title: Quantification of dose nonuniformities by voxel-based dosimetry in patients receiving 90Y-ibritumomab-tiuxetan.
abstract: Abstract Objective: To assess the impact of nonuniform dose distribution within lesions and tumor-involved organs of patients receiving Zevalin(®), and to discuss possible implications of equivalent uniform biological effective doses (EU-BED) on treatment efficacy and toxicity. MATLAB™ -based software for voxel-based dosimetry was adopted for this purpose.
  
  
  METHODS
  Eleven lesions from seven patients with either indolent or aggressive non-Hodgkin lymphoma were analyzed, along with four organs with disease. Absorbed doses were estimated by a direct integration of single-voxel kinetic data from serial tomographic images. After proper corrections, differential BED distributions and surviving cell fractions were estimated, allowing for the calculation of EU-BED. To quantify dose uniformity in each target area, a heterogeneity index was defined.
  
  
  RESULTS
  Average doses were below those prescribed by conventional radiotherapy to eradicate lymphoma lesions. Dose heterogeneity and effect on tumor control varied among lesions, with no apparent relation to tumor mass. Although radiation doses to involved organs were safe, unexpected liver toxicity occurred in one patient who presented with a pattern of diffuse infiltration.
  
  
  CONCLUSIONS
  Voxel-based dosimetry and radiobiologic modeling can be successfully applied to lesions and tumor-involved organs, representing a methodological advance over estimation of mean absorbed doses. However, effects on tumor control and organ toxicity still cannot be easily predicted.
authors.affiliation: Nuclear Medicine, Department of Translational Medicine, Faculty of Medicine and Psychology, Sant'Andrea Hospital, Sapienza University of Rome, Rome, Italy. f.cicone@iol.it
authors.forename: Francesco
authors.initials: F
authors.lastname: Cicone
authors.forename: Marco
authors.initials: M
authors.lastname: D'Arienzo
authors.forename: Andrea
authors.initials: A
authors.lastname: Carpaneto
authors.forename: Eleonora
authors.initials: E
authors.lastname: Russo
authors.forename: Angela
authors.initials: A
authors.lastname: Coniglio
authors.forename: Angelika Bischof
authors.initials: AB
authors.lastname: Delaloye
authors.forename: Francesco
authors.initials: F
authors.lastname: Scopinaro
mesh_terms: D000328:Adult; D000368:Aged; D000911:Antibodies, Monoclonal / Q000493:pharmacokinetics / Q000627:therapeutic use*; D005260:Female; D006801:Humans; D008228:Lymphoma, Non-Hodgkin / Q000000981:diagnostic imaging / Q000473:pathology / Q000532:radiotherapy*; D008297:Male; D008875:Middle Aged; D060787:Neoplasm Grading; D011877:Radionuclide Imaging; D011879:Radiotherapy Dosage; D014018:Tissue Distribution; D016896:Treatment Outcome; D015021:Yttrium Radioisotopes / Q000493:pharmacokinetics / Q000627:therapeutic use*
chemical_list: D000911:Antibodies, Monoclonal; D015021:Yttrium Radioisotopes; C422802:ibritumomab tiuxetan