General Obstetrics and Gynecology: Gynecology
Oral contraceptive use, reproductive history, and risk of epithelial ovarian cancer in women with and without endometriosis

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Abstract

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.

Study design

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).

Conclusion

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.

Section snippets

Subjects

We pooled data on the history of endometriosis from 4 population-based, ovarian cancer case-controlled studies that recruited women from 4 regions of the United States from 1993 through 2001. Cases for the analyses represent women with ovarian cancer who participated in 1 of these 4 studies. Control subjects in our analyses are women without ovarian cancer who served as control subjects in the original studies. Specific descriptions of each study's methods are provided in the original

Results

Of the 2098 cases and 2953 control subjects, 177 cases (8.5%) and 184 control subjects (6.3%) reported a history of endometriosis. After adjustments were made for study site, OC duration, parity, age, tubal ligation, and family history of ovarian cancer, we found that women with endometriosis were more likely to have ovarian cancer than women without a history of the disease (adjusted OR, 1.32; 95% CI, 1.06-1.65). The association was greater for nulliparous women (adjusted OR, 1.75; 95% CI,

Comment

In this pooled analysis, the occurrence of ovarian cancer was a significant 30% higher among women who reported a history of endometriosis compared with those women who reported no such history. This association was greater in nulliparous women, which confirms that the association is likely due to the endometriosis and not the infertility or decreased parity caused by the endometriosis.16 Using oral contraceptives, bearing children, and having a tubal ligation reduced the risk of ovarian

Acknowledgements

We thank Dr Anna Wu for data collection in Los Angeles, Randi Koenig for her help with the manuscript, and Dr Jeffrey L. Eppinger for his help with this work.

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  • Cited by (0)

    Supported in part by the National Cancer Institute grants K07-CA80668 (F.M.), R01CA61095 (R.B.N), R01-CA-58598 (M.T.G), N01-CN-67001 (M.T.G), R01-CA61093 (F.G.D.) and RO1 CA76016 (J.M.S.).

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