Fertility Drugs Not Associated With Increased Risk of Ovarian Cancer, Study Says
February 6, 2009
National Partnership for Women & Families
Fertility drugs do not significantly increase a woman's risk of ovarian cancer, although further study may be needed to determine whether the risk of such cancer increases with age, according to a study published Thursday in the British Medical Journal, the New York Times reports. For the study, researchers tracked 54,362 women who had been referred to fertility clinics in Denmark between 1963 and 1998. The researchers analyzed information about the women by examining birth, cancer and hospital discharge records. They then obtained more detailed information on medications and medical records for 1,241 women. According to the study's findings, 156 ovarian cancer cases occurred among the 54,362 women over a 15-year period. The average age of participants at the end of the study period was 47. According to the Times, the findings support other recent studies, which have "tempered an initial panic" that occurred in the 1990s when reports suggested a link between fertility drugs and ovarian cancer.
For the study, researchers analyzed medical records to determine the relative incidence of ovarian cancer among women who had taken specific fertility treatments -- including gonadotropins, clomifene citrate, human chorionic gonadotropin or a gonadotropin-releasing hormone -- compared with women who did not take those particular drugs but might have taken different medications. After adjusting for risk factors, the researchers found no link between the drugs and an increased ovarian cancer risk. In addition, they found no increased risk for women who underwent 10 or more treatment cycles or for those who never became pregnant despite taking fertility drugs. However, the study did not altogether rule out an ovarian cancer risk, according to the Times. The researchers found that women who took clomiphene citrate -- available under the brand name Clomid -- had a 67% increase in serious ovarian cancer tumors. The researchers noted that this finding could be an aberration. Allen Jensen, assistant professor of cancer epidemiology at the Danish Cancer Society and lead author of the paper, said the researchers found no significant differences in ovarian cancer risks among women who had used a fertility drug compared with women who took no drugs, but added that they did not include this finding in the study. The researchers also found no difference in cancer risk for women who took a combination of fertility treatments.
According to the Times, this type of research often is complex because infertile women generally have a higher risk of developing ovarian cancer than the overall population. Therefore, this study compared infertile women with each other rather than with women in the general population. In addition, because ovarian cancer is relatively rare, the study required a large sample size in order to obtain meaningful results. Louise Brinton, chief of the National Cancer Institute's hormonal and reproductive epidemiology branch, said the large participant group is a "major strength" of the study. According to the researchers, it might be necessary to continue tracking the study participants to determine whether the risk for ovarian cancer increases over time. The mean age for ovarian cancer diagnosis is 63, the Times reports.
According to Jensen, the study's findings "provide further evidence that fertility drugs do not increase the risk of ovarian cancer to any great extent." However, he added that women "should always balance a possible small increase in ovarian cancer risk with the physical and psychological benefits of pregnancy made possible only by use of these drugs." Brinton said she was surprised that the authors downplayed the possible association between serious ovarian cancer tumors and Clomid, which is one of the older fertility treatments. However, Roberta Ness -- dean of the University of Texas School of Public Health and author of an earlier study that found no link between cancer and fertility treatments -- said the finding about Clomid might not be significant. "When you're doing multiple analyses and splitting this way, that way and the other, the likelihood this is just a spurious finding is greater than the likelihood it's real," she said (Rabin, New York Times, 2/6).
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