title: Magnetic resonance imaging of the axial skeleton enables objective measurement of tumor response on prostate cancer bone metastases.
abstract: BACKGROUND
  There is currently no technique to image quantitatively bone metastases. Here, we assessed the value of MRI of the axial skeleton (AS-MRI) as a single step technique to quantify bone metastases and measure tumor response.
  
  
  METHODS
  AS-MRI was performed in 38 patients before receiving chemotherapy for metastatic HRPCa, in addition to PSA, computed tomography of the thorax, abdomen, and pelvis [CT-TAP]; and Tc-99m bone scintigraphy. A second AS-MRI was performed in 20 patients who completed 6 months of chemotherapy. Evaluation of tumor response was performed using RECIST.
  
  
  RESULTS
  Only 11 patients (29%) had RECIST measurable metastases in soft-tissues or lymph nodes on baseline CT-TAP. AS-MRI identified a diffuse infiltration of the bone marrow in 8 patients and focal measurable metastatic lesions in 25 patients (65%), therefore, doubling the proportion of patients with measurable lesions. Transposing RECIST on AS-MRI in 20 patients who completed 6 months of treatment, allows the accurate estimation of complete response (n = 2), partial response (n = 2), stable disease (n = 5), or tumor progression (n = 11), as it is done using CT-TAP in soft tissue solid metastases.
  
  
  CONCLUSIONS
  MRI of axial skeleton enables precise measurement and follow-up of bone metastases as it is for other soft-tissue metastasis.
authors.affiliation: Division of Urology, Université catholique de Louvain, Cliniques universitaires Saint-Luc Brussels, Belgium. bertrand.tombal@fycl.ucl.ac.be
authors.forename: Bertrand
authors.initials: B
authors.lastname: Tombal
authors.forename: Afshin
authors.initials: A
authors.lastname: Rezazadeh
authors.forename: Patrick
authors.initials: P
authors.lastname: Therasse
authors.forename: Paul J
authors.initials: PJ
authors.lastname: Van Cangh
authors.forename: Bruno
authors.initials: B
authors.lastname: Vande Berg
authors.forename: Frédéric E
authors.initials: FE
authors.lastname: Lecouvet
mesh_terms: D001859:Bone Neoplasms / Q000188:drug therapy / Q000473:pathology* / Q000556:secondary*; D023381:Endpoint Determination; D006801:Humans; D008279:Magnetic Resonance Imaging; D008297:Male; D011446:Prospective Studies; D011471:Prostatic Neoplasms / Q000188:drug therapy / Q000473:pathology*; D016896:Treatment Outcome