Oral contraceptive use, reproductive history, and risk of epithelial ovarian cancer in women with and without endometriosis.
OBJECTIVE
Women with endometriosis may be at an increased risk of ovarian cancer. It is not known whether reproductive factors that reduce the risk of ovarian cancer in general also reduce risk in women with endometriosis. We investigated whether the odds ratios for ovarian cancer that were associated with oral contraceptive use, childbearing, hysterectomy, and tubal ligation differ among women with and without endometriosis.


METHODS
We pooled information on the self-reported history of endometriosis from 4 population-based case-controlled studies of incident epithelial ovarian cancer, comprising 2098 cases and 2953 control subjects. We obtained data on oral contraceptive use, childbearing, breastfeeding, gynecologic surgical procedures, and other reproductive factors on each woman. Multivariable unconditional logistic regression was used to calculate odds ratios and 95% CI for ovarian cancer among women with endometriosis compared with women without endometriosis. Similar methods were used to assess the frequencies of risk factors among women with and without endometriosis. Adjustments were made for age, parity, oral contraceptive use, tubal ligation, family history of ovarian cancer, and study site.


RESULTS
Women with endometriosis were at an increased risk of ovarian cancer (odds ratio, 1.32; 95% CI, 1.06-1.65). Using oral contraceptives, bearing children, and having a tubal ligation or hysterectomy were associated with a similar reduction in the odds ratios for ovarian cancer among women with and without endometriosis. In particular, the use of oral contraceptives for >10 years was associated with a substantial reduction in risk among women with endometriosis (odds ratio, 0.21; 95% CI, 0.08-0.58).


CONCLUSIONS
Women with endometriosis are at an increased risk of epithelial ovarian cancer. Long-term oral contraceptive use may provide substantial protection against the disease in this high-risk population.
Department of Epidemiology, Graduate School of Public Health, University of Pittsburgh, and University of Pittsburgh Cancer Institute, Pittsburgh, Pa 15261, USA. modugno+@pitt.edu
Francesmary
F
Modugno
Roberta B
RB
Ness
Glenn O
GO
Allen
Joellen M
JM
Schildkraut
Faith G
FG
Davis
Marc T
MT
Goodman
D000328:Adult; D000368:Aged; D016022:Case-Control Studies; D003276:Contraceptives, Oral / Q000008:administration & dosage*; D004715:Endometriosis / Q000150:complications*; D005260:Female; D006801:Humans; D007044:Hysterectomy; D016015:Logistic Models; D008875:Middle Aged; D016017:Odds Ratio; D010051:Ovarian Neoplasms / Q000453:epidemiology*; D011247:Pregnancy; D012098:Reproduction; D012307:Risk Factors; D013246:Sterilization, Tubal
D003276:Contraceptives, Oral