title: The role of dosimetry in the high activity 90Y-ibritumomab tiuxetan regimens: two cases of abnormal biodistribution.
abstract: Radioimmunotherapy (RIT) with a commercially available brand of yttrium-90 ((90)Y)-ibritumomab-tiuxetan at the prescribed activity of 14.8 MBq/kg (0.4 mCi/kg) represents a complementary approach in the treatment of resistant/refractory B-cell non-Hodgkin's lymphoma. A trial based on higher activities is ongoing in our institute. In this paper, we report atypical pharmacokinetics and liver uptake in 2 patients. Before RIT, all patients underwent dosimetry with (111)In-ibritumomab-tiuxetan. Imaging data were analyzed to obtain predicted absorbed doses to nontarget organs. Therapy was administered only if a 20-Gy-limit dose to normal organs (except red marrow) was guaranteed. Both patients we describe showed abnormal liver uptake, increasing for 6 days post injection. In patient 1, there was atypical biodistribution in whole-blood images at 16 hours, with a prevalent high liver uptake (45% at 20 hours). Injected activity (IA%) was above 40% at 26 hours in the liver and lower than 60% in the total body. In patient 2, early images showed regular biodistribution. Subsequent images showed progressive increase of liver uptake (above 25% of percent injected activity at 25 hours). Liver-absorbed doses of 51 and 53 Gy, respectively, would have resulted with the administration of the prescribed 56 MBq/kg. Following these dosimetric results, both patients did not receive the planned therapy. These findings support the recommendation to include dosimetry in high-dose RIT.
authors.affiliation: Division of Nuclear Medicine, European Institute of Oncology, Milan, Italy.
authors.forename: Demetrio
authors.initials: D
authors.lastname: Aricò
authors.forename: Chiara Maria
authors.initials: CM
authors.lastname: Grana
authors.forename: Anna
authors.initials: A
authors.lastname: Vanazzi
authors.forename: Mahila
authors.initials: M
authors.lastname: Ferrari
authors.forename: Andrew
authors.initials: A
authors.lastname: Mallia
authors.forename: Maddalena
authors.initials: M
authors.lastname: Sansovini
authors.forename: Giovanni
authors.initials: G
authors.lastname: Martinelli
authors.forename: Giovanni
authors.initials: G
authors.lastname: Paganelli
authors.forename: Marta
authors.initials: M
authors.lastname: Cremonesi
mesh_terms: D000368:Aged; D000911:Antibodies, Monoclonal / Q000009:adverse effects / Q000493:pharmacokinetics* / Q000627:therapeutic use*; D005260:Female; D006801:Humans; D007205:Indium Radioisotopes; D008228:Lymphoma, Non-Hodgkin / Q000378:metabolism* / Q000532:radiotherapy*; D008875:Middle Aged; D016499:Radioimmunotherapy; D011874:Radiometry / Q000379:methods; D015021:Yttrium Radioisotopes / Q000627:therapeutic use*
chemical_list: D000911:Antibodies, Monoclonal; D007205:Indium Radioisotopes; D015021:Yttrium Radioisotopes; C422802:ibritumomab tiuxetan