- Radiotherapy: At least 2 weeks must have elapsed since local palliative XRT (small port); at least 6 weeks must have elapsed since treatment with therapeutic doses of MIBG; at least 3 months must have elapsed if prior craniospinal XRT was received, if more than 50% of the pelvis was irradiated, or if TBI was received; at least 6 weeks must have elapsed if other substantial bone marrow irradiation was given.