title: Tumor load in patients with multiple myeloma: β2-microglobulin levels versus whole-body MRI.
abstract: OBJECTIVE
  Beta-2-microglobulin is a serum maker of tumor burden in hematologic malignancies. We aimed to correlate serum β2-microglobulin levels in patients with multiple myeloma (MM) to tumor mass determined by whole-body MRI.
  
  
  METHODS
  We retrospectively included patients with newly diagnosed, untreated MM who underwent whole-body MRI at our institution between 2003 and 2011. Patients with a glomerular filtration rate of less than 60 mL/min were excluded from analysis because β2-microglobulin levels are increased in renal failure. Thirty patients could be included. Whole-body MRI examinations (T1-weighted turbo spin-echo and STIR sequences) were assessed by two musculoskeletal radiologists in consensus for focal lesions and the presence of diffuse myeloma infiltration. The presence of diffuse infiltration was confirmed by histology as the reference standard. MM was staged according to the Durie and Salmon PLUS staging system.
  
  
  RESULTS
  According to whole-body MRI findings, MM was classified as Durie and Salmon PLUS stage I (low grade) in 13 patients, stage II (intermediate grade) in six patients, and stage III (high grade) in 11 patients. As we expected, most patients with stage I disease (12/13) had normal β2-microglobulin levels (≤ 3 mg/L). Higher β2-microglobulin values were associated with a higher stage of disease (p < 0.05). However, five of six patients with stage II MM and five of 11 patients with stage III MM showed normal β2-microglobulin levels. Thus, 10 of 17 patients (58.8%) with substantial infiltration in the bone marrow showed false-negative β2-microglobulin levels.
  
  
  CONCLUSIONS
  Serum β2-microglobulin levels correlate with tumor stage in MM. However, it may be misleading as a marker of tumor load in a subset of patients with substantial myeloma infiltration in the bone marrow. Whole-body MRI may display the full tumor load and correctly show the extension of myeloma infiltrates.
authors.affiliation: 1 Institute for Clinical Radiology, University Hospitals Munich, Campus Grosshadern, Ludwig-Maximilians-Universität, Marchioninistrasse 15, 81377 Munich, Bayern, Germany.
authors.forename: Melvin
authors.initials: M
authors.lastname: D'Anastasi
authors.forename: Mike
authors.initials: M
authors.lastname: Notohamiprodjo
authors.forename: Gerwin P
authors.initials: GP
authors.lastname: Schmidt
authors.forename: Hans-Roland
authors.initials: HR
authors.lastname: Dürr
authors.forename: Maximilian Ferdinand
authors.initials: MF
authors.lastname: Reiser
authors.forename: Andrea
authors.initials: A
authors.lastname: Baur-Melnyk
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D014408:Biomarkers, Tumor / Q000097:blood*; D005260:Female; D006801:Humans; D008279:Magnetic Resonance Imaging / Q000379:methods*; D008297:Male; D008875:Middle Aged; D009101:Multiple Myeloma / Q000097:blood* / Q000473:pathology*; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D047368:Tumor Burden; D051598:Whole Body Imaging / Q000379:methods*; D001613:beta 2-Microglobulin / Q000097:blood*
chemical_list: D014408:Biomarkers, Tumor; D001613:beta 2-Microglobulin
keywords: MRI; multiple myeloma; tumor burden; whole-body imaging; β2-microglobulin