Leukemia is the cancer of different types of blood cells, including the bone marrow
cells and the lymphatic system. Leukemia is the 7th most common type of cancer in
India. In 2018, about 32,471 deaths occurred due to leukemia in India. According to
Globocan 2018, the worldwide mortality rate of leukemia was 2.5 per 100,000
About chronic leukemia
Chronic leukemia refers to the slowly progressing cancer that begins in the
blood-forming tissues. This results in the production of a large number of abnormal
white blood cells, which enter the bloodstream but are not as functional as the
normal cells. Depending on the type of white blood cells affected, chronic leukemia
types can be classified as chronic myeloblastic leukemia (CML) and chronic
lymphocytic leukemia (CLL).
Chronic myeloblastic/myeloid/ myelogenous/ leukemia (CML) is cancer that
affects the myeloid cells in the bone marrow (spongy tissue inside the blood, which
produces blood cells) and blood. Normally, myeloid cells produce platelets, red
blood cells, and most types of white blood cells (except lymphocytes). Chronic
myeloid leukemia cells grow, divide, and build up in the bone marrow and enter the
bloodstream. Over time, these cells invade other parts of the body, such as the
spleen. CML usually occurs in adults, and rarely occurs in children.
Chronic lymphocytic leukemia (CLL) is the cancer of blood and bone marrow,
which affects the lymphocytes- the white blood cells that help fight infection.
Chronic lymphocytic leukemia symptoms include cells building up slowly, over time,
without presenting any symptoms for years. After some time, these cells can grow and
invade other parts of the body, such as the spleen, lymph nodes, and liver. CLL
commonly affects older adults.
CML and CLL both occur due to a mutation in the DNA of the respective cells, which
causes the production of abnormal, ineffective blood cells.
In the case of CML, this mutation can promote cancer development, by the following
- An abnormal chromosome develops: Certain chromosome parts may get exchanged with
others, resulting in the development of an extra-short chromosome 22, called the
Philadelphia chromosome. This chromosome is present in 90% of individuals with
- A new gene is created in Philadelphia chromosome: A new gene is created in this
chromosome which ultimately promotes cancer and allows blood cells to grow
- Produces too many diseased blood cells: In CML, too many white blood cells
containing the Philadelphia chromosome are produced, which does not allow the
cells to grow and die normally. These cells crowd out the normal blood cells and
damage the bone marrow.
Several factors may increase the risk of CML and CLL, including:
- Older age (>70 years)
- Being male (in case of CLL)
- Exposure to chemicals, including certain herbicides and insecticides (in CLL)
- Radiation exposure, such as radiation therapy for certain types of cancer (in
- Family history (in case of CLL, not CML)
- Being white (in case of CLL)
Signs and symptoms
Chronic leukemia symptoms in the initial stages are not observed. But symptoms may
develop for some patients, and include:
- Night sweats
- Weight loss
- Pain or fullness below the ribs on the left side
Chronic Myeloid Leukemia symptoms include easy bleeding, bone pain, and loss of
appetite, whereas painless, enlarged lymph nodes and frequent infections may
The following tests are recommended to diagnose CML and CLL.
- Blood tests: Complete blood cell count can help to count the number of
lymphocytes and other blood cells. Blood chemistry tests can be performed to
measure organ function, which may reveal certain abnormalities.
- A high number of B cells (a type of lymphocyte) can indicate CLL. A test called
immunophenotyping or flow cytometry can determine if the increased lymphocytes
are caused due to CLL or other blood disorders. Flow cytometry also helps to
analyze the leukemia cells and predict the aggressiveness of the cells.
- Fluorescence in situ hybridization (FISH): This test examines the
for genetic abnormalities. The presence of the Philadelphia chromosome indicates
CML. Genetic evaluation can also be done with a polymerase chain reaction (PCR)
- Bone marrow tests: These tests involve the collection of bone marrow
from the hip bone, which will be analyzed in the laboratory. Bone marrow biopsy
and bone marrow aspiration are commonly used to diagnose chronic leukemia.
- Imaging tests: CT scan, MRI scan, and PET scan are performed to determine
spread of cancer, to find a suspicious area that may be cancerous, or to
estimate the effectiveness of the current treatment.
Staging of CML and CLL
The stages indicate the extent or spread of cancer. Knowing the stage of cancer helps
to plan the treatment.
CML is classified into 3 phases - chronic phase, accelerated phase, or blastic phase,
based on the number of immature white blood cells (or blast cells) and severity of
- Chronic phase: < 10% of cells in blood and bone marrow are immature white
- Accelerated phase: 10% to 19% of cells in blood and bone marrow are blast
- Blastic phase: >20% of cells in blood or bone marrow are immature white blood
cells. The occurrence of fever, tiredness, and an enlarged spleen during this
phase, is known as a blast crisis.
CLL has the following stages:
- Stage 0: Too many lymphocytes in the blood, but no other symptoms of
- Stage I: Too many lymphocytes in the blood and lymph nodes are larger
- Stage II: Too many lymphocytes in blood; liver or spleen are larger than
usual, and lymph nodes may be larger than normal.
- Stage III: Too many lymphocytes and few red blood cells in the blood.
Lymph nodes, spleen, or liver may be larger than usual.
- Stage IV: Too many lymphocytes, too few platelets, and maybe too few red
blood cells in the blood. Lymph nodes, spleen, or liver may be larger than
Treatment for chronic leukemia depends on several factors, including the type of
cancer, stage of cancer, the onset of symptoms, the overall health of the patient,
and the patient’s preferences. Some cases of early-stage CLL may not receive
treatment; doctors may opt to wait and monitor the condition closely until it
Below are the treatment options for CLL and CML:
- Targeted drug therapy: In this therapy, drugs that attack the cancer
cells by focusing on the aspect of the cells which allows them to grow
uncontrollably are used. This is the initial treatment option for patients with
- Chemotherapy: This treatment involves using drugs to kill fast-growing
leukemia cells. These drugs can be given orally (pills) or intravenously
(injecting into a vein). Sometimes, chemotherapy is combined with targeted drug
therapy, and other treatment options to treat aggressive chronic leukemia.
- Immunotherapy: In this therapy, the body’s immune system is boosted to
fight cancer. This treatment may help the immune system identify cancer cells
and/or train the immune cells to fight cancer cells.
- Bone marrow transplant (or stem cell transplant): During the bone marrow
transplant, high doses of chemo drugs are used to kill the stem cells
(blood-forming cells) in the bone marrow, following which the healthy adult
blood stem cells from a donor are infused into the blood. These healthy cells
travel to the bone marrow and produce new, healthy blood cells to replace the
leukemia cells. This treatment method is reserved for patients who haven’t
benefited from other treatment options.
- Clinical trials: Clinical trials are experiments that study the latest
treatment for diseases or new ways of using the existing treatments. Clinical
trials may give a chance for the patients to try new treatments but cannot
guarantee the treatment outcomes. The risks and benefits of the available
clinical trials can be discussed with the doctor.
CLL and CML have very few known risk factors, hence there is no definite way to
prevent chronic leukemia. Some types of cancer can be prevented by making lifestyle
modifications and avoiding risk factors, but these may not be helpful in the case of
CML and CLL. The only possibly avoidable risk factor for CML is exposure to
The prognosis and survival of CLL and CML depend on many factors, including the type
of cancer, the stage of cancer, blood cell counts, patient’s age, overall health of
the patient, chromosomal changes, treatments chosen, and response to treatment. The
5-year survival rate of CML and CLL is about 69.20% and 85.10%, respectively.