Risk of Ovarian Cancer in Relation to Estrogen and Progestin Dose and Use Characteristics of Oral Contraceptives. SHARE Study Group. Steroid Hormones and Reproductions

Reviewers: Li Liu, MD
Source: American Journal of Epidemiology, Volume 152:233-241, (August) 2000

Précis: Low-dose oral contraceptives appeared to be effective in reducing ovarian cancer risk

Introduction

The risk of ovarian cancer can be reduced by 50% or more in unselected women with long-term use of oral contraceptives (Am J Epidemiol 1992 Nov 15;136(10):1184-203). An oral contraceptive agent is appealing as a possible preventive treatment, because these agents are well tolerated and their side effects are known. In this study, the researchers assessed the risk of ovarian cancer in women taking the newer, lower-dose preparations of estrogen and progestin.

Method

The oral contraceptive use of 767 women who were diagnosed with epithelial ovarian cancer was compared with that of 1,367 age-matched control subjects. Subjects? ages ranged between 20 and 89 years.

Results

• An approximately 40% reduction in risk of ovarian cancer was found among oral contraceptive users.
• Risk reduction by oral contraceptive use continued for 30 or more years after use had stopped.
• Lower-dose preparations of estrogen and progestin were just as effective as higher-dose ones in the risk reduction of ovarian cancer.

Discussion

In this study, low-estrogen/low-progestin pills appeared to lower the risk of developing ovarian cancer to the same extent as higher dose pills used prior to 1972. It is important to know that oral contraceptive use has been associated with a small increase in the risk of breast cancer (J Natl Cancer Inst 1995 Jun 7;87(11):827-35). Patients should discuss with their physicians before they take oral contraceptives.