title: Hormonal and reproductive factors and the risk of ovarian cancer.
abstract: OBJECTIVE
  Hormone-related factors have been associated with ovarian cancer, the strongest being parity and oral contraceptive use. Given reductions in birth rates and increases in oral contraceptive use over time, associations in more recent birth cohorts may differ. Furthermore, consideration of ovarian cancer heterogeneity (i.e., Type I/II invasive cancers) may contribute to a better understanding of etiology. We examined hormone-related factors in relation to ovarian cancer risk overall, for Type I and Type II cancers, as well as borderline tumors.
  
  
  METHODS
  A population-based case-control study was carried out in Montreal, Canada from 2011 to 2016, including 496 cases and 908 controls. For each hormone-related variable, adjusted odds ratios (OR) and 95% confidence intervals (CI) were estimated using logistic regression for ovarian cancer overall, and using polytomous logistic regression for associations by tumor behavior and ovarian cancer type.
  
  
  RESULTS
  Parity was inversely associated with risk overall and by tumor behavior and type, with a stronger OR (95% CI) for Type I [0.09 (0.04-0.24) for ≥3 full-term births vs. nulliparity] vs. Type II [0.66 (0.43-1.02)] invasive cancers; the OR (95% CI) for borderline tumors was 0.41 (0.22-0.77). Oral contraceptive ever use was not associated with risk overall, but ≥10 years of use vs. never use reduced risk, particularly for invasive cancers. A history of endometriosis was most strongly associated with Type I cancers. Associations with other factors were less clear.
  
  
  CONCLUSIONS
  These results suggest that associations with some hormone-related factors may differ between borderline and invasive Type I and II ovarian cancers.
authors.affiliation: Université de Montréal Hospital Research Centre (CRCHUM), 850 Saint-Denis Street, 2nd Floor, Montreal, QC, H2X 0A9, Canada. anita.koushik@umontreal.ca.|Department of Social and Preventive Medicine, Université de Montréal, Montreal, QC, Canada. anita.koushik@umontreal.ca.
authors.forename: Anita
authors.identifier: http://orcid.org/0000-0001-5304-7660
authors.initials: A
authors.lastname: Koushik
authors.affiliation: Université de Montréal Hospital Research Centre (CRCHUM), 850 Saint-Denis Street, 2nd Floor, Montreal, QC, H2X 0A9, Canada.|Department of Social and Preventive Medicine, Université de Montréal, Montreal, QC, Canada.
authors.forename: Anne
authors.initials: A
authors.lastname: Grundy
authors.affiliation: Department of Epidemiology, Biostatistics and Occupational Health, McGill University, Montreal, QC, Canada.|Division of Clinical Epidemiology, McGill University Health Centre (MUHC), Montreal, QC, Canada.
authors.forename: Michal
authors.initials: M
authors.lastname: Abrahamowicz
authors.affiliation: Department of Pathology, McGill University Health Centre, Montreal, QC, Canada.|Gynecologic Oncology Unit, McGill University Health Centre, Montreal, QC, Canada.
authors.forename: Jocelyne
authors.initials: J
authors.lastname: Arseneau
authors.affiliation: Gynecologic Oncology Unit, McGill University Health Centre, Montreal, QC, Canada.
authors.forename: Lucy
authors.initials: L
authors.lastname: Gilbert
authors.affiliation: Gynecologic Oncology and Colposcopy, Sir Mortimer B. Davis-Jewish General Hospital, Montreal, QC, Canada.
authors.forename: Walter H
authors.initials: WH
authors.lastname: Gotlieb
authors.affiliation: Université de Montréal Hospital Research Centre (CRCHUM), 850 Saint-Denis Street, 2nd Floor, Montreal, QC, H2X 0A9, Canada.
authors.forename: Julie
authors.initials: J
authors.lastname: Lacaille
authors.affiliation: Université de Montréal Hospital Research Centre (CRCHUM), 850 Saint-Denis Street, 2nd Floor, Montreal, QC, H2X 0A9, Canada.|Department of Medicine, Université de Montréal, Montreal, QC, Canada.
authors.forename: Anne-Marie
authors.initials: AM
authors.lastname: Mes-Masson
authors.affiliation: Université de Montréal Hospital Research Centre (CRCHUM), 850 Saint-Denis Street, 2nd Floor, Montreal, QC, H2X 0A9, Canada.|Department of Social and Preventive Medicine, Université de Montréal, Montreal, QC, Canada.|INRS-Institut Armand-Frappier, University of Quebec, Laval, QC, Canada.
authors.forename: Marie-Élise
authors.initials: MÉ
authors.lastname: Parent
authors.affiliation: Université de Montréal Hospital Research Centre (CRCHUM), 850 Saint-Denis Street, 2nd Floor, Montreal, QC, H2X 0A9, Canada.|Division of Gynecologic Oncology, Department of Obstetrics and Gynecology, Centre hospitalier de l'Université de Montréal, Montreal, QC, Canada.
authors.forename: Diane M
authors.initials: DM
authors.lastname: Provencher
authors.affiliation: Université de Montréal Hospital Research Centre (CRCHUM), 850 Saint-Denis Street, 2nd Floor, Montreal, QC, H2X 0A9, Canada.
authors.forename: Lesley
authors.initials: L
authors.lastname: Richardson
authors.affiliation: Université de Montréal Hospital Research Centre (CRCHUM), 850 Saint-Denis Street, 2nd Floor, Montreal, QC, H2X 0A9, Canada.|Department of Social and Preventive Medicine, Université de Montréal, Montreal, QC, Canada.
authors.forename: Jack
authors.initials: J
authors.lastname: Siemiatycki
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D002170:Canada; D016022:Case-Control Studies; D002648:Child; D003276:Contraceptives, Oral / Q000009:adverse effects*; D005260:Female; D006801:Humans; D008875:Middle Aged; D010051:Ovarian Neoplasms / Q000453:epidemiology / Q000209:etiology*; D010298:Parity; D011247:Pregnancy; D015995:Prevalence; D017584:Reproductive History; D012307:Risk Factors; D055815:Young Adult
chemical_list: D003276:Contraceptives, Oral
keywords: Case–control study; Hormones; Ovarian cancer; Reproductive factors; Type I/II