- Patients in arms I and II also receive MTX intrathecally (IT) on weeks 7, 10, 13, 16, 19, and 22; oral mercaptopurine (6-MP) daily on weeks 5-24; oral dexamethasone (DM) twice daily on days 1-7 of weeks 8 and 17; and vincristine (VCR) IV on day 1 of weeks 8, 9, 17, and 18.