How Leukemia Progresses: An Overview from Hematologists

Understanding a complex medical condition like leukemia can feel overwhelming. If you are seeking to learn about the typical progression of this disease, you’ve come to the right place. This article provides a clear, general overview based on information from hematologists, the specialists who treat blood disorders, to help you understand how leukemia is classified and how it typically develops.

Disclaimer: This article is for informational purposes only and does not constitute medical advice. Please consult with a qualified healthcare professional for any health concerns or before making any decisions related to your health or treatment.

What Exactly Is Leukemia?

Before diving into how leukemia progresses, it’s essential to understand what it is. Leukemia is a type of cancer that affects the body’s blood-forming tissues, primarily the bone marrow and the lymphatic system.

In a healthy person, the bone marrow produces stem cells that mature into different types of blood cells:

Red blood cells: Carry oxygen throughout the body.
White blood cells: Fight infection.
Platelets: Help the blood to clot.

In a person with leukemia, the bone marrow produces a large number of abnormal white blood cells that do not function correctly. These abnormal cells, often called leukemia cells or blasts, multiply uncontrollably. Over time, they crowd out the healthy, functional blood cells in the bone marrow. This crowding-out process leads to the common symptoms associated with leukemia, such as fatigue (due to a lack of red blood cells), frequent infections (due to a lack of healthy white blood cells), and easy bruising or bleeding (due to a lack of platelets).

The First Step in Progression: Acute vs. Chronic Leukemia

According to hematologists, the single most important factor determining the progression of leukemia is whether it is acute or chronic. This classification is based on how quickly the disease develops and worsens.

Acute Leukemia: Rapid Progression

Acute leukemia is characterized by the rapid production of very immature blood cells called blasts. These cells are non-functional and multiply quickly, overwhelming the bone marrow in a short period.

Speed: The progression is very fast, often developing over a matter of weeks or a few months.
Symptoms: Because the disease advances so quickly, symptoms usually appear suddenly and can be quite severe. A person might feel perfectly healthy and then rapidly develop symptoms like high fever, extreme fatigue, and significant bruising.
Urgency: Acute leukemia requires immediate and aggressive medical treatment upon diagnosis.

The two main types are Acute Lymphoblastic Leukemia (ALL), which is more common in children, and Acute Myeloid Leukemia (AML), which is more common in adults.

Chronic Leukemia: Slow Progression

Chronic leukemia involves more mature, but still abnormal, blood cells. These cells can still perform some of their functions, but not as well as healthy cells. They also multiply at a much slower rate than acute leukemia cells.

Speed: The progression is very slow, often developing over many years.
Symptoms: Many people with chronic leukemia have no symptoms in the early stages. The disease is often discovered by chance during a routine blood test for an unrelated issue. When symptoms do appear, they develop gradually.
Management: Treatment for chronic leukemia may not be necessary right away. Specialists often recommend a period of “watchful waiting” or “active surveillance” to monitor the disease until symptoms appear or blood counts reach a certain level.

The two main types are Chronic Lymphocytic Leukemia (CLL) and Chronic Myeloid Leukemia (CML), both of which are more common in older adults.

Understanding the Stages and Phases of Progression

While acute leukemias are generally not “staged” like solid tumors because the cancer cells are already widespread in the blood and bone marrow, chronic leukemias have well-defined phases or stages that describe their progression.

The Progression of Chronic Lymphocytic Leukemia (CLL)

Hematologists often use the Rai staging system to describe the progression of CLL. This system helps predict the outlook and determine when to start treatment. The stages are based on the results of a physical exam and blood tests.

Stage 0: The only sign of disease is a high number of lymphocytes in the blood (lymphocytosis). There are no other symptoms, and the lymph nodes, spleen, and liver are not enlarged. The risk is considered low.
Stage I: In addition to a high lymphocyte count, the lymph nodes are enlarged. The risk is considered intermediate.
Stage II: Along with a high lymphocyte count, the spleen is enlarged (and possibly the liver). The lymph nodes may or may not be enlarged. The risk is also intermediate.
Stage III: The patient has a high lymphocyte count and has developed anemia (too few red blood cells). The lymph nodes, spleen, or liver may be enlarged. This is considered a high-risk stage.
Stage IV: The patient has a high lymphocyte count and a very low platelet count (thrombocytopenia). Anemia may or may not be present, and organs may be enlarged. This is also considered a high-risk stage.

The Progression of Chronic Myeloid Leukemia (CML)

The progression of CML is described in three distinct phases. The goal of treatment, often with targeted therapy drugs like imatinib (Gleevec), is to keep the patient in the first phase for as long as possible.

Chronic Phase: This is the earliest phase. Fewer than 10% of the cells in the blood and bone marrow are blast cells. Patients in this phase typically have mild symptoms or no symptoms at all. Most people are diagnosed during the chronic phase, and they usually respond very well to standard treatments.
Accelerated Phase: The disease becomes more aggressive. Blood tests show a higher number of blast cells (10% to 19%), a high number of other white blood cells called basophils, and very high or very low platelet counts. Patients may develop symptoms like fever and an enlarged spleen.
Blastic Phase (or Blast Crisis): This is the most advanced and aggressive phase. Twenty percent or more of the cells in the blood or bone marrow are blast cells. In this phase, CML behaves very much like an acute leukemia. Symptoms are more severe, and the disease is more difficult to treat.

The Role of Treatment in Changing Progression

It is crucial to remember that this overview describes the usual or natural progression of untreated leukemia. Modern medicine has dramatically changed the course of this disease for many people. Treatments such as chemotherapy, targeted therapy, immunotherapy, and stem cell transplantation can stop or slow the progression, put the leukemia into remission, and significantly improve a person’s long-term outlook.

Frequently Asked Questions

What are the most common symptoms of leukemia? Common signs and symptoms include fever or chills, persistent fatigue and weakness, frequent or severe infections, unexplained weight loss, swollen lymph nodes, an enlarged liver or spleen, easy bleeding or bruising, recurrent nosebleeds, and tiny red spots on the skin (petechiae).

How do doctors diagnose leukemia? Diagnosis typically begins with a physical exam and a review of medical history. If leukemia is suspected, doctors will order blood tests, specifically a complete blood count (CBC), to check the levels of different blood cells. A definitive diagnosis is usually made with a bone marrow biopsy, where a small sample of bone marrow is removed and examined for cancer cells.

Is leukemia a genetic disease? While certain genetic mutations are involved in the development of leukemia, it is not typically considered a hereditary disease that is passed down through families. Most cases of leukemia occur in people with no family history of the disease. However, having a first-degree relative with certain types of leukemia can slightly increase your risk.