FAQ About CA-125

Is there a method of early detection, or a way to screen for ovarian cancer?
At this time, no. No studies have shown that currently available tools or approaches are effective at preventing women from dying from ovarian cancer. MOCA is currently funding research that is focused on finding an early detection test for ovarian cancer.

What is CA-125?
CA-125, which stands for “Cancer Antigen 125,” is a protein that is found in high amounts in the blood of many, but not all, patients with ovarian cancer.  A test that determines how much CA-125 is in the blood is among the blood tests that may be ordered by a doctor if ovarian cancer is suspected.

How is the CA-125 test used?
Doctors frequently order a CA-125 test when they are concerned that a woman may have ovarian cancer. The test is also used to monitor a woman’s response to treatment. CA-125 (along with CT scans) is also frequently used to monitor for recurrence.

Can CA-125 be used to screen asymptomatic, average-risk women for ovarian cancer?
While it is sometimes used that way, there is no evidence to suggest that doing so is beneficial. The CA-125 test is most accurate in postmenopausal women with a pelvic mass. It is also important to note that in about 20 percent of cases of advanced stage disease, and 50 percent of cases of early stage disease, the CA-125 is NOT elevated, even though there is ovarian cancer present. Because CA-125 can be elevated by benign conditions, such as diverticulitis, endometriosis, liver cirrhosis, pregnancy, and uterine fibroids, the National Cancer Institute and the United States Preventive Services Task Force do not endorse it to screen women for ovarian cancer who are at ordinary risk or in the general population.

Does an elevated CA-125 level always indicate that ovarian cancer is present?
Not always. Although a CA-125 blood test can be a useful tool for the diagnosis of ovarian cancer, it is not uncommon for a CA-125 count to be elevated in premenopausal women due to benign conditions unrelated to ovarian cancer. As a result, the CA-125 is generally only one of several tools used to diagnose ovarian cancer in a patient with a pelvic mass or other suspicious clinical findings.

If there are no reliable screening tools, how is ovarian cancer diagnosed?
Once a physician suspects a woman has ovarian cancer (usually after a CA-125 test, ultrasound and other tests), an exploratory surgical procedure called laparotomy is generally required for the definitive diagnosis of ovarian cancer.

During this procedure, cysts or other suspicious areas must be removed and biopsied. After the incision is made, the surgeon assesses the fluid and cells in the abdominal cavity. If the lesion is cancerous, the surgeon continues with a process called surgical staging to ascertain how far the cancer has spread. In select cases aspiration of ascites because of metastatic lesion or laparoscopy is used to confirm the diagnosis.

Why don’t doctors give women a CA-125 test and transvaginal ultrasound each year? Isn’t an imperfect screening tool better than nothing?
Studies have found that screening women at average risk of ovarian cancer did not improve the women’s odds of surviving ovarian cancer – and actually put them at greater risk due to complications from unnecessary surgeries.

More than 78,000 women were randomized between normal care and screening arms. The screening protocol involved annual CA-125 testing for six years and a transvaginal ultrasound for four years. The study was designed to show the effect of screening on overall survival by following patients for 13 years. The study showed that more women were diagnosed in the screening arm, but more women died of ovarian cancer in the screening arm.

Additionally, more than 3,000 women had surgery based on false positive results, leading to more than 160 women with serious complications. This study showed that screening with this protocol did not reduce ovarian cancer mortality.

More recent studies have also been disappointing. A large study published in Dec. 2015, showed that a more sophisticated approach, using multiple CA-125 values taken over many years, combined with other factors and using an algorithm called ROCA, also failed to prevent women from dying from ovarian cancer. Read more on this here.

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