March 18, 2008
Myth Busters: The truth about the CA 125 test
Q.: I've been forwarded an e-mail that says a CA 125 test will detect ovarian cancer. Should I ask my doctor for an annual CA 125 blood test to check for early signs of the disease?
A.: The simple answer is no.
While women at risk for ovarian cancer may someday be screened with a blood test, the CA 125 test is too flawed for this purpose. It fails to detect ovarian cancer in some cases – 20 percent of ovarian tumors don't secrete the protein. In many others, it reads positive when cancer isn't present. That's because CA 125 isn't specific for ovarian cancer. Conditions such as fibroids, pelvic infections, liver disease, endometriosis (a condition in which uterine tissue grows in other areas of the pelvic region), menstruation, and even pregnancy can cause CA 125 levels to rise. The American Cancer Society (ACS) says the test "does not meet the standards" of accuracy to be useful for screening.
The notion that women should insist on yearly measurements of CA 125, a blood protein, has been promoted on the Internet by an ovarian cancer patient who had difficulty being diagnosed. The concern grows out of deep frustration among women, physicians, and medical researchers because of the many lives that could be saved if a screening test for early ovarian cancer existed.
Developed by Dana-Farber researchers in the 1980s, the CA 125 test does, however, have a role in managing the treatment of ovarian cancer. The rise and fall of CA 125 in the blood during chemotherapy or following surgery is a good indicator of the tumor's response to treatment, and can give warning of a recurrence. For that purpose, the ACS says, the blood test is as good as a much more expensive series of CT scans.
"Until a true early screening tool for ovarian cancer appears," says Ursula Matulonis, MD, director of Gynecologic Oncology at Dana-Farber, "women should be aware of new symptoms, including pelvic or abdominal discomfort or pain, changes in bowel habits, such as a new onset of diarrhea and/or constipation, bloating of the abdomen, or feeling unusually full after eating. If any of these symptoms persist for more than a few weeks, women should make an appointment to see their doctor."
The ACS adds that women should watch out for increased abdominal size and urinary frequency or urgency. Also, it is important to know your family history and ancestry. Women of Ashkenazi Jewish descent are at higher risk of carrying a gene that can cause an increased risk of breast and/or ovarian cancer. Women with close relatives who have ovarian cancer may be more cancer prone, even if they don't carry a mutated gene. These women should consider entering a screening program testing new ways to detect ovarian cancer.
— Dawn Stapleton
dawn_stapleton@dfci.harvard.edu
