Ovarian Cancer : Reduced Risk, Screening Test

by Food and Drug Administration (FDA)

(Page 2 of 5)

Reduced Risk

Factors associated with a reduced risk of ovarian cancer include: giving birth to more than one child, breast-feeding, tubal ligation (female sterilization), and use of birth control pills.

Evidence suggests that hormones may influence development of the disease. The risk of ovarian cancer is reduced in women who have had multiple pregnancies and in those who used birth control pills. The Cancer and Steroid Hormone Study by the national Centers for Disease Control and Prevention and the National Institute of Child Health and Human Services found that use of oral contraceptives for even a few months reduced the risk of ovarian cancer by 40 percent in women 20 to 54 years old.

The study, published in the March 12, 1987, New England Journal of Medicine, also found that the longer a woman used birth control pills, the lower her risk of ovarian cancer, and that the protective effect persisted long after stopping the pill. Based on these data, since 1989, the labeling for oral contraceptives has included decreased incidence of ovarian cancer among the noncontraceptive health benefits of the pill.

On the reverse side of the coin, in January 1993, FDA requested that drug firms revise fertility drug labels to include ovarian cancer as a potential adverse drug reaction. The action was in response to a report in the November 1992 issue of the American Journal of Epidemiology suggesting a possible relationship between use of fertility-enhancing drugs and ovarian cancer. The analysis was based on data from 12 studies comparing women with ovarian cancer to those without the disease. Only three of the studies, however, contained data on the use of fertility drugs and risk of ovarian cancer. (A 1987 article in the same journal reported no association between the drugs and ovarian cancer.)

FDA urged caution in interpreting the findings of the 1992 report because the analysis only included small numbers of women and because the article gave no information about the fertility drugs prescribed, reasons for the infertility, or tumor size or stage of disease at diagnosis.

Search for a Screening Test

According to the registry, if ovarian cancer is diagnosed while still confined to the ovaries, the chance for cure is 85 to 90 percent. According to the American Cancer Society, only 23 percent of all cases are diagnosed at this early stage. Among women whose cancer has spread beyond the ovary by the time it's diagnosed, only 20 to 25 percent survive five years. However, unlike cervical or breast cancer (which may be detected early by a Pap test or mammogram, respectively), ovarian cancer has no approved screening test, though some are under investigation.

"The traditional routine pelvic examination is largely ineffective for early detection," says Julie Beitz, M.D., a medical oncologist in FDA's division of oncology and pulmonary drug products. "Often you can't feel a normal-sized ovary. And even if you can, it's hard to tell if it's enlarged because ovaries vary in size from person to person and day to day. Ovarian cancers start very small, and by the time they're large enough to feel, the cancer is most likely already advanced." The problem with ovarian cancer, she says, is that "you have to detect very small changes, and these are hard to detect on a pelvic exam because it's a very indirect examination."

Researchers are working on developing an accurate test for the BRCA1 gene. The American Society of Human Genetics has recommended that testing for BRCA1 be limited to research in which subjects are members of families at high risk for either ovarian or breast cancer.

Researchers continue looking for tumor markers — substances that may appear in abnormal amounts in the blood or urine — that may prove useful in developing a screening test.

One such marker is CA 125, a substance in the blood that is elevated in patients with advanced ovarian tumors. Doctors now measure CA 125 levels in patients treated for advanced disease to determine if the tumor has shrunk or if disease has recurred. Its value in monitoring treatment prompted scientists to study its potential for early detection. Its use for screening, however, is investigational.

Transvaginal ultrasound is also being studied as a screening tool. With ultrasound, high-frequency sound waves are projected into the body, and the echoes produced are converted by computer into a picture. Unlike abdominal ultrasound, in which the sound wave-emitting device is placed on the outside of the belly, transvaginal ultrasound uses a probe placed in the vagina that can reach within millimeters of the ovaries, producing more detailed images.

"There is uncertainty as to the value of these tools as screening tests and their ultimate impact on mortality," says John Gohagan, Ph.D., chief of the National Cancer Institute's Early Detection Branch in the Division of Cancer Prevention and Control. NCI is conducting a clinical trial including 74,000 women aged 60 to 74 to clarify the issue. The trial is designed to assess the value of CA 125 and transvaginal ultrasound for early detection of ovarian cancer and to measure their impact on mortality.

Women in the trial are randomly assigned to either a screening group or a control group of 37,000 women each. The screening group will have periodic pelvic examinations along with CA 125 and transvaginal ultrasound tests. The control group will have routine medical care.

About the Author

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FDA is A United States government body that oversees medical devices, including contact lenses, intraocular lenses, excimer lasers and eyedrops. In the US, these products must be approved by the FDA before they can be marketed.