Chronic lymphocytic leukemia (CLL)

Chronic lymphocytic leukemia (CLL) is an “indolent” (slow-growing) form of lymphoma. This article provides an overview of the symptoms, progression, and treatment of CLL.

At a glance

  • Chronic lymphocytic leukemia (CLL) is a lymphoma. As the cancer cells are also found in the blood though, it is also referred to as leukemia or blood cancer.
  • The progression of CLL is often very slow at the early stages of the illness.
  • CLL is particularly prevalent in older people.
  • If the patient has no symptoms, regularly monitoring CLL usually suffices.
  • At present, if CLL causes symptoms, the condition is primarily treated using targeted therapies or, in rarer cases, ‘immune chemotherapy’.
  • These treatments are almost always successful in mitigating CLL and improving the symptoms but are not yet usually able to permanently cure the disease itself.

Note: The information in this article cannot and should not replace a medical consultation and must not be used for self-diagnosis or treatment.

Chronic lymphocytic leukemia (CLL): doctor sitting at his desk having a discussion with an older man and a woman.

What is chronic lymphocytic leukemia?

Chronic lymphocytic leukemia (CLL) is a malignant condition of the body’s lymphatic system. This includes, for example, lymph nodes, the spleen and bone marrow. It starts in mature B-lymphocytes. That’s why specialists also refer to it as B-CLL. B-lymphocytes are a type of white corpuscle. 

Diagram of blood cells: B-lymphocytes compared with other blood cells.

B-lymphocytes (B cells) are blood cells that are involved in immune defense. Chronic lymphocytic leukemia starts in B-lymphocytes.

In formal terms CLL is not a leukemia but an indolent lymphoma. The term “leukemia” is included in its name because the lymphocytes it degrades are not only found in the lymphatic organs. They are also generally found in blood as well.

There are rare complications of CLL which are not covered by this article. These include for example small lymphocytic lymphoma (SLL), or Richter’s syndrome.

Prevalence of chronic lymphocytic leukemia (CLL) is highest in older people. The average age of those diagnosed with the condition is 72.

What are the symptoms of chronic lymphocytic leukemia?

Progression of chronic lymphocytic leukemia (CLL) is generally slow even if left untreated. Patients can remain symptom-free for long periods particularly if the spread of the disease is limited. Around a quarter of those affected have no symptoms due to CLL at the time of diagnosis.

The most common sign of the disease is painless swelling of the lymph nodes. If lymph nodes in the chest or abdominal cavity are enlarged this can cause non-specific symptoms. These include, for example:

  • dry cough
  • dyspnea (shortness of breath)
  • feeling of pressure
  • change in bowel habits
  • pain

The spleen and liver also often become enlarged. Blood tests typically show an abnormal elevation in the white blood cell count. The technical term for this change in blood count is leukocytosis or lymphocytosis.

If the CLL has already spread significantly, those affected may suffer from what are known as B symptoms. These include:

  • high temperature
  • night sweats 
  • weight loss

Patients also feel their performance is impaired, and they are more prone to infections. The disease can also impair blood formation (hematopoiesis) in bone marrow, which can cause anemia and hemorrhagic diathesis (an unusual susceptibility to bleed).

What causes chronic lymphocytic leukemia?

Chronic lymphocytic leukemia (CLL) starts because a single white corpuscle in the mature B-lymphocyte group undergoes a malignant transformation. This single cell transformation is not visible under a microscope. A better way to put it is that the cell does not mature properly and its ability to fight off infections is severely restricted.

Scientists do not yet understand all the details of why this happens and this is a subject of intense research. What is clear is there is usually a precursor (pre-cancerous condition) to CLL. The technical term for this precursor is monoclonal B cell lymphocytosis (MBL).

Doctors detect most cases of MBL inadvertently when they send blood tests off to the lab. MBL does not cause symptoms and is also not treated.

A number of factors affect whether and if so when the precursor will transition into chronic lymphocytic leukemia (CLL).

Are there risk factors for chronic lymphocytic leukemia?

Some conditions may possibly lead to a slight increase in the risk of chronic lymphocytic leukemia (CLL), including for example a patient history containing allergies, hepatitis C infections as well as many respiratory tract infections.

Inherited (genetic) factors probably also play a role here. For example, children of patients with CLL are at slightly higher risk of having CLL or other lymphoma.

The extent to which environmental factors contribute to the onset of CLL is still unclear. However, CLL is recognized in Germany as an occupational disease for people exposed to the chemicals benzene or 1,3-butadiene. 

How does chronic lymphocytic leukemia progress?

The progression of chronic lymphocytic leukemia (CLL) differs from patient to patient. It depends, amongst other things, on the stage of the disease. 

The progression of CLL is often very slow at the early stages. Then life expectancy is comparable to healthy age cohorts. 

As the condition progresses, it impairs healthy hematopoiesis in the bone marrow at different rates. This leads to a deficit in red corpuscles, certain white blood cells and platelets in the blood. This may cause fatigue, impaired performance, infections and hemorrhagic diathesis. 

How is chronic lymphocytic leukemia diagnosed?

The tests needed to diagnose chronic lymphocytic leukemia (CLL) depend on initial findings. Most suspected cases of CLL are based on elevated white corpuscle counts in the blood and/or swollen lymph nodes. 

Doctors then do three key things to firm up the diagnosis of CLL: 

  • They take a detailed medical history, focusing particularly on impaired performance and other symptoms, prevalence of infection, results of previous blood tests and diseases in the family.  
  • They conduct a physical examination, palpating lymph nodes, spleen and liver and looking for signs of anemia or hemorrhaging.  
  • They take a blood sample and have the blood undergo comprehensive testing. 

A bone marrow biopsy is not normally required for a diagnosis of CLL. However doctors may decide to have one done as the disease progresses. It is useful for assessing unexplained changes in blood count or the treatment outcome. 

Scans such as magnetic resonance imaging or computed tomography do not play a major role in initial CLL diagnosis. Tissue samples from abnormal lymph nodes are also only tested in a few patients. 

Further tests are only required when patients are to be given drug treatment for the chronic lymphocytic leukemia. These include, for example, genetic tests of the tumor cells, or specific blood assays. Scans may then be an option, such as ultrasound scanning of the abdominal cavity or computed tomography (CT) of the neck, chest or abdomen.  

How is chronic lymphocytic leukemia treated?

There is a variety of treatment options for patients with chronic lymphocytic leukemia (CLL). Doctors have to adjust them to reflect each individual patient’s situation.

Treatment methods are as follows: Binet stage A and B, asymptomatic: observation (watch and wait); Binet stage A and B, symptomatic and stage C: chemotherapy and/or targeted therapy, in individual cases: stem cell transplant and radiotherapy.

Observation (watch and wait)

In most cases chronic lymphocytic leukemia progresses slowly at the early stages of the disease. If patients are symptom-free and there are no indications that the CLL is advancing rapidly, experts recommend observing the patient. This involves regular checks. The technical term for this is “watch and wait”.

If the CLL is symptomatic, or if the disease is already at an advanced stage, doctors will generally begin treatment. Their overarching goal is to mitigate the symptoms and slow down the progression of the disease. This works well in most patients over a long period of time. However, permanent recovery cannot as yet usually be achieved by drug therapy.

Drug treatment

Doctors generally treat chronic lymphocytic leukemia (CLL) with drugs. The following can be used:

  • Targeted drugs that attack the distinctive parts of CLL cells
  • CLL cell antibodies
  • Cytostatics (drugs that generally slow down the rate of cell growth or inhibit cell division)

Hemato-oncologists (leukemia specialists) prescribe these drugs on their own or in combination at higher or lower dosages depending on the patient’s health status and individual risk factors.

Doctors only rarely and in particular situations resort to other therapeutic procedures such as surgery or radiotherapy.

What are targeted cancer therapies?

The video below explains when targeted cancer therapies are used. How are these drugs used and how do they work?

This and other videos can also be found on YouTube

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Stem cell transplant

If there is a risk of the leukemia progressing rapidly, doctors may also opt for a transplant of donor stem cells (allogeneic stem cell transplant). Stem cell transplants are preceded by high-dose chemotherapy.

Recovery from CLL is possible in principle under this type of treatment. However the treatment is highly intensive and has its own adverse side effects. It is therefore only an option for a few patients who are medically fit and do not have any co-morbidities.

Important: Patients with chronic lymphocytic leukemia (CLL) should be treated by hemato-oncologists at a medical practice or hospital clinic as far as possible. They are specialists in disorders of the blood and lymphatic systems.

Patients in the early stages of the disease who do not require treatment can also be regularly examined and tested by a general practitioner, if agreed with the specialists.

How do targeted therapies, treatment with antibodies and chemotherapy progress and what adverse effects do they have? Why is a blood stem cell transplant stressful for the recipient? Detailed information is available on the German Cancer Research Center’s Cancer Information Service website (in German).

What aftercare is there following chronic lymphocytic leukemia?

Doctors have to tailor aftercare for patients with chronic lymphocytic leukemia (CLL) to the individual situation. Where patients are receiving treatment as part of a clinical trial there will normally be additional targeted requirements for the aftercare plan.

If patients are under initial observation (“watch and wait”) at the early stages and do not have any signs of the disease, there is no aftercare as such. Patients are given regular physical checks and blood tests for as long as the CLL remains stable.

They receive aftercare following any treatment. This is designed to help with the early detection and treatment of a relapse as well as complications arising from the treatment.

Various factors determine which aftercare examinations are required and how often they should be performed:

  • How far had the CLL spread when diagnosed? 
  • How high is the risk of recidivism estimated by the doctor? 
  • What treatment was performed for the CLL and how did the disease respond to treatment? 
  • What is the patient’s overall health status and what co-morbidities may potentially be present?

What is everyday life like with chronic lymphocytic leukemia?

Diagnosis and treatment of chronic lymphocytic leukemia (CLL) can be very distressing for patients and family members.  

Symptoms such as fatigue, susceptibility to infections and restrictions on physical performance may already be significantly impairing a patient’s quality of life when the disease is first diagnosed. For those who are working, it is also associated with changes to employment and social status. Older people may have problems coping with everyday life as a result of the disease.  

The over-riding goal of treatment is to mitigate the disease as much as possible. It is aimed at enabling patients to return to everyday life as far as possible. 

Many leukemia patients also want to take an active part in contributing to their recovery. There are a number of ways they can do this. What can help them to cope better with the disease and the consequences of treatment depends on the individual situation:  

  • Exercise can help overcome fatigue and weakness. This should be adapted to the patient’s physical ability. 
  • A healthy balanced diet, or nutritional therapy, can prevent or treat malnourishment.  
  • Psycho-oncological counseling can help when worries and fears become overwhelming. 

Points of contact for treatment of CLL:

In Germany, clinical researchers specializing in lymphomas have formed the Malignant Lymphomas Competence Network (KML). Patients and doctors can turn to the KML with any questions concerning the diagnosis and treatment of lymphomas.

The KML website offers a search function that patients and doctors can use to find hospital clinics or medical practices that treat CLL.

CLL should be treated by a team of experienced doctors from a number of different specialties. Hospitals that are particularly experienced in the treatment of patients with lymphoma can become certified as oncology centers specializing in “hematological neoplasms”. The German Cancer Society (DKG), in conjunction with the German Society for Hematology and Medical Oncology (DGHO), regularly checks these hospitals for compliance with certain requirements.

You can find the addresses of centers with this designation on the OncoMAP website. To do this, select “Hematological Neoplasms” in the search panel under “Centre”.

Important: It is not currently mandatory in Germany to gain verification of compliance with these requirements. There may also be suitable clinics that have not yet applied for this verification.

Do you have further questions about dealing with the condition in everyday life and additional support options? The website of the Cancer Information Service of the German Cancer Research Center provides a wide range of information (in German).

If you have any questions about chronic lymphocytic leukemia, you can also make personal contact with the Cancer Information Service by dialing the freephone number 0800 - 420 30 40 or writing an email to

In cooperation with the Cancer Information Service of the German Cancer Research Center (Krebsinformationsdienst des Deutschen Krebsforschungszentrums).

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