Progestin in oral contraceptives associated with lower risk of ovarian cancer

Oral contraceptives — better known as birth control pills — that contain high levels of progestin are associated with a lower risk of ovarian cancer than oral contraceptives with low progestin content, report Joellen M. Schildkraut, Ph.D., of Duke University Medical Center, and colleagues. Their findings appear in the Jan. 2 issue of the Journal of the National Cancer Institute.

Past studies have suggested that using oral contraceptives for 3 or more years may be associated with a 30% to 50% lower risk of developing ovarian cancer. One study suggested that the level of decreased risk depended on the contraceptive’s concentrations of estrogen and progestin. However, the exact relationship between hormone concentration and ovarian cancer risk remained unclear. In the new study, Schildkraut and colleagues analyzed oral contraceptive use among 390 women between the ages of 20 and 54 years who had been diagnosed with epithelial ovarian cancer. These women were identified from the Cancer and Steroid Hormone Study, in which researchers looked at ovarian cancer risk in women taking oral contraceptives for 3 or more consecutive months.

The authors separated the women into four categories depending on the formulations of contraceptives they used: high progestin/high estrogen, high progestin/low estrogen, low progestin/high estrogen, and low progestin/low estrogen.

Compared with women who took high progestin/high estrogen contraceptives, women taking low progestin/high estrogen contraceptives were more than twice as likely to develop ovarian cancer, women taking low progestin/low estrogen contraceptives were 60% more likely to develop ovarian cancer, and women taking no contraceptives were nearly three times as likely to develop ovarian cancer. The authors report that the reduction in ovarian cancer risk appeared to be related to the concentration of progestin. The concentration of estrogen in the formulations did not appear to be related to ovarian cancer risk.

The authors note that the oral contraceptives they studied existed more than 20 years ago and that newer formulations of oral contraceptives are less potent, and therefore, may be less likely to reduce the risk of ovarian cancer.

Contact: Amy Austell, Duke University Medical Center, (919) 660-1303, fax: (919) 681-7353, amy.austell@duke.edu.

Schildkraut JM, Calingaert B, Marchbanks PA, Moorman PG, Rodruiguez GC. Impact of progestin and estrogen potency in oral contraceptives on ovarian cancer risk. J Natl Cancer Inst 2002;94:32–8.

Attribution to the Journal of the National Cancer Institute is requested in all news coverage.

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