relieve symptoms
Induce durable remissions
Prolong survival
Recent studies have suggested that targeted therapy is as efficacious if not superior to upfront chemoimmunotherapy for most patients. Selection of initial therapy depends on patient characteristics, disease-specific features such as presence of del(17p), and the overarching goals of therapy.
Previously, purine analogs (eg, fludarabine) as well as alkylating agents (eg, bendamustine, chlorambucil, cyclophosphamide) have been used in combination with the anti-CD20 monoclonal antibody, rituximab. The combination of fludarabine, cyclophosphamide, and rituximab (FCR) was the prior standard of care for upfront treatment in most medically fit patients. In the past, older untreated patients were offered bendamustine and rituximab as this regimen was easier to tolerate (1 Treatment references Chronic lymphocytic leukemia (CLL) is characterized by progressive accumulation of phenotypically mature malignant B lymphocytes. Primary sites of disease include peripheral blood, bone marrow... read more ). The landmark E1912 study examined the efficacy of treatment with FCR versus the novel combination of ibrutinib, an oral inhibitor of Bruton tyrosine kinase (Btk) and rituximab in patients< 70 years of age with previously untreated CLL. The results demonstrated superior progression-free and overall survival in patients who received ibrutinib plus rituximab as compared to standard chemoimmunotherapy (2 Treatment references Chronic lymphocytic leukemia (CLL) is characterized by progressive accumulation of phenotypically mature malignant B lymphocytes. Primary sites of disease include peripheral blood, bone marrow... read more ). More recent trials in treatment-naive patients suggest that the combination of acalabrutinib, a second generation oral Btk inhibitor and obinutuzumab, a glycoengineered monoclonal antibody against CD20, is as efficacious and potentially better tolerated than conventional chemoimmunotherapy (3 Treatment references Chronic lymphocytic leukemia (CLL) is characterized by progressive accumulation of phenotypically mature malignant B lymphocytes. Primary sites of disease include peripheral blood, bone marrow... read more ). Given the advent of targeted therapy for use in upfront treatment of CLL, several studies have examined a "time limited" approach to treatment. The oral Bcl2 inhibitor venetoclax (an oral inhibitor of Bcl-2) has been used in combination with obinutuzumab to effectively treat patients for a fixed duration of 12 months (4 Treatment references Chronic lymphocytic leukemia (CLL) is characterized by progressive accumulation of phenotypically mature malignant B lymphocytes. Primary sites of disease include peripheral blood, bone marrow... read more ). More research is needed regarding use of monitoring minimal residual disease (MRD) in CLL and how MRD changes may guide treatment resumption.
Relapsed or refractory CLL
Relapsed or refractory CLL should be confirmed histologically before restarting treatment. Transformation to large cell lymphoma (Richter's transformation) should be specifically excluded. Asymptomatic patients with recurrent CLL are monitored closely for symptoms that warrant treatment. Factors that influence choice of treatment at relapse include
Initial therapy used
Initial duration of response
In patients who received upfront chemoimmunotherapy, treatment with a Btk inhibitor can improve response rate and progression-free survival in relapsed or refractory CLL. Btk inhibitors are continued until toxicity develops or disease progresses. Other effective targeted therapies for relapsed CLL included idelalisib (an oral inhibitor of phosphoinositide 3'-kinase [PI3K] delta) and venetoclax. Venetoclax can be used for patients with del(17p) who have received at least one prior therapy. The advent of upfront targeted therapy may make selection of optimal therapy challenging in patients with relapsed CLL. When applicable, clinical trial enrollment is encouraged.
Monotherapy with an anti-CD20 monoclonal antibody (rituximab, ofatumumab, obinutuzumab) may transiently palliate symptoms.
Allogeneic stem cell transplantation Hematopoietic Stem Cell Transplantation Hematopoietic stem cell (HSC) transplantation is a rapidly evolving technique that offers a potential cure for hematologic cancers ( leukemias, lymphomas, myeloma) and other hematologic disorders... read more should be considered for patients who are fit.
Radiation therapy
Palliative irradiation may be given to areas of lymphadenopathy or for liver and spleen involvement that does not respond to chemotherapy. Total body irradiation in small doses is occasionally successful in temporarily relieving symptoms.
Treatment references
1. Eichhorst B, Fink AM, Bahlo J et al: First-line chemoimmunotherapy with bendamustine and rituximab versus fludarabine, cyclophosphamide, and rituximab in patients with advanced chronic lymphocytic leukaemia (CLL10): An international, open-label, randomised, phase 3, non-inferiority trial. Lancet Oncol 17:928–942, 2016.
2. Shanafelt TD, Wang XV, Kay NE, et al: Ibrutinib-rituximab or chemoimmunotherapy for chronic lymphocytic leukemia. N Engl J Med 381:432–443, 2019. doi: 10.1056/NEJMoa1817073
3. Sharman JP, Egyed M, Jurczak W, et al: Acalabrutinib with or without obinutuzumab versus chlorambucil and obinutuzmab for treatment-naive chronic lymphocytic leukaemia (ELEVATE TN): a randomised, controlled, phase 3 trial. Lancet 395(10232):1278–1291, 2020. doi: 10.1016/S0140-6736(20)30262-2
4. Fischer K, Al-Sawaf O, Bahlo J, et al: Venetoclax and obinutuzumab in patients with CLL and coexisting conditions. N Engl J Med 380(23):2225–2236, 2019. doi: 10.1056/NEJMoa1815281
Key Points
Chronic lymphocytic leukemia (CLL) is an indolent lymphoproliferative malignancy involving mature lymphocytes, which predominantly affects older individuals.
CLL is the most common type of leukemia in the Western world.
Natural history is highly variable.
Treatment is generally not curative and so is not initiated until symptoms develop.
Chemoimmunotherapy decreases symptoms and prolongs survival.
More Information
The following is an English-language resource that may be useful. Please note that THE MANUAL is not responsible for the content of this resource.
Leukemia and Lymphoma Society: Resources for Healthcare Professionals: Provides information on research and clinical trials and resources for referrals to specialty care
