- Additional continuation (weeks 73-130): At weeks 73-130 for arms I and II, and at weeks 81-130 for arms III and IV, patients receive oral MTX weekly; oral mercaptopurine daily; vincristine IV on day 1 every 12 weeks; oral dexamethasone as during intensive continuation therapy; and IT MTX on day 1 every 12 weeks, beginning with the last week of the first course (in place of oral MTX).