title: Guidance of treatment decisions in risk-adapted primary radiotherapy for prostate cancer using multiparametric magnetic resonance imaging: a single center experience.
abstract: BACKGROUND
  Magnetic resonance imaging (MRI) of the prostate is considered to be the most precise noninvasive staging modality for localized prostate cancer. Multiparametric MRI (mpMRI) dynamic sequences have recently been shown to further increase the accuracy of staging relative to morphological imaging alone. Correct radiological staging, particularly the detection of extraprostatic disease extension, is of paramount importance for target volume definition and dose prescription in highly-conformal curative radiotherapy (RT); in addition, it may affect the risk-adapted duration of additional antihormonal therapy. The purpose of our study was to analyze the impact of mpMRI-based tumor staging in patients undergoing primary RT for prostate cancer.
  
  
  METHODS
  A total of 122 patients admitted for primary RT for prostate cancer were retrospectively analyzed regarding initial clinical and computed tomography-based staging in comparison with mpMRI staging. Both tumor stage shifts and overall risk group shifts, including prostate-specific antigen (PSA) level and the Gleason score, were assessed. Potential risk factors for upstaging were tested in a multivariate analysis. Finally, the impact of mpMRI-based staging shift on prostate RT and antihormonal therapy was evaluated.
  
  
  RESULTS
  Overall, tumor stage shift occurred in 55.7% of patients after mpMRI. Upstaging was most prominent in patients showing high-risk serum PSA levels (73%), but was also substantial in patients presenting with low-risk PSA levels (50%) and low-risk Gleason scores (45.2%). Risk group changes occurred in 28.7% of the patients with consequent treatment adaptations regarding target volume delineation and duration of androgen deprivation therapy. High PSA levels were found to be a significant risk factor for tumor upstaging and newly diagnosed seminal vesicle infiltration assessed using mpMRI.
  
  
  CONCLUSIONS
  Our findings suggest that mpMRI of the prostate leads to substantial tumor upstaging, and can considerably affect treatment decisions in all patient groups undergoing risk-adapted curative RT for prostate cancer.
authors.affiliation: Department of Radiation Oncology, Kantonsspital St. Gallen, St. Gallen, Switzerland. cedric.panje@kssg.ch.
authors.forename: Cedric
authors.initials: C
authors.lastname: Panje
authors.affiliation: Department of Radiation Oncology, Kantonsspital St. Gallen, St. Gallen, Switzerland. thierryjulian.panje@kssg.ch.
authors.forename: Thierry
authors.initials: T
authors.lastname: Panje
authors.affiliation: Department of Radiation Oncology, Kantonsspital St. Gallen, St. Gallen, Switzerland. paulmartin.putora@kssg.ch.
authors.forename: Paul Martin
authors.initials: PM
authors.lastname: Putora
authors.affiliation: Department of Radiology and Nuclear Medicine, Kantonsspital St. Gallen, St. Gallen, Switzerland. suk-kyum.kim@kssg.ch.
authors.forename: Suk-Kyum
authors.initials: SK
authors.lastname: Kim
authors.affiliation: Clinical Trials Unit, Kantonsspital St. Gallen, St. Gallen, Switzerland. sarah.haile@kssg.ch.
authors.forename: Sarah
authors.initials: S
authors.lastname: Haile
authors.affiliation: Department of Radiation Oncology, Bern University Hospital, Bern, Switzerland. daniel.aebersold@insel.ch.
authors.forename: Daniel M
authors.initials: DM
authors.lastname: Aebersold
authors.affiliation: Department of Radiation Oncology, Kantonsspital St. Gallen, St. Gallen, Switzerland. ludwig.plasswilm@kssg.ch.
authors.forename: Ludwig
authors.initials: L
authors.lastname: Plasswilm
mesh_terms: D000465:Algorithms; D003657:Decision Making; D006801:Humans; D007091:Image Processing, Computer-Assisted / Q000379:methods*; D008279:Magnetic Resonance Imaging / Q000379:methods*; D008297:Male; D015999:Multivariate Analysis; D019047:Phantoms, Imaging; D017410:Practice Guidelines as Topic; D011471:Prostatic Neoplasms / Q000473:pathology / Q000532:radiotherapy*; D011879:Radiotherapy Dosage; D011880:Radiotherapy Planning, Computer-Assisted / Q000379:methods*; D020266:Radiotherapy, Conformal / Q000379:methods; D018570:Risk Assessment