In order to treat patients with this Y-90-labeled radioimmunoconjugate, an In-labeled test dose must be administered to ensure appropriate biodistribution (as described previously). Patients should be premedicated with diphenhydra-mine and acetaminophen, and then infused with 250 mg/m2 of rituximab. Patients should be closely monitored during the rituximab infusion, as infusional reactions such as hypotension and chills can occur. Immediately following the rituximab dose, patients should be infused with approximately 5 mg of In-111-labeled ibritumomab tiuxetan. Patients should then undergo serial whole-body imaging within the first 24 hours, within 48 to 72 hours, and optional imaging between 90 and 120 hours. This should be performed with whole anterior and posterior images to ensure that there is not an altered biodistribution such as a rapid clearance from the blood pool early postinfusion, or an abnormal localization to a nontarget site.
Approximately one week after the test dose of In-111-ibritumomab tiuxe-tan, patients should be treated with the appropriate mCi/kg dose of Y-90-ibritu-momab tiuxetan. This should be carried out using 0.4 mCi/kg in patients with normal platelet counts and 0.3 mCi/kg in patients with platelet counts between 100,000 and 150,000/mL. It is important to note that the maximal dose to any patient is 32 mCi. Patients again should be premedicated with Benadryl and Tylenol and infused with the 250 mg/m2 dose of rituximab. This is then followed by the therapeutic dose of Y-90-labeled ibritumomab tiuxetan. Further details regarding the appropriate use of ibritumomab tiuxetan-based RIT can be obtained from the package insert of this drug.
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