COMBINATION ORAL CONTRACEPTIVES: 40% ENDOMETRIAL CANCER RISK REDUCTION
COMBINATION ORAL CONTRACEPTIVES: 40% ENDOMETRIAL CANCER RISK REDUCTION was shown in a large epidemiologic case-control study published in the Feb. 13 Journal of the American Medical Association. The Centers for Disease Control (CDC) study, based on data from the Cancer and Steroid Hormone Study, "found women who had used combination OCs [oral contraceptives] for at least 12 months had an age-adjusted risk of developing endometrial cancer of 0.6 relative to those women who had never used OCs," CDC found. For those who used combination oral contraceptives for longer periods, risk was reduced further, the report states. The relative risk rate for women using combination oral contraceptives for two to 10 years varied between 0.3 and 0.4. The study also examined the relative risks of endometrial cancer for eight different oral contraceptive formulations. Rates were calculated only for formulations that at least six cases had used, and the study notes that cases and controls may have used additional combination oral contraceptives. With a relative risk of 0.2, oral contraceptives containing 50 ug ethinyl estradiol and 0.5 mg norgestrel were associated with the least risk of endometrial cancer, the study states. The highest relative risk was seen with a combination of 75 ug mestranol and 0.5 mg norethynodrel, which was quantified as having a 0.7 relative risk. The report comments that "no difference in effect of various combinations of estrogen and progestin was seen using 'milligram-months' (the composite, cumulative measure of estrogen/progestin dose and months of use)." All of the major oral contraceptive manufacturers, including Syntex, Ortho, Wyeth, Parke-Davis, Searle and Mead Johnson, market combination products. In addition to CDC, the study was supported by the National Institute of Child Health and Human Development and the National Cancer Institute. The study compares 433 women diagnosed with endometrial cancer, surveyed between Dec. 1, 1980 and Dec. 31, 1982, to 3191 random cancer-free controls. Cases and controls were drawn from Atlanta, Detroit, San Francisco, Seattle, and four Utah counties. Results from an earlier report, also based on the Cancer and Steroid Hormone Study, found no link between oral contraceptive use and increased risk of breast cancer ("The Pink Sheet" Aug. 18, T&G-7). The present report notes that its results support findings from eight other studies that found a similar decrease in endometrial cancer risk with oral contraceptive use.
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