Acute Lymphoblastic Leukemia
Leukemia is the most common malignancy in pediatrics and the exact cause of acute lymphoblastic leukemia (ALL) is unknown. Less than 5% of cases have been associated with inherited genetic syndromes (Down or Bloom syndrome) or with exposure to ionizing radiation and chemotherapeutic agents. In the development of B cells and T cells, various events occur to develop a competent immune system. In ALL, mutations occur in the development of B- and T-cell progenitors leading to dysregulated proliferation and clonal expansion.
Patients present with malaise, fever, weight loss, palpitations, bruising, petechiae, bone pain, and lymphadenopathy. Many symptoms represent malignant cells replacing normal hematopoiesis. Electrolyte disturbances such as hyperkalemia, hyperphosphatemia, hyperuricemia, and hypocalcemia may occur and patients may experience tumor lysis syndrome (TLS). Physical examination findings include 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 include age (>30), immunophenotype (B lineage worse), 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, and lumbar puncture. Cytochemical studies, immunophenotyping, and cytogenetics are performed on bone marrow samples. A lumbar puncture should be performed to assess CNS involvement.
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. CNS treatment is performed throughout all phases of therapy. Intrathecal therapy consists of methotrexate and cytarabine which can be given alone or in combination. 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 in adult ALL. Specific agents used in the initial treatment of ALL are summarized in Table 15-1. Treatment of relapsed ALL typically includes aggressive chemotherapy. Single-agent treatment for relapsed ALL includes nelarabine (T-cell origin), clofarabine (B-cell origin), and blinatumomab (B-cell origin). Blinatumomab is a new monoclonal antibody that improved survival compared to standard chemotherapy in patients with B-cell origin ALL that had received multiple prior chemotherapy regimens.
TABLE 15-1Commonly Used Agents in Treatment of ALL ||Download (.pdf) TABLE 15-1Commonly Used Agents in Treatment of ALL
|Agent ||Classification ||Route of Administration ||Adverse Reactions |
|Asparaginase (Escherichia coli strain) ||Other ||IM/IV/SQ ||Allergic reactions, coagulopathy (increased prothrombin time), depression, fatigue, hyperglycemia, pancreatitis, thrombotic events |
|Cyclophosphamide ||Alkylating agent ||IV ||Alopecia, hemorrhagic cystitis, impairment of fertility, myelosuppression, N/V, secondary malignancies |
|Cytarabine ||Antimetabolite ||IV/IT ||Cerebellar dysfunction, conjunctivitis, diarrhea, myelosuppression, pulmonary edema, ...|