title: Association of anorectal dose-volume histograms and impaired fecal continence after 3D conformal radiotherapy for carcinoma of the prostate.
abstract: OBJECTIVE
  The late toxicity of fecal incontinence after pelvic radiotherapy is now frequently recognized but the etiology poorly understood. We therefore investigated associations between dose-volume histogram (DVH) parameters of the rectum and the anal canal with fecal continence as measured by an established 10-item questionnaire.
  
  
  METHODS
  Forty-four patients treated for carcinoma of the prostate with 58-72 Gy of 3D conformal radiotherapy between 1995 and 1999 who completed the questionnaire formed the study population. Total continence scores of treated patients obtained 1.5 years (median) after radiotherapy were compared to a control group of 30 patients before radiotherapy. Median, mean, minimum and maximum doses as well as the volume (% and ml) treated to 40, 50, 60 and 70 Gy were determined separately for anal canal and rectum. DVH parameters were correlated with total continence score (Spearman rank test) and patients grouped according to observed continence were compared regarding DVH values (Mann-Whitney U-test).
  
  
  RESULTS
  Median fecal continence scores were significantly worse in the irradiated than in the control group (31 vs. 35 of a maximum 36 points). In treated patients, 59%/27%/14% were classified as fully continent, slightly incontinent and severely incontinent. Continence was similar in the 58-to-62-Gy, 66-Gy and 68-to-72-Gy dose groups. No DVH parameter was significantly correlated with total continence score, but severely incontinent patients had a significantly higher minimum dose to the anal canal than fully continent/slightly incontinent, accompanied by portals extending significantly further inferiorly with respect to the ischial tuberosities.
  
  
  CONCLUSIONS
  Excluding the inferior part of the anal canal from the treated volume in 3D conformal therapy for carcinoma of the prostate appears to be a promising strategy to prevent radiation-induced fecal incontinence.
authors.affiliation: Department of Radiation Oncology, University of Würzburg, Josef-Schneider-Street 11, 97080 Würzburg, Germany.
authors.forename: Dirk
authors.initials: D
authors.lastname: Vordermark
authors.forename: Michael
authors.initials: M
authors.lastname: Schwab
authors.forename: Rhea
authors.initials: R
authors.lastname: Ness-Dourdoumas
authors.forename: Marco
authors.initials: M
authors.lastname: Sailer
authors.forename: Michael
authors.initials: M
authors.lastname: Flentje
authors.forename: Oliver
authors.initials: O
authors.lastname: Koelbl
mesh_terms: D000368:Aged; D001003:Anal Canal / Q000528:radiation effects; D004307:Dose-Response Relationship, Radiation; D005242:Fecal Incontinence / Q000209:etiology*; D006801:Humans; D008297:Male; D008875:Middle Aged; D011471:Prostatic Neoplasms / Q000532:radiotherapy*; D020266:Radiotherapy, Conformal / Q000009:adverse effects*