title: Predictive factors for erectile dysfunction in men with prostate cancer after brachytherapy: is dose to the penile bulb important?
abstract: OBJECTIVE
  To determine predictive factors for postimplant erectile dysfunction (ED) in a cohort of patients, according to prospectively collected data; specifically, to assess the impact of penile bulb volume and D50 and D95 (dose covering 50% and 95% of the penile bulb volume, respectively) on ED.
  
  
  METHODS
  Three hundred forty-two patients were identified who were potent before implant and who had at least 2 years' follow-up. Patient, tumor, treatment, and dosimetric data were collected on all patients. Postimplant ED was defined according to both physician-documented and patient-documented outcome data. Binary logistic regression analysis was used to create multivariable models of predictors for ED at 1, 2, and 3 years after implant.
  
  
  RESULTS
  Physician-documented rates of ED were 57%, 48%, and 38% at 1, 2, and 3 years after implant, respectively. Patient-documented rates of ED were 70% and 66% at 1 and 2 years, respectively. Multivariable analyses revealed age and degree of pre-implant erectile function to be consistently significant predictors of ED. Use of hormones was significant at the 1-year physician-documented ED endpoint but not thereafter, in keeping with the time course of testosterone recovery. Penile bulb volume, D50, and D95 were not found to be predictive for ED at any time point, in contrast to previous studies. In addition, planning ultrasound target volume, number of needles, and institutional case sequence number were significant predictors of ED at various time points, consistent with a traumatic etiology of ED.
  
  
  CONCLUSIONS
  We found no evidence to support penile bulb dosimetry as an independent predictive factor for ED after implant, using physician-documented or patient-documented outcomes.
authors.affiliation: Department of Radiation Oncology, Vancouver Cancer Centre, BC Cancer Agency, Vancouver, BC, Canada. gmacdonald@easynet.co.uk
authors.forename: A Graham
authors.initials: AG
authors.lastname: Macdonald
authors.forename: Mira
authors.initials: M
authors.lastname: Keyes
authors.forename: Alexandra
authors.initials: A
authors.lastname: Kruk
authors.forename: Graeme
authors.initials: G
authors.lastname: Duncan
authors.forename: Veronika
authors.initials: V
authors.lastname: Moravan
authors.forename: W James
authors.initials: WJ
authors.lastname: Morris
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D000704:Analysis of Variance; D001918:Brachytherapy / Q000009:adverse effects*; D007172:Erectile Dysfunction / Q000209:etiology*; D006801:Humans; D007457:Iodine Radioisotopes / Q000627:therapeutic use; D008297:Male; D008875:Middle Aged; D015588:Observer Variation; D010410:Penile Erection / Q000528:radiation effects; D010413:Penis / Q000528:radiation effects*; D011446:Prospective Studies; D011471:Prostatic Neoplasms / Q000532:radiotherapy*; D011879:Radiotherapy Dosage
chemical_list: D007457:Iodine Radioisotopes