title: Tumour response prediction by diffusion-weighted MR imaging: ready for clinical use?
abstract: BACKGROUND
  The efficacy of anticancer therapy is usually evaluated by anatomical imaging. However, this method may be suboptimal for the evaluation of novel treatment modalities, such as targeted therapy. Theoretically, functional assessment of tumour response by diffusion weighted imaging (DWI) is an attractive tool for this purpose and may allow an early prediction of response. The optimal use of this method has still to be determined.
  
  
  METHODS
  We reviewed the published literature on clinical DWI in the prediction of response to anticancer therapy, especially targeted therapy. Studies investigating the role of DWI in patients with cancer either for response prediction and/or response monitoring were selected for this analysis.
  
  
  RESULTS
  We identified 24 studies that met our criteria. Most studies showed a significant correlation between (changes in) apparent diffusion coefficient (ADC) values and treatment response. However, in different tumours and studies, both high and low pretreatment ADC were found to be associated with response rate. In the course of treatment, an increase in ADC was associated with response in most cases.
  
  
  CONCLUSIONS
  The potential of DWI for (early) response monitoring of anticancer therapies has been demonstrated. However, validation is hampered by the lack of reproducibility and standardisation. We recommend that these issues should be properly addressed prior to further testing the clinical use of DWI in the assessment of treatments.
authors.affiliation: Department of Medical Oncology, Radboud University Nijmegen Medical Centre, Nijmegen, The Netherlands.
authors.forename: Linda
authors.initials: L
authors.lastname: Heijmen
authors.forename: Maartje C H M
authors.initials: MC
authors.lastname: Verstappen
authors.forename: Edwin E G W
authors.initials: EE
authors.lastname: Ter Voert
authors.forename: Cornelis J A
authors.initials: CJ
authors.lastname: Punt
authors.forename: Wim J G
authors.initials: WJ
authors.lastname: Oyen
authors.forename: Lioe-Fee
authors.initials: LF
authors.lastname: de Geus-Oei
authors.forename: John J
authors.initials: JJ
authors.lastname: Hermans
authors.forename: Arend
authors.initials: A
authors.lastname: Heerschap
authors.forename: Hanneke W M
authors.initials: HW
authors.lastname: van Laarhoven
mesh_terms: D000818:Animals; D038524:Diffusion Magnetic Resonance Imaging / Q000379:methods*; D006801:Humans; D009369:Neoplasms / Q000175:diagnosis / Q000473:pathology* / Q000628:therapy*; D011379:Prognosis; D016896:Treatment Outcome