title: Clinical and biochemical responses after Gamma Knife surgery for a dopamine-secreting paraganglioma: case report.
abstract: BACKGROUND
  The efficacy of Gamma Knife surgery (GKS) in local tumor control of non-secreting paragangliomas (PGLs) has been fully described by previous studies. However, with regard to secreting PGL, only one previous case report exists advocating its efficacy at a biological level.
  
  
  METHODS
  The aims of this study were: 1) to evaluate the safety/efficacy of GKS in a dopamine-secreting PGL; 2) to investigate whether the biological concentrations of free methoxytyramine could be used as a marker of treatment efficacy during the follow-up. We describe the case of a 62-year-old man diagnosed with left PGL. He initially underwent complete surgical excision. Thirty months after, he developed recurrent biological and neuroradiological disease; the most sensitive biomarker for monitoring the disease, concentration of plasma free methoxytyramine, started to increase. GKS was performed at a maximal marginal dose of 16 Gy. During the following 30 months, concentration of free methoxytyramine gradually decreased from 0.14 nmol/l (2*URL) before GKS to 0.09 nmol/l, 6 months after GKS and 0.07 nmol/l at the last follow-up after GKS (1.1*URL), confirming the efficacy of the treatment. Additionally, at 30 months there was approximately 36.6% shrinkage from the initial target volume.
  
  
  CONCLUSIONS
  The GKS treatment was safe and effective, this being confirmed clinically, neuroradiologically and biologically. The case illustrates the importance of laboratory tests taking into account methoxytyramine when analyzing biological samples to assess the biochemical activity of a PGL. In addition, the identification of methoxytyramine as a unique positive biomarker could designate it for the monitoring of tumor relapse after treatments, including Gamma Knife surgery.
authors.affiliation: Department of Clinical Neurosciences, Neurosurgery Service and Gamma Knife Center, Centre Hospitalier Universitaire Vaudois (CHUV),Signal Processing Laboratory (LTS 5), École Polytechnique Fédérale de Lausanne,University of Lausanne, Faculty of Biology and Medicine; Lausanne, Switzerland.
authors.forename: Constantin
authors.initials: C
authors.lastname: Tuleasca
authors.affiliation: Department of Otolaryngology, Head and Neck Surgery, Lausanne, Switzerland.
authors.forename: Yves
authors.initials: Y
authors.lastname: Jaquet
authors.affiliation: Department of Otolaryngology, Head and Neck Surgery, Lausanne, Switzerland.
authors.forename: Valerie
authors.initials: V
authors.lastname: Schweizer
authors.affiliation: Radiation Oncology Service, Lausanne, Switzerland.
authors.forename: Laura
authors.initials: L
authors.lastname: Negretti
authors.affiliation: Institute of Radiation Physics, University of Lausanne, Faculty of Biology and Medicine; Lausanne, Switzerland.
authors.forename: Vera
authors.initials: V
authors.lastname: Magaddino
authors.affiliation: Radiology Department, University of Lausanne, Faculty of Biology and Medicine; Lausanne, Switzerland.
authors.forename: Philippe
authors.initials: P
authors.lastname: Maeder
authors.affiliation: Service of Biomedicine, Laboratoire des Catécholamines et Peptides, Centre Hospitalier Universitaire Vaudois (CHUV), University of Lausanne, Faculty of Biology and Medicine; Lausanne, Switzerland.
authors.forename: Karim-Alexandre
authors.initials: KA
authors.lastname: Abid
authors.affiliation: Neuropathology Department, University of Lausanne, Faculty of Biology and Medicine; Lausanne, Switzerland.
authors.forename: Benoit
authors.initials: B
authors.lastname: Lhermitte
authors.affiliation: Service of Biomedicine, Laboratoire des Catécholamines et Peptides, Centre Hospitalier Universitaire Vaudois (CHUV), University of Lausanne, Faculty of Biology and Medicine; Lausanne, Switzerland.
authors.forename: Eric
authors.initials: E
authors.lastname: Grouzmann
authors.affiliation: Department of Clinical Neurosciences, Neurosurgery Service and Gamma Knife Center, Centre Hospitalier Universitaire Vaudois (CHUV), University of Lausanne, Faculty of Biology and Medicine; Lausanne, Switzerland.
authors.forename: Marc
authors.initials: M
authors.lastname: Levivier
mesh_terms: D004298:Dopamine / Q000031:analogs & derivatives / Q000097:blood / Q000378:metabolism* / Q000652:urine; D006258:Head and Neck Neoplasms / Q000601:surgery*; D006801:Humans; D008297:Male; D008875:Middle Aged; D010235:Paraganglioma / Q000601:surgery*; D016634:Radiosurgery; D012008:Recurrence; D013997:Time Factors
chemical_list: C001746:3-methoxytyramine; D004298:Dopamine