Cancer risk among users of oral contraceptives: cohort data from the Royal College of General Practitioner's oral contraception study
Top Cited Papers
- 11 September 2007
- Vol. 335 (7621), 651
- https://doi.org/10.1136/bmj.39289.649410.55
Abstract
To examine the absolute risks or benefits on cancer associated with oral contraception, using incident data. Inception cohort study. Royal College of General Practitioners' oral contraception study. Directly standardised data from the Royal College of General Practitioners' oral contraception study. Adjusted relative risks between never and ever users of oral contraceptives for different types of cancer, main gynaecological cancers combined, and any cancer. Standardisation variables were age, smoking, parity, social class, and (for the general practitioner observation dataset) hormone replacement therapy. Subgroup analyses examined whether the relative risks changed with user characteristics, duration of oral contraception usage, and time since last use of oral contraception. The main dataset contained about 339,000 woman years of observation for never users and 744,000 woman years for ever users. Compared with never users ever users had statistically significant lower rates of cancers of the large bowel or rectum, uterine body, and ovaries, tumours of unknown site, and other malignancies; main gynaecological cancers combined; and any cancer. The relative risk for any cancer in the smaller general practitioner observation dataset was not significantly reduced. Statistically significant trends of increasing risk of cervical and central nervous system or pituitary cancer, and decreasing risk of uterine body and ovarian malignancies, were seen with increasing duration of oral contraceptive use. Reduced relative risk estimates were observed for ovarian and uterine body cancer many years after stopping oral contraception, although some were not statistically significant. The estimated absolute rate reduction of any cancer among ever users was 45 or 10 per 100,000 woman years, depending on whether the main or general practitioner observation dataset was used. In this UK cohort, oral contraception was not associated with an overall increased risk of cancer; indeed it may even produce a net public health gain. The balance of cancer risks and benefits, however, may vary internationally, depending on patterns of oral contraception usage and the incidence of different cancers.Keywords
This publication has 15 references indexed in Scilit:
- Oral contraceptive use and cancer. Findings in a large cohort study, 1968–2004British Journal of Cancer, 2006
- Carcinogenicity of combined oestrogen-progestagen contraceptives and menopausal treatmentThe Lancet Oncology, 2005
- Long term effects of hysterectomy on mortality: nested cohort studyBMJ, 2005
- [Use of oral contraceptives and risk of cancer, a cohort study].2003
- How complete and accurate are cancer registrations notified by the National Health Service Central Register for England and Wales?Journal of Epidemiology and Community Health, 2001
- Oral contraceptives and colorectal cancer risk: a meta-analysisBritish Journal of Cancer, 2001
- Oral Contraceptives and CancerDrug Safety, 2001
- Effects of changes in smoking status on risk estimates for myocardial infarction among women recruited for the Royal College of General Practitioners' Oral Contraception Study in the UKJournal of Epidemiology and Community Health, 1998
- Breast cancer and hormonal contraceptives: collaborative reanalysis of individual data on 53 297 women with breast cancer and 100 239 women without breast cancer from 54 epidemiological studiesThe Lancet, 1996
- ORAL CONTRACEPTIVE USE AND MALIGNANCIES OF THE GENITAL TRACTThe Lancet, 1988