Ovarian cancer screening: is there a test, and what CA-125 and ultrasound can show
There is no recommended screening test for ovarian cancer for women without symptoms who are not at high risk. The two tests studied, a transvaginal ultrasound and the CA-125 blood test, have not been shown to lower deaths from ovarian cancer. (USPSTF, 2018)(ACS)
Is there a screening test?
- Women without symptoms: the USPSTF recommends against screening for ovarian cancer (grade D, 2018). It applies to women without symptoms who are not known to have a high-risk hereditary cancer syndrome. (USPSTF, 2018)
- Why: it found adequate evidence that screening with transvaginal ultrasound, CA-125 or both does not reduce deaths from ovarian cancer, and that it can cause important harms, including many false positives that can lead to unnecessary surgery in women who do not have cancer. (USPSTF, 2018)
- Other groups: ACOG says there is currently no screening test for ovarian cancer, and that tests marketed to consumers as ovarian cancer screening are not accurate, not reliable for women without symptoms, not approved by the FDA, and should be avoided. (ACOG) The American Cancer Society says no major medical or professional organization recommends these tests for routine screening. (ACS)
- Pap tests: they screen for cervical cancer and only rarely detect ovarian cancer. (ACS) More: Pap and HPV test results.
The other screenings with a D grade are on screening tests you may not need. Every cancer screening the USPSTF does recommend, by age, is on cancer screenings by age.
The tests that were studied
| Test | What it is | What it cannot do |
|---|---|---|
| Transvaginal ultrasound | Sound waves from a wand placed in the vagina show the uterus, fallopian tubes and ovaries. | It can find a mass on an ovary but cannot tell whether it is cancer or benign. Most masses found during screening are not cancer. (ACS) |
| CA-125 blood test | Measures CA-125 (cancer antigen 125), a protein that is often high in women with ovarian cancer. | Many conditions that are not cancer also raise it, and not all ovarian cancers do. (MedlinePlus) (ACS) |
| Pelvic exam | A doctor feels the ovaries and nearby organs by hand. | Most early ovarian tumors are difficult or impossible to feel. A large US trial stopped this part of its screening after 5 years because it found no cancers that only the exam detected. (ACS) (USPSTF, 2018) |
Why the tests miss or over-call
- Over-calling: conditions that are not cancer also raise CA-125: endometriosis, pelvic inflammatory disease, uterine fibroids and liver disease, as well as menstrual periods and pregnancy. (MedlinePlus) In the US PLCO trial, the false-positive rate of ultrasound and CA-125 together was 9.6% across 6 screening rounds. (USPSTF, 2018)
- Surgery for a false alarm: among women who turned out not to have ovarian cancer, surgery to check a positive result happened in 0.97% of the UKCTOCS CA-125 group, 3.25% of the UKCTOCS ultrasound group and 3.17% of the PLCO group. Up to 15% of these women had major surgical complications. (USPSTF, 2018)
- Missing cancer: not all ovarian cancers cause a high CA-125, (ACS) and false-negative results can occur. (NCI)
More on why this happens with any screening test: false positives and overdiagnosis.
What the large trials found
| Trial | Who took part | Screening | Result |
|---|---|---|---|
| PLCO (United States) | 68,557 women aged 55 to 74 with at least 1 ovary | Yearly CA-125 plus transvaginal ultrasound for 4 rounds, then CA-125 alone for 2 more, vs usual care | After a median of 14.7 years, 187 deaths from ovarian cancer in the screened group and 176 in the usual care group: no mortality benefit. (PLCO, 2016) (USPSTF, 2018) |
| UKCTOCS (United Kingdom) | 202,638 postmenopausal women aged 50 to 74, not known to be at high risk | CA-125 tracked over time with a risk algorithm (multimodal), or yearly transvaginal ultrasound, vs no screening | More early-stage cancers were found in the CA-125 group, but after a median of 16.3 years, 0.6% of women in each group had died of the disease: no significant reduction in deaths. (UKCTOCS, 2021) (USPSTF, 2018) |
The UKCTOCS authors concluded that because screening did not significantly reduce deaths from ovarian and tubal cancer, general population screening cannot be recommended. (UKCTOCS, 2021)
What a raised CA-125 can mean
CA-125 is a tumor marker. The ovaries and fallopian tubes may make it when they are inflamed, including during a normal period, and the body may also make high levels in response to ovarian cancer. (MedlinePlus) Doctors use it mainly to:
- see whether ovarian cancer treatment is working or whether the cancer has come back, its most common use;
- learn more about a lump in the pelvis found on imaging, along with other tests;
- check people whose risk of ovarian cancer is very high. (MedlinePlus)
If your CA-125 is high and you do not have a cancer diagnosis, your doctor might repeat the test or suggest a transvaginal ultrasound. (ACS) Only a biopsy can diagnose ovarian cancer. (MedlinePlus)
In the UK, NICE uses age-based CA-125 levels to decide when someone with persistent symptoms should have an urgent ultrasound. These are referral thresholds for people with symptoms, not screening cutoffs. (NICE NG12)
| Age | CA-125 level for an urgent ultrasound (NICE NG12) |
|---|---|
| 39 or under | CA-125 is not used on its own; an urgent ultrasound may be considered instead |
| 40 to 49 | 35 IU/ml or greater |
| 50 to 59 | 31 IU/ml or greater |
| 60 to 69 | 24 IU/ml or greater |
| 70 to 79 | 25 IU/ml or greater |
| 80 and over | 31 IU/ml or greater |
If the level is below the threshold, or the scan is normal, NICE says the doctor should look for other causes and ask the person to come back if symptoms become more frequent or persistent. (NICE NG12)
Who is at high risk
Women with certain hereditary cancer syndromes are at high risk, and the USPSTF advice does not cover them. Women with a family history of ovarian or breast cancer may have such a syndrome and should discuss their family history with a health care professional. (USPSTF, 2018) Risk is higher with a mother or sister, or two or more other relatives, who had ovarian cancer; with relatives who had breast or colorectal cancer; or with certain inherited gene changes. (MedlinePlus) Examples are BRCA gene changes and Lynch syndrome. (ACS)
What a BRCA result means: BRCA test results. Which screenings start earlier with a family history: family history and screening. How to gather it: how to collect your family health history.
Where they differ:
- Testing people at high risk: the American Cancer Society says some organizations state that ultrasound and CA-125 may be offered to women at high risk from an inherited syndrome or a strong family history, but even for them it has not been proven to lower deaths from ovarian cancer. (ACS) NICE limits checks to a specialist team, describes them as a blood test every 4 months with an algorithm to read the CA-125 results, and says this does not reduce the risk of developing ovarian cancer, may find it earlier, but has little evidence of saving lives. (NICE NG241)
- Which test comes first when there are symptoms: NICE measures CA-125 first for people 40 and over and arranges an ultrasound if it is above the threshold for their age. (NICE NG12) ACOG describes an exam and an imaging test such as transvaginal ultrasound first, with a CA 125 blood test if a growth is found. (ACOG)
- How often counts as frequent: the NHS and NICE say roughly 12 or more times a month; (NHS)(NICE NG12) the American Cancer Society also says more than 12 times a month, and elsewhere says symptoms that happen consistently for more than a few weeks. (ACS, symptoms)(ACS)
Symptoms to report
Early ovarian cancer often causes no symptoms, and by the time it does, it has often spread. (ACS) The symptoms are also common in healthy people and can have many other causes, (USPSTF, 2018)(NHS) and the USPSTF says this makes them hard to use for picking out who is at risk. When they are caused by ovarian cancer, they tend to be persistent and a change from normal. (ACS, symptoms) The most common are:
- bloating or a swollen belly;
- pain in the belly or pelvis;
- trouble eating, no appetite, or feeling full quickly;
- needing to pee urgently or more often. (ACS, symptoms)(NHS)
Others include tiredness, back pain, constipation, indigestion, weight loss without trying, and unusual bleeding from the vagina, such as between periods or after menopause. (ACS, symptoms)(NHS) The NHS says to see a doctor about any of these, to go back if they have not gone away or are worse, and to mention any ovarian or breast cancer in your family. (NHS) Because these are symptoms, the USPSTF grade D does not apply. (USPSTF, 2018) The tests a doctor may then arrange: NHS, ovarian cancer tests and next steps.
Your doctor decides what your result means for you.
This page does not give surgery, medicine or treatment advice. If you have a flagged result, see after an abnormal screening result for questions to ask.
Questions people ask
Is there a screening test for ovarian cancer?
Not for women without symptoms who are not at high risk. The USPSTF recommends against screening them (grade D) because transvaginal ultrasound, CA-125 or both do not lower deaths from ovarian cancer and lead to false positives and unneeded surgery. ACOG says there is currently no screening test for ovarian cancer. (USPSTF, 2018) (ACOG)
Does a Pap test check for ovarian cancer?
No. The American Cancer Society says Pap and HPV tests are important for cervical cancer screening but only rarely detect ovarian cancer. (ACS)
What does a high CA-125 mean?
Not necessarily cancer. Endometriosis, pelvic inflammatory disease, uterine fibroids, liver disease, menstrual periods and pregnancy can all raise it. If it is high and you do not have a cancer diagnosis, your doctor might repeat it or suggest an ultrasound. Only a biopsy can diagnose ovarian cancer. (MedlinePlus) (ACS)
Should I have CA-125 tests if ovarian cancer runs in my family?
Talk to your doctor about your family history first. The USPSTF advice does not cover people with a known high-risk inherited syndrome. Some organizations say ultrasound and CA-125 may be offered to people at high risk, but even for them it has not been proven to lower the chance of dying from ovarian cancer. (USPSTF, 2018) (ACS)
Which symptoms should I report?
Bloating, pelvic or belly pain, trouble eating or feeling full quickly, and needing to pee urgently or often. The American Cancer Society and the NHS both say to see a doctor if these happen often, roughly 12 or more times a month. (ACS, symptoms) (NHS)