- Regimen 1 (for patients < 50 years of age and no contraindication to fractionated total-body irradiation (FTBI): Patients undergo FTBI 2-3 times a day on days -9 to -6 for a total of 11 fractions. Patients also receive cyclophosphamide IV over 2 hours on days -5 and -4 and fludarabine phosphate IV on days -5 to -2.