For patients in group B with CNS disease at diagnosis, radiotherapy is only considered in the presence of a cerebral mass documented by CT scan or MRI. Patients in group A or B who develop isolated CNS recurrence (documented by malignant CSF pleocytosis, cranial nerve palsies, or both) at any time after the first course of study therapy receive the same CNS treatment (as above) as patients with proven CNS disease in addition to whole brain irradiation for 3 weeks.