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FOUNDATION OVERVIEW

Leukemia is a cancer of the early blood-forming cells. Most often, leukemia is a cancer of the white blood cells (WBCs), but some leukemias start in other blood cell types. There are several types of leukemia, which are divided based mainly on whether the leukemia is acute (fast growing) or chronic (slower growing), and whether it starts in myeloid cells or lymphoid cells. Different types of leukemia have different treatment options and outlooks.

ACUTE LYMPHOBLASTIC LEUKEMIA

In the development of B cells and T cells, various events occur to develop a competent immune system. In acute lymphoblastic leukemia (ALL), mutations occur in the development of B- and T-cell progenitors leading to dysregulated proliferation and clonal expansion. This leads to many lymphoblasts (immature WBCs) in both the blood and bone marrow, which inhibits normal cellular maturation. If left untreated, ALL may be fatal within weeks. ALL is the most common childhood leukemia and is most frequently diagnosed among patients younger than 20 years.

Patients present with malaise, fever, weight loss, night sweats, palpitations, bruising, petechiae, gingival hyperplasia, and bone pain. Many symptoms represent malignant cells replacing normal hematopoiesis. Patients may experience tumor lysis syndrome (TLS), resulting in electrolyte disturbances such as hyperkalemia, hyperphosphatemia, hyperuricemia, and hypocalcemia. Physical examination findings may include lymphadenopathy, hepatomegaly, splenomegaly, and a mediastinal mass. Leukocytosis (WBC >30,000-50,000/µL) confers a poor prognosis, particularly in B-cell ALL. Other factors conferring a poor prognosis in adults include age (>35 years), immunophenotype (B lineage worse), unfavorable cytogenetics, Philadelphia chromosome (Ph+) disease, and central nervous system (CNS) disease.

Diagnosis is determined by evaluating the complete blood count (CBC) with differential, coagulation studies, bone marrow biopsy and aspiration (≥20% lymphoblasts required for diagnosis), and lumbar puncture. Cytochemical studies, immunophenotyping (determines B vs T cell), and cytogenetics are performed on bone marrow samples. A lumbar puncture should be performed to assess CNS involvement.

Treatment

The primary goal of treatment is to induce and maintain a complete remission (CR). A CR can be induced in 96% to 99% of children and 78% to 93% of adults. Treatment of pediatric ALL is divided into induction, consolidation, interim maintenance, delayed intensification, and maintenance. Adult ALL is divided into induction, consolidation, and maintenance (2-3 years). CNS prophylaxis is performed throughout all phases of therapy, and consists of intrathecal methotrexate and cytarabine which can be given alone or in combination, cranial irradiation, dexamethasone, or high-dose IV methotrexate or cytarabine. Patients with T-cell ALL have an increased incidence of CNS disease and should receive systemic high-dose methotrexate to penetrate the CNS. Multiple intensive chemotherapy regimens have been shown to provide benefit for induction in adult ALL, and backbone agents include corticosteroid, vincristine, and anthracycline. After induction, patients start consolidation with the goal to eliminate any remaining leukemic cells post-induction therapy. Regimens for consolidation vary widely. Maintenance therapy is ...

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