ORAL CONTRACEPTIVE USE DECREASES LONG-TERM RISK OF OVARIAN CANCER
ORAL CONTRACEPTIVE USE DECREASES LONG-TERM RISK OF OVARIAN CANCER regardless of later childbearing, a study incorporating data from 12 ovarian cancer studies concludes. "The longer you use the Pill, the more protected you are. Even women with no children who have used the Pill are protected -- they're every bit as protected by the Pill as women with children," study director Alice Whittemore, MD, Stanford University School of Medicine, explained. The Whittemore et al. study was conducted by investigators at 14 universities, hospitals and research institutions. Results of the study were released Jan. 13. They will be published in the upcoming American Journal of Epidemiology (backdated Nov. 15, 1992) under the title "Characteristics Relating to Ovarian Cancer Risk: Collaborative Analysis of Twelve U.S. Case-Control Studies. II. Invasive Epithelian Ovarian Cancer in White Women." Three other papers based on results from the collaborative study will appear in the journal, and the investigators plan to publish three additional papers. Data on 2,197 white ovarian cancer patients and 8,893 caucasian women used as controls were analyzed. The 12 studies were conducted between 1956 and 1986. Unlike a meta-analysis, the Whittemore et al. collaborative study took raw data from the 12 studies, reformatted and re-analyzed it. In the six hospital studies examined, for all women who used oral contraceptives there was an odds ratio of .70, or a 30% decreased risk of cancer. Oral contraceptive users had an odds ratio of .66 in the six population studies. Risk decreased with increased duration of use from the second to fifth year of use, with "little additional protection conferred...beyond six years," the study concludes. Study results also suggested a possible association between fertility-enhancing drugs and increased risk of ovarian cancer. Based on this finding, FDA announced in a Jan. 13 "Talk Paper" that it is asking drug manufacturers to add to the adverse reactions section of fertility drug labeling a statement indicating a "potential risk of ovarian cancer." In three studies containing data on fertility-enhancing drugs, women diagnosed as infertile who received fertility drugs used during the 1970s had almost three times the risk of ovarian cancer as those who did not have treatment. The increased risk was seen mainly among those who did not become pregnant after using the drugs; this group had a 27-fold increase in risk for cancer. However, the numbers in these groups are small and this finding is "really very tenuous," Whittemore stressed. No change in prescribing directions will be required and the drug labeling change will make no "conclusion about causality," FDA stressed. In addition to the results from the Whittemore et al. study, six cases of ovarian cancer have been reported to the agency as associated with fertility drugs. The National Cancer Institute said based on the information in the study, it could not recommend that physicians change their prescribing practices for fertility-enhancing drugs. "These findings are based on small numbers and, while they cause concern, further research is needed to confirm whether the drugs actually cause ovarian cancer and to identify the specific drugs and type of infertility that may be associated with the increase of risk," NCI noted. Ovarian cancer risk also decreases with each pregnancy and with duration of breast feeding, the study determined. "The current study supports the idea that something about pregnancy per se, whether it is ovulation suppression, gonadotropin suppression or another factor, is protective," Whittemore said. Tubal ligation and hysterectomy with ovarian conservation were also found to decrease risk for ovarian cancer. No "consistent trends" were seen between ovarian cancer incidence and age at menarche, age at menopause or duration of estrogen replacement therapy, the study abstract states. The collaborative study also found that ovarian cancer rates were lower among black women, even when it adjusted for differing pregnancy and breast feeding rates. Oral contraceptives and pregnancy afforded similar protection in white and black women. "This means that there are other unmeasured factors that we're not aware of that are making black women at lower risk. Genetic factors are a plausible explanation," Whittemore stated. Results from this portion of the study will be published in the Jan. 20 issue of the Journal of the National Cancer Institute.
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