title: Adjuvant radiotherapy is associated with increased sexual dysfunction in male patients undergoing resection for rectal cancer: a predictive model.
abstract: OBJECTIVE
  The objectives of this study were to evaluate the effect of radiotherapy (RT) on sexual function in patients undergoing oncologic resection for rectal cancer, and to develop a mathematical model for quantifying the risk of sexual dysfunction through time for this group of patients.
  
  
  METHODS
  Data were prospectively collected on patients undergoing proctosigmoidectomy (group 1: n = 101) or adjuvant radiotherapy (40-50 Gy) and resection (group 2: n = 100) for rectal cancer at a tertiary referral center between December 1998 and July 2004. Study end points were recorded at 7 time intervals (preoperatively, 4 months, 8 months, 1 year, 2 years, 3 years, and 4 years after surgery) and included: 1) ability to have an erection, 2) maintain an erection, 3) attain orgasm, 4) dry orgasm, and 5) whether they were sexually active. Multilevel logistic regression analysis for repeated measures was used to identify factors associated with the sexual dysfunction. A predictive model was developed and internally validated by comparing observed and model-predicted outcomes.
  
  
  RESULTS
  Radiotherapy had an adverse effect on the ability to get an erection, maintain an erection, attain orgasm, and being sexually active in comparison with patients undergoing surgery alone (7.4%, 12.6%, 16.2%, and 13.7% reduction 8 months after surgery respectively; P < 0.05). The effect of sexual dysfunction deteriorated with age (odds ratio for erectile function, 0.40 per 10-year increase in age; 95% confidence interval, 0.29-0.49; P < 0.001). A significant variability in sexual function was present among the 7 time points with a maximal deterioration occurring at 8 months after surgery with subsequent slow but not complete recovery (P < 0.001). The predictive model showed adequate discrimination on 4 of the 5 domains of sexual dysfunction (area under the receiver operating characteristic curve >0.70).
  
  
  CONCLUSIONS
  Radiotherapy has an adverse effect on sexual function, the effect being maximal at 8 months after surgery. The risk of sexual dysfunction can be quantified preoperatively using the proposed index and can assist patients in making better informed choices on the type of treatment they receive.
authors.affiliation: The Department of Colorectal Surgery, Cleveland Clinic Foundation, Cleveland, Ohio 44195, USA.
authors.forename: Alexander G
authors.initials: AG
authors.lastname: Heriot
authors.forename: Paris P
authors.initials: PP
authors.lastname: Tekkis
authors.forename: Victor W
authors.initials: VW
authors.lastname: Fazio
authors.forename: Paul
authors.initials: P
authors.lastname: Neary
authors.forename: Ian C
authors.initials: IC
authors.lastname: Lavery
mesh_terms: D000368:Aged; D001499:Bayes Theorem; D007172:Erectile Dysfunction / Q000453:epidemiology / Q000209:etiology*; D005500:Follow-Up Studies; D006801:Humans; D015994:Incidence; D008297:Male; D008875:Middle Aged; D009367:Neoplasm Staging; D016737:Proctocolectomy, Restorative / Q000009:adverse effects*; D011446:Prospective Studies; D018714:Radiotherapy, Adjuvant / Q000009:adverse effects; D012004:Rectal Neoplasms / Q000473:pathology / Q000532:radiotherapy* / Q000601:surgery; D012044:Regression Analysis; D015203:Reproducibility of Results; D012098:Reproduction / Q000528:radiation effects*; D012307:Risk Factors; D016896:Treatment Outcome