The same treatment (weeks 30-37) will be repeated for a total of 5 times, until week 69 (see Section 5.5.3 for intrathecal therapy). After week 69, all patients will receive daily mercaptopurine and weekly methotrexate interrupted with pulses of dexamethasone, vincristine, and mercaptopurine every 4 weeks. The dose of dexamethasone will be decreased to 6 mg/m2 between week 69 and week 101, after which only mercaptopurine and methotrexate will be given. Intrathecal treatment will be given every 8 weeks only to patients at risk of CNS relapse after week 49 and will be discontinued after week 97. Continuation therapy will be discontinued after 120 weeks.