title: Long-term effects of oral contraceptives on ovarian cancer risk.
abstract: Several epidemiologic studies have reported a protective effect of oral contraceptives (OCs) on ovarian cancer. However, there remain open issues, including better quantification of time-related factors such as time since last use, age at first use and time since first use. We performed a collaborative reanalysis of 6 case-control studies conducted between 1978 and 1999 in the United Kingdom, Greece and Italy, including a total of 2,768 incident, histologically confirmed cases of epithelial ovarian cancer and 6,274 hospital controls under age 70 years. A reduced risk of ovarian cancer was found for ever- compared to never-users [odds ratio (OR) = 0.66, 95% confidence interval (CI) 0.56-0.79], and a stronger reduction was observed for women who had used OCs for > or =5 years (OR = 0.50, 95% CI 0.33-0.76) compared to those who had used them for <5 years. The protective effect of OCs on ovarian cancer was consistent across strata of age, parity, menopausal status and family history of breast or ovarian cancer. After allowance for duration of use, no other time factor was related to ovarian cancer risk: the reduced risk was similar for women who stopped OC use > or =20 years before compared to <10 years; likewise, no significant modification of risk reduction was observed for age at first OC use and time since first OC use. The present analysis indicates that, after taking into account duration of OC use, the OC protection from ovarian cancer persists for a long time after stopping use.
authors.affiliation: Istituto di Ricerche Farmacologiche Mario Negri, Via Eritrea 62, 20157 Milan, Italy. bosetti@marionegri.it
authors.forename: Cristina
authors.initials: C
authors.lastname: Bosetti
authors.forename: Eva
authors.initials: E
authors.lastname: Negri
authors.forename: Dimitrios
authors.initials: D
authors.lastname: Trichopoulos
authors.forename: Silvia
authors.initials: S
authors.lastname: Franceschi
authors.forename: Valerie
authors.initials: V
authors.lastname: Beral
authors.forename: Anastasia
authors.initials: A
authors.lastname: Tzonou
authors.forename: Fabio
authors.initials: F
authors.lastname: Parazzini
authors.forename: Stefano
authors.initials: S
authors.lastname: Greggi
authors.forename: Carlo
authors.initials: C
authors.lastname: La Vecchia
mesh_terms: D000328:Adult; D000368:Aged; D016022:Case-Control Studies; D003276:Contraceptives, Oral / Q000627:therapeutic use*; D005260:Female; D006801:Humans; D008875:Middle Aged; D016017:Odds Ratio; D010051:Ovarian Neoplasms / Q000188:drug therapy* / Q000517:prevention & control*; D010298:Parity; D012306:Risk; D013997:Time Factors
chemical_list: D003276:Contraceptives, Oral