title: Radiation dose delivered to the proximal penis as a predictor of the risk of erectile dysfunction after three-dimensional conformal radiotherapy for localized prostate cancer.
abstract: OBJECTIVE
  In this study, we evaluated in a serial manner whether radiation dose to the bulb of the penis is predictive of erectile dysfunction, ejaculatory difficulty (EJ), and overall satisfaction with sex life (quality of life) by using serial validated self-administered questionnaires.
  
  
  METHODS
  Twenty-nine potent men with AJCC Stage II prostate cancer treated with three-dimensional conformal radiation therapy alone to a median dose 72.0 Gy (range: 66.6-79.2 Gy) were evaluated by determining the doses received by the penile bulb. The penile bulb was delineated volumetrically, and the dose-volume histogram was obtained on each patient.
  
  
  RESULTS
  The median follow-up time was 35 months (range, 16-43 months). We found that for D(30), D(45), D(60), and D(75) (doses to a percent volume of PB: 30%, 45%, 60%, and 75%), higher than the corresponding median dose (defined as high-dose group) correlated with an increased risk of impotence (erectile dysfunction firmness score = 0) (odds ratio [OR] = 7.5, p = 0.02; OR = 7.5, p = 0.02; OR = 8.6, p = 0.008; and OR = 6.9, p = 0.015, respectively). Similarly, for EJD D(30), D(45), D(60), and D(75), doses higher than the corresponding median ones correlated with worsening ejaculatory function score (EJ = 0 or 1) (OR = 8, p = 0.013; OR = 8, p = 0.013; OR = 9.2, p = 0.015; and OR = 8, p = 0.026, respectively). For quality of life, low (< or =median dose) dose groups of patients improve over time, whereas high-dose groups of patients worsen.
  
  
  CONCLUSIONS
  This study supports the existence of a penile bulb dose-volume relationship underlying the development of radiation-induced erectile dysfunction. Our data may guide the use of inverse treatment planning to maximize the probability of maintaining sexual potency after radiation therapy.
authors.affiliation: Department of Radiation Oncology, Jefferson Medical College and Kimmel Cancer Center, Thomas Jefferson University, Philadelphia, Pennsylvania 19107, USA.
authors.forename: A Gabriella
authors.initials: AG
authors.lastname: Wernicke
authors.forename: Richard
authors.initials: R
authors.lastname: Valicenti
authors.forename: Kelly
authors.initials: K
authors.lastname: Dieva
authors.forename: Christopher
authors.initials: C
authors.lastname: Houser
authors.forename: Ed
authors.initials: E
authors.lastname: Pequignot
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D000428:Alcohol Drinking / Q000009:adverse effects; D007172:Erectile Dysfunction / Q000209:etiology*; D006801:Humans; D016015:Logistic Models; D008297:Male; D008875:Middle Aged; D016017:Odds Ratio; D010410:Penile Erection / Q000528:radiation effects; D010413:Penis / Q000528:radiation effects*; D011471:Prostatic Neoplasms; D011788:Quality of Life; D011879:Radiotherapy Dosage; D020266:Radiotherapy, Conformal / Q000009:adverse effects*; D012907:Smoking / Q000009:adverse effects