title: Role of FDG-PET/CT in Extramedullary Multiple Myeloma: Correlation of FDG-PET/CT Findings With Clinical Outcome.
abstract: OBJECTIVE
  The aim of this study was to describe FDG-PET/CT findings in extramedullary multiple myeloma (EMM) correlating them with clinical outcome.
  
  
  METHODS
  In this institutional review board-approved HIPAA-compliant retrospective study, we reviewed the FDG-PET/CT scans of 35 patients with EMM (16 women, 19 men; mean age, 56 years; median follow-up after the diagnosis of EMM, 14 months) out of 156 patients diagnosed with MM at our institute between 2004 and 2012. The distribution and metabolic activity of EMM on the scans were reviewed. Clinical data were extracted from electronic medical records. Statistical analysis was performed to determine differences in outcome based on time of detection and distribution of EMM.
  
  
  RESULTS
  Extramedullary multiple myeloma was present at diagnosis in 12 of 35 patients and during disease progression in 23 of 35 patients. Indications for FDG-PET/CT were initial staging (12/35), restaging for disease progression (18/23), or assessment of response to therapy (5/23). Extramedullary multiple myeloma was FDG-avid (mean SUVmax, 8.4; range, 1.2-31), solitary in 10 patients (29%) and multifocal in 25 patients (71%). Two patterns of distribution were noted: direct extension of osseous plasmacytomas in 18 (51%) of 35 patients and hematogeneous/lymphangiogenic dissemination in 33 (94%) of 35 patients. Mean SUVmax in lesions with direct osseous extension was statistically higher than hematogeneous/lymphangiogenic EMM (Mann-Whitney U test, P = 0.03). The most common sites of hematogeneous/lymphangiogenic spread of EMM were lymph nodes (21/35 [60%]), liver (10/35 [29%]), lung (9/35 [26%]), muscles away from bones (7/35 [20%]), and peritoneum/mesentery (7/35 [20%]). There was no statistically significant difference in distribution of EMM at presentation and during disease progression (χ2 test, P > 0.05); 24 (69%) of 35 patients died (median interval after diagnosis of EMM, 7 months). There was no statistically significant difference in outcome for EMM at presentation and during disease progression (log-rank test, P = 0.068). Involvement of any of the following 3 sites: liver, lung, and muscles away from bones, was associated with statistically significant shorter survival (log-rank test, P = 0.0008).
  
  
  CONCLUSIONS
  Extramedullary multiple myeloma is more often seen on FDG-PET/CT in the context of a hematogeneous/lymphangiogenic spread pattern and less commonly as a direct extension of osseous plasmacytomas. Extramedullary multiple myeloma has poor outcome whether detected at presentation or during follow-up. Extramedullary multiple myeloma involving the liver, lung, and muscles was associated with shorter survival in our study.
authors.affiliation: From the *Department of Imaging, Dana-Farber Cancer Institute, †Department of Radiology, Brigham and Women's Hospital, and ‡Department of Medical Oncology, Dana-Farber Cancer Institute, Harvard Medical School, Boston, MA.
authors.forename: Sree Harsha
authors.initials: SH
authors.lastname: Tirumani
authors.forename: Christopher
authors.initials: C
authors.lastname: Sakellis
authors.forename: Heather
authors.initials: H
authors.lastname: Jacene
authors.forename: Atul B
authors.initials: AB
authors.lastname: Shinagare
authors.forename: Nikhil C
authors.initials: NC
authors.lastname: Munshi
authors.forename: Nikhil H
authors.initials: NH
authors.lastname: Ramaiya
authors.forename: Annick D
authors.initials: AD
authors.lastname: Van den Abbeele
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D018450:Disease Progression; D005260:Female; D019788:Fluorodeoxyglucose F18; D006801:Humans; D008297:Male; D008875:Middle Aged; D064847:Multimodal Imaging; D009101:Multiple Myeloma / Q000000981:diagnostic imaging / Q000473:pathology; D009367:Neoplasm Staging; D049268:Positron-Emission Tomography; D012189:Retrospective Studies; D014057:Tomography, X-Ray Computed
chemical_list: D019788:Fluorodeoxyglucose F18