B-cell acute lymphoblastic leukemia (B-cell ALL) is a cancer of the blood and bone marrow involving the overproduction of immature white blood cells called B-cell lymphoblasts. These abnormal cells multiply rapidly, crowding out healthy blood cells needed to fight infection, carry oxygen, and prevent bleeding. This type of leukemia can progress quickly if not treated and is the most common form of acute lymphoblastic leukemia, affecting both children and adults.
Symptoms and Risk Factors
The signs of B-cell ALL result from a shortage of normal blood cells. A lack of red blood cells (anemia) causes fatigue, pale skin, and shortness of breath. Low levels of healthy white blood cells lead to frequent infections, while a low platelet count causes easy bruising, bleeding gums, and tiny red dots on the skin.
Other symptoms can include fever, night sweats, unexplained weight loss, and a reduced appetite. Some individuals experience bone or joint pain, and swollen lymph nodes may appear as painless lumps in the neck, armpits, or groin.
While the cause is often unknown, risk factors include exposure to high radiation, some chemotherapy, and genetic conditions like Down syndrome. These factors are linked to DNA changes in bone marrow cells that disrupt B-cell maturation. However, most people who develop B-cell ALL have no identifiable risk factors.
The Diagnostic Process
Diagnosing B-cell ALL involves several tests of a patient’s blood and bone marrow. The process begins with a complete blood count (CBC) to measure red, white, and platelet cell counts. A CBC often reveals a high white blood cell count with low levels of red cells and platelets, and a peripheral blood smear is examined for lymphoblasts.
The definitive diagnostic test is a bone marrow aspiration and biopsy. A doctor uses a hollow needle to extract a small sample of liquid bone marrow and bone from the hip. Pathologists then analyze these samples to confirm the presence and quantity of leukemia cells and assess their effect on normal blood cell production.
Once leukemia is confirmed, laboratory tests classify the disease. Flow cytometry identifies specific proteins on the cell surface, confirming they are B-lymphocytes. Cytogenetic analysis examines chromosomes for structural abnormalities. Molecular tests search for genetic mutations, such as the Philadelphia chromosome, which is a fusion of the BCR and ABL1 genes.
Treatment Approaches
Treatment for B-cell ALL is administered in phases to eradicate cancer cells and prevent return. The first phase, induction therapy, is intense and uses a combination of chemotherapy drugs to achieve remission. Once no leukemia cells are detected in the bone marrow, treatment moves to the consolidation phase, which uses different chemotherapy combinations to eliminate any remaining cancer cells.
Following consolidation, patients enter the maintenance phase, a longer, less intensive period of low-dose chemotherapy to prevent relapse. This phase can last for a couple of years. Throughout these phases, central nervous system (CNS) prophylaxis is often given by injecting chemotherapy into the spinal fluid to kill cancer cells in the brain and spinal cord.
While chemotherapy is the foundation of treatment, newer approaches have improved outcomes. Targeted therapy drugs attack specific vulnerabilities in cancer cells, such as using tyrosine kinase inhibitors (TKIs) for Philadelphia chromosome-positive (Ph+) ALL. Immunotherapy uses the body’s immune system to fight cancer and includes monoclonal antibodies like blinatumomab and CAR T-cell therapy.
An allogeneic stem cell transplant may be recommended for high-risk B-cell ALL or for patients who relapse. This procedure replaces the patient’s diseased bone marrow with healthy stem cells from a matched donor. This allows for high-dose chemotherapy to eliminate the leukemia before the new stem cells are infused.
Key Prognostic Factors
Several factors help determine the course of B-cell ALL and guide treatment. A patient’s age at diagnosis is an important element, as children and adolescents have a more favorable prognosis than adults. The initial white blood cell count also provides information, with a lower count associated with a better outlook. The speed at which a patient achieves remission is another indicator of long-term outcomes.
Genetic markers identified during diagnosis also shape the prognosis. The presence of specific chromosomal abnormalities or gene mutations within the leukemia cells can classify the disease into different risk groups. For example, the presence of the Philadelphia chromosome influences the prognosis and treatment approach.
The specific subtype of B-cell ALL, determined through laboratory tests, also influences the treatment strategy and expected outcome. Understanding these prognostic factors allows the healthcare team to tailor the intensity and type of therapy to the individual’s specific disease characteristics.