Chronic lymphocytic leukemia


Chronic lymphocytic leukemia is a type of cancer in which the bone marrow makes too many lymphocytes. Early on there are typically no symptoms. Later non-painful lymph node swelling, feeling tired, fever, night sweats, or weight loss for no clear reason may occur. Enlargement of the spleen and low red blood cells may also occur. It typically worsens gradually over years.
Risk factors include having a family history of the disease. Exposure to Agent Orange and certain insecticides might also be a risk. CLL results in the buildup of B cell lymphocytes in the bone marrow, lymph nodes, and blood. These cells do not function well and crowd out healthy blood cells. CLL is divided into two main types: those with a mutated IGHV gene and those without. Diagnosis is typically based on blood tests finding high numbers of mature lymphocytes and smudge cells.
Management of early disease is generally with watchful waiting. Infections should more readily be treated with antibiotics. In those with significant symptoms, chemotherapy or immunotherapy may be used. As of 2019 ibrutinib is often the initial medication recommended. The medications fludarabine, cyclophosphamide, and rituximab were previously the initial treatment in those who are otherwise healthy.
CLL affected about 904,000 people globally in 2015 and resulted in 60,700 deaths. The disease most commonly occurs in people over the age of 50. Males are affected more often than females. It is much less common in people from Asia. Five-year survival following diagnosis is approximately 83% in the United States. It represents less than 1% of deaths from cancer.

Signs and symptoms

Most people are diagnosed as having CLL based on the result of a routine blood test that shows a high white blood cell count, specifically a large increase in the number of circulating lymphocytes. These people generally have no symptoms. Less commonly, CLL may present with enlarged lymph nodes. This is referred to as small lymphocytic lymphoma. Less commonly the disease comes to light only after the cancerous cells overwhelm the bone marrow resulting in low red blood cells, neutrophils, or platelets. Or there is fever, night sweats, weight loss, and the person feels tired.
CLL is, in virtually all cases, preceded by a particular subtype of monoclonal B-cell lymphocytosis. This subtype, termed chronic lymphocytic leukemia/small lymphocyte lymphoma MBL is an asymptomatic, indolent, and chronic disorder in which individuals exhibit an increase in the number of circulating B-cell lymphocytes. These B-cells are abnormal: they are monoclonal, i.e. produced by a single ancestral B-cell, and have some of the same cell marker proteins, chromosome abnormalities, and gene mutations found in CLL. CLL/SLL MBL consist of two groups: low-count CLL/SLL MBL has monoclonal B-cell blood counts of <0.5x9 cells/liter while high-count CLL/SLL MBL has blood monoclonal B-cell counts ≥0.5x9/L but <5x109/L. Individuals with blood counts of these monoclonal B-cells >5x9/L are diagnosed as having CLL. Low-count CLL/SLLL MBL rarely if ever progresses to CLL while high-count CLL/SLL MBL does so at a rate of 1-2% per year. Thus, CLL may present in individuals with a long history of having high-count CLL/SLL MBL. There is no established treatment for these individuals except monitoring for development of the disorder's various complications and for their progression to CLL.

Complications

Complications include a low level of antibodies in the bloodstream leading to recurrent infection, warm autoimmune hemolytic anemia in 10–15% of patients, and bone marrow failure. Chronic lymphocytic leukemia may also transform into Richter's syndrome, the development of fast-growing diffuse large B cell lymphoma, prolymphocytic leukemia, Hodgkin's lymphoma, or acute leukemia in some patients. Its incidence is estimated to be around 5% in patients with CLL.
Gastrointestinal involvement can rarely occur with chronic lymphocytic leukemia. Some of the reported manifestations include intussusception, small intestinal bacterial contamination, colitis, and others. Usually, GI complications with CLL occur after Richter transformation. Two cases to date have been reported of GI involvement in chronic lymphocytic leukemia without Richter's transformation.

Cause

CLL is caused by multiple genetic mutations and epigenetic changes. Men are about twice as likely to get CLL as women, and risk increases with age. It is relatively rare among Asians. Some relevant genetic mutations may be inherited; in around 9% of CLL cases a parent had CLL. Exposure to Agent Orange increases the risk of CLL, and exposure to hepatitis C virus may increase the risk. There is no clear association between ionizing radiation exposure and the risk of developing CLL. Blood transfusions have been ruled out as a risk factor.

Diagnosis

CLL is usually first suspected by a diagnosis of lymphocytosis, an increase in a type of white blood cell, on a complete blood count test. This frequently is an incidental finding on a routine physician visit. Most often the lymphocyte count is greater than 5000 cells per microliter of blood, but can be much higher. The presence of lymphocytosis in an elderly individual should raise strong suspicion for CLL, and a confirmatory diagnostic test, in particular flow cytometry, should be performed unless clinically unnecessary.
A peripheral blood smear showing an abundance of damaged cells known as "smudge cells" or "basket cells" can also indicate the presence of the disease.
The diagnosis of CLL is based on the demonstration of an abnormal population of B lymphocytes in the blood, bone marrow, or tissues that display an unusual but characteristic pattern of molecules on the cell surface. This atypical molecular pattern includes the coexpression of cell surface markers clusters of differentiation 5 and 23. In addition, all the CLL cells within one individual are clonal, that is, genetically identical. In practice, this is inferred by the detection of only one of the mutually exclusive antibody light chains, kappa or lambda, on the entire population of the abnormal B cells. Normal B lymphocytes consist of a stew of different antibody-producing cells, resulting in a mixture of both kappa- and lambda-expressing cells. The lack of the normal distribution of these B cells is one basis for demonstrating clonality, the key element for establishing a diagnosis of any B cell malignancy.
The combination of the microscopic examination of the peripheral blood and analysis of the lymphocytes by flow cytometry to confirm clonality and marker molecule expression is needed to establish the diagnosis of CLL. Both are easily accomplished on a small amount of blood. A flow cytometer instrument can examine the expression of molecules on individual cells in fluids. This requires the use of specific antibodies to marker molecules with fluorescent tags recognized by the instrument. In CLL, the lymphocytes are genetically clonal, of the B cell lineage, and characteristically express the marker molecules CD5 and CD23. These B cells resemble normal lymphocytes under the microscope, although slightly smaller, and are fragile when smeared onto a glass slide, giving rise to many broken cells, which are called "smudge" or "smear" cells.
The Matutes's CLL score allows the identification of a homogeneous subgroup of classical CLL, that differs from atypical/mixed CLL for the five markers' expression
Matutes's CLL scoring system is very helpful for the differential diagnosis between classical CLL and the other B cell chronic lymphoproliferative disorders, but not for the immunological distinction between mixed/atypical CLL and mantle cell lymphoma. Discrimination between CLL and MCL can be improved by adding non-routine markers such as CD54 and CD200. Among routine markers, the most discriminating feature is the CD20/CD23 mean fluorescence intensity ratio. In contrast, FMC7 expression can surprisingly be misleading for borderline cases.

Clinical staging

Staging, determining the extent of the disease, is done with the Rai staging system or the Binet classification and is based primarily on the presence of a low platelet or red cell count. Early-stage disease does not need to be treated. CLL and SLL are considered the same underlying disease, just with different appearances.
Rai staging system
Binet classification
Array-based karyotyping is a cost-effective alternative to FISH for detecting chromosomal abnormalities in CLL. Several clinical validation studies have shown >95% concordance with the standard CLL FISH panel.

Related diseases

In the past, cases with similar microscopic appearance in the blood but with a T cell phenotype were referred to as T-cell CLL. However, these are now recognized as a separate disease group and are currently classified as T-cell prolymphocytic leukemias.
CLL should not be confused with acute lymphoblastic leukemia, a highly aggressive leukemia most commonly diagnosed in children, and highly treatable in the pediatric setting.

Differential diagnosis

Hematologic disorders that may resemble CLL in their clinical presentation, behavior, and microscopic appearance include mantle cell lymphoma, marginal zone lymphoma, B cell prolymphocytic leukemia, and lymphoplasmacytic lymphoma.
All the B cell malignancies of the blood and bone marrow can be differentiated from one another by the combination of cellular microscopic morphology, marker molecule expression, and specific tumor-associated gene defects. This is best accomplished by evaluation of the patient's blood, bone marrow, and occasionally lymph node cells by a pathologist with specific training in blood disorders. A flow cytometer is necessary for cell marker analysis, and the detection of genetic problems in the cells may require visualizing the DNA changes with fluorescent probes by FISH.

Treatment

CLL treatment focuses on controlling the disease and its symptoms rather than on an outright cure. In those without or only minimal symptoms watchful waiting is generally appropriate.
CLL is treated by chemotherapy, radiation therapy, biological therapy, or bone marrow transplantation. Symptoms are sometimes treated surgically or by radiation therapy.
Initial CLL treatments vary depending on the exact diagnosis and the progression of the disease, and even with the preference and experience of the health care practitioner. Any of dozens of agents may be used for CLL therapy.

Decision to treat

While it is generally considered incurable, CLL progresses slowly in most cases. Many people with CLL lead normal and active lives for many years—in some cases for decades. Because of its slow onset, early-stage CLL is, in general, not treated since it is believed that early CLL intervention does not improve survival time or quality of life. Instead, the condition is monitored over time to detect any change in the disease pattern.
The decision to start CLL treatment is taken when the person's symptoms or blood counts indicate that the disease has progressed to a point where it may affect quality of life.
Clinical "staging systems" such as the Rai four-stage system and the Binet classification can help to determine when and how to treat the patient.
Determining when to start treatment and by what means is often difficult; no survival advantage is seen in treating the disease very early. The National Cancer Institute Working Group has issued guidelines for treatment, with specific markers that should be met before it is initiated.

Chemotherapy

Combination chemotherapy regimens are effective in both newly diagnosed and relapsed CLL. Combinations of fludarabine with alkylating agents produce higher response rates and a longer progression-free survival than single agents:
Although the purine analogue fludarabine was shown to give superior response rates to chlorambucil as primary therapy, no evidence shows early use of fludarabine improves overall survival, and some clinicians prefer to reserve fludarabine for relapsed disease.
Chemoimmunotherapy with FCR has shown to improve response rates, progression-free survival, and overall survival in a large randomized trial in CLL patients selected for good physical fitness. This has been the first clinical trial demonstrating that the choice of a first-line therapy can improve the overall survival of patients with CLL.
Alkylating agents approved for CLL include bendamustine and cyclophosphamide.

Targeted therapy

attacks cancer cells at a specific target, with the aim of not harming normal cells. Targeted drugs used in CLL include venetoclax, ibrutinib, idelalisib and duvelisib, as well as monoclonal antibodies against CD20 and CD52.

Stem cell transplantation

, using the recipient's own cells, is not curative. Younger individuals, if at high risk for dying from CLL, may consider allogeneic hematopoietic stem cell transplantation. Myeloablative forms of allogeneic stem cell transplantation, a high-risk treatment using blood cells from a healthy donor, may be curative, but treatment-related toxicity is significant. An intermediate level, called reduced-intensity conditioning allogeneic stem cell transplantation, may be better tolerated by older or frail patients.
Patients can develop a graft-versus-host disease if they receive a stem cell transplant. Therefore, Fisher et al. conducted a Cochrane review with randomised controlled trials in 2019 to measure the safety and efficacy of mesenchymal stromal cells for people suffering from a graft-versus-host disease after receiving a haematopoietic stem cell transplantation as treatment for their haematological disease. Fisher et al. included trials that used MSCs either for therapeutic or prophylactic reasons. The exact inclusion and exclusion criteria and information regarding the dose can be found in the original Cochrane review. In the therapeutic trials it was necessary that the study participants already suffered from a GvHD. Fisher et al. conducted one analysis: MSCs compared to control/ placebo for treating immune mediated inflammation post-transplantation and in autoimmunity: Mesenchymal stromal cells may reduce the all-cause mortality if they are used for a therapeutic reason. Moreover, the therapeutic use of MSCs may increase the complete response of acute and chronic GvHD, but the evidence is very uncertain. The evidence suggests that MSCs for prophylactic reason result in little to no difference in the all-cause mortality, in the relapse of malignant diseases and in the incidence of acute GvHD. The evidence suggests that MSCs for prophylactic reason reduce the incidence of chronic GvHD.

Refractory CLL

"Refractory" CLL is a disease that no longer responds favorably to treatment. In this case, more aggressive therapies, including lenalidomide, flavopiridol, and bone marrow transplantation, are considered. The monoclonal antibody alemtuzumab may be used in patients with refractory, bone marrow-based disease.

During pregnancy

Leukemia is rarely associated with pregnancy, affecting only about one in 10,000 pregnant women. Treatment for chronic lymphocytic leukemias can often be postponed until after the end of the pregnancy. If treatment is necessary, then giving chemotherapy during the second or third trimesters is less likely to result in pregnancy loss or birth defects than treatment during the first trimester.

Treatment of side effects

If people receive a stem cell transplant or a chemotherapy, they might develop a bleeding disorder. Therefore, Estcourt et al. conducted a Cochrane review with randomised controlled trials in 2012 to assess which use of platelet transfusions is the most effective one to prevent bleeding if people suffer from a haematological disorder and undergo a stem cell transplantation or a chemotherapy. A study participation was only possible if the patients did not have an active bleeding within the last 5 days and did not receive a previous platelet transfusion because of the chemotherapy or stem cell transplantation. The exact inclusion and exclusion criteria and details regarding the dose can be found in the original Cochrane review. Estcourt et al. conducted four analyses to answer their research question. In the first analysis they compared therapeutic/ non-prophylactic platelet transfusions to prophylactic platelet transfusions: The evidence suggests that therapeutic platelet transfusions result in little to no difference in the mortality secondary to bleeding. Furthermore, they may result in a slight reduction in the number of days on which a significant bleeding event occurred. The evidence suggests that therapeutic platelet transfusions result in a large increase in the number of patients with at least one significant bleeding event and they likely result in a large reduction in the number of platelet transfusions. In the second analysis, the review authors conducted a comparison of prophylactic platelet transfusions at threshold of 10.000 to a higher transfusion threshold : Prophylactic platelet transfusions at threshold of 10.000 may result in little to no difference in the mortality due to bleeding. These transfusions probably reduce the number of platelet transfusions per patient slightly. Prophylactic platelet transfusions at threshold of 10.000 probably increase the number of patients with at least one significant bleeding event and they likely result in a large increase in the number of days on which a significant bleeding event occurred. Prophylactic platelet transfusion with one dose schedules were compared to prophylactic platelet transfusions with another dose schedule in the third analysis: Prophylactic platelet transfusions at one dose schedule may result in little to no difference in the mortality secondary to bleeding if low dosage platelet transfusions are compared to standard dose platelet transfusions. Furthermore, the transfusions at one dose schedule probably result in little to no difference in the mortality secondary to bleeding if high dose platelet transfusions and standard dosage platelet transfusions are compared to each other. Prophylactic platelet transfusions with one dose schedule result in little to no difference in the number of participants with a significant bleeding event if low dosage platelet transfusions or high dosage platelet transfusions are compared to standard dose platelet transfusions. The last analysis was conducted to compare prophylactic platelet transfusions to platelet-poor plasma: The evidence is very uncertain about the effect of prophylactic platelet transfusion on mortality secondary to bleeding, the number of participants with a significant bleeding event and the number of platelet transfusions. Furthermore, Estcourt et al. renewed the second analysis from their Cochrane review from 2012 in 2015 with randomised controlled trials and aimed to evaluate whether different platelet transfusion thresholds for the management of prophylactic platelet transfusions have an influence on the safety and efficacy for patients that suffer from a haematological disorder and receive a stem cell transplantation or myelosuppressive chemotherapy. Estcourt et al. conducted the following analysis: Prophylactic platelet transfusion at threshold of 10.000 compared to higher transfusion threshold : The evidence suggests that prophylactic platelet transfusions at threshold of 10.000 result in little to no different in the time to the first bleeding episode, the number of participants with WHO Grade 3 or 4 bleeding and clinically significant bleedings per participant. The evidence suggests that prophylactic platelet transfusions at threshold of 10.000 reduce the number of platelet transfusions per participants slightly. Moreover, the evidence suggests that these transfusions increase the number of participants with at least one significant bleeding event. Prophylactic platelet transfusions at threshold of 10.000 may result in a large increase in the mortality due to all causes. Apart from the time to the first bleeding, all endpoints are related to the first 30 days after the study entry.

Supportive treatment

It might be possible that additional treatments support the main therapy. Therefore, Knips et al. conducted a Cochrane review with randomised controlled trials in 2019 to re-evaluate the safety, efficacy and feasibility of physical exercises in addition to the standard treatment for adult patients with haematological malignancies. The exact inclusion and exclusion criteria and further details can be found in the original Cochrane review. The study participants were in disease stage I to IV. As aerobic physical exercises were only an additional treatment, participants also received chemotherapies or stem cell transplantations/ bone marrow transplantations. Knips et al. compared aerobic physical exercises additional to the standard treatment to standard treatment alone: The evidence is very uncertain about the effect of aerobic physical exercises on anxiety and serious adverse events. Aerobic physical exercises may result in little to no difference in the mortality, in the quality of life and in the physical functioning. These exercises may result in a slight reduction in depression. Furthermore, aerobic physical exercises probably reduce fatigue.

Prognosis

Prognosis depends on the subtype. Some subtypes have a median survival of 6–8 years, while others have a median survival of 22 years. Telomere length has been suggested to be a valuable prognostic indicator of survival.

Epidemiology

CLL is primarily a disease of older adults, with a median age of 70 years at the time of diagnosis. Though less common, CLL sometimes affects people between 30 and 39 years of age. The incidence of CLL increases very quickly with increasing age.
In the United States during 2014, about 15,720 new cases are expected to be diagnosed, and 4,600 patients are expected to die from CLL. Because of the prolonged survival, which was typically about 10 years in past decades, but which can extend to a normal life expectancy, the prevalence is much higher than the incidence. CLL is the most common type of leukemia in the UK, accounting for 38% of all leukemia cases. Approximately 3,200 people were diagnosed with the disease in 2011.
In Western populations, subclinical "disease" can be identified in 3.5% of normal adults, and in up to 8% of individuals over the age of 70. That is, small clones of B cells with the characteristic CLL phenotype can be identified in many healthy elderly persons. The clinical significance of these cells is unknown.
In contrast, CLL is rare in Asian countries, such as Japan, China, and Korea, accounting for less than 10% of all leukemias in those regions. A low incidence is seen in Japanese immigrants to the US, and in African and Asian immigrants to Israel.
Of all cancers involving the same class of blood cell, 7% of cases are CLL/SLL.
Rates of CLL are somewhat elevated in people exposed to certain chemicals. Under U.S. Department of Veterans' Affairs regulations, Vietnam veterans who served in-country or in the inland waterways of Vietnam and who later develop CLL are presumed to have contracted it from exposure to Agent Orange and may be entitled to compensation.

Research directions

Research in 2008 is comparing different forms of bone marrow transplants to determine which patients are the best candidates and which approach is best in different situations.
Researchers at the Abramson Cancer Center of the University of Pennsylvania School of Medicine reported preliminary success in the use of gene therapy, through genetically modified T cells, to treat CLL. The findings, which were published in August 2011, were based on data from three patients who had modified T cells injected into their blood. The T cells had been modified to express genes that would allow the cells to proliferate in the body and destroy B cells including those causing the leukemia. Two patients went into remission, while the presence of leukemia in the third patient reduced by 70%.
One of the patients had been diagnosed with CLL for 13 years, and his treatment was failing before he participated in the clinical trial. One week after the T cells were injected, the leukemia cells in his blood had disappeared. The T cells were still found in the bloodstream of the patients six months after the procedure, meaning they would be able to fight the disease should leukemia cells return. This was the first time scientists "have used gene therapy to successfully destroy cancer tumors in patients with advanced disease".
Research is also investigating therapies targeting B cell receptor signalling. Syk inhibitor fostamatinib is in trials. The trial of a combination of ibrutinib and venetoclax had encouraging results in a small number of people.