On Screening for Ovarian Cancer
By Jean Talbert, M.D.
Cancer has been reported as the top health concern of many women and ovarian cancer is particularly frightening. Early symptoms of the disease are often quite subtle and generally by the time it is diagnosed it has spread to other organs. It is the leading cause of death among the gynecologic malignancies. Cure rates are approximately 90 percent when diagnosed early while the disease is confined to the ovary. But this drops to 10-20 percent once metastases have occurred. Fortunately, the lifetime risk of developing ovarian cancer is low, only 1.8 percent.
An ideal screening test should detect early disease, have a low false positive rate, and be relatively inexpensive so large numbers of people can be screened.
Pap smears, which detect the precursors to cervical cancer, have dramatically decreased the risk of dying from this form of cancer. But, unfortunately, we do not yet have a good screening test for ovarian cancer.
The blood test, CA 125, has not been shown to be an effective screen for women at average risk of ovarian cancer. This test is very nonspecific and results can be elevated by common benign conditions such as uterine fibroids, endometriosis, pelvic inflammatory disease, liver disease and menstruation. The test is a little more specific in postmenopausal women, but the false positive rate remains high. In addition, CA 125 often does not detect disease before it has spread.
Still, CA 125 is currently most useful to monitor the effect of treatment in women already diagnosed with ovarian cancer or to detect recurrent disease. Researchers are actively seeking a tumor marker that would pick up ovarian cancer while it is still confined to the ovary.
Transvaginal ultrasound also has been proposed as a potential screening test. Ultrasound can pick up small abnormalities in the size, shape and texture of the ovary that might indicate early disease. Persistent abnormalities generally need to be evaluated surgically. As only one percent of suspicious abnormalities actually turn out to be ovarian cancer, routine screening with ultrasound would subject many asymptomatic women to the risks of surgery.
Although these tests are not perfect, combined screening with CA 125 and transvaginal ultrasound currently is recommended for women at high risk, especially those with a family history of breast or ovarian cancer. A family history of ovarian cancer in one first or second-degree relative increases the risk of developing the disease threefold. Genetic testing for the BRCA gene is indicated if there are multiple affected family members, if an affected family member was diagnosed before age 50, or if the family is of Ashkenazi Jewish heritage.
This gene is rare—less than 1:3000 in the general population—but occurs in about two percent of American Jewish women. Women who carry a BRCA gene have a 25-50 percent probability of developing ovarian cancer in their lifetime as well as an increased risk of breast cancer. Women who test positive may elect to undergo surgical removal of their ovaries when they have completed childbearing and/or reach age 35. This effectively lowers the risk of ovarian cancer by 95 percent and the risk of breast cancer by half.
Women who do not test positive or who do not have a family history may be able to lower their risk of developing ovarian cancer with the choices that they make during their reproductive years. Pregnancies and breastfeeding lower the risk. Oral contraceptives lower the risk by 10-12 percent after one year of use and 50 percent after five years in average risk women.
It is not known if oral contraceptives are beneficial in women who carry a BRCA gene.
Tubal ligation and hysterectomy, even without removal of the ovaries, also decrease risk. Currently, the U.S. Preventive Services Task Force recommends screening all women for ovarian cancer by taking a detailed family history and performing an annual pelvic exam. Symptoms, such as abdominal bloating, pelvic and abdominal pain, change in bowel habits or abnormal vaginal bleeding or discharge should be reported to health care providers promptly so that appropriate diagnostic tests can be performed. Although we may never be able to eliminate the occurrence of ovarian cancer, we hope, in the near future, to have a screening test that will detect early disease and give us the best chance of achieving a cure.
(Dr. Talbert is a board certified OB/GYN specialist practicing with Cape Obstetrics, Midwifery & Gynecology in Falmouth and Sandwich, 508-457-0088.)