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    Childhood Acute Lymphoblastic Leukemia Treatment (PDQ®): Treatment - Health Professional Information [NCI] - CNS-directed Therapy for Childhood ALL

    Table 2. CNS-Directed Treatment Regimens for Newly Diagnosed Childhood ALL continued...

    Cranial Radiation

    The proportion of patients receiving cranial radiation has decreased significantly over time. At present, most newly diagnosed children with ALL are treated without cranial radiation. Many groups administer cranial radiation only to those patients considered to be at highest risk of subsequent CNS relapse, such as those with documented CNS leukemia at diagnosis (as defined above) (>5 WBC/μL with blasts; CNS3) and/or T-cell phenotype with high presenting WBC count.[10] In patients who do receive cranial radiation, the dose has been significantly reduced.

    Ongoing trials seek to determine whether radiation can be eliminated from the treatment of all children with ALL without compromising survival or leading to increased rate of toxicities from upfront and salvage therapies.[11,12] A meta-analysis of randomized trials of CNS-directed therapy has confirmed that radiation therapy can be replaced by intrathecal chemotherapy in most patients with ALL. Additional systemic therapy may be required depending on the agents and intensity used.[1][Level of evidence: 1iDi]

    CNS Therapy for Standard-risk Patients

    Intrathecal chemotherapy without cranial radiation, given in the context of appropriate systemic chemotherapy, results in CNS relapse rates of less than 5% for children with standard-risk ALL.[11,12,13,14,15,16]

    The use of cranial radiation does not appear to be a necessary component of CNS-directed therapy for these patients.[17,18]

    Evidence (triple intrathecal chemotherapy vs. intrathecal methotrexate):

    1. The CCG-1952 study for National Cancer Institute (NCI) standard-risk patients compared the relative efficacy and toxicity of triple intrathecal chemotherapy (methotrexate, hydrocortisone, and cytarabine) with methotrexate as the sole intrathecal agent in nonirradiated patients.[19]
      1. There was no significant difference in either CNS or non-CNS toxicities.
      2. Although triple intrathecal chemotherapy was associated with a lower rate of isolated CNS relapse (3.4% ± 1.0% compared with 5.9% ± 1.2% for intrathecal methotrexate; P = .004), there was no difference in event-free survival (EFS).
        • This effect was especially notable in patients with CNS2 status at diagnosis (lymphoblasts seen in CSF cytospin, but with <5 WBC/high-power field [hpf] on CSF cell count); the isolated CNS relapse rate was 7.7% ± 5.3% for CNS2 patients who received triple intrathecal chemotherapy compared with 23.0% ± 9.5% for those who received intrathecal methotrexate alone (P = .04).
        • There were more bone marrow relapses in the group that received the triple intrathecal chemotherapy, leading to a worse overall survival (OS) (90.3% ± 1.5%) compared with the intrathecal methotrexate group (94.4% ± 1.1%; P = .01).
        • When the analysis was restricted to patients with precursor B-cell ALL and rapid early response (M1 marrow on day 14), there was no difference between triple and single intrathecal chemotherapy in terms of rates of CNS relapse rate, OS, or EFS.
        • The findings of this trial need to be interpreted within the context of other therapy administered to patients. Dexamethasone, which has been associated with lower CNS relapse rates and improved EFS in standard-risk patients in other trials,[7,20] was not used in CCG-1952 (prednisone was the only steroid administered to patients).[21] It is not clear whether the results of the CCG-1952 trial are generalizable to protocols that include the use of dexamethasone and/or other CNS-directed systemic therapies.
      3. In a follow-up study of neurocognitive functioning in the two groups, there were no clinically significant differences.[22][Level of evidence: 1iiC]
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