title: Pretreatment endorectal magnetic resonance imaging and magnetic resonance spectroscopic imaging features of prostate cancer as predictors of response to external beam radiotherapy.
abstract: OBJECTIVE
  To evaluate whether pretreatment combined endorectal magnetic resonance imaging (MRI) and magnetic resonance spectroscopic imaging (MRSI) findings are predictive of outcome in patients who undergo external beam radiotherapy for prostate cancer.
  
  
  METHODS
  We retrospectively identified 67 men with biopsy-proven prostate cancer who underwent combined endorectal MRI and MRSI at our institution between January 1998 and October 2003 before whole-pelvis external beam radiotherapy. A single reader recorded tumor presence, stage, and metabolic abnormality at combined MRI and MRSI. Kaplan-Meier survival and Cox univariate and multivariate analyses explored the relationship between clinical and imaging variables and outcome, using biochemical or metastatic failure as endpoints.
  
  
  RESULTS
  After a mean follow-up of 44 months (range, 3-96), 6 patients developed both metastatic and biochemical failure, with an additional 13 patients developing biochemical failure alone. Multivariate Cox analysis demonstrated that the only independent predictor of biochemical failure was the volume of malignant metabolism on MRSI (hazard ratio [HR] 1.63, 95% confidence interval [CI] 1.29-2.06; p < 0.0001). The two independent predictors of metastatic failure were MRI tumor size (HR 1.34, 95% CI 1.03-1.73; p = 0.028) and the finding of seminal vesicle invasion on MRI (HR 28.05, 95% CI 3.96-198.67; p = 0.0008).
  
  
  CONCLUSIONS
  In multivariate analysis, MRI and MRSI findings before EBRT in patients with prostate cancer are more accurate independent predictors of outcome than clinical variables, and in particular, the findings of seminal vesicle invasion and extensive tumor predict a worse prognosis.
authors.affiliation: Department of Radiology, University of California-San Francisco, San Francisco, CA 94143-0628, USA.
authors.forename: Tim
authors.initials: T
authors.lastname: Joseph
authors.forename: David A
authors.initials: DA
authors.lastname: McKenna
authors.forename: Antonio C
authors.initials: AC
authors.lastname: Westphalen
authors.forename: Fergus V
authors.initials: FV
authors.lastname: Coakley
authors.forename: Shoujun
authors.initials: S
authors.lastname: Zhao
authors.forename: Ying
authors.initials: Y
authors.lastname: Lu
authors.forename: I-Chow
authors.initials: IC
authors.lastname: Hsu
authors.forename: Mack
authors.initials: M
authors.lastname: Roach
authors.forename: John
authors.initials: J
authors.lastname: Kurhanewicz