title: Three methods assessing red marrow dosimetry in lymphoma patients treated with radioimmunotherapy.
abstract: BACKGROUND
  Maximum injected activity in radioimmunotherapy (RIT) is limited by bone marrow toxicity. Many dosimetric approaches have been proposed, leading to high variability in the results and elusive absorbed dose-effect relations. This study presents the results of red marrow (RM) absorbed dose estimates performed with 3 methods.
  
  
  METHODS
  Five patients received 2 co-infusions of (90)Y-labeled (370 MBq/m2) and (111)In- labeled (120 MBq) epratuzumab (1.5 mg/kg) 1 week apart. RM-absorbed dose was estimated by 3 methodologies. The first approach (M1) used L(2)-L(4) lumbar vertebrae imaging. M2 and M3 methods used different red marrow to blood ratios (RMBLR) to assess RM-absorbed dose. RMBLR was set to a fixed value of 0.36 in M2 or assessed according to each patient's hematocrit in M3.
  
  
  RESULTS
  Median RM-absorbed doses were 4.1 (2.9-8.4), 2.3 (2.0-2.7), and 2.3 (1.6-2.5) mGy/MBq for M1, M2, and M3, respectively. No trend could be found between total RM-absorbed dose and toxicity for M2 and M3. Conversely, M1 seemed to provide the best absorbed dose-effect relation. The 4 patients with the highest RM-absorbed doses exhibited grade 4 toxicity. The fifth patient, with the lowest RB absorbed dose, exhibited only a mild (grade 2) toxicity.
  
  
  CONCLUSIONS
  Image-based methodology (M1) seems to better predict hematological toxicity as compared with blood-based methods. Only this method provides for bone marrow involvement.
authors.affiliation: Medical Physics Department, CLCC Gauducheau, St Herblain, France. l-ferrer@nantes.fnclcc.fr
authors.forename: Ludovic
authors.initials: L
authors.lastname: Ferrer
authors.forename: Françoise
authors.initials: F
authors.lastname: Kraeber-Bodéré
authors.forename: Caroline
authors.initials: C
authors.lastname: Bodet-Milin
authors.forename: Caroline
authors.initials: C
authors.lastname: Rousseau
authors.forename: Stephen
authors.initials: S
authors.lastname: Le Gouill
authors.forename: William A
authors.initials: WA
authors.lastname: Wegener
authors.forename: David M
authors.initials: DM
authors.lastname: Goldenberg
authors.forename: Manuel
authors.initials: M
authors.lastname: Bardiès
mesh_terms: D000293:Adolescent; D000328:Adult; D001853:Bone Marrow / Q000528:radiation effects*; D005260:Female; D006801:Humans; D016393:Lymphoma, B-Cell / Q000532:radiotherapy*; D008297:Male; D016499:Radioimmunotherapy / Q000379:methods*; D011874:Radiometry / Q000379:methods*; D011879:Radiotherapy Dosage; D015021:Yttrium Radioisotopes / Q000378:metabolism* / Q000627:therapeutic use
chemical_list: D015021:Yttrium Radioisotopes