title: Risk of Colorectal Cancer After Ovarian Stimulation for In Vitro Fertilization.
abstract: OBJECTIVE
  Apart from lifestyle factors, sex hormones also seem to have a role in the etiology of colorectal cancer. This raises interest in the possible effects of fertility drugs, especially because the use of ovarian stimulation for in vitro fertilization (IVF) has strongly increased over the past decades.
  
  
  METHODS
  In 1996, a nationwide cohort study was set up to examine cancer risk in a population that included 19,158 women who received ovarian stimulation for IVF (IVF group) and 5950 women who underwent subfertility treatments other than IVF (non-IVF group). Cancer incidence was ascertained through linkage with the Netherlands Cancer Registry. Colorectal cancer risk in the IVF group was compared with those in the general population and in the non-IVF group.
  
  
  RESULTS
  After a median follow-up of 21 years, 109 colorectal cancers were observed. Compared with the general population, risk of colorectal cancer was not increased in the IVF group (standardized incidence ratio, 1.00; 95% confidence interval [CI], 0.80-1.23), and was significantly decreased in the non-IVF group (standardized incidence ratio, 0.58; 95% CI, 0.36-0.88). Women in the IVF group had a significant increase in risk compared with women in the non-IVF group (multivariable-adjusted hazard ratio, 1.80; 95% CI, 1.10-2.94). No trend emerged with more IVF cycles or more ampules of gonadotropins administered. Colorectal cancer risk did not increase with longer follow-up periods.
  
  
  CONCLUSIONS
  Although women who receive ovarian stimulation for IVF do not have an increased risk for colorectal cancer compared with the general population, findings from our nationwide cohort study indicate that their risk is increased compared with women who received subfertility treatments other than IVF. Further research is warranted to examine whether ovarian stimulation for IVF contributes to development of colorectal cancer.
authors.affiliation: Department of Epidemiology, The Netherlands Cancer Institute, Amsterdam, The Netherlands.
authors.forename: Mandy
authors.initials: M
authors.lastname: Spaan
authors.affiliation: Department of Epidemiology, The Netherlands Cancer Institute, Amsterdam, The Netherlands.
authors.forename: Alexandra W
authors.initials: AW
authors.lastname: van den Belt-Dusebout
authors.affiliation: Department of Obstetrics and Gynecology, Erasmus Medical Center, Rotterdam, The Netherlands.
authors.forename: Curt W
authors.initials: CW
authors.lastname: Burger
authors.affiliation: Department of Epidemiology, The Netherlands Cancer Institute, Amsterdam, The Netherlands. Electronic address: f.v.leeuwen@nki.nl.
authors.forename: Flora E
authors.initials: FE
authors.lastname: van Leeuwen
mesh_terms: D000328:Adult; D015331:Cohort Studies; D015179:Colorectal Neoplasms / Q000453:epidemiology*; D005307:Fertilization in Vitro / Q000009:adverse effects*; D006801:Humans; D008875:Middle Aged; D009426:Netherlands / Q000453:epidemiology; D010062:Ovulation Induction / Q000009:adverse effects*; D018570:Risk Assessment; D055815:Young Adult
keywords: CRC; Colon Cancer; Fertility Drugs; Parity; Subfertility