title: Vasectomy and prostate cancer: results from a multiethnic case-control study.
abstract: BACKGROUND
  Vasectomy, a widely used form of contraception, has been associated in some studies with increased prostate cancer risk.
  
  
  OBJECTIVE
  We assessed this association on the basis of data collected in a large multiethnic case-control study of prostate cancer that was conducted in the United States (Los Angeles, San Francisco, and Hawaii) and Canada (Toronto and Vancouver).
  
  
  METHODS
  In home interviews conducted with newly diagnosed prostate cancer case patients and population control subjects, we obtained information on the participants' medical history, including a history of vasectomy and the age at which the procedure was performed, as well as other potential risk factors. Blood samples were collected from control subjects only and were assayed for concentration of sex hormones and sex hormone-binding globulin.
  
  
  RESULTS
  The present analysis was based on 1642 prostate cancer patients and 1636 control subjects. A history of vasectomy was not significantly associated with prostate cancer risk among all racial/ethnic groups combined (odds ratio [OR] = 1.1; 95% confidence interval [CI] = 0.83-1.3), whites (OR = 0.94; 95% CI = 0.69-1.3), blacks (OR = 1.0; 95% CI = 0.59-1.8), or Chinese-Americans (OR = 0.96; 95% CI = 0.42-2.2). Among Japanese-Americans, the OR was 1.8 (95% CI = 0.97-3.4), but the statistically nonsignificant elevation in risk was limited to more educated men and those with localized cancers. ORs did not vary significantly by age at vasectomy or years since vasectomy. We found a lower serum concentration of sex hormone-binding globulin and a higher ratio of dihydrotestosterone to testosterone among vasectomized control subjects than among nonvasectomized control subjects.
  
  
  CONCLUSIONS
  The findings of this study do not support previous reports of increased prostate cancer risk associated with vasectomy. However, the altered endocrine profiles of vasectomized control subjects seen in this cross-sectional comparison warrant further evaluation in longitudinal studies.
authors.affiliation: Department of Health Research and Policy, Stanford University School of Medicine, Calif, USA.
authors.forename: E M
authors.initials: EM
authors.lastname: John
authors.forename: A S
authors.initials: AS
authors.lastname: Whittemore
authors.forename: A H
authors.initials: AH
authors.lastname: Wu
authors.forename: L N
authors.initials: LN
authors.lastname: Kolonel
authors.forename: T G
authors.initials: TG
authors.lastname: Hislop
authors.forename: G R
authors.initials: GR
authors.lastname: Howe
authors.forename: D W
authors.initials: DW
authors.lastname: West
authors.forename: J
authors.initials: J
authors.lastname: Hankin
authors.forename: D M
authors.initials: DM
authors.lastname: Dreon
authors.forename: C Z
authors.initials: CZ
authors.lastname: Teh
mesh_terms: D000368:Aged; D000728:Androgens / Q000097:blood; D044466:Asian People; D044383:Black People; D016022:Case-Control Studies; D006801:Humans; D008297:Male; D017430:Prostate-Specific Antigen / Q000097:blood; D011471:Prostatic Neoplasms / Q000453:epidemiology*; D012738:Sex Hormone-Binding Globulin / Q000378:metabolism; D014659:Vasectomy / Q000009:adverse effects*; D044465:White People
chemical_list: D000728:Androgens; D012738:Sex Hormone-Binding Globulin; D017430:Prostate-Specific Antigen