What Is Leukemia?

Leukemia is cancer that affects the cells that make up the blood, bone marrow, and lymphatic system. Leukemia forms in the developing blood cells of the bone marrow. All blood cells begin as stem cells. These stem cells go through multiple stages before they reach full maturity. Blood stem cells first develop into either myeloid cells or lymphoid cells. Healthy myeloid cells become red blood cells, platelets, and certain types of white blood cells (basophils, eosinophils, and neutrophils). Lymphoid cells become certain types of white cells (lymphocytes and natural killer cells). Stem cells in bone marrow develop into certain types of blood cells needed by the body. Leukemia causes the bone marrow to produce excessive amounts of abnormal white blood cells that interfere with the bone marrow’s ability to make red blood cells and platelets. Red blood cells help distribute oxygen from the lungs to other tissues in the body and then take carbon dioxide back to the lungs to be removed. Platelets help with blood clotting by plugging up holes in blood vessels caused by cuts or bruises. Overcrowding of leukemia cells in the bloodstream impedes normal blood cells’ ability to distribute oxygen to the body’s organs and tissues, fight off infection, and clot blood.

→ Acute Myeloid Leukemia (AML) Won’t Slow World Champion Triathlete Down

According to the American Cancer Society, more than 62,770 new cases of leukemia are diagnosed in the U.S. each year, resulting in about 23,670 deaths. Leukemia accounts for about one-third of blood cancers diagnosed and was the sixth most common cause of cancer deaths in both men and women in the U.S. from 2012 to 2016. It is the most common cancer in children and teens, accounting for almost one-third of all childhood cancer diagnoses. 

The prognosis for a patient with leukemia depends on the type.

Why Come to CU Cancer Center for Leukemia

The CU Cancer Center is home to world-class leukemia care teams. The team’s research has led to many different breakthroughs in how to treat cancers that affect the blood and bone marrow. As the only National Cancer Institute Designated Comprehensive Cancer Center in Colorado and one of only four in the Rocky Mountain region, CU Cancer Center doctors provide multidisciplinary, patient-centered care, and innovative treatments unavailable at most other medical centers in the country.

CU Cancer Center doctors are the only physicians in a 500-mile radius who are part of the National Comprehensive Cancer Network (NCCN) advisory panel. The NCCN establishes treatment guidelines that doctors across the U.S. use as a reference. 

There are over 30 leukemia clinical trials currently being offered by CU Cancer Center members, giving patients many different new treatment options as well as the standard care choices.

→ Two Studies by CU Cancer Center Researchers Explore Link Between Inflammation and Leukemia

Learn more about the Center for Cancer and Blood Disorders, diagnosis and treatment options for pediatric leukemia from our clinical partners at Children’s Hospital Colorado.

Our clinical partnership with UCHealth has produced survival rates higher than the state average for all stages of leukemia.

Acute Lymphocytic Leukemia Graph

Number of Patients Diagnosed – UCHealth 78 – State of Colorado – 343
Number of Patients Surviving – UCHealth 59 – State of Colorado – 257
*n<30, 5 Year Survival – (Date of diagnosis 1/1/2010–12/31/2014)

Chronic Myeloid Leukemia Graph

Number of Patients Diagnosed – UCHealth 73 – State of Colorado 385
Number of Patients Surviving – UCHealth 46 – State of Colorado 236
*n<30, 5 Year Survival – (Date of diagnosis 1/1/2010–12/31/2014)

Chronic Lymphocytic Leukemia Graph

Number of Patients Diagnosed – UCHealth 134 – State of Colorado 1,012
Number of Patients Surviving – UCHealth 107 – State of Colorado 755
*n<30, 5 Year Survival – (Date of diagnosis 1/1/2010–12/31/2014)

Other Leukemia Graph

Number of Patients Diagnosed – UCHealth 72 – State of Colorado 327
Number of Patients Surviving – UCHealth 44 – State of Colorado 164
*n<30, 5 Year Survival – (Date of diagnosis 1/1/2010–12/31/2014)

Leukemia Types

There are many different types of leukemias. The type is classified by how quickly the disease progresses and by the blood cell type involved. 

Myelogenous or myeloid leukemia develops from the myeloid cell line that normally matures into red blood cells, some white blood cells, and platelets.

Lymphocytic leukemia develops from the lymphoid cell line that normally matures into white blood cells that play an important role in the body’s immune system.

Acute leukemia is the accumulation of abnormal immature blood cells. Acute leukemia cells are aggressive and multiply rapidly. Acute lymphocytic leukemia is the most common pediatric cancer and acute myeloid leukemia is the most common acute leukemia in adults.

Acute Lymphocytic Leukemia (ALL) is the most common type of leukemia in children and teens. ALL risk is highest in children under the age of 5. The risk slowly declines until the mid-20s, and then rises after age 50. About four in 10 cases of ALL are in adults. ALL starts in the bone marrow and develops from an immature form of white blood cell called a lymphocyte. These leukemia cells invade the blood quickly and can spread to other parts of the body.

Acute Myeloid Leukemia (AML) is the most common type of acute leukemia in adults. AML is more common among adults 65 years of age and older, and is more common in men than women. About 19,940 new cases of AML are diagnosed in the U.S. each year. AML starts in the bone marrow and can quickly move into the blood. It can spread to other parts of the body including the lymph nodes, liver, spleen, central nervous system, and testicles.

Chronic leukemia involves mature blood cells that replicate or accumulate slowly. Some of these cells have developed to the point where they can function as they were meant to, but not to their normal extent. 

Chronic Lymphocytic Leukemia (CLL) is the most common chronic leukemia in adults, accounting for about one-fourth of all leukemias. It starts in the bone marrow in cells that become a type of white blood cell called lymphocytes. This slow-moving cancer slowly builds up, over time spreading to other parts of the body. 

Chronic Myeloid Leukemia (CML) accounts for about 15% of leukemias in adults. Chronic myeloid leukemia is a genetic change that takes place in immature myeloid cells. Myeloid cells make red blood cells, platelets, and most white cells. This genetic change causes leukemia cells to grow and divide, building up in the bone marrow and blood.

Causes of Leukemia 

Leukemia occurs when the DNA in blood cells called leukocytes changes or mutates, manipulating the cells’ ability to grow and divide properly. These mutated cells can grow out of control, unchecked by the immune system, and overcrowd the healthy cells in the bloodstream.

Risk Factors for Leukemia

There are several factors that might increase the chance of developing certain types of leukemia. These risk factors include:

Gender: Men are more likely than women to develop leukemia.

Age: Risk of developing leukemia increases with age. The median age for patients diagnosed with acute myeloid leukemia (AML), chronic lymphocytic leukemia (CLL), or chronic myeloid leukemia (CML) is 65. Acute lymphocytic leukemia (ALL) is more common among people under 20 years old.

Previous cancer treatment: People who have received certain types of chemotherapy and radiation therapy have an increased risk of developing leukemia. 

Blood disorders: Blood disorders including chronic myeloproliferative disorders like polycythemia vera, idiopathic myelofibrosis, and essential thrombocytopenia increase the chances of developing acute myeloid leukemia. 

Genetic disorders: Certain genetic disorders, including Down syndrome, Fanconi anemia, Bloom syndrome, ataxia-telangiectasia, and Blackfan-Diamond syndrome, have been connected to an increased risk of leukemia.

Symptoms of Leukemia

Symptoms of leukemia vary depending on the type of leukemia. Common symptoms include:

  • Fever, chills, or night sweats.
  • Shortness of breath.
  • Persistent fatigue or weakness.
  • Frequent infections.
  • Bone or joint pain/tenderness.
  • Unexplained weight loss.
  • Swollen lymph nodes.
  • Easy bleeding and bruising. 
  • Nosebleeds and bleeding gums. 
  • Red spots on the skin, called petechiae.

Diagnosing Leukemia

Tests for Leukemia

If a patient has signs or symptoms that suggest leukemia, a doctor may order one of the following diagnostic exams:

Physical exam: During a physical exam, a doctor will look for signs of leukemia, including swollen lymph nodes, pale skin from anemia, swollen or bleeding gums, bruises or small red bumps (petechiae), or signs of an enlarged liver or spleen. 

Blood tests: A sample of blood can help determine if there are abnormal levels of red or white blood cells or platelets, which may suggest leukemia. A blood test may also indicate the presence of leukemia cells, though they tend to stay within the bone marrow.

Complete blood count (CBC): This blood test provides details on red and white blood cells and platelets. Lower than normal counts of red blood cells and platelets, and higher than normal counts of white blood cells, indicates the patient has leukemia.

Blood cell examination: Blood samples may be taken to check for type and shape of blood cells. Other blood tests may help identify abnormalities on cells that help determine the type of leukemia. 

Bone marrow biopsy: A bone marrow aspiration may be recommended to test for leukemia cells in the marrow. During this procedure, a sample of bone marrow is removed from the hipbone using a long, thin needle. Tests may be performed on the sample to reveal characteristics that may help determine treatment options.

Imaging tests: A chest X-ray, CT scan, or MRI scan may be ordered if the patient’s symptoms indicate leukemia.

Spinal tap: A lumbar puncture may be ordered to see if leukemia cells are found in the spinal fluid surrounding the brain and spinal cord.

Stages of Leukemia  

Most cancers are staged based on the size and spread of the tumors; however, since leukemia occurs in developing blood cells in the bone marrow, leukemia has a different staging process. Instead of using traditional staging methods, such as the TNM staging system, a physician determines the leukemia subtype by evaluating the results of cytologic tests, flow cytometry, or other lab tests. Factors affecting leukemia staging and prognosis include:

  • White blood cell and platelet count and hemoblogin.
  • Age.
  • Personal history of blood disorders.
  • Chromosomal abnormalities
  • Gene mutations.
  • Enlarged liver or spleen. 

Each subtype of leukemia has its own unique staging system:

Acute lymphocytic leukemia: Staged based on the type of lymphocyte and maturity of the cells.

Acute myelogenous leukemia: No staging system; prognosis is based on factors related to the patient and biological properties of the disease.

Chronic lymphocytic leukemia: Staged using the Rai system, which considers the number of lymphocytes in the blood, the degree of lymph node, enlargement of the spleen or liver, and the presence of anemia or thrombocytopenia.

Chronic myelogenous leukemia: Can be diagnosed in chronic phase, accelerated phase or blast crisis. 

Chronic Leukemia Stages

Chronic leukemia is staged using the Rai system:

Stage 0: There are high levels of white blood cells, but no physical symptoms.

Stage 1: There are high levels of white blood cells, and the lymph nodes are enlarged.

Stage 2: There are high levels of white blood cells, and the patient is anemic. The patient may have enlarged lymph nodes.

Stage 3: There are high levels of white blood cells, and the patient is anemic. The patient may also have enlarged lymph nodes and/or an enlarged liver or spleen.

Stage 4: There are high levels of white blood cells and low platelets. The patient may be anemic, have enlarged lymph nodes, and have an enlarged liver or spleen.

Treatments for Leukemia

Treatments for leukemia are tailored to each patient and depend on the patient’s age, overall health, type of leukemia, and diagnosis stage. 

Chemotherapy for Leukemia

Chemotherapy uses chemicals given in pill form, through an IV into a vein or central line, or given in shots, to kill leukemia cells or stop them from dividing. Chemotherapy is the most common form of treatment for leukemia and consists of cycles of treatment and rest days.

Radiation Therapy for Leukemia

Radiation is a treatment that uses X-rays or other strong beams of energy to damage leukemia cells and stop them from growing. These high-energy beams are directed to precise points on the body where there is a collection of cancer cells.

Targeted Therapy for Leukemia 

Targeted drug therapy focuses on specific abnormalities within leukemia cells. These drugs work by blocking the leukemia cells’ ability to divide or by cutting off blood supply to the cells.

Immunotherapy for Leukemia 

Immunotherapy drugs trick the body’s immune system to fight off the cancer. Cancer cells produce proteins that help hide and protect them from the body’s immune system. Immunotherapy blocks this process.

→ CU Cancer Members Recognized for Contributions to Immunotherapy in Pediatric Cancer

Bone Marrow Transplant 

A bone marrow transplant, or stem cell transplant, replaces unhealthy bone marrow with leukemia-free stem cells that regenerate healthy bone marrow. Before a bone marrow transplant, patients are treated with chemotherapy and/or radiation therapy. Once the healthy cells are infused back into the patient’s blood, the healthy cells can grow and multiply to form new bone marrow. 

CAR T-Cell Therapy for Leukemia 

A specialized treatment called chimeric antigen receptor (CAR) T-cell therapy engineers T-cells, a type of white blood cell that plays an essential role in the immune system, to fight cancer. 

→ The Role of T Cells in Fighting Cancer

The University of Colorado (CU) Cancer Center partners with UCHealth, Children’s Hospital Colorado, and Rocky Mountain Regional VA to provide clinical care. Please make an appointment with one of our clinical partners to be seen by a CU Cancer Center doctor.


UCHealth Cancer Care - Anschutz Medical Campus
1665 Aurora Court Anschutz Cancer Pavilion
Aurora, CO 80045

UCHealth Cherry Creek Medical Center
100 Cook Street
Denver, CO 80206

UCHealth Cancer Center - Highlands Ranch
1500 Park Central Drive
Highlands Ranch, CO 80129

UCHealth Lone Tree Medical Center
9548 Park Meadows Drive
Lone Tree, CO 80124

Children's Hospital Colorado:
13123 East 16th Avenue
Aurora, CO 80045

Rocky Mountain Regional VA Medical Center:
1700 North Wheeling Street
Aurora, CO 80045-7211

A Journey of Healing & Hope: Mark & Sharon Koenig and Manali Kamdar, MD

Latest in Leukemia from the CU Cancer Center

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Information reviewed by Dan Pollyea, MD, MS, in September 2022.
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