title: Characteristics of dynamic magnetic resonance image enhancement in prolactinomas resistant to dopamine agonist therapy.
abstract: OBJECTIVE
  The objective of this study was to determine whether dynamic magnetic resonance imaging (dMRI) enhancement parameters could predict dopamine agonist (DA) resistance in prolactinomas.
  
  
  METHODS
  We retrospectively identified patients with prolactinomas who were treated with DA and underwent dMRI from 2001 through 2012 at Mayo Clinic (Rochester, MN). Intensities of the adenoma and pituitary gland were measured by drawing regions of interest on the images. Enhancement ratio, enhancement peak, prepeak slope (PPS), and enhancement time were compared between DA-resistant and DA-responsive groups, between DA-treated and DA-naive groups, and between the first and follow-up dMRIs.
  
  
  RESULTS
  We identified 49 patients with prolactinomas, with 6 (12.2%) showing DA resistance. Thirty-seven patients (75.5%) underwent dMRI while receiving treatment, 12 (25.5%) underwent dMRI before starting therapy, and 10 (20.4%) had follow-up dMRI after DA therapy. The PPS of the tumor was higher in the treatment-resistant group versus the responsive group (mean [SD], 4.42 [3.19] vs 2.65 [1.59]; P = 0.03), whereas no difference was noted in the pituitary gland (5.79 [2.21] vs 4.06 [2.48]; P = 0.11). Logistic regression analysis indicated that tumor PPS was associated with DA resistance (odds ratio, 1.71; 95% confidence interval, 1.07-3.27; P = 0.02).
  
  
  CONCLUSIONS
  Dynamic MRI with PPS analysis potentially can be used early in the treatment course to evaluate DA resistance in pituitary prolactinomas.
authors.affiliation: From the *Division of Endocrinology, Chinese PLA General Hospital, Beijing, China; and †Department of Radiology and ‡Division of Endocrinology, Diabetes, Metabolism, and Nutrition, Mayo Clinic, Rochester, MN.
authors.forename: Qinghua
authors.initials: Q
authors.lastname: Guo
authors.forename: Bradley J
authors.initials: BJ
authors.lastname: Erickson
authors.forename: Alice Y
authors.initials: AY
authors.lastname: Chang
authors.forename: Dana
authors.initials: D
authors.lastname: Erickson
mesh_terms: D000328:Adult; D018491:Dopamine Agonists / Q000494:pharmacology* / Q000627:therapeutic use*; D019008:Drug Resistance, Neoplasm / Q000187:drug effects*; D005260:Female; D006801:Humans; D007089:Image Enhancement; D008279:Magnetic Resonance Imaging; D008297:Male; D015175:Prolactinoma / Q000188:drug therapy*
chemical_list: D018491:Dopamine Agonists