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Cancer risk among users of oral contraceptives: cohort data from the Royal College of General Practitioner's oral contraception study.
BMJ. 2007 Sep 29; 335(7621):651.BMJ

Abstract

OBJECTIVE

To examine the absolute risks or benefits on cancer associated with oral contraception, using incident data.

DESIGN

Inception cohort study.

SETTING

Royal College of General Practitioners' oral contraception study.

PARTICIPANTS

Directly standardised data from the Royal College of General Practitioners' oral contraception study.

MAIN OUTCOME MEASURES

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.

RESULTS

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.

CONCLUSION

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.

Authors+Show Affiliations

Department of General Practice and Primary Care, University of Aberdeen, Aberdeen AB25 2AY. p.hannaford@abdn.ac.ukNo affiliation info availableNo affiliation info availableNo affiliation info availableNo affiliation info availableNo affiliation info available

Pub Type(s)

Journal Article
Multicenter Study
Research Support, Non-U.S. Gov't

Language

eng

PubMed ID

17855280

Citation

Hannaford, Philip C., et al. "Cancer Risk Among Users of Oral Contraceptives: Cohort Data From the Royal College of General Practitioner's Oral Contraception Study." BMJ (Clinical Research Ed.), vol. 335, no. 7621, 2007, p. 651.
Hannaford PC, Selvaraj S, Elliott AM, et al. Cancer risk among users of oral contraceptives: cohort data from the Royal College of General Practitioner's oral contraception study. BMJ. 2007;335(7621):651.
Hannaford, P. C., Selvaraj, S., Elliott, A. M., Angus, V., Iversen, L., & Lee, A. J. (2007). Cancer risk among users of oral contraceptives: cohort data from the Royal College of General Practitioner's oral contraception study. BMJ (Clinical Research Ed.), 335(7621), 651.
Hannaford PC, et al. Cancer Risk Among Users of Oral Contraceptives: Cohort Data From the Royal College of General Practitioner's Oral Contraception Study. BMJ. 2007 Sep 29;335(7621):651. PubMed PMID: 17855280.
* Article titles in AMA citation format should be in sentence-case
TY - JOUR T1 - Cancer risk among users of oral contraceptives: cohort data from the Royal College of General Practitioner's oral contraception study. AU - Hannaford,Philip C, AU - Selvaraj,Sivasubramaniam, AU - Elliott,Alison M, AU - Angus,Valerie, AU - Iversen,Lisa, AU - Lee,Amanda J, Y1 - 2007/09/11/ PY - 2007/9/15/pubmed PY - 2007/10/16/medline PY - 2007/9/15/entrez SP - 651 EP - 651 JF - BMJ (Clinical research ed.) JO - BMJ VL - 335 IS - 7621 N2 - OBJECTIVE: To examine the absolute risks or benefits on cancer associated with oral contraception, using incident data. DESIGN: Inception cohort study. SETTING: Royal College of General Practitioners' oral contraception study. PARTICIPANTS: Directly standardised data from the Royal College of General Practitioners' oral contraception study. MAIN OUTCOME MEASURES: 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. RESULTS: 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. CONCLUSION: 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. SN - 1756-1833 UR - https://www.unboundmedicine.com/medline/citation/17855280/Cancer_risk_among_users_of_oral_contraceptives:_cohort_data_from_the_Royal_College_of_General_Practitioner's_oral_contraception_study_ L2 - http://www.bmj.com/cgi/pmidlookup?view=long&pmid=17855280 DB - PRIME DP - Unbound Medicine ER -