title: Cervical cancer and hormonal contraceptives: collaborative reanalysis of individual data for 16,573 women with cervical cancer and 35,509 women without cervical cancer from 24 epidemiological studies.
abstract: BACKGROUND
  Combined oral contraceptives are classified by the International Agency for Research on Cancer as a cause of cervical cancer. As the incidence of cervical cancer increases with age, the public-health implications of this association depend largely on the persistence of effects long after use of oral contraceptives has ceased. Information from 24 studies worldwide is pooled here to investigate the association between cervical carcinoma and pattern of oral contraceptive use.
  
  
  METHODS
  Individual data for 16,573 women with cervical cancer and 35,509 without cervical cancer were reanalysed centrally. Relative risks of cervical cancer were estimated by conditional logistic regression, stratifying by study, age, number of sexual partners, age at first intercourse, parity, smoking, and screening.
  
  
  RESULTS
  Among current users of oral contraceptives the risk of invasive cervical cancer increased with increasing duration of use (relative risk for 5 or more years' use versus never use, 1.90 [95% CI 1.69-2.13]). The risk declined after use ceased, and by 10 or more years had returned to that of never users. A similar pattern of risk was seen both for invasive and in-situ cancer, and in women who tested positive for high-risk human papillomavirus. Relative risk did not vary substantially between women with different characteristics.
  
  
  CONCLUSIONS
  The relative risk of cervical cancer is increased in current users of oral contraceptives and declines after use ceases. 10 years' use of oral contraceptives from around age 20 to 30 years is estimated to increase the cumulative incidence of invasive cervical cancer by age 50 from 7.3 to 8.3 per 1000 in less developed countries and from 3.8 to 4.5 per 1000 in more developed countries.
authors.affiliation: Cancer Research UK Epidemiology Unit, Oxford, UK.
authors.forename: Paul
authors.initials: P
authors.lastname: Appleby
authors.forename: Valerie
authors.initials: V
authors.lastname: Beral
authors.forename: Amy
authors.initials: A
authors.lastname: Berrington de González
authors.forename: Didier
authors.initials: D
authors.lastname: Colin
authors.forename: Silvia
authors.initials: S
authors.lastname: Franceschi
authors.forename: Adrian
authors.initials: A
authors.lastname: Goodhill
authors.forename: Jane
authors.initials: J
authors.lastname: Green
authors.forename: Julian
authors.initials: J
authors.lastname: Peto
authors.forename: Martyn
authors.initials: M
authors.lastname: Plummer
authors.forename: Siân
authors.initials: S
authors.lastname: Sweetland
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D003277:Contraceptives, Oral, Combined / Q000009:adverse effects*; D005260:Female; D006801:Humans; D015994:Incidence; D008875:Middle Aged; D030361:Papillomavirus Infections / Q000150:complications; D012306:Risk; D013997:Time Factors; D002583:Uterine Cervical Neoplasms / Q000453:epidemiology* / Q000209:etiology / Q000821:virology; D002578:Uterine Cervical Dysplasia / Q000139:chemically induced / Q000150:complications / Q000453:epidemiology*
chemical_list: D003277:Contraceptives, Oral, Combined