title: Regarding the focal treatment of prostate cancer: inference of the Gleason grade from magnetic resonance spectroscopic imaging.
abstract: OBJECTIVE
  To quantify, as a function of average magnetic resonance spectroscopy (MRS) score and tumor volume, the probability that a cancer-suspected lesion has an elevated Gleason grade.
  
  
  METHODS
  The data consist of MRS imaging ratios R stratified by patient, lesion (contiguous abnormal voxels), voxels, biopsy and pathologic Gleason grade, and lesion volume. The data were analyzed using a logistic model.
  
  
  RESULTS
  For both low and high Gleason score biopsy lesions, the probability of pathologic Gleason score >/=4+3 increases with lesion volume. At low values of R a lesion volume of at least 15-20 voxels is needed to reach a probability of success of 80%; the biopsy result helps reduce the prediction uncertainty. At larger MRS ratios (R > 6) the biopsy result becomes essentially uninformative once the lesion volume is >12 voxels. With the exception of low values of R, for lesions with low Gleason score at biopsy, the MRS ratios serve primarily as a selection tool for assessing lesion volumes.
  
  
  CONCLUSIONS
  In patients with biopsy Gleason score >/=4+3, high MRS imaging tumor volume and (creatine + choline)/citrate ratio may justify the initiation of voxel-specific dose escalation. This is an example of biologically motivated focal treatment for which intensity-modulated radiotherapy and especially brachytherapy are ideally suited.
authors.affiliation: CMS, Inc., St. Louis, MO, USA.
authors.forename: Ryan S
authors.initials: RS
authors.lastname: Brame
authors.forename: Marco
authors.initials: M
authors.lastname: Zaider
authors.forename: Kristen L
authors.initials: KL
authors.lastname: Zakian
authors.forename: Jason A
authors.initials: JA
authors.lastname: Koutcher
authors.forename: Amita
authors.initials: A
authors.lastname: Shukla-Dave
authors.forename: Victor E
authors.initials: VE
authors.lastname: Reuter
authors.forename: Michael J
authors.initials: MJ
authors.lastname: Zelefsky
authors.forename: Peter T
authors.initials: PT
authors.lastname: Scardino
authors.forename: Hedvig
authors.initials: H
authors.lastname: Hricak
mesh_terms: D000465:Algorithms; D001706:Biopsy; D002794:Choline / Q000032:analysis; D019343:Citric Acid / Q000032:analysis; D003401:Creatine / Q000032:analysis; D006801:Humans; D016015:Logistic Models; D009682:Magnetic Resonance Spectroscopy; D008297:Male; D011467:Prostate / Q000473:pathology*; D011471:Prostatic Neoplasms / Q000473:pathology*; D047368:Tumor Burden
chemical_list: D019343:Citric Acid; D003401:Creatine; D002794:Choline