Oral contraceptives, reproductive history and risk of colorectal cancer in the European Prospective Investigation into Cancer and Nutrition.
BACKGROUND
Oral contraceptive use and reproductive factors may initiate long-term changes to the hormonal milieu and thereby, possibly influence colorectal cancer risk.


METHODS
We examined the association of hormonal and reproductive factors with risk of colorectal cancer among 337,802 women in the European Prospective Investigation into Cancer and Nutrition, of whom 1878 developed colorectal cancer.


RESULTS
After stratification for center and age, and adjustment for body mass index, smoking, diabetes mellitus, physical activity and alcohol consumption, ever use of oral contraceptives was marginally inversely associated with colorectal cancer risk (hazard ratio (HR), 0.92; 95% confidence interval (CI), 0.83-1.02), although this association was stronger among post-menopausal women (HR, 0.84; 95% CI: 0.74-0.95). Duration of oral contraceptive use and reproductive factors, including age at menarche, age at menopause, type of menopause, ever having an abortion, parity, age at first full-term pregnancy and breastfeeding, were not associated with colorectal cancer risk.


CONCLUSIONS
Our findings provide limited support for a potential inverse association between oral contraceptives and colorectal cancer risk.
Cancer Epidemiology Unit, Nuffield Department of Clinical Medicine, University of Oxford, Richard Doll Building, Roosevelt Drive, OX3 7LF Oxford, UK. kostas.tsilidis@ceu.ox.ac.uk
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Tsilidis
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Allen
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Key
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Bakken
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Lund
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Berrino
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Fournier
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Olsen
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Bergmann
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Boeing
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Koumantaki
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Palli
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Tagliabue
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Panico
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Tumino
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Vineis
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Bueno-de-Mesquita
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van Duijnhoven
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Peeters
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González
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Barricarte
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Dorronsoro
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Borgquist
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Manjer
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Hallmans
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Khaw
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Norat
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Romaguera
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Riboli
D000328:Adult; D000368:Aged; D015179:Colorectal Neoplasms / Q000209:etiology*; D003276:Contraceptives, Oral / Q000009:adverse effects*; D005260:Female; D006801:Humans; D008875:Middle Aged; D011446:Prospective Studies; D012098:Reproduction; D012306:Risk
D003276:Contraceptives, Oral