尽管儿童急性淋巴细胞白血病（ALL）很少初次涉及中枢神经系统（CNS），但面向风险的CNS定向治疗对所有患者至关重要。治疗强度取决于最初的CNS状况。在试验AIEOP-BFM ALL 2009中，最初脑脊液中检测到白血病细胞分化被分为CNS2或CNS3，并在诱导疗法中接受五次脑脊液注射甲氨蝶呤与CNS1状态（未检测到爆炸的患者）接受三次剂量的患者进行比较。额外的硬膜外注射甲氨蝶呤对诱导疗法的全身毒性的影响尚不清楚。在2010年6月1日至2017年2月28日期间，6136名年龄在1至17岁之间的ALL患者被纳入到AIEOP-BFM ALL 2009试验。分析了诱导疗法期间三次与五次硬膜外注射甲氨蝶呤对严重感染并发症发生率的影响。在接受三次硬膜外注射甲氨蝶呤治疗的4706名患者中，有77人（1.6％）在诱导期间发生了生命威胁性感染，而在接受五次注射的1350名患者中，有59人（4.4％）发生了同样的感染（p。

Although initial central nervous system (CNS) involvement is rarely detected in childhood acute lymphoblastic leukemia (ALL), risk-adapted CNS-directed therapy is essential for all patients. Treatment intensity depends on the initial CNS status. In trial AIEOP-BFM ALL 2009, patients with cytomorphological detection of leukemic blasts in initial cerebrospinal fluid were classified as CNS2 or CNS3 and received five intrathecal doses of methotrexate in induction therapy compared to patients with CNS1 status (no blasts detected) who received three doses. The impact of additional intrathecal methotrexate on systemic toxicity in induction therapy is unknown. Between June 01, 2010 and February 28, 2017, 6136 patients at the age of 1 to 17 years with ALL were enrolled onto the trial AIEOP-BFM ALL 2009. The effect of three versus five doses of intrathecal methotrexate during induction therapy on the incidence of severe infectious complications was analyzed. Among 4706 patients treated with three intrathecal methotrexate doses, 77 (1.6%) had a lifethreatening infection during induction as compared to 59 of 1350 (4.4%) patients treated with five doses (p.