title: Comparing the sensitivity of linear and volumetric MRI measurements to detect changes in the size of vestibular schwannomas in patients with neurofibromatosis type 2 on bevacizumab treatment.
abstract: OBJECTIVE
  To compare the sensitivity of linear and volumetric measurements on MRI in detecting schwannoma progression in patients with neurofibromatosis type 2 on bevacizumab treatment as well as the extent to which this depends on the size of the tumour.
  
  
  METHODS
  We compared retrospectively, changes in linear tumour dimensions at a range of thresholds to volumetric tumour measurements performed using Brainlab iPlan(®) software (Feldkirchen, Germany) and classified for tumour progression according to the Response Evaluation in Neurofibromatosis and Schwannomatosis (REiNS) criteria.
  
  
  RESULTS
  Assessment of 61 schwannomas in 46 patients with a median follow-up of 20 months (range 3-43 months) was performed. There was a mean of 7 time points per tumour (range 2-12 time points). Using the volumetric REiNS criteria as the gold standard, a sensitivity of 86% was achieved for linear measurement using a 2-mm threshold to define progression.
  
  
  CONCLUSIONS
  We propose that a change in linear measurement by 2 mm (particularly in tumours with starting diameters 20-30 mm, the majority of this cohort) could be used as a filter to identify cases of possible progression requiring volumetric analysis. This pragmatic approach can be used if stabilization of a previously growing schwannoma is sufficient for a patient to continue treatment in such a circumstance.
  
  
  CONCLUSIONS
  We demonstrate the real-world limitations of linear vs volumetric measurement in tumour response assessment and identify limited circumstances where linear measurements can be used to determine which patients require the more resource-intensive volumetric measurements.
authors.affiliation: 1 St Vincent's Clinical School, University of New South Wales, Sydney, NSW, Australia.|2 Department of Neurology, John Radcliffe Hospital, Oxford University Hospitals NHS Foundation Trust, Oxford, UK.
authors.forename: Katrina A
authors.identifier: http://orcid.org/0000-0003-1075-8424
authors.initials: KA
authors.lastname: Morris
authors.affiliation: 2 Department of Neurology, John Radcliffe Hospital, Oxford University Hospitals NHS Foundation Trust, Oxford, UK.
authors.forename: Allyson
authors.initials: A
authors.lastname: Parry
authors.affiliation: 3 Department of Neuroradiology, John Radcliffe Hospital, Oxford University Hospitals NHS Foundation Trust, Oxford, UK.
authors.forename: Pieter M
authors.initials: PM
authors.lastname: Pretorius
mesh_terms: D020533:Angiogenesis Inhibitors / Q000627:therapeutic use*; D000068258:Bevacizumab / Q000627:therapeutic use*; D018450:Disease Progression; D004428:Ear Neoplasms / Q000188:drug therapy / Q000473:pathology*; D006801:Humans; D053208:Kaplan-Meier Estimate; D008279:Magnetic Resonance Imaging; D009442:Neurilemmoma / Q000188:drug therapy / Q000473:pathology*; D017253:Neurofibromatoses / Q000188:drug therapy / Q000473:pathology*; D016518:Neurofibromatosis 2 / Q000188:drug therapy / Q000473:pathology*; D011446:Prospective Studies; D012189:Retrospective Studies; D012878:Skin Neoplasms / Q000188:drug therapy / Q000473:pathology*; D047368:Tumor Burden; D015837:Vestibular Diseases / Q000188:drug therapy / Q000473:pathology*
chemical_list: D020533:Angiogenesis Inhibitors; D000068258:Bevacizumab