title: Ovarian Stimulation for In Vitro Fertilization and Long-term Risk of Breast Cancer.
abstract: OBJECTIVE
  Previous studies of breast cancer risk after in vitro fertilization (IVF) treatment were inconclusive due to limited follow-up.
  
  
  OBJECTIVE
  To assess long-term risk of breast cancer after ovarian stimulation for IVF.
  
  
  METHODS
  Historical cohort (OMEGA study) with complete follow-up through December 2013 for 96% of the cohort. The cohort included 19,158 women who started IVF treatment between 1983 and 1995 (IVF group) and 5950 women starting other fertility treatments between 1980 and 1995 (non-IVF group) from all 12 IVF clinics in the Netherlands. The median age at end of follow-up was 53.8 years for the IVF group and 55.3 years for the non-IVF group.
  
  
  METHODS
  Information on ovarian stimulation for IVF, other fertility treatments, and potential confounders was collected from medical records and through mailed questionnaires.
  
  
  METHODS
  Incidence of invasive and in situ breast cancers in women who underwent fertility treatments was obtained through linkage with the Netherlands Cancer Registry (1989-2013). Breast cancer risk in the IVF group was compared with risks in the general population (standardized incidence ratios [SIRs]) and the non-IVF group (hazard ratios [HRs]).
  
  
  RESULTS
  Among 25,108 women (mean age at baseline, 32.8 years; mean number of IVF cycles, 3.6), 839 cases of invasive breast cancer and 109 cases of in situ breast cancer occurred after a median follow-up of 21.1 years. Breast cancer risk in IVF-treated women was not significantly different from that in the general population (SIR, 1.01 [95% CI, 0.93-1.09]) and from the risk in the non-IVF group (HR, 1.01 [95% CI, 0.86-1.19]). The cumulative incidences of breast cancer at age 55 were 3.0% for the IVF group and 2.9% for the non-IVF group (P = .85). The SIR did not increase with longer time since treatment (≥20 years) in the IVF group (0.92 [95% CI, 0.73-1.15]) or in the non-IVF group (1.03 [95% CI, 0.82-1.29]). Risk was significantly lower for those who underwent 7 or more IVF cycles (HR, 0.55 [95% CI, 0.39-0.77]) vs 1 to 2 IVF cycles and after poor response to the first IVF cycle (HR, 0.77 [95% CI, 0.61-0.96] for <4 vs ≥4 collected oocytes).
  
  
  CONCLUSIONS
  Among women undergoing fertility treatment in the Netherlands between 1980 and 1995, IVF treatment compared with non-IVF treatment was not associated with increased risk of breast cancer after a median follow-up of 21 years. Breast cancer risk among IVF-treated women was also not significantly different from that in the general population. These findings are consistent with absence of a significant increase in long-term risk of breast cancer among IVF-treated women.
authors.affiliation: Department of Epidemiology and Biostatistics, the Netherlands Cancer Institute, Amsterdam, the Netherlands.
authors.forename: Alexandra W
authors.initials: AW
authors.lastname: van den Belt-Dusebout
authors.affiliation: Department of Epidemiology and Biostatistics, the Netherlands Cancer Institute, Amsterdam, the Netherlands.
authors.forename: Mandy
authors.initials: M
authors.lastname: Spaan
authors.affiliation: Department of Obstetrics and Gynecology, VU University Medical Center, Amsterdam, the Netherlands.
authors.forename: Cornelis B
authors.initials: CB
authors.lastname: Lambalk
authors.affiliation: Department of Reproductive Medicine and Gynecology, University Medical Center Utrecht, Utrecht, the Netherlands.
authors.forename: Marian
authors.initials: M
authors.lastname: Kortman
authors.affiliation: Department of Obstetrics and Gynecology, Erasmus Medical Center, Rotterdam, the Netherlands.
authors.forename: Joop S E
authors.initials: JS
authors.lastname: Laven
authors.affiliation: Department of Reproductive Medicine, Reinier de Graaf Hospital, Voorburg, the Netherlands.
authors.forename: Evert J P
authors.initials: EJ
authors.lastname: van Santbrink
authors.affiliation: Department of Obstetrics, Gynecology, and Reproductive Medicine, Leiden University Medical Center, Leiden, the Netherlands.
authors.forename: Lucette A J
authors.initials: LA
authors.lastname: van der Westerlaken
authors.affiliation: Department of Obstetrics and Gynecology, Isala Clinics, Zwolle, the Netherlands.
authors.forename: Ben J
authors.initials: BJ
authors.lastname: Cohlen
authors.affiliation: Department of Obstetrics and Gynecology, Radboud University Nijmegen Medical Center, Nijmegen, the Netherlands.
authors.forename: Didi D M
authors.initials: DD
authors.lastname: Braat
authors.affiliation: Department of Obstetrics and Gynecology, St Elisabeth Hospital, Tilburg, the Netherlands.
authors.forename: Jesper M J
authors.initials: JM
authors.lastname: Smeenk
authors.affiliation: Department of Obstetrics and Gynecology, University Medical Center Groningen, University Groningen, Groningen, the Netherlands.
authors.forename: Jolande A
authors.initials: JA
authors.lastname: Land
authors.affiliation: Center for Reproductive Medicine, Department of Obstetrics and Gynecology, Academic Medical Center, Amsterdam, the Netherlands.
authors.forename: Mariëtte
authors.initials: M
authors.lastname: Goddijn
authors.affiliation: Department of Obstetrics and Gynecology, Maastricht University Medical Center, Maastricht, the Netherlands.
authors.forename: Ron J T
authors.initials: RJ
authors.lastname: van Golde
authors.affiliation: Department of Obstetrics and Gynecology, Catharina Hospital, Eindhoven, the Netherlands.
authors.forename: Minouche M
authors.initials: MM
authors.lastname: van Rumste
authors.affiliation: Department of Obstetrics and Gynecology, VU University Medical Center, Amsterdam, the Netherlands.
authors.forename: Roel
authors.initials: R
authors.lastname: Schats
authors.affiliation: Department of Epidemiology and Biostatistics, the Netherlands Cancer Institute, Amsterdam, the Netherlands.
authors.forename: Katarzyna
authors.initials: K
authors.lastname: Józwiak
authors.affiliation: Department of Epidemiology and Biostatistics, the Netherlands Cancer Institute, Amsterdam, the Netherlands.
authors.forename: Michael
authors.initials: M
authors.lastname: Hauptmann
authors.affiliation: Department of Epidemiology and Biostatistics, the Netherlands Cancer Institute, Amsterdam, the Netherlands.
authors.forename: Matti A
authors.initials: MA
authors.lastname: Rookus
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 and Biostatistics, the Netherlands Cancer Institute, Amsterdam, the Netherlands.
authors.forename: Flora E
authors.initials: FE
authors.lastname: van Leeuwen
mesh_terms: D000328:Adult; D001943:Breast Neoplasms / Q000453:epidemiology*; D015331:Cohort Studies; D005260:Female; D005307:Fertilization in Vitro / Q000009:adverse effects*; D006801:Humans; D015994:Incidence; D008875:Middle Aged; D009426:Netherlands / Q000453:epidemiology; D010062:Ovulation Induction / Q000009:adverse effects*; D012042:Registries / Q000706:statistics & numerical data; D012307:Risk Factors