title: Tubal ligation and risk of ovarian cancer subtypes: a pooled analysis of case-control studies.
abstract: BACKGROUND
  Tubal ligation is a protective factor for ovarian cancer, but it is unknown whether this protection extends to all invasive histological subtypes or borderline tumors. We undertook an international collaborative study to examine the association between tubal ligation and ovarian cancer subtypes.
  
  
  METHODS
  We pooled primary data from 13 population-based case-control studies, including 10,157 patients with ovarian cancer (7942 invasive; 2215 borderline) and 13,904 control women. Invasive cases were analysed by histological type, grade and stage, and borderline cases were analysed by histological type. Pooled odds ratios were estimated using conditional logistic regression to match on site, race/ethnicity and age categories, and to adjust for age, oral contraceptive use duration and number of full-term births.
  
  
  RESULTS
  Tubal ligation was associated with significantly reduced risks of invasive serous (OR, 0.81; 95% CI, 0.74-0.89; P < 0.001), endometrioid (OR, 0.48; 95% CI, 0.40-0.59; P < 0.001), clear cell (OR, 0.52; 95% CI, 0.40-0.67; P < 0.001) and mucinous (OR, 0.68; 95% CI, 0.52-0.89; P = 0.005) cancers. The magnitude of risk reduction was significantly greater for invasive endometrioid (P < 0.0001) and clear cell (P = 0.0018) than for serous cancer. No significant associations were found with borderline serous or mucinous tumours.
  
  
  CONCLUSIONS
  We found that the protective effects of tubal ligation on ovarian cancer risk were subtype-specific. These findings provide insights into distinct aetiologies of ovarian cancer subtypes and mechanisms underlying the protective effects of tubal ligation.
authors.affiliation: Department of Health Research and Policy, Stanford University, Stanford, CA 94305-5405, USA. wsieh@stanford.edu
authors.forename: Weiva
authors.initials: W
authors.lastname: Sieh
authors.forename: Shannon
authors.initials: S
authors.lastname: Salvador
authors.forename: Valerie
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authors.lastname: McGuire
authors.forename: Rachel Palmieri
authors.initials: RP
authors.lastname: Weber
authors.forename: Kathryn L
authors.initials: KL
authors.lastname: Terry
authors.forename: Mary Anne
authors.initials: MA
authors.lastname: Rossing
authors.forename: Harvey
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authors.lastname: Risch
authors.forename: Anna H
authors.initials: AH
authors.lastname: Wu
authors.forename: Penelope M
authors.initials: PM
authors.lastname: Webb
authors.forename: Kirsten
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authors.lastname: Moysich
authors.forename: Jennifer A
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authors.lastname: Doherty
authors.forename: Anna
authors.initials: A
authors.lastname: Felberg
authors.forename: Dianne
authors.initials: D
authors.lastname: Miller
authors.forename: Susan J
authors.initials: SJ
authors.lastname: Jordan
authors.forename: Marc T
authors.initials: MT
authors.lastname: Goodman
authors.forename: Galina
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authors.lastname: Lurie
authors.forename: Jenny
authors.initials: J
authors.lastname: Chang-Claude
authors.forename: Anja
authors.initials: A
authors.lastname: Rudolph
authors.forename: Susanne Krüger
authors.initials: SK
authors.lastname: Kjær
authors.forename: Allan
authors.initials: A
authors.lastname: Jensen
authors.forename: Estrid
authors.initials: E
authors.lastname: Høgdall
authors.forename: Elisa V
authors.initials: EV
authors.lastname: Bandera
authors.forename: Sara H
authors.initials: SH
authors.lastname: Olson
authors.forename: Melony G
authors.initials: MG
authors.lastname: King
authors.forename: Lorna
authors.initials: L
authors.lastname: Rodriguez-Rodriguez
authors.forename: Lambertus A
authors.initials: LA
authors.lastname: Kiemeney
authors.forename: Tamara
authors.initials: T
authors.lastname: Marees
authors.forename: Leon F
authors.initials: LF
authors.lastname: Massuger
authors.forename: Anne M
authors.initials: AM
authors.lastname: van Altena
authors.forename: Roberta B
authors.initials: RB
authors.lastname: Ness
authors.forename: Daniel W
authors.initials: DW
authors.lastname: Cramer
authors.forename: Malcolm C
authors.initials: MC
authors.lastname: Pike
authors.forename: Celeste Leigh
authors.initials: CL
authors.lastname: Pearce
authors.forename: Andrew
authors.initials: A
authors.lastname: Berchuck
authors.forename: Joellen M
authors.initials: JM
authors.lastname: Schildkraut
authors.forename: Alice S
authors.initials: AS
authors.lastname: Whittemore
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D016022:Case-Control Studies; D005260:Female; D006801:Humans; D016015:Logistic Models; D008875:Middle Aged; D016017:Odds Ratio; D010051:Ovarian Neoplasms / Q000145:classification / Q000209:etiology / Q000473:pathology*; D012042:Registries; D012307:Risk Factors; D013246:Sterilization, Tubal / Q000009:adverse effects*; D055815:Young Adult