Precursor B-lymphoblastic leukemia, also known as B-cell acute lymphoblastic leukemia and B-cell acute lymphocytic leukemia, is the most common type of acute lymphoblastic leukemia (ALL).

An aggressive cancer of the blood, it is characterized by an abundance of B-cell lymphoblasts (immature white blood cells) in the blood and bone marrow. Precursor B-lymphoblastic leukemia does not affect older, mature cells; instead, it attacks immature blood cells.

As an acute lymphoblastic leukemia, it is also one of the most common types of cancer affecting children under age 15. When detected and treated, acute lymphoblastic leukemia generally has a positive prognosis, leading to a cure. Adult cases are more difficult to treat.

Risk Factors

Common factors that contribute to acute lymphoblastic leukemia risk are few. Some can include:

• Age: People of any age can get it, and it commonly affects children under the age of 15; however, risk does increase after age 45.
• Gender: Males have a higher risk for leukemia in general.
• Radiation: High doses of radiation can increase risk. This can be either in the form of previous cancer treatments, or exposure to an atomic bomb blast or a nuclear reactor accident (including during prenatal development).
• Location: Living in a more developed country can increase risk.
• Background: Most patients live in a higher socioeconomic group.
• Phosphocol P32: This drug, used to treat symptoms of adult infections and cancers, has been linked to leukemia in children.
• Genetic Disorders: Disorders such as Down syndrome may increase the risk.
• Siblings with Acute Lymphoblastic Leukemia: Risk slightly increases for people who may have a sibling, including a twin, with leukemia. However, doctors have determined that the disease is usually not inherited.

Other potential risk factors, many linked to lifestyle, are currently under study. Precursor B-lymphoblastic leukemia is not contagious.

Signs and Symptoms

Precursor B-lymphoblastic leukemia symptoms mirror flu symptoms in many ways. One important distinction is that while the flu is typically short-lived, leukemia symptoms will persist for a lengthy period of time. Signs and symptoms can include:

• Unexplained Fever
• Weight Loss
• Loss of Appetite
• Pale Skin
• Gum Bleeding
• Vomiting
• Unexplained Black-and-Blue Marks on Body
• Lumps Around Neck, Stomach, Underarm, or Groin: These lumps may be caused by swollen lymph nodes.
• Fatigue, Weakness, or Decrease of Energy
• Shortness of Breath
• Continuous or Prolonged Bleeding from Minor Cuts
• Red Spots Beneath Skin: These spots are the size of pinheads.
• Aching of Legs, Back, or Arms
• Headaches
• Recurrent or Frequent Infections
• Severe or Frequent Nosebleeds

Diagnosis

About 5,430 people within the United States are thought to have been diagnosed with acute lymphocytic leukemia within the last year; most of these were diagnosed with Precursor B-lymphoblastic leukemia.

To diagnose leukemia, specific blood and bone marrow tests are conducted:

• A CBC, or Complete Blood Count: This is used to determine whether or not a patient has leukemia.
• A Bone Marrow Aspirate: A bone marrow aspirate – typically conducted with a bone marrow biopsy – tests the cells in the bone marrow by removing a small amount of marrow with a needle. This procedure can be completed in a doctor’s office, and the patient is given a local anesthesia, or a medication to numb the specific area from which the marrow is drawn. This area is typically the hipbone. The cells are then studied beneath a microscope to determine what kind of abnormality they contain, if any.
• Bone Marrow Biopsy: This procedure involves taking an actual piece of bone (still containing marrow) and performing a similar examination with a microscope. It is important that both procedures be completed, as an aspirate does not always yield conclusive information. Some cells detected, such as leukemic blast cells, can help provide a diagnosis. The biopsy can also inform the doctor about how much of the marrow is infected. Finally, the bone marrow tests can also help a doctor decide what kind of treatment the patient needs–and, post-treatment, to discover whether or not the treatment is working.
• Cytogenetic Analysis: This test examines the chromosonal makeup of the blood, bone marrow and lymph node cells. A cytogenetic analysis can be crucial in determining whether cells are cancerous, malignant, and even type of treatment necessary.
• Immunophenotyping: This procedure is used to determine whether the patient’s leukemia cells, once detected, are B cells or T cells (both are types of white blood cells). Precursor B-lymphoblastic leukemia patients will have B-type cells.
• Spinal Tap: This test may be conducted to check the spine for cancer cells, as many patients develop leukemia in the spine.

Treatment

Patients with Precursor B-lymphoblastic leukemia must begin chemotherapy immediately after the disease is detected. While children are typically cured following treatment, adults have a larger chance of remission. Doctors refer to bone marrow tests to decide which type and lengthy of treatment is best.

Other considerations prior to treatment include:

• Number of ALL Cells in Patient’s Blood
• Patient’s Age
• ALL Cell Location: Whether or not the cells have spread to the brain or spinal cord
• Patient Chromosomal Changes

Two forms of treatment will commence following the patient assessment:

• Induction Therapy: This first part of treatment includes ridding the patient of as many ALL cells as possible and stabilizing blood counts back to normal. This includes administering multiple drugs (either orally or through a catheter through the chest) to kill the cancerous cells. These drugs may include but are not limited to methotrexate, imatinib mesylate, pegaspargase, mitoxantrone, clofarabine, vincristine, cytarabine, cyclophosphamide, daunorubicin, dexamethasone and prednisone. Drugs may also be administered into spinal fluid if needed. Radiation therapy may also be given to the patient’s spine or brain if necessary. As patients tend to develop uric acid (a chemical waste created by the body) within their blood, they may also be given medication to prevent kidney stones that may develop.
• Post-Induction Therapy: Once a patient is in remission (free from all signs of the disease for a lengthy period of time), more treatment must be given. In cycles of two to three years, patients are routinely tested, given medication to kill any possible remaining infected cells and prevent further recurrence.

Outlook (Prognosis)

Most children are cured following a successful treatment. Though survival rates are high, treatment typically lasts two to three years; the first six months are usually the most difficult. 66% of patients survive overall, with children under 5 having the highest survival rate at 91%.

Prevention

With so few risk factors, there is little that can be done to prevent Precursor B-lymphoblastic leukemia. Limiting or eliminating exposure to radiation, as well as keeping children away from the drug Phosphocol P32, are the only precise measures that can be taken for prevention.

Resources

National Cancer Institute
Mayo Foundation for Medical Education and Research
The Leukemia & Lymphoma Society