Oral contraceptives and the risk of breast cancer.
BACKGROUND
It is uncertain whether the use of an oral contraceptive increases the risk of breast cancer later in life, when the incidence of breast cancer is increased. We conducted a population-based, case-control study to determine the risk of breast cancer among former and current users of oral contraceptives.


METHODS
We interviewed women who were 35 to 64 years old. A total of 4575 women with breast cancer and 4682 controls were interviewed. Conditional logistic regression was used to calculate odds ratios as estimates of the relative risk (incidence-density ratios) of breast cancer.


RESULTS
The relative risk was 1.0 (95 percent confidence interval, 0.8 to 1.3) for women who were currently using oral contraceptives and 0.9 (95 percent confidence interval, 0.8 to 1.0) for those who had previously used them. The relative risk did not increase consistently with longer periods of use or with higher doses of estrogen. The results were similar among white and black women. Use of oral contraceptives by women with a family history of breast cancer was not associated with an increased risk of breast cancer, nor was the initiation of oral-contraceptive use at a young age.


CONCLUSIONS
Among women from 35 to 64 years of age, current or former oral-contraceptive use was not associated with a significantly increased risk of breast cancer.
Marchbanks
Polly A
PA
Division of Reproductive Health, Centers for Disease Control and Prevention, Atlanta, USA.
McDonald
Jill A
JA
Wilson
Hoyt G
HG
Folger
Suzanne G
SG
Mandel
Michele G
MG
Daling
Janet R
JR
Bernstein
Leslie
L
Malone
Kathleen E
KE
Ursin
Giske
G
Strom
Brian L
BL
Norman
Sandra A
SA
Wingo
Phyllis A
PA
Burkman
Ronald T
RT
Berlin
Jesse A
JA
Simon
Michael S
MS
Spirtas
Robert
R
Weiss
Linda K
LK
D000328:Adult; D015992:Body Mass Index; D001943:Breast Neoplasms / Q000453:epidemiology* / Q000235:genetics; D016022:Case-Control Studies; D003276:Contraceptives, Oral / Q000009:adverse effects*; D005260:Female; D006801:Humans; D016015:Logistic Models; D008593:Menopause; D008875:Middle Aged; D012307:Risk Factors
D003276:Contraceptives, Oral